The Experts below are selected from a list of 2019 Experts worldwide ranked by ideXlab platform
Dieter Oesterhelt - One of the best experts on this subject based on the ideXlab platform.
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regulatory proteins in Halobacterium salinarum R1
2016Co-Authors: Rita Schwaiger, Valery Tarasov, Katarina Furtwangler, Andy Wende, Christoph Schwarz, Dieter OesterheltAbstract:Background: Archaea combine bacterial-as well as eukaryotic-like features to regulate cellular processes. Halobacterium salinarum R1 encodes eight leucine-responsive regulatory protein (Lrp)-homologues. The function of two of them, Irp (OE3923F) and lrpA1 (OE2621R), were analyzed by gene deletion and overexpression, including genome scale impacts using microarrays. Results: It was shown that Lrp affects the transcription of multiple target genes, including those encoding enzymes involved in amino acid synthesis, central metabolism, transport processes and other regulators of transcription. In contrast, LrpA1 regulates transcription in a more specific manner. The aspB3 gene, coding for an aspartate transaminase, was repressed by LrpA1 in the presence of L-aspartate. Analytical DNA-affinity chromatography was adapted to high salt, and demonstrated binding of LrpA1 to its own promoter, as well as L-aspartate dependent binding to the aspB3 promoter. Conclusion: The gene expression profiles of two archaeal Lrp-homologues report in detail their role in H. salinarum R1. LrpA1 and Lrp show similar functions to those already described in bacteria, but in addition they play a key role in regulatory networks, such as controlling the transcription of other regulators. In a more detailed analysis ligand dependent binding of LrpA1 was demonstrated to its target gene aspB3
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1 Phosphate Dependent Behavior of the Archaeon Halobacterium salinarum Strain R1 1 2 Running title: Phosphate Regulation in H. salinarum 3
2016Co-Authors: Andy Wende, Katarina Furtwangler, Dieter OesterheltAbstract:Abstract 9 Phosphate is essential for life on earth being an integral part of important biomolecules. The 10 mechanisms applied by bacteria and eukarya to combat phosphate limitation are fairly well 11 understood. However, it is neither known how archaea sense phosphate limitation nor which 12 genes are regulated upon limitation. We have conducted a microarray analysis to explore the 13 phosphate dependent gene expression of Halobacterium salinarum strain R1. A set of 17 14 genes was identified, whose transcript levels increased up to several hundredfold upon 15 phosphate limitation. Analysis of deletion mutants showed that this set of genes, the PHO 16 stimulon, is very likely independent of signaling via two-component systems. Our 17 experiments further indicate that PHO stimulon induction might be dependent on the 18 intracellular phosphate concentration, which turned out to be subject to substantial changes. 19 Finally, the study revealed that H. salinarum exhibits a phosphate directed chemotaxis, which 20 is induced by phosphate starvation. 21
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model construction and analysis of respiration in Halobacterium salinarum
PLOS ONE, 2016Co-Authors: Cherryl O Talaue, Friedhelm Pfeiffer, Eduardo R Mendoza, Ricardo C H Del Rosario, Dieter OesterheltAbstract:The archaeon Halobacterium salinarum can produce energy using three different processes, namely photosynthesis, oxidative phosphorylation and fermentation of arginine, and is thus a model organism in bioenergetics. Compared to its bacteriorhodopsin-driven photosynthesis, less attention has been devoted to modeling its respiratory pathway. We created a system of ordinary differential equations that models its oxidative phosphorylation. The model consists of the electron transport chain, the ATP synthase, the potassium uniport and the sodium-proton antiport. By fitting the model parameters to experimental data, we show that the model can explain data on proton motive force generation, ATP production, and the charge balancing of ions between the sodium-proton antiporter and the potassium uniport. We performed sensitivity analysis of the model parameters to determine how the model will respond to perturbations in parameter values. The model and the parameters we derived provide a resource that can be used for analytical studies of the bioenergetics of H. salinarum.
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a small basic protein from the brz brb operon is involved in regulation of bop transcription in Halobacterium salinarum
BMC Molecular Biology, 2011Co-Authors: Valery Tarasov, Rita Schwaiger, Katarina Furtwangler, Mike Dyallsmith, Dieter OesterheltAbstract:Background The halophilic archaeon Halobacterium salinarum expresses bacteriorhodopsin, a retinal-protein that allows photosynthetic growth. Transcription of the bop (b acterioop sin) gene is controlled by two transcription factors, Bat and Brz that induce bop when cells are grown anaerobically and under light.
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transcriptional control by two leucine responsive regulatory proteins in Halobacterium salinarum r1
BMC Molecular Biology, 2010Co-Authors: Rita Schwaiger, Valery Tarasov, Katarina Furtwangler, Andy Wende, Christoph Schwarz, Dieter OesterheltAbstract:Background: Archaea combine bacterial-as well as eukaryotic-like features to regulate cellular processes. Halobacterium salinarum R1 encodes eight leucine-responsive regulatory protein (Lrp)-homologues. The function of two of them, Irp (OE3923F) and lrpA1 (OE2621R), were analyzed by gene deletion and overexpression, including genome scale impacts using microarrays. Results: It was shown that Lrp affects the transcription of multiple target genes, including those encoding enzymes involved in amino acid synthesis, central metabolism, transport processes and other regulators of transcription. In contrast, LrpA1 regulates transcription in a more specific manner. The aspB3 gene, coding for an aspartate transaminase, was repressed by LrpA1 in the presence of L-aspartate. Analytical DNA-affinity chromatography was adapted to high salt, and demonstrated binding of LrpA1 to its own promoter, as well as L-aspartate dependent binding to the aspB3 promoter. Conclusion: The gene expression profiles of two archaeal Lrp-homologues report in detail their role in H. salinarum R1. LrpA1 and Lrp show similar functions to those already described in bacteria, but in addition they play a key role in regulatory networks, such as controlling the transcription of other regulators. In a more detailed analysis ligand dependent binding of LrpA1 was demonstrated to its target gene aspB3.
Christof Lenz - One of the best experts on this subject based on the ideXlab platform.
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how to cope with heavy metal ions cellular and proteome level stress response to divalent copper and nickel in Halobacterium salinarum r1 planktonic and biofilm cells
Frontiers in Microbiology, 2020Co-Authors: Sabrina Völkel, Felicitas Pfeifer, Christof Lenz, Sascha Hein, Nathalie Benker, Gerald LosenskyAbstract:Halobacterium salinarum R1 is an extremely halophilic archaeon capable of adhesion and forming biofilms, allowing it to adjust to a range of growth conditions. We have recently shown that living in biofilms facilitates its survival under Cu2+ and Ni2+ stress, with specific rearrangements of the biofilm architecture observed following exposition. In this study, quantitative analyses were performed by SWATH mass spectrometry to determine the respective proteomes of planktonic and biofilm cells after exposition to Cu2+ and Ni2+.Quantitative data for 1180 proteins were obtained, corresponding to 46% of the predicted proteome. In planktonic cells, 234 of 1180 proteins showed significant abundance changes after metal ion treatment, of which 47% occurred in Cu2+ and Ni2+ treated samples. In biofilms, significant changes were detected for 52 proteins. Only three proteins changed under both conditions, suggesting metal-specific stress responses in biofilms. Deletion strains were generated to assess the potential role of selected target genes. Strongest effects were observed for 1OE5245F and 1OE2816F strains which exhibited increased and decreased biofilm mass after Ni2+ exposure, respectively. Moreover, EPS obviously plays a crucial role in H. salinarum metal ion resistance. Further efforts are required to elucidate the molecular basis and interplay of additional resistance mechanisms.
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shedding light on biofilm formation of Halobacterium salinarum r1 by swath lc ms ms analysis of planktonic and sessile cells
Proteomics, 2017Co-Authors: Gerald Losensky, Felicitas Pfeifer, Sabrina Fröls, Klaus Jung, Henning Urlaub, Christof LenzAbstract:Early and mature biofilm formation in the extremely halophilic euryarchaeon Halobacterium salinarum strain R1 was characterized by SWATH-LC/MS/MS. Using a simple surfactant-assisted protein solubilization protocol and one-dimensional ultra-high performance nanoflow chromatography on the front end, 63.2% and 58.6% of the predicted Hbt. salinarum R1 proteome could be detected and quantified, respectively. Analysis of biophysical protein properties, functional analysis and pathway mapping indicated comprehensive characterization of the proteome. Sixty point eight percent of the quantified proteins (or 34.5% of the predicted proteome) exhibited significant abundance changes between planktonic and sessile states, demonstrating that haloarchaeal biofilm formation represents a profound “lifestyle change” on the molecular level. Our results and analysis constitute the first comprehensive study to track molecular changes from planktonic cultures to initial and mature archaeal biofilms on the proteome level. Data are available via ProteomeXchange, identifier PXD003667. Proteins exemplifying different protein expression level profiles were selected, and their corresponding gene transcripts targeted by qRT-PCR to test the feasibility of establishing rapid PCR-based assays for archaeal biofilm formation. This article is protected by copyright. All rights reserved
Jocelyne Diruggiero - One of the best experts on this subject based on the ideXlab platform.
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a major role for nonenzymatic antioxidant processes in the radioresistance of Halobacterium salinarum
Journal of Bacteriology, 2011Co-Authors: Courtney K Robinson, Kim Webb, Pawel Jaruga, Miral Dizdaroglu, Nitin S Baliga, Amardeep Kaur, Jocelyne DiruggieroAbstract:Oxidative stress occurs when the generation of reactive oxygen species (ROS) exceeds the capacity of the cell’s endogenous systems to neutralize them. Our analyses of the cellular damage and oxidative stress responses of the archaeon Halobacterium salinarum exposed to ionizing radiation (IR) revealed a critical role played by nonenzymatic antioxidant processes in the resistance of H. salinarum to IR. ROS-scavenging enzymes were essential for resistance to chemical oxidants, yet those enzymes were not necessary for H. salinarum’s resistance to IR. We found that protein-free cell extracts from H. salinarum provided a high level of protection for protein activity against IR in vitro but did not protect DNA significantly. Compared with cell extracts of radiation-sensitive bacteria, H. salinarum extracts were enriched in manganese, amino acids, and peptides, supporting an essential role in ROS scavenging for those small molecules in vivo. With regard to chemical oxidants, we showed that the damage caused by gamma irradiation was mechanistically different than that produced by hydrogen peroxide or by the superoxide-generating redox-cycling drug paraquat. The data presented support the idea that IR resistance is most likely achieved by a “metabolic route,” with a combination of tightly coordinated physiological processes.
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muts and mutl are dispensable for maintenance of the genomic mutation rate in the halophilic archaeon Halobacterium salinarum nrc 1
PLOS ONE, 2010Co-Authors: Courtney R Busch, Jocelyne DiruggieroAbstract:Background The genome of the halophilic archaeon Halobacterium salinarum NRC-1 encodes for homologs of MutS and MutL, which are key proteins of a DNA mismatch repair pathway conserved in Bacteria and Eukarya. Mismatch repair is essential for retaining the fidelity of genetic information and defects in this pathway result in the deleterious accumulation of mutations and in hereditary diseases in humans. Methodology/Principal Findings We calculated the spontaneous genomic mutation rate of H. salinarum NRC-1 using fluctuation tests targeting genes of the uracil monophosphate biosynthesis pathway. We found that H. salinarum NRC-1 has a low incidence of mutation suggesting the presence of active mechanisms to control spontaneous mutations during replication. The spectrum of mutational changes found in H. salinarum NRC-1, and in other archaea, appears to be unique to this domain of life and might be a consequence of their adaption to extreme environmental conditions. In-frame targeted gene deletions of H. salinarum NRC-1 mismatch repair genes and phenotypic characterization of the mutants demonstrated that the mutS and mutL genes are not required for maintenance of the observed mutation rate. Conclusions/Significance We established that H. salinarum NRC-1 mutS and mutL genes are redundant to an alternative system that limits spontaneous mutation in this organism. This finding leads to the puzzling question of what mechanism is responsible for maintenance of the low genomic mutation rates observed in the Archaea, which for the most part do not have MutS and MutL homologs.
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salt shield intracellular salts provide cellular protection against ionizing radiation in the halophilic archaeon Halobacterium salinarum nrc 1
Environmental Microbiology, 2009Co-Authors: Adrienne Kish, Pawel Jaruga, Miral Dizdaroglu, Guldal Kirkali, C Robinson, R Rosenblatt, Jocelyne DiruggieroAbstract:Summary The halophilic archaeon Halobacterium salinarum NRC-1 was used as a model system to investigate cellular damage induced by exposure to high doses of ionizing radiation (IR). Oxidative damages are the main lesions from IR and result from free radicals produc- tion via radiolysis of water. This is the first study to quantify DNA base modification in a prokaryote, revealing a direct relationship between yield of DNA lesions and IR dose. Most importantly, our data dem- onstrate the significance of DNA radiation damage other than strand breaks on cell survival. We also report the first in vivo evidence of reactive oxygen species scavenging by intracellular halides in H. sali- narum NRC-1, resulting in increased protection against nucleotide modification and carbonylation of protein residues. Bromide ions, which are highly reac- tive with hydroxyl radicals, provided the greatest pro- tection to cellular macromolecules. Modified DNA bases were repaired in 2 h post irradiation, indicating effective DNA repair systems. In addition, measure- ments of H. salinarum NRC-1 cell interior revealed a high Mn/Fe ratio similar to that of Deinococcus radio- durans and other radiation-resistant microorganisms, which has been shown to provide a measure of protection for proteins against oxidative damage. The work presented here supports previous studies showing that radiation resistance is the product of mechanisms for cellular protection and detoxification, as well as for the repair of oxidative damage to cellular macromolecules. The finding that not only Mn/Fe but also the presence of halides can decrease the oxida- tive damage to DNA and proteins emphasizes the significance of the intracellular milieu in determining microbial radiation resistance.
Felicitas Pfeifer - One of the best experts on this subject based on the ideXlab platform.
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how to cope with heavy metal ions cellular and proteome level stress response to divalent copper and nickel in Halobacterium salinarum r1 planktonic and biofilm cells
Frontiers in Microbiology, 2020Co-Authors: Sabrina Völkel, Felicitas Pfeifer, Christof Lenz, Sascha Hein, Nathalie Benker, Gerald LosenskyAbstract:Halobacterium salinarum R1 is an extremely halophilic archaeon capable of adhesion and forming biofilms, allowing it to adjust to a range of growth conditions. We have recently shown that living in biofilms facilitates its survival under Cu2+ and Ni2+ stress, with specific rearrangements of the biofilm architecture observed following exposition. In this study, quantitative analyses were performed by SWATH mass spectrometry to determine the respective proteomes of planktonic and biofilm cells after exposition to Cu2+ and Ni2+.Quantitative data for 1180 proteins were obtained, corresponding to 46% of the predicted proteome. In planktonic cells, 234 of 1180 proteins showed significant abundance changes after metal ion treatment, of which 47% occurred in Cu2+ and Ni2+ treated samples. In biofilms, significant changes were detected for 52 proteins. Only three proteins changed under both conditions, suggesting metal-specific stress responses in biofilms. Deletion strains were generated to assess the potential role of selected target genes. Strongest effects were observed for 1OE5245F and 1OE2816F strains which exhibited increased and decreased biofilm mass after Ni2+ exposure, respectively. Moreover, EPS obviously plays a crucial role in H. salinarum metal ion resistance. Further efforts are required to elucidate the molecular basis and interplay of additional resistance mechanisms.
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Data_Sheet_1_Heavy Metal Ion Stress on Halobacterium salinarum R1 Planktonic Cells and Biofilms.PDF
2018Co-Authors: Sabrina Völkel, Sabrina Fröls, Felicitas PfeiferAbstract:Halobacterium salinarum R1 is an extremely halophilic archaeon, able to attach to the surface and to form characteristic biofilm structures under physiological conditions. However, the effect of environmental stress factors like heavy metals on biofilms was still unknown. Here, we report on the first insights into H. salinarum biofilm formation when exposed to copper, nickel and zinc and describe the effects of metal ions on the architecture of mature biofilms. We also studied the effects on gene expression in planktonic cells. Investigation of planktonic growth and cell adhesion in the presence of sub-lethal metal concentrations yielded an up to 60% reduced adhesion in case of copper and a significantly enhanced adhesion in case of zinc, whereas nickel treatment had no effect on adhesion. A PMA-qPCR assay was developed to quantify live/dead cells in planktonic cultures and mature biofilms, enabling the investigation of cell vitality after metal exposure. An increased resistance was observed in biofilms with up to 80% in case of copper- and up to 50% in case of zinc exposure compared to planktonic cells. However, nickel-treated biofilms showed no significant increase of cell survival. Microscopic investigation of the architecture of mature biofilms exposed to lethal metal concentrations demonstrated an increased detachment and the formation of large microcolonies after copper treatment, whereas the number of adherent cells increased strongly in nickel-exposed biofilms. In contrast, zinc exposed-biofilms showed no differences compared to the control. Analysis of the expression of genes encoding putative metal transporters by qRT-PCR revealed specific changes upon treatment of the cells with heavy metals. Our results demonstrate diverse effects of heavy metal ions on H. salinarum and imply a metal-specific protective response of cells in biofilms.
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shedding light on biofilm formation of Halobacterium salinarum r1 by swath lc ms ms analysis of planktonic and sessile cells
Proteomics, 2017Co-Authors: Gerald Losensky, Felicitas Pfeifer, Sabrina Fröls, Klaus Jung, Henning Urlaub, Christof LenzAbstract:Early and mature biofilm formation in the extremely halophilic euryarchaeon Halobacterium salinarum strain R1 was characterized by SWATH-LC/MS/MS. Using a simple surfactant-assisted protein solubilization protocol and one-dimensional ultra-high performance nanoflow chromatography on the front end, 63.2% and 58.6% of the predicted Hbt. salinarum R1 proteome could be detected and quantified, respectively. Analysis of biophysical protein properties, functional analysis and pathway mapping indicated comprehensive characterization of the proteome. Sixty point eight percent of the quantified proteins (or 34.5% of the predicted proteome) exhibited significant abundance changes between planktonic and sessile states, demonstrating that haloarchaeal biofilm formation represents a profound “lifestyle change” on the molecular level. Our results and analysis constitute the first comprehensive study to track molecular changes from planktonic cultures to initial and mature archaeal biofilms on the proteome level. Data are available via ProteomeXchange, identifier PXD003667. Proteins exemplifying different protein expression level profiles were selected, and their corresponding gene transcripts targeted by qRT-PCR to test the feasibility of establishing rapid PCR-based assays for archaeal biofilm formation. This article is protected by copyright. All rights reserved
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novel pili like surface structures of Halobacterium salinarum strain r1 are crucial for surface adhesion
Frontiers in Microbiology, 2015Co-Authors: Gerald Losensky, Felicitas Pfeifer, Lucia Vidakovic, Andreas Klingl, Sabrina FrölsAbstract:It was recently shown that haloarchaeal strains of different genera are able to adhere to surfaces and form surface-attached biofilms. However the surface structures mediating the adhesion were still unknown. We have identified a novel surface structure with Halobacterium salinarum strain R1, crucial for surface adhesion. Electron microscopic studies of surface-attached cells frequently showed pili-like surface structures of two different diameters that were irregularly distributed on the surface. The thinner filaments, 7 - 8 nm in diameter, represented a so far unobserved novel pili-like structure. Examination of the Hbt. salinarum R1 genome identified two putative gene loci (pil-1 and pil-2) encoding type IV pilus biogenesis complexes besides the archaellum encoding fla gene locus. Both pil-1 and pil-2 were expressed as transcriptional units, and the transcriptional start of pil-1 was identified. In silico analyses revealed that the pil-1 locus is present with other euryarchaeal genomes whereas the pil-2 is restricted to haloarchaea. Comparative real time qRT-PCR studies indicated that the general transcriptional activity was reduced in adherent versus planktonic cells. In contrast, the transcription of pilB1 and pilB2, encoding putative type IV pilus assembly ATPases, was induced in comparison to the archaella assembly/motor ATPase (flaI) and the ferredoxin gene. Mutant strains were constructed that incurred a flaI deletion or flaI/pilB1 gene deletions. The absence of flaI caused the loss of the archaella while the additional absence of pilB1 led to loss of the novel pili-like surface structures. The ΔflaI/ΔpilB1 double mutants showed a 10-fold reduction in surface adhesion compared to the parental strain. Since surface adhesion was not reduced with the non-archaellated ΔflaI mutants, the pil-1 filaments have a distinct function in the adhesion process.
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expression of multiple tfb genes in different Halobacterium salinarum strains and interaction of tfb with transcriptional activator gvpe
Archives of Microbiology, 2012Co-Authors: Anne Bleiholder, Regina Frommherz, Katharina Teufel, Felicitas PfeiferAbstract:Halobacterium salinarum NRC-1 contains multiple TBP and TFB proteins required for the recruitment of RNA polymerase for transcription initiation. The presence and the expression of genes encoding TFB were investigated in the two Hbt. salinarum strains NRC-1 and PHH1 and the mutant strain PHH4. The plasmid-encoded tfbC and tfbE genes of NRC-1 were lacking in PHH1 and PHH4. The 5′-end of the tfbF transcript was determined and contained a 5′-untranslated region of 39 nucleotides able to form a stem-loop structure. The expression of these tfb genes was studied in cultures growing at 15, 37°C and under heat shock conditions. Cold temperatures reduced growth and except for tfbF also the amounts of all tfb transcripts. However, the formation of gas vesicles increased in PHH1 and NRC-1. Heat shock reduced growth of PHH1 and NRC-1, but PHH4 was not affected. A 100-fold increase in tfbA and tfbB mRNA was observed in PHH1 and PHH4, whereas NRC-1 reduced the amounts of these transcripts and increased the expression of tfbG. All TFB proteins tested were able to interact with the transcription activator GvpE involved in gas vesicle formation that thus is able to recruit TFB to the gvp promoter.
Gerald Losensky - One of the best experts on this subject based on the ideXlab platform.
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how to cope with heavy metal ions cellular and proteome level stress response to divalent copper and nickel in Halobacterium salinarum r1 planktonic and biofilm cells
Frontiers in Microbiology, 2020Co-Authors: Sabrina Völkel, Felicitas Pfeifer, Christof Lenz, Sascha Hein, Nathalie Benker, Gerald LosenskyAbstract:Halobacterium salinarum R1 is an extremely halophilic archaeon capable of adhesion and forming biofilms, allowing it to adjust to a range of growth conditions. We have recently shown that living in biofilms facilitates its survival under Cu2+ and Ni2+ stress, with specific rearrangements of the biofilm architecture observed following exposition. In this study, quantitative analyses were performed by SWATH mass spectrometry to determine the respective proteomes of planktonic and biofilm cells after exposition to Cu2+ and Ni2+.Quantitative data for 1180 proteins were obtained, corresponding to 46% of the predicted proteome. In planktonic cells, 234 of 1180 proteins showed significant abundance changes after metal ion treatment, of which 47% occurred in Cu2+ and Ni2+ treated samples. In biofilms, significant changes were detected for 52 proteins. Only three proteins changed under both conditions, suggesting metal-specific stress responses in biofilms. Deletion strains were generated to assess the potential role of selected target genes. Strongest effects were observed for 1OE5245F and 1OE2816F strains which exhibited increased and decreased biofilm mass after Ni2+ exposure, respectively. Moreover, EPS obviously plays a crucial role in H. salinarum metal ion resistance. Further efforts are required to elucidate the molecular basis and interplay of additional resistance mechanisms.
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shedding light on biofilm formation of Halobacterium salinarum r1 by swath lc ms ms analysis of planktonic and sessile cells
Proteomics, 2017Co-Authors: Gerald Losensky, Felicitas Pfeifer, Sabrina Fröls, Klaus Jung, Henning Urlaub, Christof LenzAbstract:Early and mature biofilm formation in the extremely halophilic euryarchaeon Halobacterium salinarum strain R1 was characterized by SWATH-LC/MS/MS. Using a simple surfactant-assisted protein solubilization protocol and one-dimensional ultra-high performance nanoflow chromatography on the front end, 63.2% and 58.6% of the predicted Hbt. salinarum R1 proteome could be detected and quantified, respectively. Analysis of biophysical protein properties, functional analysis and pathway mapping indicated comprehensive characterization of the proteome. Sixty point eight percent of the quantified proteins (or 34.5% of the predicted proteome) exhibited significant abundance changes between planktonic and sessile states, demonstrating that haloarchaeal biofilm formation represents a profound “lifestyle change” on the molecular level. Our results and analysis constitute the first comprehensive study to track molecular changes from planktonic cultures to initial and mature archaeal biofilms on the proteome level. Data are available via ProteomeXchange, identifier PXD003667. Proteins exemplifying different protein expression level profiles were selected, and their corresponding gene transcripts targeted by qRT-PCR to test the feasibility of establishing rapid PCR-based assays for archaeal biofilm formation. This article is protected by copyright. All rights reserved
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novel pili like surface structures of Halobacterium salinarum strain r1 are crucial for surface adhesion
Frontiers in Microbiology, 2015Co-Authors: Gerald Losensky, Felicitas Pfeifer, Lucia Vidakovic, Andreas Klingl, Sabrina FrölsAbstract:It was recently shown that haloarchaeal strains of different genera are able to adhere to surfaces and form surface-attached biofilms. However the surface structures mediating the adhesion were still unknown. We have identified a novel surface structure with Halobacterium salinarum strain R1, crucial for surface adhesion. Electron microscopic studies of surface-attached cells frequently showed pili-like surface structures of two different diameters that were irregularly distributed on the surface. The thinner filaments, 7 - 8 nm in diameter, represented a so far unobserved novel pili-like structure. Examination of the Hbt. salinarum R1 genome identified two putative gene loci (pil-1 and pil-2) encoding type IV pilus biogenesis complexes besides the archaellum encoding fla gene locus. Both pil-1 and pil-2 were expressed as transcriptional units, and the transcriptional start of pil-1 was identified. In silico analyses revealed that the pil-1 locus is present with other euryarchaeal genomes whereas the pil-2 is restricted to haloarchaea. Comparative real time qRT-PCR studies indicated that the general transcriptional activity was reduced in adherent versus planktonic cells. In contrast, the transcription of pilB1 and pilB2, encoding putative type IV pilus assembly ATPases, was induced in comparison to the archaella assembly/motor ATPase (flaI) and the ferredoxin gene. Mutant strains were constructed that incurred a flaI deletion or flaI/pilB1 gene deletions. The absence of flaI caused the loss of the archaella while the additional absence of pilB1 led to loss of the novel pili-like surface structures. The ΔflaI/ΔpilB1 double mutants showed a 10-fold reduction in surface adhesion compared to the parental strain. Since surface adhesion was not reduced with the non-archaellated ΔflaI mutants, the pil-1 filaments have a distinct function in the adhesion process.
