The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Elizabeth R Sockett - One of the best experts on this subject based on the ideXlab platform.

  • microbe profile Bdellovibrio Bacteriovorus a specialized bacterial predator of bacteria
    Microbiology, 2021
    Co-Authors: Andrew L Lovering, Elizabeth R Sockett
    Abstract:

    Bdellovibrio Bacteriovorus is an environmentally-ubiquitous bacterium that uses unique adaptations to kill other bacteria. The best-characterized strain, HD100, has a multistage lifestyle, with both a free-living attack phase and an intraperiplasmic growth and division phase inside the prey cell. Advances in understanding the basic biology and regulation of predation processes are paving the way for future potential therapeutic and bioremediation applications of this unusual bacterium.

  • a lysozyme with altered substrate specificity facilitates prey cell exit by the periplasmic predator Bdellovibrio Bacteriovorus
    Nature Communications, 2020
    Co-Authors: Christopher J Harding, Carey Lambert, Elizabeth R Sockett, Rob Till, Simona G Huwiler, Hannah Somers, Luke J Ray, Georgina Taylor, Patrick J Moynihan, Andrew L Lovering
    Abstract:

    Lysozymes are among the best-characterized enzymes, acting upon the cell wall substrate peptidoglycan. Here, examining the invasive bacterial periplasmic predator Bdellovibrio Bacteriovorus, we report a diversified lysozyme, DslA, which acts, unusually, upon (GlcNAc-) deacetylated peptidoglycan. B. Bacteriovorus are known to deacetylate the peptidoglycan of the prey bacterium, generating an important chemical difference between prey and self walls and implying usage of a putative deacetyl-specific "exit enzyme". DslA performs this role, and ΔDslA strains exhibit a delay in leaving from prey. The structure of DslA reveals a modified lysozyme superfamily fold, with several adaptations. Biochemical assays confirm DslA specificity for deacetylated cell wall, and usage of two glutamate residues for catalysis. Exogenous DslA, added ex vivo, is able to prematurely liberate B. Bacteriovorus from prey, part-way through the predatory lifecycle. We define a mechanism for specificity that invokes steric selection, and use the resultant motif to identify wider DslA homologues.

  • dynamics of chromosome replication and its relationship to predatory attack lifestyles in Bdellovibrio Bacteriovorus
    Applied and Environmental Microbiology, 2019
    Co-Authors: łukasz Makowski, Carey Lambert, Elizabeth R Sockett, Rob Till, Damian Trojanowski, Rebecca Lowry, Jolanta Zakrzewskaczerwinska
    Abstract:

    Bdellovibrio Bacteriovorus is a small Gram-negative, obligate predatory bacterium that is largely found in wet, aerobic environments (e.g., soil). This bacterium attacks and invades other Gram-negative bacteria, including animal and plant pathogens. The intriguing life cycle of B. Bacteriovorus consists of two phases: a free-living nonreplicative attack phase, in which the predatory bacterium searches for its prey, and a reproductive phase, in which B. Bacteriovorus degrades a host's macromolecules and reuses them for its own growth and chromosome replication. Although the cell biology of this predatory bacterium has gained considerable interest in recent years, we know almost nothing about the dynamics of its chromosome replication. Here, we performed a real-time investigation into the subcellular localization of the replisome(s) in single cells of B. Bacteriovorus Our results show that in B. Bacteriovorus, chromosome replication takes place only during the reproductive phase and exhibits a novel spatiotemporal arrangement of replisomes. The replication process starts at the invasive pole of the predatory bacterium inside the prey cell and proceeds until several copies of the chromosome have been completely synthesized. Chromosome replication is not coincident with the predator cell division, and it terminates shortly before synchronous predator filament septation occurs. In addition, we demonstrate that if this B. Bacteriovorus life cycle fails in some cells of Escherichia coli, they can instead use second prey cells to complete their life cycle.IMPORTANCE New strategies are needed to combat multidrug-resistant bacterial infections. Application of the predatory bacterium Bdellovibrio Bacteriovorus, which kills other bacteria, including pathogens, is considered promising for combating bacterial infections. The B. Bacteriovorus life cycle consists of two phases, a free-living, invasive attack phase and an intracellular reproductive phase, in which this predatory bacterium degrades the host's macromolecules and reuses them for its own growth. To understand the use of B. Bacteriovorus as a "living antibiotic," it is first necessary to dissect its life cycle, including chromosome replication. Here, we present a real-time investigation into subcellular localization of chromosome replication in a single cell of B. Bacteriovorus This process initiates at the invasion pole of B. Bacteriovorus and proceeds until several copies of the chromosome have been completely synthesized. Interestingly, we demonstrate that some cells of B. Bacteriovorus require two prey cells sequentially to complete their life cycle.

  • engulfment persistence and fate of Bdellovibrio Bacteriovorus predators inside human phagocytic cells informs their future therapeutic potential
    Scientific Reports, 2019
    Co-Authors: Dhaarini Raghunathan, Rob Till, David Negus, Christopher I Moore, Paul M Radford, Christopher Gell, Patrick J Tighe, Sally P Wheatley, Luisa Martinezpomares, Elizabeth R Sockett
    Abstract:

    In assessing the potential of predatory bacteria, such as Bdellovibrio Bacteriovorus, to become live therapeutic agents against bacterial infections, it is crucial to understand and quantify Bdellovibrio host cell interactions at a molecular level. Here, we quantify the interactions of live B. Bacteriovorus with human phagocytic cells, determining the uptake mechanisms, persistence, associated cytokine responses and intracellular trafficking of the non-growing B. Bacteriovorus in PMA-differentiated U937 cells. B. Bacteriovorus are engulfed by U937 cells and persist for 24 h without affecting host cell viability and can be observed microscopically and recovered and cultured post-uptake. The uptake of predators is passive and depends on the dynamics of the host cell cytoskeleton; the engulfed predators are eventually trafficked through the phagolysosomal pathway of degradation. We have also studied the prevalence of B. Bacteriovorus specific antibodies in the general human population. Together, these results quantify a period of viable persistence and the ultimate fate of B. Bacteriovorus inside phagocytic cells. They provide new knowledge on predator availability inside hosts, plus potential longevity and therefore potential efficacy as a treatment in humans and open up future fields of work testing if predators can prey on host-engulfed pathogenic bacteria.

  • dynamics of chromosome replication and its relationship to predatory attack lifestyles in Bdellovibrio Bacteriovorus
    bioRxiv, 2019
    Co-Authors: Lukasz Makowski, Carey Lambert, Elizabeth R Sockett, Rob Till, Damian Trojanowski, Rebecca Lowry, Jolanta Zakrzewskaczerwinska
    Abstract:

    Abstract Bdellovibrio Bacteriovorus is a small Gram-negative, an obligate predatory bacterium that is largely found in wet, aerobic environments (i.e. soil). This bacterium attacks and invades other Gram-negative bacteria, including animal and plant pathogens. The intriguing life cycle of B. Bacteriovorus consists of two phases: a free-living non-replicative attack phase wherein the predatory bacterium searches for its prey, and a reproductive phase, in which B. Bacteriovorus degrades a host’s macromolecules and reuses them for its own growth and chromosome replication. Although the cell biology of this predatory bacterium has gained considerable interest in recent years, we know almost nothing about the dynamics of chromosome replication in B. Bacteriovorus. Here, we performed a real-time investigation into the subcellular localization of the replisome(s) in single cells of B. Bacteriovorus. Our results confirm that in B. Bacteriovorus chromosome replication fires only during the reproductive phase, and show for the first time that this predatory bacterium exhibits a novel spatiotemporal arrangement of chromosome replication. The replication process starts at the invasive pole of the predatory bacterium inside the prey cell and proceeds until several copies of the chromosome have been completely synthesized. This chromosome replication is not coincident with the predator-cell division, and it terminates shortly before synchronous predator-filament septation occurs. In addition, we demonstrate that if this lifecycle fails in some cells of B. Bacteriovorus, they can instead use two prey cells sequentially to complete their life cycle. Importance New strategies are needed to combat multidrug-resistant bacterial infections. Application of the predatory bacterium, Bdellovibrio Bacteriovorus, which kills other bacteria including pathogens, is considered promising for bacterial infections. The B. Bacteriovorus life cycle consists of two phases, a free-living, invasive attack phase and an intracellular reproductive phase, in which this predatory bacterium degrades the host’s macromolecules and reuses them for its own growth. To understand the use of B. Bacteriovorus as a ‘living antibiotic’, it is first necessary to dissect its life cycle including chromosome replication. Here, we present for the first time a real-time investigation into subcellular localization of chromosome replication in a single cells of B. Bacteriovorus. This process initiates at the invasion pole of B. Bacteriovorus and proceeds until several copies of the chromosome have been completely synthesized. Interestingly, we demonstrate that some cells of B. Bacteriovorus require two prey cells sequentially to complete their life cycle.

Carey Lambert - One of the best experts on this subject based on the ideXlab platform.

  • a lysozyme with altered substrate specificity facilitates prey cell exit by the periplasmic predator Bdellovibrio Bacteriovorus
    Nature Communications, 2020
    Co-Authors: Christopher J Harding, Carey Lambert, Elizabeth R Sockett, Rob Till, Simona G Huwiler, Hannah Somers, Luke J Ray, Georgina Taylor, Patrick J Moynihan, Andrew L Lovering
    Abstract:

    Lysozymes are among the best-characterized enzymes, acting upon the cell wall substrate peptidoglycan. Here, examining the invasive bacterial periplasmic predator Bdellovibrio Bacteriovorus, we report a diversified lysozyme, DslA, which acts, unusually, upon (GlcNAc-) deacetylated peptidoglycan. B. Bacteriovorus are known to deacetylate the peptidoglycan of the prey bacterium, generating an important chemical difference between prey and self walls and implying usage of a putative deacetyl-specific "exit enzyme". DslA performs this role, and ΔDslA strains exhibit a delay in leaving from prey. The structure of DslA reveals a modified lysozyme superfamily fold, with several adaptations. Biochemical assays confirm DslA specificity for deacetylated cell wall, and usage of two glutamate residues for catalysis. Exogenous DslA, added ex vivo, is able to prematurely liberate B. Bacteriovorus from prey, part-way through the predatory lifecycle. We define a mechanism for specificity that invokes steric selection, and use the resultant motif to identify wider DslA homologues.

  • A novel method to determine antibiotic sensitivity in Bdellovibrio Bacteriovorus reveals a DHFR-dependent natural trimethoprim resistance.
    Scientific Reports, 2020
    Co-Authors: Emanuele Marine, David Stephen Milner, Carey Lambert, Renee Elizabeth Sockett, Klaas M. Pos
    Abstract:

    Bdellovibrio Bacteriovorus is a small Gram-negative bacterium and an obligate predator of other Gram-negative bacteria. Prey resistance to B. Bacteriovorus attack is rare and transient. This consideration together with its safety and low immunogenicity makes B. Bacteriovorus a valid alternative to antibiotics, especially in the treatment of multidrug resistant pathogens. In this study we developed a novel technique to estimate B. Bacteriovorus sensitivity against antibiotics in order to make feasible the development and testing of co-therapies with antibiotics that would increase its antimicrobial efficacy and at the same time reduce the development of drug resistance. Results from tests performed with this technique show that among all tested antibiotics, trimethoprim has the lowest antimicrobial effect on B. Bacteriovorus. Additional experiments revealed that the mechanism of trimethoprim resistance in B. Bacteriovorus depends on the low affinity of this compound for the B. Bacteriovorus dihydrofolate reductase (Bd DHFR).

  • dual predation by bacteriophage and Bdellovibrio Bacteriovorus can eradicate escherichia coli prey in situations where single predation cannot
    Journal of Bacteriology, 2020
    Co-Authors: Laura Hobley, Rob Till, Kimberley J Summers, Michael J Capeness, David S Milner, Robert J Atterbury, Amy Stroud, Stephanie Gray, Andreas Leidenroth, Carey Lambert
    Abstract:

    Bacteria are preyed upon by diverse microbial predators, including bacteriophage and predatory bacteria, such as Bdellovibrio Bacteriovorus While bacteriophage are used as antimicrobial therapies in Eastern Europe and are being applied for compassionate use in the United States, predatory bacteria are only just beginning to reveal their potential therapeutic uses. However, predation by either predator type can falter due to different adaptations arising in the prey bacteria. When testing poultry farm wastewater for novel Bdellovibrio isolates on Escherichia coli prey lawns, individual composite plaques were isolated containing both an RTP (rosette-tailed-phage)-like-phage and a B. Bacteriovorus strain and showing central prey lysis and halos of extra lysis. Combining the purified phage with a lab strain of B. Bacteriovorus HD100 recapitulated haloed plaques and increased killing of the E. coli prey in liquid culture, showing an effective side-by-side action of these predators compared to their actions alone. Using approximate Bayesian computation to select the best fitting from a variety of different mathematical models demonstrated that the experimental data could be explained only by assuming the existence of three prey phenotypes: (i) sensitive to both predators, (ii) genetically resistant to phage only, and (iii) plastic resistant to B. Bacteriovorus only. Although each predator reduces prey availability for the other, high phage numbers did not abolish B. Bacteriovorus predation, so both predators are competent to coexist and are causing different selective pressures on the bacterial surface while, in tandem, controlling prey bacterial numbers efficiently. This suggests that combinatorial predator therapy could overcome problems of phage resistance.IMPORTANCE With increasing levels of antibiotic resistance, the development of alternative antibacterial therapies is urgently needed. Two potential alternatives are bacteriophage and predatory bacteria. Bacteriophage therapy has been used, but prey/host specificity and the rapid acquisition of bacterial resistance to bacteriophage are practical considerations. Predatory bacteria are of interest due to their broad Gram-negative bacterial prey range and the lack of simple resistance mechanisms. Here, a bacteriophage and a strain of Bdellovibrio Bacteriovorus, preyed side by side on a population of E. coli, causing a significantly greater decrease in prey numbers than either alone. Such combinatorial predator therapy may have greater potential than individual predators since prey surface changes selected for by each predator do not protect prey against the other predator.

  • dynamics of chromosome replication and its relationship to predatory attack lifestyles in Bdellovibrio Bacteriovorus
    Applied and Environmental Microbiology, 2019
    Co-Authors: łukasz Makowski, Carey Lambert, Elizabeth R Sockett, Rob Till, Damian Trojanowski, Rebecca Lowry, Jolanta Zakrzewskaczerwinska
    Abstract:

    Bdellovibrio Bacteriovorus is a small Gram-negative, obligate predatory bacterium that is largely found in wet, aerobic environments (e.g., soil). This bacterium attacks and invades other Gram-negative bacteria, including animal and plant pathogens. The intriguing life cycle of B. Bacteriovorus consists of two phases: a free-living nonreplicative attack phase, in which the predatory bacterium searches for its prey, and a reproductive phase, in which B. Bacteriovorus degrades a host's macromolecules and reuses them for its own growth and chromosome replication. Although the cell biology of this predatory bacterium has gained considerable interest in recent years, we know almost nothing about the dynamics of its chromosome replication. Here, we performed a real-time investigation into the subcellular localization of the replisome(s) in single cells of B. Bacteriovorus Our results show that in B. Bacteriovorus, chromosome replication takes place only during the reproductive phase and exhibits a novel spatiotemporal arrangement of replisomes. The replication process starts at the invasive pole of the predatory bacterium inside the prey cell and proceeds until several copies of the chromosome have been completely synthesized. Chromosome replication is not coincident with the predator cell division, and it terminates shortly before synchronous predator filament septation occurs. In addition, we demonstrate that if this B. Bacteriovorus life cycle fails in some cells of Escherichia coli, they can instead use second prey cells to complete their life cycle.IMPORTANCE New strategies are needed to combat multidrug-resistant bacterial infections. Application of the predatory bacterium Bdellovibrio Bacteriovorus, which kills other bacteria, including pathogens, is considered promising for combating bacterial infections. The B. Bacteriovorus life cycle consists of two phases, a free-living, invasive attack phase and an intracellular reproductive phase, in which this predatory bacterium degrades the host's macromolecules and reuses them for its own growth. To understand the use of B. Bacteriovorus as a "living antibiotic," it is first necessary to dissect its life cycle, including chromosome replication. Here, we present a real-time investigation into subcellular localization of chromosome replication in a single cell of B. Bacteriovorus This process initiates at the invasion pole of B. Bacteriovorus and proceeds until several copies of the chromosome have been completely synthesized. Interestingly, we demonstrate that some cells of B. Bacteriovorus require two prey cells sequentially to complete their life cycle.

  • dynamics of chromosome replication and its relationship to predatory attack lifestyles in Bdellovibrio Bacteriovorus
    bioRxiv, 2019
    Co-Authors: Lukasz Makowski, Carey Lambert, Elizabeth R Sockett, Rob Till, Damian Trojanowski, Rebecca Lowry, Jolanta Zakrzewskaczerwinska
    Abstract:

    Abstract Bdellovibrio Bacteriovorus is a small Gram-negative, an obligate predatory bacterium that is largely found in wet, aerobic environments (i.e. soil). This bacterium attacks and invades other Gram-negative bacteria, including animal and plant pathogens. The intriguing life cycle of B. Bacteriovorus consists of two phases: a free-living non-replicative attack phase wherein the predatory bacterium searches for its prey, and a reproductive phase, in which B. Bacteriovorus degrades a host’s macromolecules and reuses them for its own growth and chromosome replication. Although the cell biology of this predatory bacterium has gained considerable interest in recent years, we know almost nothing about the dynamics of chromosome replication in B. Bacteriovorus. Here, we performed a real-time investigation into the subcellular localization of the replisome(s) in single cells of B. Bacteriovorus. Our results confirm that in B. Bacteriovorus chromosome replication fires only during the reproductive phase, and show for the first time that this predatory bacterium exhibits a novel spatiotemporal arrangement of chromosome replication. The replication process starts at the invasive pole of the predatory bacterium inside the prey cell and proceeds until several copies of the chromosome have been completely synthesized. This chromosome replication is not coincident with the predator-cell division, and it terminates shortly before synchronous predator-filament septation occurs. In addition, we demonstrate that if this lifecycle fails in some cells of B. Bacteriovorus, they can instead use two prey cells sequentially to complete their life cycle. Importance New strategies are needed to combat multidrug-resistant bacterial infections. Application of the predatory bacterium, Bdellovibrio Bacteriovorus, which kills other bacteria including pathogens, is considered promising for bacterial infections. The B. Bacteriovorus life cycle consists of two phases, a free-living, invasive attack phase and an intracellular reproductive phase, in which this predatory bacterium degrades the host’s macromolecules and reuses them for its own growth. To understand the use of B. Bacteriovorus as a ‘living antibiotic’, it is first necessary to dissect its life cycle including chromosome replication. Here, we present for the first time a real-time investigation into subcellular localization of chromosome replication in a single cells of B. Bacteriovorus. This process initiates at the invasion pole of B. Bacteriovorus and proceeds until several copies of the chromosome have been completely synthesized. Interestingly, we demonstrate that some cells of B. Bacteriovorus require two prey cells sequentially to complete their life cycle.

Robert J Mitchell - One of the best experts on this subject based on the ideXlab platform.

  • viscosity has dichotomous effects on Bdellovibrio Bacteriovorus hd100 predation
    Environmental Microbiology, 2019
    Co-Authors: Heeun Kwon, Gayoung Cho, Jisoo Kwon, Seong Yeol Choi, Robert J Mitchell
    Abstract:

    Bdellovibrio Bacteriovorus HD100 is a highly motile predatory bacterium that consumes other Gram-negative bacteria for its sustenance. Here, we describe the impacts the media viscosity has both on the motility of predator and its attack rates. Experiments performed in polyethylene glycol (PEG) solutions, a linear polymer, found a viscosity of 10 mPa s (5% PEG) negatively impacted predation over a 24-h period. When the viscosity was increased to 27 mPa s (10% PEG), predation was nearly abolished. Tests with three other B. Bacteriovorus strains, i.e., 109J and two natural isolates, found identical results. Short-term (2-h) experiments, however, found attack rates were improved in 1% PEG, which had a viscosity of 5.4 mPa s, using bioluminescent prey and their viabilities. In contrast, when experiments were performed in dextran, a branched polymer, no increase in predation was seen even though the viscosity was a comparable 5.1 mPa s. The enhanced attack rates in this solution coincided with a 31% increase in B. Bacteriovorus HD100 swimming speeds (62 μm s-1 in 1% PEG vs. 47.5 μm s-1 in HEPES-salt).

  • Bdellovibrio Bacteriovorus hd100 a predator of gram negative bacteria benefits energetically from staphylococcus aureus biofilms without predation
    The ISME Journal, 2018
    Co-Authors: Mohammed Dwidar, Robert J Mitchell
    Abstract:

    Bdellovibrio Bacteriovorus HD100 is a predatory bacterium which lives by invading the periplasm of Gram-negative bacteria and consuming them from within. Although B. Bacteriovorus HD100 attacks only Gram-negative bacterial strains, our work here shows attack-phase predatory cells also benefit from interacting with Gram-positive biofilms. Using Staphylococcus aureus biofilms, we show this predator degrades the biofilm matrix, obtains nutrients and uses these to produce and secrete proteolytic enzymes to continue this process. When exposed to S. aureus biofilms, the transcriptome of B. Bacteriovorus HD100 was analogous to that seen when present intraperiplasmically, suggesting it is responding similarly as when in a prey. Moreover, two of the induced proteases (Bd2269 and Bd2692) were purified and their activities against S. aureus biofilms verified. In addition, B. Bacteriovorus HD100 gained several clear benefits from its interactions with S. aureus biofilms, including increased ATP pools and improved downstream predatory activities when provided prey.

  • serum albumin and osmolality inhibit Bdellovibrio Bacteriovorus predation in human serum
    Scientific Reports, 2017
    Co-Authors: Sangmo Son, Robert J Mitchell, Cheolmin Ghim
    Abstract:

    We evaluated the bactericidal activity of Bdellovibrio Bacteriovorus, strain HD100, within blood sera against bacterial strains commonly associated with bacteremic infections, including E. coli, Klebsiella pneumoniae and Salmonella enterica. Tests show that B. Bacteriovorus HD100 is not susceptible to serum complement or its bactericidal activity. After a two hour exposure to human sera, the prey populations decreased 15- to 7,300-fold due to the serum complement activity while, in contrast, the B. Bacteriovorus HD100 population showed a loss of only 33%. Dot blot analyses showed that this is not due to the absence of antibodies against this predator. Predation in human serum was inhibited, though, by both the osmolality and serum albumin. The activity of B. Bacteriovorus HD100 showed a sharp transition between 200 and 250 mOsm/kg, and was progressively reduced as the osmolality increased. Serum albumin also acted to inhibit predation by binding to and coating the predatory cells. This was confirmed via dot blot analyses and confocal microscopy. The results from both the osmolality and serum albumin tests were incorporated into a numerical model describing bacterial predation of pathogens. In conclusion, both of these factors inhibit predation and, as such, they limit its effectiveness against pathogenic prey located within sera.

  • attack phase Bdellovibrio Bacteriovorus responses to extracellular nutrients are analogous to those seen during late intraperiplasmic growth
    Microbial Ecology, 2017
    Co-Authors: Mohammed Dwidar, Jeong Kon Seo, Robert J Mitchell
    Abstract:

    Bdellovibrio Bacteriovorus is a predatory bacterium which lives by invading the periplasm of gram-negative bacteria and consuming them from within. This predator was thought to be dependent upon prey for nutrients since it lacks genes encoding for critical enzymes involved in amino acid biosynthesis. This study, however, found that planktonic attack-phase predators are not just dependent upon prey for nutrients, but rather, they respond to nutrients in the surrounding medium and, subsequently, synthesize and secrete proteases in a nutrient-dependent manner. The major secreted proteases were identified through mass spectrometry analyses. Subsequent RT-qPCR analyses found that the nutrient-induced proteases are similar to those expressed within the prey periplasm during the late intraperiplasmic growth phase. Furthermore, RNA sequencing found that incubating the planktonic attack-phase cells in a nutritious environment for a short period of time (4 h) changes its gene expression pattern to a status that is akin to the late intraperiplasmic phase, with more than 94% of the genes previously identified as being late intraperiplasmic-specific also being induced by nutrient broth in this study. This strong correlation between the gene expression patterns hints that the availability of hydrolyzed prey cell components to the predator is likely the stimulus controlling the expression of late intraperiplasmic B. Bacteriovorus genes during predation.

  • Cyanide Production by Chromobacterium piscinae Shields It from Bdellovibrio Bacteriovorus HD100 Predation
    American Society for Microbiology, 2017
    Co-Authors: Wonsik Mun, Robert J Mitchell, Heeun Kwon, Seong Yeol Choi, Ajay K. Monnappa, Karen Bush
    Abstract:

    Predation of Chromobacterium piscinae by Bdellovibrio Bacteriovorus HD100 was inhibited in dilute nutrient broth (DNB) but not in HEPES. Experiments showed that the effector responsible was present in the medium, as cell-free supernatants retained the ability to inhibit predation, and that the effector was not toxic to B. Bacteriovorus. Violacein, a bisindole secondary metabolite produced by C. piscinae, was not responsible. Further characterization of C. piscinae found that this species produces sufficient concentrations of cyanide (202 µM) when grown in DNB to inhibit the predatory activity of B. Bacteriovorus, but that in HEPES, the cyanide concentrations were negligible (19 µM). The antagonistic role of cyanide was further confirmed, as the addition of hydroxocobalamin, which chelates cyanide, allowed predation to proceed. The activity of cyanide against B. Bacteriovorus was found to be twofold, depending on the life cycle stage of this predator. For the attack-phase predatory cells, cyanide caused the cells to lose motility and tumble, while for intraperiplasmic predators, development and lysis of the prey cell were halted. These findings suggest that cyanogenesis in nature may be employed by the bacterial strains that produce this compound to prevent and reduce their predation by B. Bacteriovorus

Daniel E Kadouri - One of the best experts on this subject based on the ideXlab platform.

  • predation by Bdellovibrio Bacteriovorus transforms the landscape and community assembly of bacterial biofilms
    bioRxiv, 2020
    Co-Authors: Benjamin R Wucher, Daniel E Kadouri, Mennat Elsayed, Carey D Nadell
    Abstract:

    The predatory bacterium Bdellovibrio Bacteriovorus follows a life cycle in which it attaches to the exterior of a Gram-negative prey cell, enters the periplasm, and harvests resources to replicate before lysing the host to find new prey. Predatory bacteria such as this are common in many natural environments, as are groups of matrix-bound clusters of prey cells, termed biofilms. Despite the ubiquity of both predatory bacteria and biofilm-dwelling prey, the interaction between B. Bacteriovorus and prey cells inside biofilms has received little attention and has not yet been studied at the micrometer scale. Filling this knowledge is critical to understanding the nature of predator-prey interaction in nature. Here we show that B. Bacteriovorus is able to prey upon biofilms of the pathogen Vibrio cholerae, but only up until a critical maturation threshold past which the prey biofilms are protected from their predators. We determine the contribution of matrix secretion and cell-cell packing of the prey biofilm toward this protection mechanism. Our results demonstrate that B. Bacteriovorus predation in the context of this protection threshold fundamentally transforms the sub-millimeter scale landscape of biofilm growth, as well as the process of community assembly as new potential biofilm residents enter the system.

  • high throughput analysis of gene function in the bacterial predator Bdellovibrio Bacteriovorus
    Mbio, 2019
    Co-Authors: Miles C Duncan, Robert M Q Shanks, Daniel E Kadouri, Rebecca K Gillette, David W Lazinski, Micah A Maglasang, Elizabeth A Corn, Albert K Tai, Andrew Camilli
    Abstract:

    ABSTRACT Bdellovibrio Bacteriovorus is a bacterial predator capable of killing and replicating inside most Gram-negative bacteria, including antibiotic-resistant pathogens. Despite growing interest in this organism as a potential therapeutic, many of its genes remain uncharacterized. Here, we perform a high-throughput genetic screen with B. Bacteriovorus using transposon sequencing (Tn-seq) to explore the genetic requirements of predation. Two hundred one genes were deemed essential for growth in the absence of prey, whereas over 100 genes were found to be specifically required for predative growth on the human pathogens Vibrio cholerae and Escherichia coli in both planktonic and biofilm states. To further this work, we created an ordered-knockout library in B. Bacteriovorus and developed new high-throughput techniques to characterize the mutants by their stage of deficiency in the predator life cycle. Using microscopy and flow cytometry, we confirmed 10 mutants defective in prey attachment and eight mutants defective in prey rounding. The majority of these genes are hypothetical and previously uncharacterized. Finally, we propose new nomenclature to group B. Bacteriovorus mutants into classes based on their stage of predation defect. These results contribute to our basic understanding of bacterial predation and may be useful for harnessing B. Bacteriovorus to kill harmful pathogens in the clinical setting. IMPORTANCEBdellovibrio Bacteriovorus is a predatory bacterium that can kill a wide range of Gram-negative bacteria, including many human pathogens. Given the global rise of antibiotic resistance and dearth of new antibiotics discovered in the past 30 years, this predator has potential as an alternative to traditional antibiotics. For many years, B. Bacteriovorus research was hampered by a lack of genetic tools, and the genetic mechanisms of predation have only recently begun to be established. Here, we comprehensively identify and characterize predator genes required for killing bacterial prey, as well as genes that interfere in this process, which may allow us to design better therapeutic predators. Based on our study, we and other researchers may ultimately be able to genetically engineer strains that have improved killing rates, target specific species of prey, or preferentially target prey in the planktonic or biofilm state.

  • vibrio cholerae motility exerts drag force to impede attack by the bacterial predator Bdellovibrio Bacteriovorus
    Nature Communications, 2018
    Co-Authors: Miles C Duncan, Robert M Q Shanks, John C Forbes, Y Nguyen, Lauren M Shull, Rebecca K Gillette, David W Lazinski, Afsar Ali, Daniel E Kadouri
    Abstract:

    The bacterial predator Bdellovibrio Bacteriovorus is evolved to attack and kill other bacteria, including the human intestinal pathogen Vibrio cholerae. Although B. Bacteriovorus exhibit a broad prey range, little is known about the genetic determinants of prey resistance and sensitivity. Here we perform a genetic screen on V. cholerae and identify five pathways contributing to predation susceptibility. We find that the essential virulence regulators ToxR/S increase susceptibility to predation, as mutants of these genes are more resistant to predation. We observe by flow cytometry that lipopolysaccharide is a critical defense, as mutants lacking O-antigen are rapidly attacked by predatory B. Bacteriovorus. Using polymer solutions to alter media viscosity, we find that when B. Bacteriovorus attacks motile V. cholerae, increased drag forces slow its ability to prey. These results provide insights into key prey resistance mechanisms, and may be useful in the application of B. Bacteriovorus in treating infections.

  • visualizing Bdellovibrio Bacteriovorus by using the tdtomato fluorescent protein
    Applied and Environmental Microbiology, 2016
    Co-Authors: Somdatta Mukherjee, Robert M Q Shanks, Daniel E Kadouri
    Abstract:

    Bdellovibrio Bacteriovorus is a Gram-negative bacterium that belongs to the delta subgroup of proteobacteria and is characterized by a predatory life cycle. In recent years, work has highlighted the potential use of this predator to control bacteria and biofilms. Traditionally, the reduction in prey cells was used to monitor predation dynamics. In this study, we introduced pMQ414, a plasmid that expresses the tdTomato fluorescent reporter protein, into a host-independent strain and a host-dependent strain of B. Bacteriovorus 109J. The new construct was used to conveniently monitor predator proliferation in real time, in different growth conditions, in the presence of lytic enzymes, and on several prey bacteria, replicating previous studies that used plaque analysis to quantify B. Bacteriovorus. The new fluorescent plasmid also enabled us to visualize the predator in liquid cultures, in the context of a biofilm, and in association with human epithelial cells.

  • inhibition of predation by Bdellovibrio Bacteriovorus and micavibrio aeruginosavorus via host cell metabolic activity in the presence of carbohydrates
    Applied and Environmental Microbiology, 2011
    Co-Authors: Aliza Dashiff, Thomas G Keeling, Daniel E Kadouri
    Abstract:

    Bdellovibrio Bacteriovorus and Micavibrio aeruginosavorus are highly motile Gram-negative predatory bacteria with the potential of being used as biocontrol agents or living antibiotics. It was suggested previously that sugar-binding proteins play a role in M. aeruginosavorus and B. Bacteriovorus host specificity and predator-prey interactions. The effect of carbohydrates on predation was reexamined in this study. It was demonstrated that the presence of carbohydrates could indeed block predation. However, further investigation demonstrated that inhibition of predation was due to medium acidification by the metabolic activity of the host and not to a blocking of a putative sugar-binding protein. The data presented here might be of value when storing, growing, and cultivating predatory bacteria, as well as when considering environmental conditions that might influence predation in the field.

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  • dual predation by bacteriophage and Bdellovibrio Bacteriovorus can eradicate escherichia coli prey in situations where single predation cannot
    Journal of Bacteriology, 2020
    Co-Authors: Laura Hobley, Rob Till, Kimberley J Summers, Michael J Capeness, David S Milner, Robert J Atterbury, Amy Stroud, Stephanie Gray, Andreas Leidenroth, Carey Lambert
    Abstract:

    Bacteria are preyed upon by diverse microbial predators, including bacteriophage and predatory bacteria, such as Bdellovibrio Bacteriovorus While bacteriophage are used as antimicrobial therapies in Eastern Europe and are being applied for compassionate use in the United States, predatory bacteria are only just beginning to reveal their potential therapeutic uses. However, predation by either predator type can falter due to different adaptations arising in the prey bacteria. When testing poultry farm wastewater for novel Bdellovibrio isolates on Escherichia coli prey lawns, individual composite plaques were isolated containing both an RTP (rosette-tailed-phage)-like-phage and a B. Bacteriovorus strain and showing central prey lysis and halos of extra lysis. Combining the purified phage with a lab strain of B. Bacteriovorus HD100 recapitulated haloed plaques and increased killing of the E. coli prey in liquid culture, showing an effective side-by-side action of these predators compared to their actions alone. Using approximate Bayesian computation to select the best fitting from a variety of different mathematical models demonstrated that the experimental data could be explained only by assuming the existence of three prey phenotypes: (i) sensitive to both predators, (ii) genetically resistant to phage only, and (iii) plastic resistant to B. Bacteriovorus only. Although each predator reduces prey availability for the other, high phage numbers did not abolish B. Bacteriovorus predation, so both predators are competent to coexist and are causing different selective pressures on the bacterial surface while, in tandem, controlling prey bacterial numbers efficiently. This suggests that combinatorial predator therapy could overcome problems of phage resistance.IMPORTANCE With increasing levels of antibiotic resistance, the development of alternative antibacterial therapies is urgently needed. Two potential alternatives are bacteriophage and predatory bacteria. Bacteriophage therapy has been used, but prey/host specificity and the rapid acquisition of bacterial resistance to bacteriophage are practical considerations. Predatory bacteria are of interest due to their broad Gram-negative bacterial prey range and the lack of simple resistance mechanisms. Here, a bacteriophage and a strain of Bdellovibrio Bacteriovorus, preyed side by side on a population of E. coli, causing a significantly greater decrease in prey numbers than either alone. Such combinatorial predator therapy may have greater potential than individual predators since prey surface changes selected for by each predator do not protect prey against the other predator.

  • A small predatory core genome in the divergent marine Bacteriovorax marinus SJ and the terrestrial Bdellovibrio Bacteriovorus
    The ISME Journal, 2013
    Co-Authors: Lisa C Crossman, R. Elizabeth Sockett, Huan Chen, Ana-m Cerdeño-tárraga, Karen Brooks, Michael A Quail, Silvia A Pineiro, Laura Hobley, Stephen D Bentley, Julian Parkhill
    Abstract:

    Bacteriovorax marinus SJ is a predatory delta-proteobacterium isolated from a marine environment. The genome sequence of this strain provides an interesting contrast to that of the terrestrial predatory bacterium Bdellovibrio Bacteriovorus HD100. Based on their predatory lifestyle, Bacteriovorax were originally designated as members of the genus Bdellovibrio but subsequently were re-assigned to a new genus and family based on genetic and phenotypic differences. B. marinus attaches to Gram-negative bacteria, penetrates through the cell wall to form a bdelloplast, in which it replicates, as shown using microscopy. Bacteriovorax is distinct, as it shares only 30% of its gene products with its closest sequenced relatives. Remarkably, 34% of predicted genes over 500 nt in length were completely unique with no significant matches in the databases. As expected, Bacteriovorax shares several characteristic loci with the other delta-proteobacteria. A geneset shared between Bacteriovorax and Bdellovibrio that is not conserved among other delta-proteobacteria such as Myxobacteria (which destroy prey bacteria externally via lysis), or the non-predatory Desulfo-bacteria and Geobacter species was identified. These 291 gene orthologues common to both Bacteriovorax and Bdellovibrio may be the key indicators of host-interaction predatory-specific processes required for prey entry. The locus from Bdellovibrio Bacteriovorus is implicated in the switch from predatory to prey/host-independent growth. Although the locus is conserved in B. marinus , the sequence has only limited similarity. The results of this study advance understanding of both the similarities and differences between Bdellovibrio and Bacteriovorax and confirm the distant relationship between the two and their separation into different families.

  • discrete cyclic di gmp dependent control of bacterial predation versus axenic growth in Bdellovibrio Bacteriovorus
    PLOS Pathogens, 2012
    Co-Authors: Laura Hobley, Carey Lambert, Robert Till, Rowena K Y Fung, Maximilian A T S Harris, Jayesh M Dabhi, Simon S King, Sarah M Basford, Kaoru Uchida, Rashidah Ahmad
    Abstract:

    Bdellovibrio Bacteriovorus is a Delta-proteobacterium that oscillates between free-living growth and predation on Gram-negative bacteria including important pathogens of man, animals and plants. After entering the prey periplasm, killing the prey and replicating inside the prey bdelloplast, several motile B. Bacteriovorus progeny cells emerge. The B. Bacteriovorus HD100 genome encodes numerous proteins predicted to be involved in signalling via the secondary messenger cyclic di-GMP (c-di-GMP), which is known to affect bacterial lifestyle choices. We investigated the role of c-di-GMP signalling in B. Bacteriovorus, focussing on the five GGDEF domain proteins that are predicted to function as diguanylyl cyclases initiating c-di-GMP signalling cascades. Inactivation of individual GGDEF domain genes resulted in remarkably distinct phenotypes. Deletion of dgcB (Bd0742) resulted in a predation impaired, obligately axenic mutant, while deletion of dgcC (Bd1434) resulted in the opposite, obligately predatory mutant. Deletion of dgcA (Bd0367) abolished gliding motility, producing bacteria capable of predatory invasion but unable to leave the exhausted prey. Complementation was achieved with wild type dgc genes, but not with GGAAF versions. Deletion of cdgA (Bd3125) substantially slowed predation; this was restored by wild type complementation. Deletion of dgcD (Bd3766) had no observable phenotype. In vitro assays showed that DgcA, DgcB, and DgcC were diguanylyl cyclases. CdgA lacks enzymatic activity but functions as a c-di-GMP receptor apparently in the DgcB pathway. Activity of DgcD was not detected. Deletion of DgcA strongly decreased the extractable c-di-GMP content of axenic Bdellovibrio cells. We show that c-di-GMP signalling pathways are essential for both the free-living and predatory lifestyles of B. Bacteriovorus and that obligately predatory dgcC- can be made lacking a propensity to survive without predation of bacterial pathogens and thus possibly useful in anti-pathogen applications. In contrast to many studies in other bacteria, Bdellovibrio shows specificity and lack of overlap in c-di-GMP signalling pathways.

  • the Bdellovibrio Bacteriovorus twin arginine transport system has roles in predatory and prey independent growth
    Microbiology, 2011
    Co-Authors: Chienyi Chang, Laura Hobley, Pratik D Jagtap, Rob Till, Michael J Capeness, Shinichi Aizawa, Machi Kanna, William Burtt, Elizabeth R Sockett
    Abstract:

    Bdellovibrio Bacteriovorus grows in one of two ways: either (i) predatorily [in a host-dependent (HD) manner], when it invades the periplasm of another Gram-negative bacterium, exporting into the prey co-ordinated waves of soluble enzymes using the prey cell contents for growth; or (ii) in a host-independent (HI) manner, when it grows (slowly) axenically in rich media. Periplasmic invasion potentially exposes B. Bacteriovorus to extremes of pH and exposes the need to scavenge electron donors from prey electron transport components by synthesis of metalloenzymes. The twin-arginine transport system (Tat) in other bacteria transports folded metalloenzymes and the B. Bacteriovorus genome encodes 21 potential Tat-transported substrates and Tat transporter proteins TatA1, TatA2 and TatBC. GFP tagging of the Tat signal peptide from Bd1802, a high-potential iron-sulfur protein (HiPIP), revealed it to be exported into the prey bacterium during predatory growth. Mutagenesis showed that the B. Bacteriovorus tatA2 and tatC gene products are essential for both HI and HD growth, despite the fact that they partially complement (in SDS resistance assays) the corresponding mutations in Escherichia coli where neither TatA nor TatC are essential for life. The essentiality of B. Bacteriovorus TatA2 was surprising given that the B. Bacteriovorus genome encodes a second tatA homologue, tatA1. Transcription of tatA1 was found to be induced upon entry to the bdelloplast, and insertional inactivation of tatA1 showed that it significantly slowed the rates of both HI and HD growth. B. Bacteriovorus is one of a few bacterial species that are reliant on a functional Tat system and where deletion of a single tatA1 gene causes a significant growth defect(s), despite the presence of its tatA2 homologue.

  • effects of orally administered Bdellovibrio Bacteriovorus on the well being and salmonella colonization of young chicks
    Applied and Environmental Microbiology, 2011
    Co-Authors: Robert J Atterbury, Carey Lambert, Andy Fenton, Laura Hobley, Thomas R Lerner, Michael J Capeness, Robert Till, Paul A Barrow, Elizabeth R Sockett
    Abstract:

    Bdellovibrio Bacteriovorus is a bacterium which preys upon and kills Gram-negative bacteria, including the zoonotic pathogens Escherichia coli and Salmonella. Bdellovibrio has potential as a biocontrol agent, but no reports of it being tested in living animals have been published, and no data on whether Bdellovibrio might spread between animals are available. In this study, we tried to fill this knowledge gap, using B. Bacteriovorus HD100 doses in poultry with a normal gut microbiota or predosed with a colonizing Salmonella strain. In both cases, Bdellovibrio was dosed orally along with antacids. After dosing non-Salmonella-infected birds with Bdellovibrio, we measured the health and well-being of the birds and any changes in their gut pathology and culturable microbiota, finding that although a Bdellovibrio dose at 2 days of age altered the overall diversity of the natural gut microbiota in 28-day-old birds, there were no adverse effects on their growth and well-being. Drinking water and fecal matter from the pens in which the birds were housed as groups showed no contamination by Bdellovibrio after dosing. Predatory Bdellovibrio orally administered to birds that had been predosed with a gut-colonizing Salmonella enterica serovar Enteritidis phage type 4 strain (an important zoonotic pathogen) significantly reduced Salmonella numbers in bird gut cecal contents and reduced abnormal cecal morphology, indicating reduced cecal inflammation, compared to the ceca of the untreated controls or a nonpredatory ΔpilA strain, suggesting that these effects were due to predatory action. This work is a first step to applying Bdellovibrio therapeutically for other animal, and possibly human, infections.