Disconnect of microbial structure and function: enzyme activities and bacterial communities in nascent stream corridors

Abstract

A fundamental issue in microbial and general ecology is the question to what extent environmental conditions dictate the structure of communities and the linkages with functional properties of ecosystems (that is, ecosystem function). We approached this question by taking advantage of environmental gradients established in soil and sediments of small stream corridors in a recently created, early successional catchment. Specifically, we determined spatial and temporal patterns of bacterial community structure and their linkages with potential microbial enzyme activities along the hydrological flow paths of the catchment. Soil and sediments were sampled in a total of 15 sites on four occasions spread throughout a year. Denaturing gradient gel electrophoresis (DGGE) was used to characterize bacterial communities, and substrate analogs linked to fluorescent molecules served to track 10 different enzymes as specific measures of ecosystem function. Potential enzyme activities varied little among sites, despite contrasting environmental conditions, especially in terms of water availability. Temporal changes, in contrast, were pronounced and remarkably variable among the enzymes tested. This suggests much greater importance of temporal dynamics than spatial heterogeneity in affecting specific ecosystem functions. Most strikingly, bacterial community structure revealed neither temporal nor spatial patterns. The resulting disconnect between bacterial community structure and potential enzyme activities indicates high functional redundancy within microbial communities even in the physically and biologically simplified stream corridors of early successional landscapes.

Litter Supply as a Driver of Microbial Activity and Community Structure on Decomposing Leaves: a Test in Experimental Streams

“…), there were notable differences in fungal and bacterial community composition among the five successional stages. The observed disconnect between microbial community composition and metabolic activity (i.e., between community structure and function) parallels a previous field survey of sediment microbial communities (32). It suggests that microbial communities on decomposing litter are as effective at exploiting their substrate in streams simulating very early successional conditions (i.e., no litter or only wood small-reed litter present) as in streams receiving litter of higher quality and in greater amounts.…”

“…Bacterial and fungal biomass. Bacterial abundance was determined by flow cytometry after detaching bacterial cells from leaves and sediments by treating the leaves and sediments with an ultrasonic probe three times for 20 s each time (31,32). Briefly, the detached bacterial cells were separated from other particles by collecting them on top of Histodenz solution (33), staining with SYBR green I, and counting on a CyFlow space flow cytometer system (Partec, Görlitz, Germany) equipped with a 200-mW solid-state laser (light emission at 488 nm) and volumetric counting hardware (34).…”

Metatranscriptomic Evidence for Co-Occurring Top-Down and Bottom-Up Controls on Toxic Cyanobacterial Communities

“…Application of deep sequencing technologies to the study of microbial community structure and function has resulted in the observation that variability in microbial community composition does not necessarily reflect differences in the functional potential of that community (19,36,37). Here we tested this hypothesis using RNA sequencing to identify the transcriptionally active microbial community members and the function of the genes being transcribed.…”

Response of lotic microbial communities to altered water source and nutritional state in a glaciated alpine floodplain

“…Frossard et al (2012) investigated EF and BCC in a nascent stream corridor and found a pronounced uncoupling between community composition and ecosystem functioning, with EF being mainly driven by seasonality, whereas BCC showed no seasonal pattern. They concluded that bacterial communities have a high functional redundancy within these early successional landscapes.…”