Community composition and activity of prokaryotes associated to detrital particles in two contrasting lake ecosystems

Abstract

The composition, distribution and extracellular enzyme activities of bacteria attached to small (2-50 microm in size) transparent exopolymer and Coomassie-stained proteinaceous particles (TEP and CSP) were examined in two lakes of different trophic status located in the Massif Central of France. TEP concentrations (10(4)-10(6) particle per L) were significantly higher in the more productive lake and were significantly related to chlorophyll a concentrations. The majority of TEP and CSP were colonized by bacteria that constituted 2.6% and 7.4% of the total 4',6-diamidino-2-phenylindole-stained bacteria in lakes Pavin and Aydat, respectively. In both lakes, the composition of particle-associated bacteria was different from that of free-living bacteria, the Betaproteobacteria and Bacteroidetes (i.e. former Cytophaga-Flavobacteria group) being the dominant groups on particles. We also found that 2-5 microm TEP were more colonized than 2-5 microm CSP in the two lakes, and that TEP colonization was higher in the less productive lake. Measurements of Leucine aminopeptidase and alpha-glucosidase activities in fractionated lake water (0.2-1.2, 1.2-5 and >5 microm fractions) indicated that proteolytic activity was always higher and that particle-associated bacteria have higher enzymatic activities than free-living bacteria. The glycolytic activities in the 1.2-5 and >5 microm fractions were related to the abundance of TEP. We conclude that small freshwater detrital organic particles constitute microhabitats with high bacterial activities in pelagic environments and, undoubtedly, present significant ecological implications for the prokaryotic community structure and function in aquatic ecosystems.

Glycolytic activities in size-fractionated water samples: emphasis on rhamnosidase, arabinosidase and fucosidase activities

“…However, based on the results, it was observed that arabinosidase, fucosidase and rhamnosidase presented lower activity in the attached form than in the free-living form, and free enzymes revealed an important proportion (38-55 %) compared to the former (Table 2). Glucosidases (α-and β-) reached values comparable to other freshwater studies (Worm et al, 2001;Lemarchand et al, 2006). Working with fractionated samples Richardot et al (1999) registered the highest enzymatic activities for glucosidases (α-and β-) in the attached fraction (2-100 µm).…”

A Guide to the Natural History of Freshwater Lake Bacteria

“…In lake epilimnia, the Bacteroidetes may comprise a large proportion of particle-associated bacteria (120,143) and seem to play a particularly important role in the degradation of complex biopolymers (115). In agreement with this inferred niche, several studies using PCR-based clone libraries and/or quantitative PCR (qPCR) have documented an increase in the propen- sity of the Bacteroidetes to occur during periods or at sites characterized by high external dissolved organic carbon (DOC) loading or alga-derived DOC inputs (48,49,116,237).…”

“…Members of the Betaproteobacteria are often cocultured with algae such as Cryptomonas sp. (156), are associated with the Cyanobacteria (52), and are often particle associated (120,191,227).…”

Indirect effect of environmental factors on interactions between microbial and classical food webs in freshwater ecosystems

“…Some studies have reported that more than half of the bacterioplankton in aquatic ecosystems can be attached to detrital particles (Simon, 1987;Riemann et al, 2000), and the abundance of those particles influences the density, biomass and production of the attached bacteria (Kepkay, 1994;Carrias et al, 2002). Both cladocerans and copepods can consume particles, including the attached bacteria (Shimeta, 1993;Lemarchand et al, 2006), and detrital particles with attached bacteria can often be more quantitatively important food for zooplankton than algae (Gons et al, 1992). Thus, such particles could be an important non-algal food source for crustaceans; all the more that according to Marzolf (1990), phytoplankton alone do not satisfy all of the nutritional requirements of zooplankton.…”