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At least 883 records · Page 49Linked to original sources
PubMed1983

Alkalotolerance of Yersinia enterocolitica as a basis for selective isolation from food enrichments.

Alkalotolerance of Yersinia enterocolitica measured in solutions of potassium hydroxide with 0.5% sodium chloride was influenced by the cell suspension medium, temperature, and growth phase. The rate of cell destruction (delta log N per minute) was five times greater at 30 degrees C than at 20 degrees C. Differences in the degree of cell destruction at various concentrations of potassium hydroxide were related to pH and not to osmolarity. The addition of peptones to potassium hydroxide provided a protective effect that was greater for cells suspended in Trypticase soy broth than for those suspended in phosphate-buffered sorbitol-bile salts broth. Log-phase cells were less alkalotolerant than cells in the stationary phase of growth. A modified procedure for alkali treatment, using peptone-supplemented 0.5% potassium hydroxide-0.5% sodium chloride and the addition of a pH 6.6 buffer after treatment to prevent further cell destruction, was used to observe a marked difference in alkalotolerance between Y. enterocolitica and other gram-negative bacteria. Despite this difference, alkali treatment was not highly successful for recovery of Y. enterocolitica from enrichments of seeded foods in comparison with selective enrichment in bile-oxalate-sorbose broth.

Culture Media↗
PubMed1986

Activity of an Attached and Free-Living Vibrio sp. as Measured by Thymidine Incorporation, p-Iodonitrotetrazolium Reduction, and ATP/DNA Ratios.

Three independent techniques, [H]thymidine incorporation, the reduction rate of p-iodonitrotetrazolium violet (INT) to INT formazan normalized to DNA, and the ratio of ATP to DNA, were adapted to measure the activity of attached and unattached estuarine bacteria. In experiments employing the estuarine isolate Vibrio proteolytica, nutrient concentrations were manipulated by varying the concentration of peptone-yeast extract. In the presence of exogenous nutrients, the activity of free-living cells was greater than that of attached cells as measured by [H]thymidine incorporation and ATP/DNA ratios. In the absence of peptone-yeast extract, however, the activity of attached cells surpassed that of free-living cells as determined by [H]thymidine incorporation and INT formazan normalized to DNA. Of the three techniques, [H]thymidine incorporation was deemed most sensitive for detecting changes in activity resulting from slight differences in nutrient concentration. By this technique, attached cells were much less sensitive to changing nutrient concentrations than were free-living cells. Below a threshold concentration, attached cell activity remained constant, while the activity of unattached cells decreased as a function of decreasing nutrient concentration. The results suggest that loss of cell surface area available for substrate uptake due to attachment may be an important factor in determining the relative activities of attached and free-living cells.

Journal Article↗
PubMed1986

Magnesium limitation and its role in apparent toxicity of ethanol during yeast fermentation.

The rate of ethanol production per milligram of cell protein begins to decline in the early stage of batch fermentation before high concentrations of ethanol have accumulated. In yeast extract-peptone medium (20% glucose), this initial decline appears to be related to growth and to result in part from a nutrient deficiency. The addition of yeast extract, peptone, and ashed preparations of these restored the ability of glucose-reconstituted medium (in which cells had been previously grown) to support vigorous growth. Magnesium was identified as the active component. Supplementing fermentations with 0.5 mM magnesium prolonged exponential growth, resulting in increased yeast cell mass. The addition of magnesium also reduced the decline in fermentative activity (micromoles of CO2 evolved per hour per milligram of protein) during the completion of batch fermentations. These two effects reduced the time required for the conversion of 20% glucose into ethanol by 1/3 with no measurable loss in ethanol yield (98% of theoretical maximum yield). It is possible that some of the reported beneficial effects of complex nutrients (soy flour and yeast extract) for ethanol production also result from the correction of a simple inorganic ion deficiency, such as magnesium.

Culture Media↗
PubMed1989

Biosynthesis of fusarochromanone and its monoacetyl derivative by Fusarium equiseti.

One fluorescent compound previously named TDP-2 was isolated and purified from a rice culture of Fusarium equiseti (Alaska 2-2). Mass spectral and nuclear magnetic resonance data indicated that it is a C-3'-N-acetyl derivative of fusarochromanone, a newly discovered mycotoxin. Time course studies of synthesis of these two compounds on autoclaved rice and Czapek-Dox medium enriched with soybean peptone indicated that fusarochromanone was converted to TDP-2 in the cultures. A high concentration of peptone in the liquid medium may stimulate both fusarochromanone synthesis and its conversion to TDP-2.

Amino Acids↗
PubMed1990

Influence of water activity and temperature on survival of and colony formation by heat-stressed Chrysosporium farinicola aleuriospores.

The ability of sublethally heat-stressed aleuriospores of Chrysosporium farinicola to form colonies on yeast extract-glucose agar (YGA) supplemented with sufficient glucose, sorbitol, glycerol, and NaCl to achieve reduced water activity (aw) in the range of 0.88 to 0.95 was determined. The effects of the aw of diluent and incubation temperature during recovery and colony formation were also investigated. Aleuriospores harvested from 14-day-old cultures grown at 25 degrees C were less resistant to heat inactivation compared with aleuriospores from 20-day-cultures. Increased populations of heat-stressed aleuriospores were recovered as the aw of YGA was decreased from 0.95 (glucose and glycerol) and 0.94 (sorbitol) to 0.89 and 0.88, respectively. In NaCl-supplemented YGA, populations recovered at an aw of 0.94 were greatly reduced compared with populations detected at an aw of 0.92; no colonies were formed on NaCl-supplemented YGA at an aw of 0.88. Tolerance to aw values above 0.88 to 0.89 as influenced by solute type was in the order of glucose greater than sorbitol greater than glycerol greater than NaCl. Incubation at 20 degrees generally resulted in an increase in recoverable aleuriospores compared with incubation at 25 degrees C or at 30 degrees C for 14 days followed by 20 degrees C for 10 days. The lethal effect of NaCl on heat-stressed aleuriospores was enhanced at 30 degrees C. The retention of viability of aleuriospores held in sucrose-peptone water diluent (aw, 0.936) for 20 min was essentially the same as that observed when aleuriospores were held in peptone water (aw, 0.997).(ABSTRACT TRUNCATED AT 250 WORDS)

Chrysosporium↗
PubMed1992

Application of ribotyping for differentiating aeromonads isolated from clinical and environmental sources.

We have investigated the usefulness of ribotyping for the differentiation of aeromonads isolated from five patients with gastroenteritis and from the source water, treatment plant, and distribution system of a small public water supply. Aeromonas hydrophila and Aeromonas caviae were isolated from fecal specimens preserved in Cary-Blair transport medium by using blood ampicillin agar or alkaline peptone water (pH 8.4) subcultured to blood ampicillin agar plates. A. hydrophila, Aeromonas sobria, and A. caviae were isolated from duplicate 100-ml water samples by the membrane filter technique by using ampicillin dextrin agar for quantitative determination of growth and alkaline peptone water enrichment for detection of the presence or absence of aeromonads below the detection limit of the membrane filter method. In addition, free chlorine residuals and pH values were determined for all water samples and heterotrophic plate counts and total and fecal coliform analyses were performed on them. Ribotyping patterns of aeromonads recovered from well 1, detention basin, sand filter, softener, and distribution samples were compared with those of the five clinical isolates. All patient strains were unique; however, identical ribotypes of A. hydrophila and A. sobria isolated from multiple sites in the water system indicated colonization of a well, sand filters, and the softener, with the potential for sporadic contamination of distribution water. Plant operational deficiencies were noted and corrected. Ribotyping can effectively differentiate otherwise indistinguishable strains of bacteria, thus providing a powerful tool for investigation of waterborne diseases and bacteriological problems within water treatment plants and distribution systems.

Aeromonas↗
PubMed1992

Influence of solid surface, adhesive ability, and inoculum size on bacterial colonization in microcosm studies.

Microcosm studies were performed to evaluate the effect of solid surfaces, bacterial adhesive ability, and inoculum size on colonization success and persistence of Pseudomonas fluorescens and Xanthomonas maltophilia, each with a Tn5 insertion that conferred resistance to kanamycin and streptomycin. Two types of microcosms were used: (i) a simple system that was colonized by Aeromonas hydrophila and a coryneform and (ii) a complex system produced from lake water enrichment cultures. Simple microcosms contained 100 ml of peptone- and yeast extract-supplemented artificial lake water or 60 ml of peptone- and yeast extract-supplemented artificial lake water with 70 g of 3-mm glass beads. Complex microcosms contained 100 ml of lake water with no nutrient additions or 100 ml of lake water with 70 g of glass beads. The microcosms were incubated for 35 days at 20 degrees C. In lake water enrichment microcosms, the presence of beads increased the abilities of P. fluorescens or X. maltophilia to colonize, but their numbers decreased with time in microcosms both with and without beads. The adhesiveness of the bacteria, measured in an in vitro assay, did not relate to colonization success. In simple microcosms, the inoculum size (10, 10, or 10) of P. fluorescens did not influence colonization success. However, in complex microcosms, an inoculum of 10 cells was insufficient to ensure colonization by P. fluorescens, while 10 cells resulted in colonization of liquid and beads. Simple microcosm studies, utilizing only a few species, were poor models for complex natural systems. In complex enrichment systems, colonization of surfaces resulted in higher numbers of organisms but did not noticeably promote persistence. Adhesiveness of a particular organism may be a relatively minor factor influencing its ability to colonize solid surfaces in complex natural environments.

Journal Article↗
PubMed1993

Stimulation of Ligninolytic Peroxidase Activity by Nitrogen Nutrients in the White Rot Fungus Bjerkandera sp. Strain BOS55.

Bjerkandera sp. strain BOS55, a newly isolated wild-type white rot fungus, produced lignin peroxidase (LiP) in nitrogen (N)-sufficient glucose-peptone medium, whereas no LiP was detectable in N-limited medium. The production of LiP was induced by the peptide-containing components of this medium and also by soy bean protein. Furthermore, the production of manganese-dependent peroxidase was stimulated by organic N sources, although lower production was also evident in N-limited medium. Further research showed that the induction of LiP depended on the combination of pH and the type of N source. An amino acid mixture and ammonium induced LiP only at either pH 6 or 7.3, respectively. Peptone induced LiP activity at all pH values tested; however, the highest activity was observed at pH 7.3. The results presented here indicate that Bjerkandera spp. are distinct from the model white rot fungus, Phanerochaete chrysosporium, which produces ligninolytic peroxidases in response to N limitation.

Journal Article↗
PubMed1993

Rapid detection of salmonellae in poultry with the magnetic immuno-polymerase chain reaction assay.

Rapid detection of salmonellae in chicken meat was accomplished by using the magnetic immuno-polymerase chain reaction assay (MIPA). A direct polymerase chain reaction assay performed with chicken meat spiked with Salmonella typhimurium resulted in poor sensitivity (approximately 10(7) CFU/g of meat). The use of immunoseparation with a Salmonella serogroup B-specific monoclonal antibody improved the sensitivity, but enrichment was required for the detection of low levels of contamination. Enrichment for 6 h in either buffered peptone water, lactose broth containing tergitol-7, or selenite-cystine broth resulted in the detection of an initial inoculum of 100 CFU per g of meat. Enrichment of the salmonellae present on 25 g of spiked chicken meat for 24 h in either buffered peptone water or selenite-cystine broth before detection by the MIPA yielded a detection limit of approximately 0.1 CFU/g of meat. A detection limit of approximately 1 CFU/g of meat was obtained when the spiked meat was stored at -20 degrees C before enrichment for 24 h and analysis with the MIPA. Although the MIPA was developed for S. typhimurium, a MIPA in which a panel of six monoclonal antibodies specific for Salmonella serogroups A through E was used detected the presence of 0.1 CFU of Salmonella enteritidis per g of chicken meat. These data indicate that the method is applicable to other commonly isolated serotypes.

Animals↗
PubMed1997

Production of Clostridium bifermentans Spores as Inoculum for Bioremediation of Nitroaromatic Contaminants.

Spores of Clostridium bifermentans KMR-1 were produced for use as a microbial inoculum for bioremediation and were preserved in both liquid and dry forms. All spore formulations showed good viability and ability to biodegrade the target compound, 2,4,6-trinitrotoluene (TNT), after 4 months of storage. For low-cost bulk spore production, several medium compositions, based on soy peptone, corn steep liquor, and meat peptone, were tested and yielded 10(sup7) spores per ml. A medium pH above 7.0, a low glucose concentration, and a sufficient concentration of protein favored the sporulation of C. bifermentans KMR-1.

Journal Article↗
PubMed1998

Effects of temperature, salinity, and medium composition on compatible solute accumulation by thermococcus spp

The effects of salinity and growth temperature on the accumulation of intracellular organic solutes were examined by nuclear magnetic resonance spectroscopy (NMR) in Thermococcus litoralis, Thermococcus celer, Thermococcus stetteri, and Thermococcus zilligii (strain AN1). In addition, the effects of growth stage and composition of the medium were studied in T. litoralis. A novel compound identified as beta-galactopyranosyl-5-hydroxylysine was detected in T. litoralis grown on peptone-containing medium. Besides this newly discovered compound, T. litoralis accumulated mannosylglycerate, aspartate, alpha-glutamate, di-myo-inositol-1,1'(3,3')-phosphate, hydroxyproline, and trehalose. The hydroxyproline and beta-galactopyranosyl-5-hydroxylysine were probably derived from peptone, while the trehalose was derived from yeast extract; none of these three compounds was detected in the other Thermococcus strains examined. Di-myo-inositol-1,1'(3,3')-phosphate, aspartate, and mannosylglycerate were detected in T. celer and T. stetteri, and the latter organism also accumulated alpha-glutamate. The only nonmarine species studied, T. zilligii, accumulated very low levels of alpha-glutamate and aspartate. The levels of mannosylglycerate and aspartate increased in T. litoralis, T. celer, and T. stetteri in response to salt stress, while di-myo-inositol-1,1'(3,3')-phosphate was the major intracellular solute at supraoptimal growth temperatures. The phase of growth had a strong influence on the types and levels of compatible solutes in T. litoralis; mannosylglycerate and aspartate were the major solutes during exponential growth, while di-myo-inositol-1,1'(3,3')-phosphate was the predominant organic solute during the stationary phase of growth. This work revealed an unexpected ability of T. litoralis to scavenge suitable components from the medium and to use them as compatible solutes.

Journal Article↗
PubMed2000

Analysis of gyrB and toxR gene sequences of Vibrio hollisae and development of gyrB- and toxR-targeted PCR methods for isolation of V. hollisae from the environment and its identification.

Isolation of Vibrio hollisae strains, particularly from the environment, is rare. This may be due, in part, to the difficulty encountered when using conventional biochemical tests to identify the microorganism. In this study, we evaluated whether two particular genes may be useful for the identification of V. hollisae. The two genes are presumed to be conserved among the bacterial species (gyrB) or among the species of the genus Vibrio (toxR). A portion of the gyrB sequence of V. hollisae was cloned by PCR using a set of degenerate primers. The sequence showed 80% identity with the corresponding Vibrio parahaemolyticus gyrB sequence. The toxR gene of V. hollisae was cloned utilizing a htpG gene probe derived from the V. parahaemolyticus htpG gene, which is known to be linked to the toxR gene in V. hollisae. The coding sequence of the cloned V. hollisae toxR gene had 59% identity with the V. parahaemolyticus toxR coding sequence. The results of DNA colony hybridization tests using the DNA probes derived from the two genes of V. hollisae indicated that these gene sequences could be utilized for differentiation of V. hollisae from other Vibrio species and from microorganisms found in marine fish. PCR methods targeting the two gene sequences were established. Both PCR methods were shown to specifically detect the respective target sequences of V. hollisae but not other organisms. A strain of V. hollisae added at a concentration of 1 to 10(2) CFU/ml to alkaline peptone water containing a seafood sample could be detected by a 4-h enrichment incubation in alkaline peptone water at 37 degrees C followed by quick DNA extraction with an extraction kit and 35-cycle PCR specific for the V. hollisae toxR gene. We conclude that screening of seafood samples by this 35-cycle, V. hollisae toxR-specific PCR, followed by isolation on a differential medium and identification by the above htpG- and toxR-targeted PCR methods, can be useful for isolation from the environment and identification of V. hollisae.

Animals↗
PubMed2001

Inactivation of Mycobacterium paratuberculosis by pulsed electric fields.

The influence of treatment temperature and pulsed electric fields (PEF) on the viability of Mycobacterium paratuberculosis cells suspended in 0.1% (wt/vol) peptone water and in sterilized cow's milk was assessed by direct viable counts and by transmission electron microscopy (TEM). PEF treatment at 50 degrees C (2,500 pulses at 30 kV/cm) reduced the level of viable M. paratuberculosis cells by approximately 5.3 and 5.9 log(10) CFU/ml in 0.1% peptone water and in cow's milk, respectively, while PEF treatment of M. paratuberculosis at lower temperatures resulted in less lethality. Heating alone at 50 degrees C for 25 min or at 72 degrees C for 25 s (extended high-temperature, short-time pasteurization) resulted in reductions of M. paratuberculosis of approximately 0.01 and 2.4 log(10) CFU/ml, respectively. TEM studies revealed that exposure to PEF treatment resulted in substantial damage at the cellular level to M. paratuberculosis.

Animals↗
PubMed2002

Proline reverses the abnormal phenotypes of Colletotrichum trifolii associated with expression of endogenous constitutively active Ras.

Colletotrichum trifolii is the causative organism of alfalfa anthracnose. We previously cloned and characterized the small prototypical G protein, Ras, of C. trifolii, which is involved in the signaling pathways that mediate interaction between the pathogen and its host. Transformants expressing constitutively active forms of Ras have growth medium-dependent phenotypes. In nutrient-rich media (e.g., yeast extract and peptone), the phenotype of the transformants was indistinguishable from that of the wild type. However, during nutrient starvation, the transformants lose polarity, have distended hyphae, and fail to sporulate and produce appressoria. Since peptone caused the phenotype to revert, amino acids were tested singly and in combination to identify the responsible amino acid(s). We found that 1.6 mM proline in the medium reverses the constitutively active Ras phenotype.

Amino Acids↗
PubMed2003

Isolation of a methanogen from deep marine sediments that contain methane hydrates, and description of Methanoculleus submarinus sp. nov.

We isolated a methanogen from deep in the sediments of the Nankai Trough off the eastern coast of Japan. At the sampling site, the water was 950 m deep and the sediment core was collected at 247 m below the sediment surface. The isolated methanogen was named Nankai-1. Cells of Nankai-1 were nonmotile and highly irregular coccoids (average diameter, 0.8 to 2 micro m) and grew with hydrogen or formate as a catabolic substrate. Cells required acetate as a carbon source. Yeast extract and peptones were not required but increased the growth rate. The cells were mesophilic, growing most rapidly at 45 degrees C (no growth at </=10 degrees C or >/=55 degrees C). Cells grew with a maximum specific growth rate of 2.43 day(-1) at 45 degrees C. Cells grew at pH values between 5.0 and 8.7 but did not grow at pH 4.7 or 9.0. Strain Nankai-1 grew in a wide range of salinities, from 0.1 to 1.5 M Na(+). The described phenotypic characteristics of this novel isolate were consistent with the in situ environment of the Nankai Trough. This is the first report of a methanogenic isolate from methane hydrate-bearing sediments. Phylogenetic analysis of its 16S rRNA gene sequence indicated that it is most closely related to Methanoculleus marisnigri (99.1% sequence similarity), but DNA hybridization experiments indicated a DNA sequence similarity of only 49%. Strain Nankai-1 was also found to be phenotypically similar to M. marisnigri, but two major phenotypic differences were found: strain Nankai-1 does not require peptones, and it grows fastest at a much higher temperature. We propose a new species, Methanoculleus submarinus, with strain Nankai-1 as the type strain.

Culture Media↗
PubMed1966

Effect of pimaricin on the resistance of Saccharomyces cerevisiae to heat, freezing, and ultraviolet irradiation.

Exposure of washed cells of Saccharomyces cerevisiae C-299 to inhibitory concentrations of pimaricin decreased resistance to lethal temperatures and to freezing and thawing. Varying the pH of the recovery medium had little effect on the decrease in heat resistance, but addition of peptone or yeast extract resulted in a partial recovery of apparent heat resistance. Addition of peptone or calcium ion to the heating menstruum did not affect the reduction in resistance caused by pimaricin. Varying the composition of the recovery medium similarly affected the resistance to freezing the thawing of pimaricin-exposed and unexposed cells. Sensitivity to ultraviolet light was apparently not affected by pimaricin either by preliminary exposure or when irradiated in the presence of pimaricin. It is suggested that pimaricin lowers the heat resistance of S. cerevisiae by depleting essential nutrients of the cells through a disruption of permeability, and that heat-damaged cells cannot resynthesize these nutrients. It is also suggested that spoilage of acid foods by S. cerevisiae may be retarded by a combination of mild heat treatment and the addition of pimaricin.

Antifungal Agents↗
PubMed1969

Sporulation, heat resistance, and biological properties of Clostridium perfringens.

A sporulation medium for 134 Clostridium perfringens strains, including types A, B, C, D, E, and F, was devised according to Grelet's observation that sporulation occurred when cultural environment became limited in any nutritional requirement indispensable for the growth of the organism. Sporulation took place most prominently when 10% cooked-meat broth (pH 7.2) containing 3% Proteose Peptone and 1% glucose was used for the preculture and 2% Poli Peptone medium (pH 7.8) was used for the subculture medium. Sometimes, terminal spores could be observed. A correlation between sporulation and heat resistance was examined by use of C. perfringens strains isolated from samples heated at different temperatures. Almost all strains isolated from unheated samples and from those heated at lower temperatures gave rise to spores in our sporulation medium, but the spores were weakly heat-resistant, whereas strains isolated from samples heated at 100 C for 60 min were highly heat-resistant but sporulated poorly. A majority of these heat-resistant strains were non-gelatinolytic and definitely salicin-fermenting.

Clostridium perfringens↗