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Research has been conducted on bacteria of gamma-subclass Proteobacteria. The hypotheses that these bacteria are assiociated with zooplankton in the environment and that the composition of zooplankton-associated bacterial communities is the sane or different from that of water column have been tested, and the results are reported.

Some non-cholera-toxin-producing strains of Vibrio cholerae produce a toxin that is different from the toxin produced by O1 and O139 strains. Many of these non-cholera-toxin-producing stains are found in aquatic environments.

Research conducted on three human isolates of pathogenic bacteria Campylobacter jejuni to investigate their ability to recover culturability after egg passage is analyzed. Results demonstrate that viable but not culturable C. jejuni cells maintain adhesion potential after the passage.

Microbiological research shows that total cell count procedures are more accurate in assessing the number of virulent airborne bacterial cells than other enumeration techniques. Total cell count methods count viable but nonculturable bacteria. Thus, they are particularly effective in assessing indoor air pollution. The effects of aerosolization on the growth and viability of gram-negative bacteria is evaluated.

Enterotoxigenic strains of Escherichia coli H10407 retain pathogenicity even after being exposed to sunlight, and entering the viable but nonculturable state. When exposed to sunlight, the direct counts of viable cells fail to change. Escherichia coli cells are culturable in the absence of sunlight only when exposed to seawater. Ganglioside-enzyme-linked immunosorbent assay (GM1-ELISA) shows that Escherichia coli continues to produce enterotoxin after exposure to sunlight. GM1-ELISA is found to be superior to the conventional rabbit intestinal loop assay.

Filtering raw water with a nylon net or sari material removes 99% of the Vibrio cholerae cells attached to planktons. The filtration method is effective for V. cholerae cells of different serogroups, and environmental and clinical strains. It removes the O1 and O139 strains that cause cholera. Three folds of the filter material are necessary for effective filtration. The filter material can be freed from V. cholerae cells by exposing it to direct sunlight for two hours. The method is useful for preventing cholera epidemics in developing countries, especially during monsoons.

The viable but nonculturable (VBNC) cells of Shigella dysenteriae type 1 are potentially virulent as they possess many virulence factors. PCR amplification shows that a biologically active Shiga toxin gene and Shiga toxin are present in the VBNC cells. The VBNC cells adhere to the intestinal epithelial Henle 407 cells. The bacterial cells however, lose the capacity to invade Henle 407 cells after entering the VBNC state.

Laboratory studies show that Shigella dysenteriae type 1 is capable of surviving for a long time in laboratory microcosms in a viable but nonculturable state (VBNC). VBNC cells of S. dysenteriae transport methionine and incorporate it into protein. Amino acid transport and protein synthesis explain the existence of S. dysenteriate type 1 in the VBNC state. Standard bacteriological methods fail to culture these cells in the laboratory medium.

Huge quantity of sewage sludge influences the epibenthic bacterial population at deep-sea sewage sludge disposal site DWD-106, situated about 196km off the coast of New Jersey, and this makes the disposal site (DS) population different from the population at a reference station (RS) which is a clean site. Hybridization of DNAs obtained directly from water samples and estimation of the total and culturable bacteria at both sites reveal the variations in bacterial populations in the DS and the RS. Sewage sludge disrupts in situ the culturable portions of autochthonous bacterial population and enhanced pressure and portions of allochthonous bacterial population at the DS.

The detection of metabolic activity of viable but nonculturable cells of Helicobacter pylori in water by autoradiographic methods is discussed. False-positive reactions were avoided by the processing of the samples with three controls. Temperature was found to be a significant environmental factor regarding the viability of of H. pylori cells in water as the waterborne rout of H. pylori infection was established.

A broiler farm was investigated regarding the occurence of possible sources and transmission routes of Campylobacter jejuni to chickens. The presence of presumptive campylobacters was determined in the farm's water system by direct microscopy and fluorescent antibody methods. An intervention program was developed for the reduction of campylobacter infection. The utility of the study design was demonstrated.

Many tube-wells in Bangladesh are contaminated with zooplankton and bacteria and do not meet the drinking water standards of the World Health Organization. About 90% of the rural population of Bangladesh use these wells for their drinking water.

Fluorescent oligonucleotide eubacterial probe technique aids the enumeration of Vibrio vulnificus on membrane filters. The oligonucleotide probes are fluorescently labelled and are complementary to kingdom-level 16S rRNA sequences. Liquid buffer hybridization and direct membrane filter hybridization are employed and there is no variation in the mean number of cells detected by fluorescent oligonucleotide direct counts (FODC) and acridine orange direct counts (AODC).

Abstract Aims: The study was undertaken with the objective of understanding the virulence-associated genes of the CTX and TCP gene clusters in environmental isolates of Vibrio cholerae , an important human pathogen, isolated from the aquaculture environment. The involvement of the omp U gene in conferring bile resistance in these isolates was also evaluated. Methods and Results: The V. cholerae isolates were tested by PCR and fluorescent antibody test for O1 (Ogawa and Inaba) and O139 serotypes. All isolates were found to be non-toxigenic V. cholerae confirmed by their positive PCR reaction for tox R but negative for ctx , zot and tcp gene. The hly A gene was detected in 85% of the strains and omp U in 77%. The results on the bactericidal effect of bile salts suggest that omp U may play a role in conferring bile resistance in non-O1/non-O139 strains. Conclusion: The results of the study indicate that most environmental strains lacked the CTX and TCP gene clusters. However, most isolates had the hly A gene indicating the potential of these environmental strains to cause mild gastroenteritis. It was also observed that strains lacking omp U showed less tolerance to bile salts. Significance and Impact of the Study: Information on virulence factors of V. cholerae associated with aquaculture environment and products would be of value in risk assessment for human health. [ABSTRACT FROM AUTHOR]

Aims: Physiological responses of marine luminous bacteria, Fibrio harveyi (ATCC 14216) and F. fischeri (UM1373) to nutrient-limited normal strength (35 ppt iso-osmolarity) and low (10 ppt hypo-osmolarity) salinity conditions were determined. Methods and Results: Plate counts, direct viable counts, actively respiring cell counts, nucleoid-containing cell counts, and total counts were determined. Fibrio harveyi incubated at 22°C in nutrient-limited artificial seawater (ASW) became nonculturable after approximately 62 and 45 d in microcosms of 35 ppt and 10 ppt ASW, respectively. In contrast, F. fischeri became nonculturable at approximately 55 and 31 d in similar microcosms. Recovery of both culturability and luminescence of cells in the viable but nonculturable state was achieved by addition of nutrient broth or nutrient broth supplemented with a carbon source, including luminescence-stimulating compounds. Temperature upshift from 22°C to 30°C or 37°C did not result in recovery from nonculturability. Conclusions: The study confirms entry of F. harveyi and F. fischeri into the viable but nonculturable state under low-nutrient conditions and demonstrates nutrient-dependent resuscitation from this state. Significance and Impact of the Study: This study confirms loss of luminescence of F. harveyi and F. fischeri on entry into the viable but nonculturable state and suggests that enumeration of luminescent cells in water samples may be a rapid method to deduce the nutrient status of a water sample. [ABSTRACT FROM AUTHOR]

Examines the microbiology of pond ecosystem in Matlab, Bangladesh. Concentration of fecal coliforms in urban area ponds; Potential of the ponds for transmission of diarrheal and water-borne diseases; Degree of Escherichia coli counts in the ponds.