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Biomedical subjects

R R Colwell

Publications and source records attributed to R R Colwell.

At least 181 records · Page 10Linked to original sources
PubMed1984

Influence of water temperature, salinity, and pH on survival and growth of toxigenic Vibrio cholerae serovar 01 associated with live copepods in laboratory microcosms.

The influence of water temperature, salinity, and pH on the multiplication of toxigenic Vibrio cholerae serovar O1 cells and their attachment to live planktonic crustaceans, i.e., copepods, was investigated by using laboratory microcosms. By increasing water temperatures up to 30 degrees C, a pronounced effect on the multiplication of V. cholerae was demonstrated, as was attachment of the cells to live copepods. These were measured by culturable counts on agar plates and direct observation by scanning electron microscopy, respectively. Of the three salinities examined (5, 10, and 15%), maximum growth of V. cholerae and attachment to copepods occurred at 15%. An alkaline pH (8.5) was optimal both for attachment and multiplication of V. cholerae, as compared with pH 6.5 and 7.5. It is concluded that conditions affecting attachment of V. cholerae serovar O1 to live copepods observed under laboratory conditions may also occur in the natural estuarine environment and, thereby, are significant in the epidemiology of cholera.

Animals↗
PubMed1984

Numerical taxonomy of phenanthrene-degrading bacteria isolated from the Chesapeake Bay.

Phenanthrene-degrading bacteria were isolated from Chesapeake Bay samples by the use of a solid medium which had been overlaid with an ethanol solution of phenanthrene before inoculation. Eighteen representative strains of phenanthrene-degrading bacteria with 21 type and reference bacteria were examined for 123 characteristics representing physiological, biochemical, and nutritional properties. Relationships between strains were computed with several similarity coefficients. The phenogram constructed by unweighted-pair-group arithmetic average linkage and use of the simple Jaccard (SJ) coefficient was used to identify seven phena. Phenanthrene-degrading bacteria were identified as Vibrio parahaemolyticus and Vibrio fluvialis by their clustering with type and reference strains. Several phenanthrene-degrading bacteria resembled Enterobacteriaceae family members, although some Vibrio-like phenanthrene degraders could not be identified.

Bacteria↗
PubMed1984

Enhancement of Vibrio parahaemolyticus virulence by lysed erythrocyte factor and iron.

The effect of lysed blood on the virulence of Vibrio parahaemolyticus for mice was investigated. A factor present in lysed erythrocytes was found to greatly reduce the 50% lethal dose of V. parahaemolyticus for mice. Similar effects were observed with ferric ammonium citrate and manganous sulfate. V. parahaemolyticus grown in brain heart infusion containing lysed erythrocyte factor appeared to produce a lethal toxin which was either inapparent or absent when the organism was grown in brain heart infusion alone.

Animals↗
PubMed1984

Wound infection caused by Kanagawa-negative Vibrio parahaemolyticus.

Kanagawa-positive Vibrio parahaemolyticus strains are considered to be human pathogens and are most commonly associated with summer diarrhea. Kanagawa-negative strains are most frequently isolated from the environment and are generally considered to be nonpathogens. We report a wound infection caused by a Kanagawa-negative V. parahaemolyticus strain. The infection occurred in October, an unusual time of the year for a V. parahaemolyticus infection to occur in the mid-Atlantic region of the United States.

Adult↗
PubMed1984

Viable but nonrecoverable stage of Salmonella enteritidis in aquatic systems.

An environmental isolate (13- 1BB ) of Salmonella enteritidis serogroup C1 was inoculated into sterile Potomac River water microcosms to observe survival and culturability of the organism by employing acridine orange direct count, fluorescent antibody direct count, direct viable count, plate count on veal infusion agar and xylose lysine decarboxylase agar, and indirect enumeration by the most-probable-number method (MPN), using media selective for Salmonella. Loss of culturability on laboratory media was observed within 48 h. However, cultures could be "resuscitated" and cultured on solid media, following addition of nutrients to the microcosms . Cells, resuscitated 4 days after apparent "die-off" (0 colony-forming units (cfu)/mL) using plate count techniques, yielded numbers of cfu in the same order of magnitude as had been observed before the onset of nutrient limitation. Microscopic techniques for direct viable counting indicated that viability is maintained for as long as 60 days after depletion of nutrients, although attempts to culture these cells, by addition of nutrient, after 21 days yielded apparently sterile plates. Thus, longer periods of "dormancy" appear to require conditions other than simple nutrient addition for resumption of cell growth and division.

Bacteriological Techniques↗
PubMed1984

The nucleotide sequence of 5 S ribosomal RNA from Vibrio marinus.

The complete nucleotide base sequence of the 5 S ribosomal RNA from Vibrio marinus MP-1 has been determined and compared with those of other members of the Vibrionaceae for which 5S rRNA sequences are available. Comparisons among 5S rRNA nucleotide base sequences confirm that V. marinus (MP-1) belongs to the family Vibrionaceae, but may represent a new genus. Addition of the V. marinus MP-1 5S rRNA sequence to those already determined, and consideration of all data available to date on 5S rRNA sequences, provides fresh insight into the phylogeny of the Vibrionaceae.

Base Sequence↗
PubMed1983

Ecological relationships between Vibrio cholerae and planktonic crustacean copepods.

Strains of Vibrio cholerae, both O1 and non-O1 serovars, were found to attach to the surfaces of live copepods maintained in natural water samples collected from the Chesapeake Bay and Bangladesh environs. The specificity of attachment of V. cholerae to live copepods was confirmed by scanning electron microscopy, which revealed that the oral region and egg sac were the most heavily colonized areas of the copepods. In addition, survival of V. cholerae in water was extended in the presence of live copepods. Attachment of viable V. cholerae cells to copepods killed by exposure to -60 degrees C was not observed. Furthermore, survival of V. cholerae was not as long in the presence of dead copepods as in the live copepod system. A strain of Vibrio parahaemolyticus was also seen to attach to copepod surfaces without effect on survival of the organism in water. The attachment of vibrios to copepods was concluded to be significant since strains of other bacteria, including Pseudomonas sp. and Escherichia coli, did not adhere to live or dead copepods. Attachment of V. cholerae to live copepods is suggested to be an important factor of the ecology of this species in the aquatic environment, as well as in the epidemiology of cholera, for which V. cholerae serovar O1 is the causative agent.

Animals↗
PubMed1983

Computation of most probable numbers.

A rapid computational method for maximum likelihood estimation of most-probable-number values, incorporating a modified Newton-Raphson method, is presented. The method offers a much greater reliability for the most-probable-number estimate of total viable bacteria, i.e., those capable of growth in laboratory media.

Bacteria↗
PubMed1983

Characterization of plasmids in bacterial fish pathogen.

Plasmid profiles of representative fish pathogens, Aeromonas salmonicida, Aeromonas hydrophila, Vibrio anguillarum, Pasteurella piscicida, Yersinia ruckeri, Edwardsiella tarda, and Renibacterium salmoninarum, were determined by agarose gel electrophoresis with four different plasmid detection methods. A combination of two methods was required to detect the plasmids present in these strains and to calculate precisely the molecular weights of the plasmids. Of 38 strains, 28 harbored one or more plasmids, with the majority of strains demonstrating multiplasmid banding. Similarity in plasmid banding between strains was noted and related to geographic source. Five strains of A. salmonicida possessed six plasmid bands having molecular weights of 8.6 X 10(6), 8.4 X 10(6), 8.1 X 10(6), 3.6 X 10(6), 3.5 X 10(6), and 3.4 X 10(6). Four P. piscicida isolates shared three plasmid bands having molecular weights of 37 X 10(6), 15 X 10(6), and 5 X 10(6), and five A. hydrophila strains harbored a common plasmid having a molecular weight of ca. 20 X 10(6) to 30 X 10(6). The highest-molecular-weight plasmids (145 X 10(6) and 130 X 10(6) were detected in V. anguillarum. From curing experiments, it was found that in A. hydrophila strain 79-62, a loss of resistance to tetracycline was associated with loss of plasmid content in all susceptible derivatives, suggesting plasmid-mediated tetracycline resistance. Cell surface characteristics and metabolic properties were also modified in cured derivatives of A. hydrophila strain 79-62.

Aeromonas↗
PubMed1983

Molecular factors associated with virulence of marine vibrios isolated from striped bass in Chesapeake Bay.

On the basis of cultural and biochemical properties as well as DNA homology assays, 81 Vibrio strains isolated from diseased striped bass and from Chesapeake Bay water were assigned to eight distinct groups. All organisms belonging to two of the groups were pathogenic for striped bass and were identified as Vibrio anguillarum, whereas organisms classified in the other six groups were nonpathogenic and were designated as Vibrio spp. Unlike the pathogenic V. anguillarum strain 775 isolated in the Pacific Northwest, strains pathogenic for striped bass did not contain any plasmids; however, they were similar to the Northwest isolates in that virulence was correlated with their ability to grow in the presence of nonimmune striped bass serum or under conditions of iron limitation. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of outer membranes showed that additional proteins were induced in those organisms capable of growth under conditions of iron limitation. It was of interest that 22 of the nonpathogenic isolates harbored one or more plasmids which, by restriction endonuclease analyses, were shown to be clearly different from the virulence plasmid pJM1.

Animals↗
PubMed1983

New selective plating medium for isolation of Vibrio vulnificus biogroup 1.

A new plating medium (VV agar) has been developed as an alternative to thiosulfate-citrate-bile salts-sucrose (TCBS) agar for the isolation of Vibrio vulnificus. Salicin (2% wt/vol) is employed as the source of carbohydrate, with potassium tellurite (0.0005% wt/vol), crystal violet (0.00015% wt/vol), oxgall (0.8% wt/vol), and a pH of 8.6 to inhibit growth of gram-positive and gram-negative organisms other than V. vulnificus. Because strains of V. vulnificus do not strongly ferment salicin in VV agar, a pH indicator has not been included in the medium. Growth of V. vulnificus appears on VV agar as large grey colonies with black centers. Other non-Vibrio strains which grow on the medium produce smaller colonies and fail to take up tellurite. VV agar has proved to be more effective than TCBS agar in inhibiting members of the Enterobacteriaceae as well as gram-positive cocci. Only Vibrio strains capable of utilizing salicin grow well on VV agar. Recovery and growth of V. vulnificus are superior on VV agar, compared with TCBS agar.

Benzyl Alcohols↗
PubMed1983

Numerical taxonomy of Vibrio cholerae and related species isolated from areas that are endemic and nonendemic for cholera.

A total of 165 strains of vibrios isolated from clinical and environmental sources in the United States, India, and Bangladesh, 11 reference cultures, and 4 duplicated cultures were compared in a numerical taxonomic study using 83 unit characters. Similarity between strains was computed by using the simple matching coefficient and the Jaccard coefficient. Strains were clustered by unweighted average linkage and single linkage algorithms. All methods gave similar cluster compositions. The estimated probability of error in the study was obtained from a comparison of the results of duplicated strains and was within acceptable limits. A total of 174 of the 180 organisms studied were divided into eight major clusters. Two clusters were identified as Vibrio cholerae, one as Vibrio mimicus, one as Vibrio parahaemolyticus, three as Vibrio species, and one as Aeromonas hydrophila. The V. mimicus cluster could be further divided into two subclusters, and the major V. cholerae group could be split into seven minor subclusters. Phenotypic traits routinely used to identify clinical isolates of V. cholerae can be used to identify environmental V. cholerae isolates. No distinction was found between strains of V. cholerae isolated from regions endemic for cholera and strains from nonendemic regions.

Aeromonas↗
PubMed1982

Use of epifluorescence microscopy in studies of the germination and recovery of thermoactinomycetes.

Spore germination and growth of thermoactinomycetes were observed by epifluorescence microscopy. Each of the principal stages in germination was recognized and found to correspond to changes in phase-contrast appearance commonly monitored during endospore germination. The effects of novobiocin and nalidixic acid on germination of Thermoactinomyces vulgaris and T. thalpophilus were studied by using epifluorescence microscopy. Outgrowth but not initiation was inhibited by 100 mug of nalidixic acid per ml and 50 mug of novobiocin per ml. When each of the compounds, at various concentrations, was incorporated into a medium for thermoactinomycete recovery, the antibiotics were found to inhibit colony development. Samples of water and sediment incubated in a growth medium containing novobiocin and selective for thermoactinomycete species were examined by epifluorescence microscopy for total numbers of outgrown spores. Direct viable counts of outgrown spores indicated that the standard plate count enumerated less than 10% of the viable population of thermoactinomycetes.

Journal Article↗
PubMed1982

Influence of salinity and organic nutrient concentration on survival and growth of Vibrio cholerae in aquatic microcosms.

Laboratory microcosms were employed to evaluate the influence of selected environmental parameters, organic nutrient concentration, and salinity on the growth and survival of a toxigenic strain of Vibrio cholerae LA4808. Over the range conditions tested, this strain of V. cholerae showed maximum response as determined by increased plate counts and direct microscopic counts in microcosms prepared with a chemically defined sea salts solution at a salinity of 25%, but with lower or higher salinity levels, the maximum population size declined. When added organic concentrations of less than 1,000 micrograms/liter were present, a marked salinity effect on the growth of V. cholerae was detected. However, at or above an organic nutrient concentration of 1,000 micrograms/liter, the need for an optimum salinity level was spared. From the results of this study, it is concluded that V. cholerae can grow under conditions of organic nutrient concentration and salinity typical of estuaries. Results obtained support the hypothesis that V. cholerae is an autochthonous member of the estuarine microbial community.

Dose-Response Relationship, Drug↗
PubMed1982

Activity and growth of microbial populations in pressurized deep-sea sediment and animal gut samples.

Benthic animals and sediment samples were collected at deep-sea stations in the northwest (3,600-m depth) and southeast (4,300- and 5200-m depths) Atlantic Ocean. Utilization rates of [14C]glutamate (0.67 to 0.74 nmol) in sediment suspensions incubated at in situ temperatures and pressures (3 to 5 degrees C and 360, 430, or 520 atmospheres) were relatively slow, ranging from 0.09 to 0.39 nmol g-1 day-1, whereas rates for pressurized samples of gut suspensions varied widely, ranging from no detectable activity to a rapid rate of 986 nmol g-1 day-1. Gut flora from a holothurian specimen and a fish demonstrated rapid, barophilic substrate utilization, based on relative rates calculated for pressurized samples and samples held at 1 atm (101.325 kPa). Substrate utilization by microbial populations in several sediment samples was not inhibited by in situ pressure. Deep-sea pressures did not restrict growth, measured as doubling time, of culturable bacteria present in a northwest Atlantic sediment sample and in a gut suspension prepared from an abyssal scavenging amphipod. From the results of this study, it was concluded that microbial populations in benthic environments can demonstrate significant metabolic activity under deep-ocean conditions of temperature and pressure. Furthermore, rates of microbial activity in the guts of benthic macrofauna are potentially more rapid than in surrounding deep-sea sediments.

Acetates↗
PubMed1982

Effects of temperature and salinity on Vibrio cholerae growth.

Laboratory microecosystems (microcosms) prepared with a chemically defined sea salt solution were used to study effects of selected environmental parameters on growth and activity of Vibrio cholerae. Growth responses under simulated estuarine conditions of 10 strains of V. cholerae, including clinical and environmental isolates as well as serovars O1 and non-O1, were compared, and all strains yielded populations of approximately the same final size. Effects of salinity and temperature on extended survival of V. cholerae demonstrated that, at an estuarine salinity (25%) and a temperature of 10 degrees C, V. cholerae survived (i.e., was culturable) for less than 4 days. Salinity was also found to influence activity, as measured by uptake of 14C-amino acids. Studies on the effect of selected ions on growth and activity of V. cholerae demonstrated that Na+ was required for growth. The results of this study further support the status of V. cholerae as an estuarine bacterium.

Amino Acids↗
PubMed1982

Barophilic bacteria associated with digestive tracts of abyssal holothurians.

Abyssal holothurians and sediment samples were collected at depths of 4,430 to 4,850 m in the Demerara abyssal plain. Bacterial concentrations in progressive sections of the holothurian digestive tract, as well as in surrounding surface sediments, were determined by epifluorescence microscopy. Total bacterial counts in sediments recently ingested by the animals were 1.5- to 3-fold higher than in surrounding sediments at the deepest station. Lowest counts were observed consistently in the foregut, where the digestive processes of the holothurian are believed to occur. In most animals, counts increased 3- to 10-fold in the hindgut. Microbial activity at 3 degrees C and in situ and atmospheric pressure were determined for gut and sediment samples by measuring the utilization of [C]glutamic acid, the doubling time of the mixed-population of culturable bacteria, and the percentage of the total bacterial count responsive to yeast extract in the presence of nalidixic acid, using epifluorescence microscopy. A barophilic microbial population, showing elevated activity under deep-sea pressure, was detected by all three methods in sediments removed from the hindgut. Transmission electron micrographs revealed intact bacteria directly associated with the intestinal lining only in the hindgut. The bacteria are believed to be carried as an actively metabolizing, commensal gut flora that transforms organic matter present in abyssal sediments ingested by the holothurian. Using data obtained in this study, it was calculated that sediment containing organic matter altered by microbial activity cleared the holothurian gut every 16 h, suggesting that abyssal holothurians and their associated gut flora are important participants in nutrient cycles of the abyssal benthic ocean.

Journal Article↗