Contrasting dynamics in activity and community composition of free-living and particle-associated bacteria in spring

Abstract

Phytoplankton development affects the community structure and dynamics of freshwater bacteria by changing the availability of nutrients, algal exudates and biological surfaces. To elucidate these effects of phytoplankton development in spring in oligotrophic Lake Stechlin (Germany), we measured limnological and biological parameters, including the bacterial community composition (BCC), at the depth of the highest chlorophyll a concentration. To increase the resolution of BCC measurements, we separated particle-associated (PA) and free-living (FL) bacteria using serial filtration through 5.0 and 0.2 µm pore size filters, respectively. The BCC of ultramicrobacteria was also determined by collecting the 0.2 µm filtrate on 0.1 µm filters. Changes in the community composition of Bacteria and particularly of Actinobacteria, one of the most important bacterial groups in temperate freshwater habitats, were studied via DGGE analysis of PCR-amplified 16S rRNA gene fragments. Patterns in BCC dynamics of FL Bacteria and Actinobacteria remained fairly constant throughout the study period, while patterns of PA Bacteria were more variable over time. At the breakdown of the diatom spring bloom, bacterial production and abundance sharply increased, indicating a close coupling between heterotrophic bacteria and algal detritus. The succession in BCC revealed life-style dependent patterns related to specific environmental variables. Our results indicate independent dynamics of PA and FL Bacteria as well as Actinobacteria during succession of phytoplankton spring blooms. These differences in bacterial lifestyle can only be resolved when the PA and FL fractions of microorganisms are separated.KEY WORDS: Bacterial community composition (BCC) · Spring bloom · Bacteria-phytoplankton coupling · Pollen · Free-living and particle-associated bacteria · Lake Stechlin Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 66: [169][170][171][172][173][174][175][176][177][178][179][180][181] 2012 More recently, it has been shown that phytoplankton bloom developments have the potential to affect bacterial community composition (BCC). For example, Eiler & Bertilsson (2004) reported that a cyano bacterial spring bloom had consequences for different groups of bacteria at the same time. In addition, other studies have investigated interactions between specific phytoplankton and heterotrophic bacteria, i.e. the occurrence of specific bacterial phylotypes associated to specific algal species. Many of these studies, however, have been performed in mar ine waters or in laboratory studies (e.g. Grossart et al. 2005, Rink et al. 2011, Šimek et al. 2011, whereas in freshwater ecosystems, only a few studies have investigated these interactions in situ or in field experiments with a high temporal resolution (Salcher et al. 2010, Eckert et al. 2012. Hence, there is a great need for more intensive studies of the relationship between phytoplankton blooms and shortterm changes of BCC in freshwater ecosystems...

Dynamics of size-fractionated bacterial communities during the coastal dispersal of treated municipal effluents

“…Meanwhile, high alpha 16S copy number per ml seawater and beta diversities in the PA community also indicated that the dynamics of their populations are higher and more complex than that of FL community. Reports have suggested that PA bacteria have higher growth rates and possess multiple enzymatic activities (Crump et al 1998;Riemann and Winding 2001) as well as higher community dynamics during seasonal variations (Rösel and Grossart 2012). However, our results indicate greater dynamics within a short distance of several kilometers.…”

River bacterioplankton community responses to a high inflow event

“…While successional patterns among bacterial communities associated with algal blooms and nutrient upwellings have been widely reported in marine and lake environments (Kritzberg et al 2004, Rösel & Grossart 2012, Teeling et al 2012, investigations of large freshwater inflow events that describe successional changes in bacterial communities in lotic systems, particularly of the magnitude we observed in the Hunter River, are rarer. However, extrinsic, climaterelated factors have previously been identified as the best predictors of seasonal microbial community patterns, whereby in a 3 year temporal study of 2 independent temperate rivers temperature and flow rates were found to be key drivers of bacterial diversity (Crump & Hobbie 2005).…”

“…The 5 µm pore size membrane filter was employed to capture bacteria attached to suspended particles (Nair & Simidu 1987, Gram et al 2010, Tang et al 2011, Rösel & Grossart 2012, allowing discrimination from the free-living bacterial community captured on 0.2 µm membrane filters. In the absence of a universally agreed filter size standard appropriate for discriminating attached and free-living bacterial communities, we conservatively selected a 5 µm membrane pore size which will allow for the capture of medium to large particles colonised by bacteria (Azam & Hodson 1977, Acinas et al 1999, Riemann & Winding 2001.…”

Comparative single-cell genomics reveals potential ecological niches for the freshwater acI Actinobacteria lineage

“…They are also abundant in some marine estuaries (Glockner et al, 2000). Moreover, as a lineage, acI shows a smaller seasonal abundance variation when compared to other major freshwater bacteria (Allgaier and Grossart, 2006;Salcher et al, 2010;Newton et al, 2011;Eckert et al, 2012;Rö sel and Grossart, 2012). Due to their high abundance and high metabolic activity (Warnecke et al, 2005;Allgaier and Grossart, 2006;Salcher et al, 2010), the acI bacteria likely have a critical role in carbon and other nutrient cycling in freshwater systems, yet their genomic features remain elusive.…”