External control of bacterial community structure in lakes

Abstract

Abstract-We investigated the importance of a regional factor for bacterial communities in lakes. External factors dominated the control of community structures in lakes with retention times up to 200 d, most likely as a result of bacterial import. Because these lakes are numerous in the boreal zone, regional processes can be of great importance for bacterial communities in general. Consequently, we propose that lakes function more like flow through systems, as opposed to the classical ''lake as microcosm '' concept. During the last decade, our knowledge about the diversity of bacteria in nature has increased enormously; however, little is understood about which factors are shaping bacterial communities (DeLong and Pace 2001;Zwart et al. 2002). Central to understanding patterns in community structure is knowledge about the relative importance of local versus regional processes (Chase 2003;Cottenie and De Meester 2004). It can be assumed that the degree of isolation, and thereby the rate of exchange of cells and genes between communities, should have consequences for which forces shape local microbial communities (Curtis and Sloan 2004;Papke and Ward 2004). In nature, a gradient in isolation of communities should exist from endosymbionts to those exhibiting a cosmopolitan distribution (Papke and Ward 2004).Early on, lakes and their ecosystems were assigned as isolated units in the ''lake as microcosm '' concept (Forbes 1887). This view of the lake was later revised, for instance, because of the discovery of the importance of allochthonous carbon for lake ecosystem function (Hessen and Tranvik 1998;Pace et al. 2004). Thus, lakes today are more often ecologically regarded as a part of a larger unit, i.e., the drainage basin (Soranno et al. 1999). Still, efforts in lake microbial ecology and diversity have largely focused on within-lake selective forces, rather than external influences on community structure and diversity, although it has been shown that lake (Crump et al. 2003;Masin et al. 2003; Lindström and Bergström 2004) and estuarine (Crump et al. 2004) community compositions can be largely influenced by inflowing bacteria. It can be assumed that the degree of isolation a lake bacterioplankton community experiences, and thereby the degree of influence by inflowing bacteria on local community structure, depends on the hydrological retention time of the lakes. Therefore, we used a range of lakes of different hydrological retention times to determine the magnitude of external influence on bacterial community structure in lakes. Our hypothesis was that lakes with short hydrological retention time should have bacterial communities that are more similar to those of the inflowing water than lakes with longer hydrological retention times because of the larger amount of imported bacteria to the former type of lake. Twelve relatively unproductive Swedish lakes with different hydrological retention times were studied (Table 1). We used denaturing gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified...

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

“…Previous studies have shown that the bacterial community composition strongly depends on the physicochemical conditions of the environment (Lindströ m, 2000; Yannarell and Triplett, 2004;Lindströ m et al, 2006b), interspecific interactions (Pernthaler et al, 2004;Schwalbach et al, 2005;Kent et al, 2006), available resources (Pinhassi et al, 1999;van Hannen et al, 1999;Crump et al, 2003;Newton et al, 2006) and dispersal (Curtis and Sloan, 2004;Langenheder et al, 2006;Lindströ m et al, 2006a). However, in none of these studies were there any attempts to predict bacterial distribution patterns from nonbacterial parameters.…”

Temporal variation of β-diversity and assembly mechanisms in a bacterial metacommunity

“…It has been shown that bacterial communities can be assembled by species sorting (Beisner et al, 2006;Van der Gucht et al, 2007;Logue and Lindströ m, 2010) as well as mass effects (Lindströ m et al, 2006;Crump et al, 2007). It has also been demonstrated that frequency and abundance distributions in bacterial communities are, and often to a considerable extend, consistent with the neutral model (Sloan et al, 2006;Woodcock et al, 2007;Drakare and Liess, 2010;Ö stman et al, 2010).…”

Effects of dispersal and selection on stochastic assembly in microbial communities

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