Mariana Trench represents the deepest and one of least explored biosphere on 
Earth, and its carbon sources include euphotic sinking, lateral transportation 
and diffusion from underlying crust, etc. By far the spatial variation of 
microbial community with associated organic carbon degradation potential 
in the surface sediments of the Mariana Trench were still largely unknown. 
Based on the high-throughput 16S rRNA amplicon sequencing, significantly 
different microbial community structure was overserved between the shallow 
(<10,000 m) and deep stations (>10,000 m), which could be explained by spatial 
variation of Chloroflexi, Proteobacteria and Crenarchaeota, with sampling 
depth and total organic carbon (TOC) content as the environmental driving 
forces. During the 109-day incubation with Biolog EcoPlate™ microplate, 
polymers and carbohydrates were preferentially used, followed by amino 
acids and carboxylic acids, and microbial metabolic diversity was significantly 
different between the shallow and deep stations. The metabolic diversity of 
microorganisms at most shallow stations was significantly lower than that at 
deep stations. This could potentially be attributed the metabolic capabilities 
of different microbial groups with varied ecological niches, and reflected the 
initial preference of carbon source by the nature microbes as well. Our study 
obtained a rough assessment of physiological and taxonomic characteristics 
of the trench sediment microbial community with polyphasic approaches. 
Distinct microbial structure and potential carbon metabolic functions in 
different sampling depths might led to the differentiation of ecological niches, 
which enable various microorganisms to make full use of the limited resources 
in the deep sea, and provided a research basis for further exploration of the 
carbon cycle in different deep-sea regions.