Project description:In hypersaline brines, biodegradation of recalcitrant plant polymers can be inhibited by salt-induced microbial stress and/or caused by inadequate metabolic capabilities of extremely halophilic microbes. Therefore, woody materials can be well-preserved even in NaCl brines that are less biologically hostile than most other brines. Here, we considered whether the nanohaloarchaea, that live alongside (the related) haloarchaea, ever partake in the degradation of xylan, a major hemicellulose component of wood. Samples were taken from natural evaporitic brines and anthropogenic solar salterns located in various parts of Europe and Asia. We recently demonstrated that nanohaloarchaeon Ca. Nanohalobium constans lives as an ectosymbiont associated with the chitinolytic haloarchaeon Halomicrobium. Here, we describe an extremely halophilic xylan-degrading consortium with three members, where nanohaloarchaea act as ectosymbionts of Haloferax lucertensis, which in turn acts as a scavenger of xylan-degradation products, produced by a primary xylan hydrolytic Halorhabdus species. The two corresponding binary associations of nanohaloarchaea, Candidatus Nanohalococcus occultus SVXNc and Candidatus Nanohalovita haloferacivicina BNXNv and their hosts were obtained, stably cultivated and characterized. In contrast to the previously described association of chitinolytic haloarchaeon Halomicrobium and its amylolytic symbiont Ca. Nanohalobium, the host haloarchaea within the xylan-degrading consortium could metabolize α-glucans (glycogen and starch), and, thus, obtained no obvious trophic benefit from ectosymbionts. The current study has broadened the range of culturable ectosymbiontic nanohaloarchaea and demonstrates that they are an important ecophysiological component of polysaccharide-degrading halophilic microbial communities and can be readily isolated in binary co-cultures by using the appropriate enrichment strategy.
Project description:Waste decomposition in landfills is a complex and microbe-mediated process. Understanding the microbial community composition and structure is critical for accelerating decomposition and reducing adverse impact on the environment. Here, we examined the microbial communities along with landfill depth and age (LDA) in a sanitary landfill in Beijing, China using 16s rRNA Illumina sequencing and GeoChip 4.6. We found that Clostridiales and Methanofollis were the predominant bacteria and archaea in the present landfill, respectively. Interestingly, in contrast with the decreasing trend of microbial diversity in soil, both phylogenetic and functional diversities were higher in deeper and older refuse in the landfill. Phylogenetic compositions were obviously different in the refuse with the same LDA and such difference is mainly attributed to the heterogeneity of refuse instead of random process. Nevertheless, functional structures were similar within the same LDA, indicating that microbial community assembly in the landfill may be better reflected by functional genes rather than phylogenetic identity. Mantel test and canonical correspondence analysis suggested that environmental variables had significant impacts on both phylogenetic composition and functional structure. Higher stress genes, genes for degrading toxic substances and endemic genes in deeper and older refuse indicated that they were needed for the microorganisms to survive in the more severe environments. This study suggests that landfills are a repository of stress-resistant and contaminant-degrading microorganisms, which can be used for accelerating landfill stabilization and enhancing in situ degradation. Fifteen refuse samples with five landfill depths and ages (6m/2a, 12m/4a, 18m/6a, 24m/8a and 30m/10a) were collected from a sanitary landfill in Beijing, China. Three replicates in every landfill depth and age