Survival of allochthonous bacteria in aquatic systems: a biological approach

Abstract

The survival of allochthonous bacteria in aquatic systems is affected by biotic and abiotic environmental factors. Grazing by protozoa is one of the main biological processes that control allochthonous bacterial density. Its extent depends on the concentration of bacteria and the digestion capacity of the grazer. The physiological state of bacteria is affected by multiple physicochemical stresses, to which they respond by entering a dormant, viable but non‐culturable state. Starved bacteria show a tendency to shrink, and a generally enhanced resistance to heat, oxidative and osmotic shock is observed. Nutrient scarcity, temperature, osmotic stress and visible light seem to be the abiotic factors that most negatively influence survival. The negative effect of light upon the culturability of enterobacteria in aquatic systems has long been recognized. In relation to the influence of plasmids on bacterial survival, heterogeneous and contradictory results have been reported. Some authors reported that plasmid‐bearing strains can survive as well as their wild‐type counterparts or even better, whereas in other reports the effects of various plasmids on the survival of their hosts were very variable. Plasmid transfer could be affected by the physiological status of donors and recipients during survival. Flow cytometry is a recent approach with great potential, especially for assessing the heterogeneity of cell size, metabolic state and molecular content in the population.

Bacterial diversity in rice-field water in Rio Grande do Sul

“…Bacterial survival in water ecosystems can be defined as the cellular state that results from their presence in a hostile environment where microbial predation, nutrients' insufficiency, inadequate physical conditions, occasional toxins and naturally or anthropogenic produced biocides coexist or interact (2).…”

Use of multiparameter analysis for Vibrio alginolyticus viable but nonculturable state determination

“…In this state, the cells are viable but not culturable on routine microbiological media, thus they are not detectable by current microbiological methods, posing a public health threat. The ability to enter a VBNC state is a strategy commonly employed by some microorganisms to survive under environmental conditions nonoptimal for growth and propagation (4)(5)(6)(7). From the VBNC state, it is possible to re-enter into the culturable state.…”

Distribution and persistence of fecal bacterial populations in liquid and dewatered sludge from a biological treatment plant

“…The ecology of microbial populations in water and wastewater environments has been extensively studied (Barcina et al, 1997;Scott et al, 2002;. Commonly, the reduction of fecal indicator bacteria is attributed to biotic and non-biotic factors such as predation, nutrient scarcity, temperature, osmotic stress and visible light.…”