富硫沉积生境中微生物群落的垂直分布特征

为探讨富硫沉积环境中特定微生物类群对硫循环的贡献,人工建立富含硫酸盐的模型,对模型中各种环境化学参数进行监测,并采用不依赖于培养的微生物分子生态学技术对微生物群落垂向分布特征进行解析.结果表明,以沉积物-水界面为分界线,上层水相为好氧环境,硫化物浓度较底;而沉积物相中硫化物浓度较高,为厌氧生境.微生物群落分布与环境特征具有很好的吻合性,沉积物相中微生物群落相似性较高,多样性相对较低,而水相中微生物多样性较高,且与沉积物中微生物分离距离较大.在水-沉积物垂向剖面中,细菌域中的变形菌门(Protebacteria)(丰度为7.6%~32.8%)、绿弯菌门(Chloroflexi)(13.6%~22.3%)以及古菌域中的广古菌门(Euryarchaeota)(19.3%~29.2%)是微生物群落中的绝对优势类群.在该生境中,存在微生物主导的硫循环过程,在厌氧沉积物表层,δ变形菌纲(Deltaprotebacteria)中的硫酸盐还原细菌还原硫酸盐产生硫化物,同时降解有机质.硫化物向上层扩散时,被Thiobacillus、Acidithiobacillus和Halothiobacillus等属的硫氧化微生物氧化为单质硫,并进一步氧化为硫酸盐,在硫循环过程中有机质被逐渐降解.特定微生物种群的富集需要在不同的环境因素,多种微生物共同参与硫循环过程,完成有机质降解.

Vertical distribution of microbial community along the sulfide gradient in a sulfide-rich marine sediment model

To explore the contribution of some characteristic microbial populations to the sulfur cycle in the sulfate-rich environment, an artificial sulfate-rich sediment model was set up. Environmental chemical parameters in the model were monitored and the vertical distribution of microbial community was investigated by cultured-independent molecular microbial ecological techniques. The water phase above the sediment-water interface was aerobic environment and contained low sulfide; while the sediment below the interface contained high sulfide and belonged to the typical anaerobic environment. The distribution of microbial community accorded well with the environment. The microbial communities in the sediment were more similar and had low diversity, but the diversity of microbial communities in water phase was high and they diverged distance far from the sediment. In the sediment-water environment, the bacterial phyla Protebacteria (abundance is 7.6%~32.8%) and Chloroflexi (13.6%~22.3%), and the Archaea phylum Euryarchaeota (19.3%~29.2%) were the predominant groups. This model, which involved in a microbes-driven sulfur-cycle, included an anaerobic sediments where the sulfate-reducing bacteria in the Deltaprotebacteria reduced the sulfate to sulfide along with the organic matter degrading. During the sulfide spread up, it would be oxidized to sulfur or even to sulfate by the bacteria in genera Thiobacillus, Acidithiobacillus and Halothiobacillus. Enrichment of specific microbial populations depended on different environmental factors. It required diverse microorganisms to be involved in the sulfur cycle and achieve the degradation of organic matter.