Effect of Trophic Status on the Culturability and Activity of Bacteria from a Range of Lakes in the English Lake District

Abstract

The bacterioplankton from a number of lakes that differed in nutrient status in the English Lake District was examined with a number of techniques for enumeration and activity assessment. Natural water samples showed a clear correlation between total counts and trophic status. Esterase activity measurements with Chemchrome B were able to distinguish high-and low-nutrient-status lakes, whereas tetrazolium salt (5-cyano-2,3-ditoyltetrazolium chloride) reduction, the direct viable count-cell elongation assay, and culturability measurements could not. Tetrazolium salt reduction and esterase activity measurements labeled a significant number of cells from water of all nutrient levels, whereas the direct viable count-cell elongation method was of use only in oligotrophic waters. Size fractionation of samples showed that the culturable cells were retained by the larger filters, especially in nutrient-rich waters. Esterase activity measurements also favored the larger cells. The differences observed between assays using water that differed in trophic status raise questions about the use of these tests as a definitive measure of viability.

Increased Diversity of Predacious Bdellovibrio-Like Organisms (BLOs) as a Function of Eutrophication in Kumaon Lakes of India

“…Eutrophication impacts are known to last for decades and include a variety of changes to the ecosystem such as increased bacterial numbers and activities [3, 8, 14, 20, 29, 40]. Taken together, these results are indicative that nutrient enrichments result in increased diversity of specific bacterial processes such as predation by BLOs, which potentially impact carbon cycling within the aquatic microbial food web processes.…”

“…Given that the trophic status of lake ecosystems have significant influences on total bacterial communities [14, 20, 29, 40], we measured predator–prey numbers in lakes with variable trophic status. Estimates of the numbers of total bacteria and BLOs in water samples collected from the four lakes were determined by the 3-tube MPN method.…”

“…Previous reports have shown a direct correlation between the trophic status of the environment to bacterial numbers and even activities [8, 14, 20, 29, 40]. In another study, total bacterial biomass was found to increase 2-fold in hypertrophic vs. oligotrophic streams [3].…”

“…Therefore, in all likelihood, BLO environmental niche preferences are not merely a function of the physicochemical conditions but more importantly, likely upon the availability of a suite of susceptible prey bacteria [7, 26]. Since nutrient loading generally results in enrichment of bacterial species, abundance and even diversity of total assemblages [14, 20, 29, 40], we hypothesized that nutrient-rich systems should possess an increased diversity of obligate bacterial predators, triggered by the availability of both, higher numbers and diversity of native prey micro-biota. Results presented here from lakes with variable trophic status validate our hypothesis.…”

Diversity and distribution of pigmented heterotrophic bacteria in marine environments

“…Previous reports have also revealed that the culturability of bacteria varies with peptone concentration in the medium and source of samples, whereas pigmented colonies are easier to grow on low‐peptone media (Buck, 1974). Investigation of lakes showed that more CFU can be obtained in nutrient‐rich waters than in nutrient‐poor waters (Porter et al , 2004).…”