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Adrian Ponce - One of the best experts on this subject based on the ideXlab platform.

  • Detection and Viability Assessment of Endospore-Forming Pathogens
    Principles of Bacterial Detection: Biosensors Recognition Receptors and Microsystems, 2020
    Co-Authors: Adrian Ponce, Stephanie A Connon, Pun To Yung
    Abstract:

    In this chapter, we explore technology developments for the rapid detection, identification, and viability assessment of Endospore-forming pathogens with a focus on Bacillus anthracis. First, we introduce various toxin-producing species and their role as bioinsecticides, probiotics, and bioweapons. We also review the role of Endospores as biological indicators (i.e., dosimeters) for evaluating sterilization regimens, such as autoclaving and wastewater remediation. Monitoring the effectiveness of cleaning and sterilization regimens to maintain good hygiene is required in several major industries, including health care, food, and pharmaceutical industries. In the next section, we review recent developments in DNA-, immuno-, and dipicolinic acid assays, and their applications for detection and monitoring of Bacillus anthracis and other Endospore-forming pathogens. Finally, we review viability assays capable of rapid validation of Endospore inactivation after sterilization, including assays based on ATP synthesis during stage II germination, and DPA release during stage I germination.

  • quantitative and fast sterility assurance testing of surfaces by enumeration of germinable Endospores
    Scientific Reports, 2020
    Co-Authors: Elizabeth D Lester, Pun To Yung, Adrian Ponce
    Abstract:

    A fast Endospore Germinability Assay (EGA) was validated with traditional plate counts to enumerate single Endospore germination events for monitoring surface sterilization. The assay is based on a time-gated luminescence microscopy technique enabling visualization and enumeration of individual germinating Endospores. Germinating Endospores release calcium dipicolinate to form highly luminescent terbium dipicolinate complexes surrounding each germinating Endospore. EGA and heterotrophic plate counting (HPC) were used to evaluate the swab/rinse recovery efficiency of Endospores from stainless steel surfaces. EGA and HPC results were highly correlated for Endospore recovery from stainless steel coupons inoculated with range of 1,000 Endospores per coupon down to sterility. Dosage-dependent decrease of surface Endospore germinability were observed in dry heat, UV irradiation, oxygen plasma and vaporized hydrogen peroxide treatments, measured with EGA and HPC. EGA is a fast and complementary method to traditional HPC for quantitative sterility assurance testing of surfaces. This work introduces and validates a 15-minute or faster assay for germinable Endospores to complement the conventional lengthy, culture-based surface sterility validation, which is critical in hospitals, food and pharmaceutical industries to help minimize nosocomial infection, food spoilage, and pharmaceutical contamination.

  • validation of a clostridium Endospore viability assay and analysis of greenland ices and atacama desert soils
    Applied and Environmental Microbiology, 2011
    Co-Authors: Wanwan Yang, Adrian Ponce
    Abstract:

    Bacterial Endospores are dormant microbial structures that are highly resistant to chemical, physical, and radiation sterilization processes (20, 31). They represent one of the most successful survival strategies of microorganisms and are formed when members of spore-forming genera (e.g., Bacillus and Clostridium) face unfavorable conditions, such as environmental extremes or starvation (19, 34). Once they are formed, Endospores can stay dormant for extended periods of time, from thousands (8, 13, 20, 25, 33) to millions (3, 35) of years, although for the more extreme claims of longevity it is difficult to rule out modern contamination (37). Anaerobic spore-forming clostridia include numerous pathogenic species that are dangerous contaminants. For example, Clostridium botulinum and C. perfringens are common food-poisoning agents that produce toxins which cause diseases such as botulism and human necrotic enteritis (9, 17). C. perfringens, C. difficile, and C. tetani are causative agents of gas gangrene, pseudomembranous colitis, and tetanus (9, 30). Some psychrotrophic clostridia are also responsible for the spoilage of chilled vacuum-packed meat (9). In addition, C. perfringens has been used as an indicator of fecal contamination, because it is present in large numbers in human and animal wastes (4, 6). Due to their resistance to various extreme conditions, Clostridium Endospores are also employed as biological indicators to monitor the effectiveness of various sterilization processes (11, 12). Currently, the standard method for quantifying viable Clostridium Endospores is measuring CFU after heat shock killing of vegetative cells. This method requires several days of incubation and a tedious anaerobic culturing technique, and it is amenable for culturing only fewer than 1% of environmental species (24). Other molecular Endospore viability assays include ATP assay (26) and quantitative PCR (qPCR) coupled with propidium monoazide (PMA) (28), which, unlike microscopy-based Endospore viability assay (micro-EVA), require extensive sample preparation and are labor-intensive. Previously, we described a spectroscopy-based Endospore viability assay (spectro-EVA) to quantify dipicolinic acid (DPA) released from germinating Clostridium spores in liquid suspension (39). Germination was triggered by various germinants, such as l-alanine/NaHCO3, l-lactate, or d-alanine, which cause the release of approximately 108 molecules of a unique biomarker, DPA, from the spore core. Spectro-EVA is based on the detection of DPA in bulk solution via Tb3+-DPA luminescence spectroscopy, with a limit of detection (LOD) of 1,000 spores/ml. Unfortunately, spectro-EVA has even lower detection limits when environmental extracts are analyzed due to sensitivity to interference from contaminants. Previously, this limitation was overcome for the case of Bacillus Endospores by employing a microscopy-based EVA (41), where individual spores are enumerated as they germinate in a microscope field of view. Here we report details of a rapid microscopy-based Endospore viability assay (micro-EVA) that enables enumeration of single germinating Clostridium Endospores on Tb3+- and d-alanine-doped agarose. d-Alanine was used as a germinant, which serves to trigger Clostridium spore germination while inhibiting Bacillus spore germination (2, 14, 38). Germination releases DPA from Endospores, and subsequent Tb3+-DPA binding results in green luminescent spots under pulsed UV excitation in a field of view of a time-gated microscope. These were enumerated as germinable Clostridium Endospores (GCEs) using time-gated Tb3+-DPA luminescence microscopy (i.e., micro-EVA). A parallel comparison of micro-EVA data with culturing data validated this method. Finally, we compared micro-EVA to culturing methods to quantify GCEs from two Mars analog environments, Greenland ice core and Atacama Desert.

  • Fast Sterility Assessment by Germinable-Endospore Biodosimetry†
    Applied and Environmental Microbiology, 2008
    Co-Authors: Pun To Yung, Adrian Ponce
    Abstract:

    The era of modern microbiology began in the 1870s when the life cycle of an Endospore-forming pathogen, Bacillus anthracis, was elucidated using new methods for isolating pure cultures from single-cell clones on solid growth media. Bacterial Endospores are dormant microbial structures that are highly resistant to chemical, physical, and radiation sterilization processes (2, 6, 19, 26). In fact, Bacillus subtilis Endospores have survived for 6 years in space while exposed to high-vacuum conditions, temperature extremes, and intense solar and galactic radiation (12, 18). Bacterial Endospores are routinely employed as biological indicators (i.e., biodosimeters) to validate the effectiveness of sterilization methods (e.g., autoclaves) used in the medical device (15, 16), pharmaceutical, health care (5), food preparation, wastewater remediation (23), and biodefense (29) industries. The effectiveness of sterilization processes is measured and reported in terms of sterility assurance levels (SALs), which are defined as the expected probability that a product remains contaminated with viable microorganisms after exposure to a validated sterilization process. A sterilization process that yields predictable SALs is considered to be validated. Confidence in achieving a required SAL is obtained by the use of biological indicators that present a considerably greater population and resistance challenge than the expected bioburden (21), and the most effective way to test the efficiency of a sterilization process is to place biological indicators within and on test products of interest. Currently, Endospore inactivation is quantified by measuring the log reduction in CFU. This method, however, requires several days of incubation, during which 20 cycles of cell replication ultimately yield visible colonies that can then be enumerated. In contrast, Endospore germination can be initiated and monitored on a timescale of minutes. Germination of Bacillus Endospores can be triggered by simple biomolecules, such as l-alanine, l-asparagine, or glucose (8, 24, 27), which cause the release of approximately 108 molecules of dipicolinic acid (DPA) from the core of the Endospore during the first stage of germination. DPA exists in all bacterial Endospores as 5 to 15% of the cellular dry weight and is a unique, defining constituent of the cellular dry weight of Endospores (10, 14, 22). Here we report details of a rapid Endospore viability assay (EVA) in which Bacillus atrophaeus Endospores were immobilized on terbium ion (Tb3+)/l-alanine-doped agarose. The l-alanine serves to trigger germination, during which DPA is released from Endospores. The Tb3+ subsequently binds DPA, resulting in green luminescent spots under UV excitation in a microscope field of view, which were enumerated as germinable Endospores using time-gated Tb-DPA luminescence microscopy (i.e., μEVA). Here we validate μEVA against culturing as a method for rapid Endospore viability assessment and evaluate its application for monitoring Endospore inactivation by thermal and UV sterilization regimens.

  • an automated front end monitor for anthrax surveillance systems based on the rapid detection of airborne Endospores
    Biotechnology and Bioengineering, 2007
    Co-Authors: Pun To Yung, Adrian Ponce, Elizabeth D Lester, Greg Bearman
    Abstract:

    A fully automated anthrax smoke detector (ASD) has been developed and tested. The ASD is intended to serve as a cost effective front-end monitor for anthrax surveillance systems. The principle of operation is based on measuring airborne Endospore concentrations, where a sharp concentration increase signals an anthrax attack. The ASD features an air sampler, a thermal lysis unit, a syringe pump, a time-gated spectrometer, and Endospore detection chemistry comprised of dipicolinic acid (DPA)-triggered terbium ion (Tb3+) luminescence. Anthrax attacks were simulated using aerosolized Bacillus atrophaeus spores in fumed silica, and corresponding Tb-DPA intensities were monitored as a function of time and correlated to the number of airborne Endospores collected. A concentration dependence of 102–106 spores/mg of fumed silica yielded a dynamic range of 4 orders of magnitude and a limit of detection of 16 spores/L when 250 L of air were sampled. Simulated attacks were detected in less than 15 min. Biotechnol. Bioeng. 2007; 98: 864–871. © 2007 Wiley Periodicals, Inc.

Philip C Hanna - One of the best experts on this subject based on the ideXlab platform.

Michael G Ganzle - One of the best experts on this subject based on the ideXlab platform.

  • the copy number of the spova2mob operon determines pressure resistance of bacillus Endospores
    Applied and Environmental Microbiology, 2019
    Co-Authors: Zhen Li, Felix Schottroff, David J. Simpson, Michael G Ganzle
    Abstract:

    The spoVA2mob operon confers heat resistance to Bacillus spp., and the resistance correlates to the copy number of the operon. Bacillus Endospores also exhibit a strong variation in resistance to pressure, but the underlying mechanisms of Endospore resistance to pressure are not fully understood. We determined the effects of multiple spoVA2mob operons on high-pressure resistance in Bacillus Endospores. The copy numbers of the spoVA2mob operon in 17 strains of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus cereus, Bacillus velezensis, and Bacillus pumilus were determined via droplet digital PCR (ddPCR) and genome sequencing. These strains contained between 0 and 3 copies of the spoVA2mob operon; the quantification of the gene copy number by ddPCR was as accurate as whole-genome sequencing. We further tested the pressure resistance of 17 Bacillus Endospores at 600 MPa and 80°C. Strains with one or no spoVA2mob operon had significantly lower pressure resistance than strains with two or three copies of the operons (P < 0.001), indicating that redundant spoVA2mob operons in Bacillus contributed to higher pressure resistance of Endospores. The copy number of the spoVA2mob operon was not related to the dipicolinic acid (DPA) content of Endospores. Overall, the copy number of the spoVA2mob operon contributes to pressure resistance of Bacillus Endospores. This improves our understanding of the pressure resistance mechanisms in Bacillus spp. and may inform the development of high-pressure sterilization in food processing.IMPORTANCEBacillus spp. are considered pressure-resistant microorganisms, but the resistance mechanisms remain unknown. The spoVA2mob operon is a mobile genetic element, and it can transfer to pathogenic or spoilage organisms by horizontal gene transfer. Results in this study indicate that multiple copies of the spoVA2mob operon mediate high-pressure resistance of Bacillus Endospores, and it might contribute to the identification of the source of pressure-resistant pathogens and spoilage organisms that may contaminate the food supply. The droplet digital PCR (ddPCR) system is well suited for analysis in some human diseases due to its high efficiency and capability to provide high precision; however, no relevant studies in food microbiology have been reported so far. This study demonstrates a novel application of ddPCR in food microbiology.

  • effects of nisin and reutericyclin on resistance of Endospores of clostridium spp to heat and high pressure
    Food Microbiology, 2013
    Co-Authors: Simmon Hofstetter, David Gebhardt, Linda Ho, Michael G Ganzle, Lynn M Mcmullen
    Abstract:

    Abstract The effects of high pressure, temperature, and antimicrobial compounds on Endospores of Clostridium spp. were examined. Minimal inhibitory concentrations (MIC) of nisin and reutericyclin were determined for vegetative cells and Endospores of Clostridium sporogenes ATCC 7955, Clostridium beijerinckii ATCC 8260, and Clostridium difficile 3195. Endospores of C. sporogenes ATCC 7955 and C. beijerinckii ATCC 8260 were exposed to 90 °C and 90 °C/600 MPa in the presence of 16 mg L −1 nisin or 6.4 mg L −1 reutericyclin for 0–60 min in a 0.9% saline solution. Dipicolinic acid (DPA) release was measured using a terbium-DPA fluorescence assay, and Endospore permeability was assessed using 4′,6-diamidino-2-phenylindole (DAPI) fluorescence. Vegetative cells of C. sporogenes ATCC 7955 exhibited higher sensitivity to nisin relative to Endospores, with MIC values 0.23 ± 0.084 mg L −1 and 1.11 ± 0.48 mg L −1 , respectively. Nisin increased DPA release when Endospores were treated at 90 °C; however, only C. sporogenes ATCC 7955 exhibited higher inactivation, suggesting strain or species specific effects. Reutericyclin did not enhance spore inactivation or DPA release. Use of nisin in combination with high pressure, thermal treatments enhanced inactivation of Endospores of Clostridium spp. and may have application in foods.

  • use of the fluorescent probe laurdan to label and measure inner membrane fluidity of Endospores of clostridium spp
    Journal of Microbiological Methods, 2012
    Co-Authors: Simmon Hofstetter, Christian Denter, Roland Winter, Lynn M Mcmullen, Michael G Ganzle
    Abstract:

    Abstract A method for measuring the fluidity of inner membranes of populations of Endospores of Clostridium spp. with a fluorescent dye was developed. Cells of Clostridium beijerinckii ATCC 8260 and Clostridium sporogenes ATCC 7955 were allowed to sporulate in the presence of 6-dodecanoyl-2-dimethylaminonaphthalene (LAURDAN) on a soil-based media. Labeling of Endospores with LAURDAN did not affect Endospore viability. Removal of the outer membranes of Endospores was done using a chemical treatment and confirmed using transmission electron microscopy (TEM). Two-photon confocal laser scanning microscopy (CLSM), and generalized polarization (GP) measurements were used to assess fluorescence of Endospores. Lipid composition analysis of cells and Endospores was done to determine whether differences in GP values are attributable to differences in membrane composition. Removal of the outer membranes of Endospores did not significantly impact GP values. Decoated, labeled Endospores of C. sporogenes ATCC 7955 and C. beijerinckii ATCC 8260 exhibited GP values of 0.77 ± 0.031 and 0.74 ± 0.027 respectively. Differences in ratios of fatty acids between cells and Endospores are unlikely to be responsible for high GP values observed in Endospores. These GP values indicate high levels of lipid order and the exclusion of water from within inner membranes of Endospores.

Lynn M Mcmullen - One of the best experts on this subject based on the ideXlab platform.

  • effects of nisin and reutericyclin on resistance of Endospores of clostridium spp to heat and high pressure
    Food Microbiology, 2013
    Co-Authors: Simmon Hofstetter, David Gebhardt, Linda Ho, Michael G Ganzle, Lynn M Mcmullen
    Abstract:

    Abstract The effects of high pressure, temperature, and antimicrobial compounds on Endospores of Clostridium spp. were examined. Minimal inhibitory concentrations (MIC) of nisin and reutericyclin were determined for vegetative cells and Endospores of Clostridium sporogenes ATCC 7955, Clostridium beijerinckii ATCC 8260, and Clostridium difficile 3195. Endospores of C. sporogenes ATCC 7955 and C. beijerinckii ATCC 8260 were exposed to 90 °C and 90 °C/600 MPa in the presence of 16 mg L −1 nisin or 6.4 mg L −1 reutericyclin for 0–60 min in a 0.9% saline solution. Dipicolinic acid (DPA) release was measured using a terbium-DPA fluorescence assay, and Endospore permeability was assessed using 4′,6-diamidino-2-phenylindole (DAPI) fluorescence. Vegetative cells of C. sporogenes ATCC 7955 exhibited higher sensitivity to nisin relative to Endospores, with MIC values 0.23 ± 0.084 mg L −1 and 1.11 ± 0.48 mg L −1 , respectively. Nisin increased DPA release when Endospores were treated at 90 °C; however, only C. sporogenes ATCC 7955 exhibited higher inactivation, suggesting strain or species specific effects. Reutericyclin did not enhance spore inactivation or DPA release. Use of nisin in combination with high pressure, thermal treatments enhanced inactivation of Endospores of Clostridium spp. and may have application in foods.

  • use of the fluorescent probe laurdan to label and measure inner membrane fluidity of Endospores of clostridium spp
    Journal of Microbiological Methods, 2012
    Co-Authors: Simmon Hofstetter, Christian Denter, Roland Winter, Lynn M Mcmullen, Michael G Ganzle
    Abstract:

    Abstract A method for measuring the fluidity of inner membranes of populations of Endospores of Clostridium spp. with a fluorescent dye was developed. Cells of Clostridium beijerinckii ATCC 8260 and Clostridium sporogenes ATCC 7955 were allowed to sporulate in the presence of 6-dodecanoyl-2-dimethylaminonaphthalene (LAURDAN) on a soil-based media. Labeling of Endospores with LAURDAN did not affect Endospore viability. Removal of the outer membranes of Endospores was done using a chemical treatment and confirmed using transmission electron microscopy (TEM). Two-photon confocal laser scanning microscopy (CLSM), and generalized polarization (GP) measurements were used to assess fluorescence of Endospores. Lipid composition analysis of cells and Endospores was done to determine whether differences in GP values are attributable to differences in membrane composition. Removal of the outer membranes of Endospores did not significantly impact GP values. Decoated, labeled Endospores of C. sporogenes ATCC 7955 and C. beijerinckii ATCC 8260 exhibited GP values of 0.77 ± 0.031 and 0.74 ± 0.027 respectively. Differences in ratios of fatty acids between cells and Endospores are unlikely to be responsible for high GP values observed in Endospores. These GP values indicate high levels of lipid order and the exclusion of water from within inner membranes of Endospores.

D. W. Dickson - One of the best experts on this subject based on the ideXlab platform.

  • Extraction and purification of Pasteuria spp. Endospores.
    Journal of Nematology, 2000
    Co-Authors: Senyu Chen, Jonathan H. Charnecki, James F. Preston, D. W. Dickson
    Abstract:

    Pasteuria penetrans is an Endospore-forming bacterial parasite of root-knot nematodes that has potential as a biological control agent. Biochemical investigations of P. penetrans are limited because of difficulty in obtaining large quantities of Endospores free of plant debris and contaminating microorganisms. Our objective was to develop a technique for extraction and purification of P. penetrans Endospores from root-knot nematodes. Tomato roots infected with Meloidogyne arenaria that was parasitized by P. penetrans were digested with cytolase. The nematode females along with plant debris were washed with a jet stream of water onto an 800-µm-pore sieve nested on a 250-µm-pore sieve. The materials retained on the 250-µm-pore sieve were centrifuged through a 20% sucrose solution. The resulting loose pellet fraction was collected on a 250-µm-pore sieve and then centrifuged through a 47% sucrose solution. Endospore-filled females were handpicked from the 47% sucrose pellicle fraction. Endospores were released by grinding the females with a glass tissue grinder. The Endospores were then filtered through a nylon filter with 8-µm openings, collected by centrifugation, and subjected to buoyant density centrifugation in different media. Further purification by buoyant density centrifugation in a linear gradient of sodium diatrizoate resulted in a preparation of Endospores free of debris. This additional step may be desirable for the further characterization of components unique to the Endospores.

  • Temperature Effects on the Attachment of Pasteuria penetrans Endospores to Meloidogyne arenaria Race 1
    Journal of Nematology, 1997
    Co-Authors: L. G. Freitas, D. J. Mitchell, D. W. Dickson
    Abstract:

    Pasteuria penetrans is a gram positive bacterium that prevents Meloidogyne spp. from reproducing and diminishes their ability to penetrate roots. The attachment of the Endospores to the cuticle of the nematodes is the first step in the life cycle of the bacterium and is essential for its reproduction. As a preliminary study to a field solarization test, the effects of temperature on the attachment of P. penetrans on Meloidogyne arenaria race 1 were investigated. Preexposing second-stage juveniles (J2) of M. arenaria to approximately 30 °C in water before exposing them to Endospores increased their receptivity to Endospore attachment when compared to treating J2 at 25 °C or 35 °C. In tests with soil, highest attachment occurred when J2 were incubated in soil infested with Endospores and maintained at 20 °C to 30 °C for 4 days. Heating J2 in soil to sublethal temperatures (35 °C to 40 °C) decreased Endospore attachment. Incubating P. penetrans Endospores in soil at 30 °C to 70 °C for 5 hours a day over 10 days resulted in reductions of Endospore attachment to nematodes as temperatures of incubation increased to 50 °C and higher.

  • Estimating Incidence of Attachment of Pasteuria penetrans Endospores to Meloidogyne spp. with Tally Thresholds.
    Journal of Nematology, 1997
    Co-Authors: Z. X. Chen, D. W. Dickson
    Abstract:

    Pasteuria penetrans has .been identified as an important biological control agent of root-knot nematodes. In this study the use of tally thresholds was evaluated for estimating P. penetrans Endospore attachment to second-stage juveniles (J2) of Meloidogyne spp. A tally threshold (T) is defined as the maximum number of individuals in a sample unit that may be treated as absent based on binomial sampling. Three different data sets that originated from centrifugal bioassay, incubation bioassay, and field experiments were investigated. The data sets each contained 70, 33, and 111 estimates of the mean number of Endospores attached per J2 (m), respectively. Empirical relationships between m and proportions of J2 with =T Endospores attached (P[subT]) were developed using parameters from the linear regression of ln(m) on P[subT] (0 P[subT] 1): ln(m) = a + b P[subT], T was set to 0, 1, 2, 3, 4, 5, 8, and 10 Endospores/J2. The results indicated that the variances of linear equations tended to decrease with increasing Tvalues for all three data sets. T values of 0, 1, 8, and 10 Endospores/J2 for centrifugal bioassay and incubation bioassay, and of 0, 1, 2, and 3 Endospores/J2 for field experiments were associated with an r² of = 0.8. These T values were robust for estimating m from P[subT], reducing the variability as well as the time and effort spent in estimating the mean number of Endospores attached per J2. Key words: bacterium, biological control, Endospore, Meloidogyne spp., nematode, Pasteuria penetrans, root-knot nematode, sampling, tally threshold.

  • suppression of meloidogyne arenaria race 1 by soil application of Endospores of pasteuria penetrans
    Journal of Nematology, 1996
    Co-Authors: Z. X. Chen, D. J. Mitchell, D. W. Dickson, R Mcsorley, T. E. Hewlett
    Abstract:

    The potential of Pasteuria penetrans for suppressing Meloidogyne arenaria race 1 on peanut (Arachis hypogaea) was tested over a 2-year period in a field microplot experiment. Endospores of P. penetrans were mass-produced on M. arenaria race 1 infecting tomato plants. Endospores were inoculated in the first year only at rates of 0, 1,000, 3,000, 10,000, and 100,000 Endospores/g of soil, respectively, into the top 20 cm of microplots that were previously infested with M. arenaria race 1. One peanut seedling was planted in each microplot. In the first year, root gall indices and pod galls per microplot were significantly reduced by 60% and 95% for 100,000 Endospores/g of soil, and 20% and 65% for 10,000 Endospores/g of soil, respectively. Final densities of second-stage juveniles (J2) in soil were not significantly different among the treatments. The number of Endospores attached to J2 and percentage of J2 with attached Endospores significantly increased with increasing Endospore inoculation levels. Pasteuria penetrans significantly reduced the densities of J2 that overwintered. In the second year, root and pod gall indices, respectively, were significantly reduced by 81% and 90% for 100,000 Endospores/g of soil, and by 61% and 82% of 10,000 Endospores/g of soil. Pod yields were significantly increased by 94% for 100,000 and by 57% for 10,000 Endospores/g of soil, respectively. The effect of P. penetrans on final densities of J2 in soil was not significant. Regression analyses verified the role of P. penetrans in the suppression of M. arenaria. The minimum number of Endospores required for significantly suppressing M. arenaria race 1 on peanut was 10,000 Endospores/g of soil.

  • Quantification of Endospore Concentrations of Pasteuria penetrans in Tomato Root Material.
    Journal of Nematology, 1996
    Co-Authors: Z. X. Chen, D. W. Dickson, T. E. Hewlett
    Abstract:

    Six methods for quantification of the Endospore concentrations of Pasteuria penetrans from tomato roots are described. Mortar disruption and machine disruption methods gave the highest estimations (Endospores per gram of root material) of 83.7 and 79.0 million, respectively. These methods were significantly superior to incubation bioassay (47.7 million), enzymatic disruption (32.1 million), and enzymatic disruption + flotation (25.8 million) methods. A centrifugation bioassay method gave the lowest estimation of 12.7 million.