Project description:Peatlands of the Lehstenbach catchment (Germany) house so far unidentified microorganisms with phylogenetically novel variants of the dissimilatory (bi)sulfite reductase genes dsrAB. These genes are characteristic for microorganisms that reduce sulfate, sulfite, or some organosulfonates for energy conservation, but can also be present in anaerobic syntrophs. However, nothing is currently known regarding the abundance, community dynamics, and biogeography of these dsrAB-carrying microorganisms in peatlands. To tackle these issues, soils from a Lehstenbach catchment site (Schlöppnerbrunnen II fen) from different depths were sampled at three time points over a six-year period to analyze the diversity and distribution of dsrAB-containing microorganisms by a newly developed functional gene microarray and quantitative PCR assays. Members of novel, uncultivated dsrAB lineages (approximately representing species-level groups) (i) dominated a temporally stable but spatially structured dsrAB community and (ii) represented ‘core’ members (up to 1-1.7% relative abundance) of the autochthonous microbial community in this fen. In addition, denaturing gradient gel electrophoresis (DGGE)- and clone library-based comparison of the dsrAB diversity in soils from a wet meadow, three bogs, and five fens of various geographic locations (distance ~1-400 km), identified one Syntrophobacter-related and nine novel dsrAB lineages to be widespread in low-sulfate peatlands. Signatures of biogeography in dsrB-DGGE data were not correlated with geographic distance but could largely be explained by soil pH and wetland type, implying that distribution of dsrAB-carrying microorganisms in wetlands on the scale of a few hundred kilometers is not limited by dispersal but determined by contemporary environmental conditions. 36 dsrAB clones for chip evaluation, 33 hybridizations of labeled dsrAB RNA from environmental peatsoil samples
Project description:Colorectal cancer (CRC) is one of the most common cancer worldwide. Initiation and progression of CRC involve complex interactions among genetic, epigenetic and environmental factors. Given that hereditary and familial CRC only accounts for 2% to 5% of cases, environmental factors are the key triggers of CRC. Emerging evidence has indicated that gut microbes are an important environmental factor promoting CRC development. Gut dysbiosis has been shown to promote colorectal carcinogenesis in mice. Several individual bacterial species, such as the enterotoxigenic Bacteroides fragilis (ETBF), Fusobacterium nucleatum and Peptostreptococcus anaerobius, could exert carcinogenic effects by inducing direct DNA damage, oxidative damage and activating oncogenic signaling pathways. Recent studies have shown that the appendix plays an important role in maintaining homeostasis and biodiversity of gut microbiome by providing an ideal ecological niche for commensal bacteria and production of immunoglobulin A. Considering the key role of microorganisms in gastrointestinal pathophysiology, absence of appendix may result in disruption of microbiome homeostasis, which could potentially influence the risk of developing CRC. In terms of epidemiological evidence, the association of appendectomy with the risk of CRC development has been controversial, and to date no consensus has been attained. Although gut microorganisms could be a crucial pivot between appendectomy and risk of subsequent CRC development, the direct contribution of appendectomy and the underlying mechanisms are still largely unexplored. In this study, we aim to study
1. the association between appendectomy and colorectal cancer, and
2. the role of appendectomy in CRC risk through causing gut microbial dysbiosis.