Dynamics of organic‐aggregate‐associated bacterial communities and related environmental factors in Lake Taihu, a large eutrophic shallow lake in China

Abstract

To investigate the spatial and temporal variations of organic-aggregate-associated bacterial communities (OABC), a 25-month observation was conducted at two contrasting sites (Meiliang Bay and the lake center) in Lake Taihu, China. The structures and dynamics of the OABC were determined by partially sequencing cloned 16S rRNA genes, and by terminal restriction fragment length polymorphism (T-RFLP) analysis. One hundred ninety-two T-RFs were detected from the two sites, but only 17 T-RFs were dominant, suggesting that specific microbial populations were adapted to the unique niche provided by the organic aggregates (OA). Phylogenetically, Beta-and Alphaproteobacteria constituted the numerically most important heterotrophic bacterial group. Analysis of similarity revealed significant intra-lake heterogeneity, and significant temporal shifts in OABC. Canonical correspondence analysis demonstrated that site-specific differences in sediment resuspension and nutrient enrichment (namely nitrate and total phosphorus) were the forces driving the intra-lake differences in OABC. Water temperature and dissolved oxygen were related to the seasonal dynamics of OABC. The annual succession in OABC was significant in Meiliang Bay, but not in the lake center. In addition, nearly 35% of the bacterial sequences from OA related to bacteria from soils, activated sludge, sediments, and other habitats, indicating the potential importance of allochthonous bacteria in OABC.

Spatiotemporal dynamics of bacterial community composition in large shallow eutrophic Lake Taihu: High overlap between free‐living and particle‐attached assemblages

“…In support of this assumption, Polynucleobacter (Pnec), well known as single, freely suspended cells, also found to be abundant in PA fraction in the present study ( Fig. 4) and in a previously study on organic-aggregates (Tang et al 2010). Hence, FL and PA bacteria, as suggested by Riemann and Winding (2001), might be considered interacting entities that may move from a FL lifestyle to a PA lifestyle and vice versa.…”

“…Seasonal succession in BCC have been demonstrated by previous studies in lakes with different trophic levels (Van Der Gucht et al 2001;Zwisler et al 2003;P erez and Sommaruga 2011;Eiler et al 2012). In Lake Taihu, seasonal variation in planktonic bacterial communities (Li et al 2015b) and in organic aggregates-attached bacterial communities (Tang et al 2010) were reported recently. In addition, phytoplankton community (Niu et al 2011), cyanobacterial bloom, and nutrients (Tian et al 2009) were found to be the main factors that shaped plankton and total bacterial community composition, respectively.…”

“…Polymerase chain reaction (PCR) was performed with a Cy5-labeled forward bacterial primer 8F (5 0 -AGAGTTT-GATCMTGGCTCAG-3 0 ) and 1492R (5 0 -GGTTACCTTGTTAC-GACTT-3 0 ) (Newton et al 2006). Amplification was carried out using a touchdown program (Tang et al 2010). The quality and quantity of the amplified DNA fragment was checked by agarose gel electrophoresis and by by using a NanoDrop ND-1000 UV/Vis spectral photometer.…”

“…Enzymatic digestions were performed simultaneously with the two restriction enzymes HaeIII and MvnI (Fermentas) and the terminal restriction fragments (T-RFs) were separated on a Beckman Coulter CEQ TM 8000 capillary electrophoretic sequencer, as described previously (Tang et al 2010). T-RF sizes between 60 bp and 640 bp, with peak area of > 100 fluorescence units, were binned and standardized for subsequent analysis (Boucher et al 2006).…”

“…Moreover, the seasonal and spatial dynamics of FL and PA bacteria and environmental factors driving this relationship are poorly understood. Due to strong hydrodynamic stress and eutrophication, abundant organic particles/microaggregates (5-500 lm) dominate this shallow and turbid system (Tang et al 2009(Tang et al , 2010, which likely influence the dynamics of FL and PA bacterial communities.…”