Combined niche and neutral effects in a microbial wastewater treatment community

Abstract

It has long been assumed that differences in the relative abundance of taxa in microbial communities reflect differences in environmental conditions. Here we show that in the economically and environmentally important microbial communities in a wastewater treatment plant, the population dynamics are consistent with neutral community assembly, where chance and random immigration play an important and predictable role in shaping the communities. Using dynamic observations, we demonstrate a straightforward calibration of a purely neutral model and a parsimonious method to incorporate environmental influence on the reproduction (or birth) rate of individual taxa. The calibrated model parameters are biologically plausible, with the population turnover and diversity in the heterotrophic community being higher than for the ammonia oxidizing bacteria (AOB) and immigration into AOB community being relatively higher. When environmental factors were incorporated more of the variance in the observations could be explained but immigration and random reproduction and deaths remained the dominant driver in determining the relative abundance of the common taxa. Consequently we suggest that neutral community models should be the foundation of any description of an open biological system. microbial community assembly

Community history affects the predictability of microbial ecosystem development

“…This view is supported by studies of replicate aquatic microcosms inoculated from different environmental sources; after 3 weeks' development, the final communities were no more similar than the starting communities, and inter-replicate variation was high (Langenheder et al, 2006). Similar results have been reported for community development in simple hypolithic communities in desert environments (Caruso et al, 2011), wastewater treatment plants (Ofiteru et al, 2010), replicate laboratory phototrophic biofilms (Roeselers et al, 2006) and laboratory-scale wetlands (Baptista et al, 2008). It is important to note, however, that variable final community composition may be associated with stable broad-scale ecosystem function (Fernández et al, 1999;Langenheder et al, 2006).…”

Effects of dispersal and selection on stochastic assembly in microbial communities

“…At high dispersal, within-group distance decreased. High dispersal rates are thought to lead to communities overwhelmed by mass effects that can alter the importance of stochasticity on microbial community composition (Ofiteru et al, 2010;Adams et al, 2014). Our model allows us to distinguish between two possible outcomes of mass effects.…”

“…For example, Ofiteru et al (2010) studied communities in wastewater treatment plants that are subject to high dispersal rates, and found that deterministic selection had little influence on microbial community composition, and was instead driven by neutral dynamics (drift and random immigration). In lakes, high immigration rates rarely overwhelm local selection (Jones and McMahon, 2009;Logue and Lindström, 2010) but can cause local communities to become more similar to the composition of communities immigrating (for example, from a stream inlet) (Lindström et al, 2006;Crump et al, 2007;Adams et al, 2014).…”

Stochastic and deterministic processes interact in the assembly of desert microbial communities on a global scale

“…T Caruso et al enhance niche-selection processes (Chase, 2007;Ofiteru et al, 2010). The important novelty is that a key component of the equation appears to be the differences in patterns of community structure for the functional groups that form the system (phototrophs and heterotrophs).…”

“…Conversely, more deterministic processes driven by species interaction and niche partitioning are predicted to produce segregation in terms of species co-occurrence or even aggregation (Chave, 2004;Dornelas et al, 2006;Chase, 2007), if niche partitioning interacts with environmental stochasticity (that is, disturbance regime) or with extreme changes in key abiotic variables such as water availability and temperature. Theories have been tested against communities with a single trophic level including microorganisms (Volkov et al, 2003(Volkov et al, , 2004Dumbrell et al, 2010;Ofiteru et al, 2010) and recently by manipulating relatively simple systems such as aquatic bacterial communities (Bell, 2010). Community assembly is highly dependent on a multitude of bottom-up and top-down trophic influences, which depend upon a biological diversity encompassing multiple phyla and realms.…”