Importance of rare and abundant populations for the structure and functional potential of freshwater bacterial communities

Abstract

Dilution-to-extinction cultures of freshwater bacterial communities were incubated in unamended, phenol-enriched and humic substance-enriched lake water, to study the importance of rare and abundant bacteria for community performance. Biomass yield was not strongly affected by dilution, but exploitation of humic substances and resistance to phenol were restricted to less abundant populations, demonstrating that the performance of microbial communities may depend on rare as well as on abundant species.

Fine-scale spatial patterns in bacterial community composition and function within freshwater ponds

“…We recommend future studies of bacterial community composition in freshwater document macrophyte species density using analogous sampling techniques such that the relative importance of both spatial and physicochemical environmental factors on bacterial community attributes may be compared against local variability in macrophyte community attributes. Although studies of the biogeographic distribution of various microbial phyla remain scarce, research on the biogeography of microbial functional traits remains particularly rare, with the exception of a number of experimental manipulations (Szabo et al, 2007;Rousk et al, 2010;Lindstrom and Ostman, 2011;Chaparro et al, 2012). In these naturally diverse freshwater communities, we found no evidence to suggest that the composition of a given bacterial community will predictably constrain it to performing certain biological functions.…”

“…This question is relevant because high levels of functional redundancy are proposed to exist among bacterial taxa, whereby compositionally distinct communities perform similar functions, such as the degradation or mineralisation of organic matter (Rousk et al, 2009). The relationships between microbial community composition, diversity and functional potential have been explored in several aquatic bacterial community studies (Langenheder et al, 2005;Szabo et al, 2007;Comte and del Giorgio, 2010;Peter et al, 2011). However, such studies are rarely undertaken in natural systems (but see Parnell et al, 2010;Jiang et al, 2012) and are often conducted as analyses of 'island-like' systems such as batch culture microcosms (Langenheder et al, 2005) where species richness is frequently lowered artificially (Peter et al, 2011;Ylla et al, 2013) or in poorly connected environments where the exchange of microbial taxa among microcosms is otherwise impeded.…”

Links between bacterial production, amino-acid utilization and community composition in productive lakes

“…This study indicates the existence of specific niches of individual populations within planktonic bacterial communities. If this is a general feature, one consequence might be that functional responses to environmental change may vary depending on the bacterial community composition on hand (Langenheder et al, 2006;Szabó et al, 2007). However, more experimental studies are certainly needed to verify if the rivet theory, which states that every niche is filled by a single species, applies to microbial communities (Ehrlich and Ehrlich, 1981).…”

“…This uncoupling of function from bacterial community composition is proposed to be caused by a high degree of functional redundancy within the bacterial community (Groffman and Bohlen, 1999). However, recent laboratory experiments suggest that the composition of bacterial communities and the presence of specific populations can affect general community functions (for example, ability to degrade organic matter: Eiler et al, 2003;Bell et al, 2005;Szabó et al, 2007).…”

Function-specific response to depletion of microbial diversity

“…In freshwater ecosystems, Langenheder et al (2005) observed that specific enzyme activities varied in differently composed bacterial communities, whereas more universal bacterial functions such as biomass accrual and respiration remained similar because of the high number of similarly performing species. Recently, Szabo et al (2007) applied a dilution-to-extinction approach to an aquatic bacterial community. Although biomass yield was only slightly affected by the loss of rare species in this experiment, those rare species were crucial for community functioning after an environmental perturbation.…”