Characterization of Bacterial Communities Associated with Organic Aggregates in a Large, Shallow, Eutrophic Freshwater Lake (Lake Taihu, China)

Abstract

Although organic-aggregate-associated bacteria play a pivotal role in microbial food webs and in the cycling of major elements, their community composition and diversity have not been extensively studied, especially in shallow freshwater systems. This study is among the first to explore intra-lake horizontal heterogeneity of organic-aggregate-associated bacterial community composition (OABC) in the large, shallow, and eutrophic Lake Taihu. During November 2006, samples were collected at four locations representing different trophic states and food web structures. Regional variability of OABC and diversity were studied by amplified ribosomal DNA restriction analysis and comparative analysis of four large 16S ribosomal RNA clone libraries. Our results demonstrate that OABC were numerically dominated by members of the beta-proteobacteria (19.2-38.6%), Bacteroidetes (3.6-20.0%), and alpha-proteobacteria (11.5-19.2%) groups. The dominance of the Bacteroidetes group was related to algae-based aggregates. Horizontal heterogeneity of OABC exists within habitats, suggesting that the trophic state of the water and the physicochemical properties of organic aggregates (OA) play a key role. Diverse bacterial communities found on OA were substantially different from free-living ones. Comparative statistical analyses of the habitats of OA-associated bacteria highlight the potential ecological importance of the exchange between OABC and the surrounding planktonic community. Lastly, we found at least 45% of sequences closely related to ones previously found in soils, sludge, sediments, and other habitats. This demonstrates that microorganisms from terrestrial and sediment habitats are an important component of OA.

Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

“…The elevated phylogenetic diversity may be attributed to the downward metabolite fluxes that favor niche diversity through the maintenance of various nutrient sources. Furthermore, visual and microscopy observations showed increased levels of suspended particulate and floc matter in the lakes' monimolimnia that may contribute to increased phylogenetic divergence through habitat diversification (Tang et al, 2009). Another hypothesis may be that low oxygen environments have the capacity to maintain a higher variety of energetic pathways than oxygen-rich environments, leading to retention of higher ecological diversity coupled with lowered interspecific competition (Humayoun et al, 2003).…”

Bacterial composition and spatiotemporal variation in sediments of Jiaozhou Bay, China

“…Previous findings have highlighted the importance of Bacteroidetes, formerly known as the Cytophaga-Flavobacteria-Bacteroidetes phylum, on submerged surfaces, suspended particles, and during phytoplankton blooms (Eiler and Bertilsson 2004). Bacteroidetes has been shown especially abundant in samples derived from Cyanobacterial aggregates (Tang et al 2009). In this study, the higher percentage of Bacteroidetes and the only observation of Cyanobacterial in B2 and D7 stations might be reasonable.…”

The Contribution of Attached Bacteria to Microcystis Bloom: Evidence From Field Investigation and Microcosm Experiment

“…The abundance of attached bacteria was determined by epifluorescence microscopy after DAPI (4 ' ,6-diamidino-2-phenylindole) staining (Porter and Feig, 1980) as described previously (Tang et al, 2009). Total nucleic acids from the particle-attached bacteria on the filters were extracted and purified using proteinase K, sodium dodecyl sulfate concomitant with chloroform extraction and isopropanol precipitation.…”

“…Previous study has shown that the abundance of a Bacteroidetes species capable of lysing cyanobacteria cells was tightly coupled to the development of a bloom event (Rashidan and Bird, 2001). Futhermore, Tang et al (2009) also pointed out that members of the Bacteroidetes formed a substantial component of the bacterial communities associated with algae-based organic aggregates in Lake Taihu. Second, Eiler et al (2006) and Maruyama et al (2003) suggested that both Alphaproteobacteria and Betaproteobacteria were dominant in the mucilage of Cyanobacteria during bloom events, and several members of the Proteobacteria can attach to Cyanobacteria and cause cell lyses and death of some cyanobacterial species (Eiler et al, 2006;Maruyama et al, 2003).…”

“…The attached bacteria are important in the trophic dynamics of aquatic food webs and in the remineralization of dissolved and particulate organic matter (Tang et al, 2009), and understanding the response of the particle-attached bacterial community composition (PABCC) to decomposition of Microcystis blooms is very important for a better understanding of the metabolic processes in eutrophic aquatic ecosystems. Meanwhile, the interactions of algae with bacteria are diverse and complex, and have a key impact on the occurrence or duration of the algae bloom (Grossart et al, 2005(Grossart et al, , 2006Maruyama et al, 2003).…”