Search PubMed⌕ Search

Biomedical subjects

R R Colwell

Publications and source records attributed to R R Colwell.

At least 163 records · Page 9Linked to original sources
PubMed1986

Effects of microcosm salinity and organic substrate concentration on production of Vibrio cholerae enterotoxin.

The effects of aquatic processes on production of cholera toxin by Vibrio cholerae were studied with seawater microcosms. Several salinity and organic nutrient concentrations were employed. At 10 g of organic nutrient per liter of seawater, toxin production increased as the salinity was increased. At lower organic nutrient concentrations, toxin production was markedly enhanced when the salinity was 20 and 25%. Toxin concentration increased with salinity, independent of cell concentration and toxin stability. From the results obtained in this study, it is concluded that physical and chemical parameters of the aquatic environment affect not only the physiological state of V. cholerae, but also its potential pathogenicity.

Culture Media↗
PubMed1986

Viable but nonculturable stage of Campylobacter jejuni and its role in survival in the natural aquatic environment.

Conditions influencing the survival of Campylobacter jejuni in the natural aquatic environment have been determined. Release of Campylobacter spp. into natural waters by animal hosts is postulated to play a key role in the maintenance of viability and transmission of the organism in the environment. Laboratory flask microcosms containing filter-sterilized stream water were used to test C. jejuni for the ability to remain viable in simulated natural systems. The microcosms were compared with the biphasic and shaking broth procedures used routinely for growth of Campylobacter spp. in the research laboratory. The stream-water microcosms were analyzed to determine effects of temperature and aeration on the survival of a well-characterized C. jejuni strain isolated originally from a human campylobacteriosis patient. Morphological characteristics were evaluated by phase-contrast microscopy and scanning or transmission electron microscopy. Survival curves were quantified on the basis of plate counts, epifluorescent microscopy, optical density measurements, and direct viable counts associated with protein synthesis in the absence of DNA replication. A significant difference was observed between results of direct enumeration, i.e., direct viable counts or acridine orange direct counts, and those from spread plate cultures. In all cases, increasing temperature of cultivation resulted in decreased recoverability on laboratory media, due possibly to an increased metabolic rate, as analyzed by CO2 evolution in the presence of radiolabeled glutamate. Stream water held at low temperature (4 degrees C) sustained significant numbers of campylobacters for greater than 4 months. Microcosms, aerated with shaking, exhibited logarithmic decline in recoverable C. jejuni, while stationary systems underwent a more moderate rate of decrease to the nonculturable state.(ABSTRACT TRUNCATED AT 250 WORDS)

Campylobacter fetus↗
PubMed1986

Colonization of the gut of the blue crab (Callinectes sapidus) by Vibrio cholerae.

Attachment of Vibrio cholerae to the mucosal surface of the intestine is considered to be an important virulence characteristic. Vibrio cholerae, an autochthonous member of brackish water and estuarine bacterial communities, also attaches to crustacea, a significant factor in multiplication and survival of V. cholerae in nature. The ability of V. cholerae to attach to the gut wall of the blue crab (Callinectes sapidus) was examined, and attachment was observed only in the hindgut and not the midgut of crabs, confirming a requirement for chitin in the attachment of V. cholerae to invertebrate and zooplankton surfaces. The new finding of attachment of V. cholerae to the hindgut of crabs may be correlated with the epidemiology and transmission of cholera in the aquatic environment. The crab model may also prove useful in elucidating the mechanism(s) of ion transport in crustacea.

Animals↗
PubMed1986

Vibrio cincinnatiensis sp. nov., a new human pathogen.

A halophilic gram-negative rod was isolated from blood and cerebrospinal fluid collected from a 70-year-old male having no known contact with seafood or salt water. Positive biochemical tests included oxidase, sensitivity to 0/129, O-nitrophenyl-beta-D-galactopyranoside, lysine decarboxylase and fermentation of glucose, salicin, n-inositol, sucrose, L-mannose, L-arabinose, and arbutin. Negative tests included indole, ornithine decarboxylase, arginine dihydrolase fermentation of lactose, and production of gelatinase and urease. The DNA base composition was 45.0 mol% guanine plus cytosine. Numerical taxonomy indicated 70% similarity with known reference Vibrio sp. strains. The 5S rRNA sequence for this strain has been determined: 5'-U G C C U G G C G A C C A U A G C G U U U U G G A C C C A C C U G A U U C C A U G C C G A A C U C A G U A G U G A A A C G A A A C A G C G U C G A U G G U A G U G U G G G G U C U C C C C A U G U G A G A G U A G A A C A U C G C C A G G C A U-3'. Based on the phenetic, molecular genetic, and nucleic acid sequencing data, it is concluded that Vibrio cincinnatiensis represents a new species of the genus Vibrio sensu strictu (as defined by 5S rRNA sequencing results). On a basis of 5S rRNA comparative sequence analysis, the organism appears to share a recent common ancestor with V. gazogenes (98% homology) and close ancestry with V. mimicus, V. fluvialis, and V. metschnikovii.

Aged↗
PubMed1986

Ribosomal RNA phylogenies for the vibrio-enteric group of eubacteria.

Comparisons between the ribonucleotide sequences of 5S rRNAs of the Gram-negative eubacteria indicate that several families, namely Enterobacteriaceae, Vibrionaceae and Aeromonadaceae possess remarkably similar evolutionary histories. A study of the phylogenetic relationships among these groups, through cluster analysis and construction of evolutionary trees, suggests the existence of dissimilar rates of evolution along the several lineages. These dissimilarities are most evident in comparisons between the phylogenetic depths of the Enterobacteriaceae and Vibrionaceae. Detection of disparate rates of evolution, as well as their influence on the interpretation of the natural taxonomy of this group of bacteria, is discussed.

Aeromonas↗
PubMed1986

The fate of enteric pathogenic bacteria in estuarine and marine environments.

Sufficient laboratory and field data are now available to hypothesize that enteric pathogens survive for very long periods of time in sea-water. In fact, these Gram-negative bacteria probably enter into dormancy, during which they remain viable and potentially virulent, yet are non-culturable when traditional bacteriological methods are employed. Increasing use of the world's oceans-for discharge of domestic wastes may result in public health problems in the future from the allochthonous human pathogens accumulating in the marine environment at disposal sites.

Enterobacteriaceae↗
PubMed1985

Nuclease S1 analysis of eubacterial 5S rRNA secondary structure.

Single-strand-specific nuclease S1 was employed as a structural probe to confirm locations of unpaired nucleotide bases in 5S rRNAs purified from prokaryotic species of rRNA superfamily I. Limited nuclease S1 digests of 3'- and 5'-end-labeled [32P]5S rRNAs were electrophoresed in parallel with reference endoribonuclease digests on thin sequencing gels. Nuclease S1 primary hydrolysis patterns were comparable for 5S rRNAs prepared from all 11 species examined in this study. The locations of base-paired regions determined by enzymatic analysis corroborate the general features of the proposed universal five-helix model for prokaryotic 5S rRNA, although the results of this study suggest a significant difference between prokaryotic and eukaryotic 5S rRNAs in the evolution of helix IV. Furthermore, the extent of base-pairing predicted by helix IV needs to be reevaluated for eubacterial species. Clipping patterns in helices II and IV appear to be consistent with a secondary structural model that undergoes a conformational rearrangement between two (or more) structures. Primary clipping patterns in the helix II region, obtained by S1 analysis, may provide useful information concerning the tertiary structure of the 5S rRNA molecule.

Aeromonas↗
PubMed1985

Characterization of a Marine Bacterium Associated with Crassostrea virginica (the Eastern Oyster).

A gram-negative bacterium found to be closely associated with oysters has been isolated and characterized. The organism, designated LST, has a generation time of 106 min in Marine broth under optimal growth conditions at 25 degrees C. During the decline phase of growth, it exhibits a morphological transition from a motile rod (ca. 1 mum in length) to an elongated, 3- to 40-mum, nonmotile, tightly coiled helix. LST synthesizes and releases a pigment in the stationary and decline phases of growth. Identified as melanin on the basis of chemical properties and UV absorbance maxima, the pigment comprises polymers of heterogeneous molecular weights, ranging from 12,000 to 120,000. The guanosine-plus-cytosine content of the LST DNA is 46%, and results of phenetic analysis and DNA-DNA hybridization indicate that this bacterium represents a new species. LST adheres to a variety of surfaces, including glass, plastics, and oyster shell, and has been shown to promote the settlement of oyster larvae.

Journal Article↗
PubMed1985

Enumeration, isolation, and characterization of n(2)-fixing bacteria from seawater.

Marine pelagic N(2)-fixing bacteria have not, in general, been identified or quantified, since low or negligible rates of N(2) fixation have been recorded for seawater when blue-green algae (cyanobacteria) are absent. In the study reported here, marine N(2)-fixing bacteria were found in all samples of seawater collected and were analyzed by using a most-probable-number (MPN) method. Two different media were used which allowed growth of microaerophiles, as well as that of aerobes and facultative anaerobes. MPN values obtained for N(2)-fixing bacteria ranged from 0.4 to 1 x 10 per liter for water collected off the coast of Puerto Rico and from 2 to 5.5 x 10 per liter for Chesapeake Bay water. Over 100 strains of N(2)-fixing bacteria were isolated from the MPN tubes and classified, yielding four major groups of NaCl-requiring bacteria based on biochemical characteristics. Results of differential filtration studies indicate that N(2)-fixing bacteria may be associated with phytoplankton. In addition, when N(2)-fixing bacteria were inoculated into unfiltered seawater and incubated in situ, nitrogenase activity could be detected within 1 h. However, no nitrogenase activity was detected in uninoculated seawater or when bacteria were incubated in 0.2-mum-filtered (phytoplankton-free) seawater. The ability of these isolates to fix N(2) at ambient conditions in seawater and the large variety of N(2)-fixing bacteria isolated and identified lead to the conclusion that N(2) fixation in the ocean may occur to a greater degree than previously believed.

Journal Article↗
PubMed1985

Observations of barophilic microbial activity in samples of sediment and intercepted particulates from the demerara abyssal plain.

To better understand the ecological significance of pressure effects on bacteria in the abyssobenthic boundary layer, experimental suspensions of sediments and sinking particulates were prepared from samples collected in boxcore and bottom-moored sediment traps at two stations (depth, 4,470 and 4,850m) in the Demerara abyssal plain off the coast of Brazil. Replicate samples were incubated shipboard at 3 degrees C and at both atmospheric and deep-sea pressures (440 or 480 atm [4.46 x 10 or 4.86 x 10 kPa]) following the addition of [C]glutamic acid (<10 mug liter) or yeast extract (0.025%) and the antibiotic nalidixic acid (0.002%). In seven of the eight samples supplemented with isotope, a barophilic microbial response was detected, i.e., substrate incorporation and respiration were greater under in situ pressure than at 1 atm (101.3 kPa). In the remaining sample, prepared from a sediment trap warmed to 24 degrees C before recovery, pressure was observed to inhibit substrate utilization. Total bacterial counts by epifluorescence microscopy decreased with depth in each sediment core, as did utilization of glutamic acid. Significant percentages of the total bacterial populations in cold sediment trap samples (but not the prewarmed one or any boxcore sample) were abnormally enlarged and orange fluorescing after incubation with yeast extract and nalidixic acid under deep-sea conditions. Results indicated that in the deep sea, barophilic bacteria play a predominant role in the turnover of naturally low levels of glutamic acid, and the potential for intense microbial activity upon nutrient enrichment is more likely to occur in association with recently settled particulates, especially fecal pellets, than in buried sediments.

Journal Article↗
PubMed1985

Characterization and distribution of Vibrio alginolyticus and Vibrio parahaemolyticus isolated in Indonesia.

Previous studies have shown that Vibrio alginolyticus and Vibrio parahaemolyticus can be isolated from similar types of marine samples. In this report, the results of an examination of 567 V. alginolyticus and V. parahaemolyticus strains, isolated from seawater in Jakarta Bay and from more than 30 types of seafood from markets in Jakarta, Indonesia, are presented. Most isolates were from mackerel, shrimp, or squid. Numerical taxonomic analyses clustered 337 isolates and three V. alginolyticus reference strains at S greater than or equal to 80%. These strains produced acid from sucrose, but only approximately 80% produced acetoin or grew in the presence of 10% NaCl. The frequency of occurrence of V. alginolyticus in seawater samples ranged from 0% (in February and March 1972) to 100% (in September and December 1972) and was highest in seafood samples from August to December 1972. A second cluster of 230 isolates and seven V. parahaemolyticus reference strains was observed at S greater than or equal to 82%. These strains did not produce acetoin or acid from sucrose, and approximately 20% grew in the presence of 10% NaCl. V. parahaemolyticus was detected in seawater samples each month, with the highest frequency of occurrence (83.3%) in May 1972. Twenty-nine K antigen serotypes were demonstrated in V. parahaemolyticus isolates, and another 40% were untypable. The modal antibiotic resistance pattern for each species included five drugs. Only 12% of the V. parahaemolyticus strains were Kanagawa positive, and 10% elicited fluid accumulation in ligated rabbit ileal loops. All of the 7 V. alginolyticus strains and 94 (70%) of the V. parahaemolyticus strains tested killed mice when inoculated intraperitoneally.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Nucleotide base sequence of vibrionaceae 5 S rRNA.

Nucleotide base sequences of 5 S rRNAs isolated from Vibrio vulnificus, Vibrio anguillarum, and Aeromonas hydrophila were determined. Comparisons among these and sequences of 5 S rRNAs from other species of Vibrionaceae provide information useful in the evaluation of the evolution of bacterial species.

Aeromonas↗
PubMed1984

The ribonucleotide sequence of 5s rRNA from two strains of deep-sea barophilic bacteria.

Deep-sea bacteria were isolated from the digestive tract of animals inhabiting depths of 5900 m in the Puerto Rico Trench and 4300 m near the Walvis Ridge. Growth of two bacterial strains was measured in marine broth and in solid media under a range of pressures and temperatures. Both strains were barophilic at 2 degrees C (+/- 1 degrees C) with an optimal growth rate of 0.22 h-1 at a pressure 30% lower than that encountered in situ. At 1 atm they grew at temperatures ranging from 1.2 to 18.2 degrees C (+/- 0.3 degrees C), while in situ pressures increased the upper temperature limit to 23.3 degrees C. Both strains were identified as members of the genus Vibrio, based on standard taxonomic tests and mol% G + C values (47.0 and 47.1). Ribonucleotide sequences determined for 5S ribosomal RNA from each strain confirmed relationship to the Vibrio-Photobacterium group, as represented by V. harveyi and P. phosphoreum, but the barophiles were clearly distinct from these species. Secondary structure conformed to the established model for eubacterial 5S rRNA.

Animals↗
PubMed1984

Allogenic succession of marine bacterial communities in response to pharmaceutical waste.

Vibrio spp. predominated in the culturable bacterial community of surface waters of the Puerto Rico Trench at the site of disposal for nearly ten years of pharmaceutical wastes. In this area and surrounding waters as far as 1000 km north of the dumpsite and south into the Caribbean Sea, Vibrio spp. comprised up to 100% of the culturable bacteria, with Acinetobacter spp. being the second most prevalent group. Pseudomonas spp., reported to be common in these waters a decade earlier, were virtually absent from all samples examined during a three year study involving 9 cruises. Staphylococcus spp. were also found in water samples collected within the dumpsite. Using cultures isolated from surface water samples collected at the dumpsite, laboratory experiments confirmed that pharmaceutical waste can enrich for Vibrio spp., in preference to Pseudomonas spp., with growth of the strains proportional to the amount of waste added.

Bacteria↗
PubMed1984

Identical 5S rRNA nucleotide sequence of Vibrio cholerae strains representing temporal, geographical, and ecological diversity.

Enzymatic determination of the nucleotide sequence of 5S rRNA prepared from a Vibrio cholerae non-O1 serovar isolated from a canal in Louisiana in 1978 revealed it to be identical to that of V. cholerae O1 isolated in 1905 from a pilgrim at the E1 Tor quarantine station. The two strains are associated with sharply contrasting habitats. Ranges of variation of 5 to 15% in procaryotic 5S rRNA sequences between species are typical; variation within species may be 2% or greater. Because the 5S rRNA sequences were identical, it is concluded that they have a common phylogenic origin.

Base Sequence↗