Journal ArticleDOI
Sunlight and the survival of enteric bacteria in natural waters
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TLDR
Direct viable counts and culturable counts decreased at a similar rate in seawater and in freshwater in visible light and the presence of humic acids significantly reduced loss of culturability but only in low salinity conditions.Abstract:
Escherichia coli and some salmonellas were exposed in seawater and freshwater to natural sunlight, visible light of comparable intensity, and light containing a similar proportion of u.v. as natural sunlight but of a much lower intensity. Direct viable bacterial counts and culturable counts on selective and non-selective media were made at intervals. The rate of decrease in numbers of culturable bacteria was significantly faster in seawater than in freshwater when exposed to natural sunlight. No significant difference was found between the rates of decrease in numbers of culturable bacteria in seawater and those in freshwater when bacteria were exposed to light with a small u.v. component of similar intensity. The effect of salinity no loss of culturability is, therefore, more significant in the presence of u.v. radiation. Direct counts by the acridine orange direct viable count method decreased much more slowly than the culturable counts in seawater but comparably with culturable counts in freshwater in natural sunlight. Direct viable counts and culturable counts decreased at a similar rate in seawater and in freshwater in visible light. This may signify the evolution of enteric bacteria towards a viable but non-culturable form in seawater when exposed to natural sunlight. The presence of humic acids significantly reduced loss of culturability but only in low salinity conditions. Salinity appears to be an important factor influencing culturability in bacteria exposed to sunlight.read more
Citations
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Influence of pH, Oxygen, and Humic Substances on Ability of Sunlight To Damage Fecal Coliforms in Waste Stabilization Pond Water
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References
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TL;DR: Polycarbonate Nuclepore filters are better than cellulose filters for the direct counting of bacteria because they have uniform pore size and a flat surface that retains all of the bacteria on top of the filter.
Journal ArticleDOI
Use of nuclepore filters for counting bacteria by fluorescence microscopy.
TL;DR: Polycarbonate Nuclepore filters are better than cellulose filters for the direct counting of bacteria because they have uniform pore size and a flat surface that retains all of the bacteria on top of the filter.
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Survival and viability of nonculturableEscherichia coli andVibrio cholerae in the estuarine and marine environment.
TL;DR: It was shown that both E. coli and V. cholerae undergo a “nonrecoverable” stage of existence, but remain viable, and the “die-off” or “decay” concept may not be completely valid.
Journal ArticleDOI
A tentative direct microscopic method for counting living marine bacteria
TL;DR: Yeast extract and nalidixic acid were added to seawater samples and the samples were incubated for 6 h at 20 degrees C in the dark and the number of cells obtained is proposed as a direct cound of viable bacterial cells (DVC).
Journal ArticleDOI
Viable but nonrecoverable stage of Salmonella enteritidis in aquatic systems.
TL;DR: Microscopic techniques for direct viable counting indicated that viability is maintained for as long as 60 days after depletion of nutrients, although longer periods of "dormancy" appear to require conditions other than simple nutrient addition for resumption of cell growth and division.