Effect of arsenic input on microbial anaerobic fermentation of estuarine sediments
The effect of exogenous arsenate(As(Ⅴ))input on the anaerobic fermentation and community struc-ture in situ in arsenic(As)-contaminated sediments was investigated to elucidate the interaction between As(Ⅴ)and microbial community composition in the arsenic-contaminated estuarine sediments.The As-contaminated sedi-ments were collected from the Wuli River in Huludao City,Liaoning Province,China.The sediment samples were incubated after adding As(Ⅴ)(i.e.,1,10,60 mg·L-1,respectively).Physicochemical parameters(e.g.,hydrogen production,acid production,pH,and carbon consumption)and microbial community composition were measured during incubation.The dominant strains were isolated from culture solution with high As(Ⅴ)concentra-tion using plate dilution method.During the enrichment culture,transformation of arsenic form was observed in all treatments.Among them,about 43％of As(Ⅴ)was converted to arsenite(As(Ⅲ))in the treatment with 60 mg·L-1 As(Ⅴ).At the end of the incubation,the phylum number in the original sediment decreased from eleven to one(Firmicutes),and the dominant genus Clostridium_sensu_stricto_1 occupied the dominant ecological niche.An an-aerobic fermentative Clostridium butyricum CXL-1 with the high As(Ⅲ)tolerance(≥ 200 mg·L-1)was isolated from the treatment with the addition of 60 mg·L-1 As(Ⅴ),which showed the capacity to produce fermentation products such as organic acids and H2 by glucose fermentation metabolism,thereby providing hydrogen and carbon sources for sulfate-reducing bacteria and methanogens.Our results can provide reference for the anaerobic minerali-zation remediation of As-contaminated environments by microorganisms.
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