| Benthic microbial fuel cell (BMFC) is a device in which the anode is embedded in anoxic marine sediments while the cathode is placed in the overlying aerobic seawater. The electricigens on the surface of the anode of the BMFC convert biological energy into energy. The BMFC has several advantages such as maintenance-free, supply continuously, rich substrate and environmental friendly, etc. So it is promising to be used as energy installations to support a low-power monitoring instrument in the remote marine environment. But low output power density and poor stability are the main problems for BMFC now. It has been reported that there is a direct relationship among power density, the electricigens on the surface of the anode and microbial community. In order to improve its operation stability and efficiency, we constructed a BMFC in the laboratory, and studied the influence of microbial community (including some culturable heterotrophic bacteria) on the surface of the anode in electricity efficiency.In this study, 52 bacterial strains are isolated from the surface of anode of BMFC and sequenced respectively. The results show that they belong to three phyla: Proteobacteria (10), Firmicutes (40) and Bacteroidetes (2). Firmicutes is the predominant bacterial group. 77% of the total bacterial isolated belongs to Firmicutes, and 61.5% of Firmicutes strains belongs to genus of Bacillus. Bacillus is dominant in heterotrophic bacteria community on the surface of anode in this system, and Bacillus cereus is the dominant strain.16S rDNA sequence analysis demonstrates that strain LYX05 showing 95.8% sequence similarities to Algoriphagus maincola. The cell extracts of strain LYX05T showes an absorption peak maximum at 482 nm, negative tests for acid production from amygdalin, salicin and D-melezitose, negative tests for utilization of D-fructose, D-lactose, D-maltose and D-mannose. For the component of fatty acids, the dominant fatty acids of LYX05T is iso-C15:0 (40.82%). The DNA G+C content of strain LYX05T is 42.5 mol%. After identification on the basis of phenotypic, chemotaxonomic and phylogenetic data, strain LYX05T is considered to represent a novel species of the genus Algoriphagus, for which the name Algoriphagus faecimaris sp. nov. is proposed. The type strain is LYX05T (=JCM 16561T =DSM 23095T=LMG 25474T).The bacterial communities on the surface of anode of BMFC show a higher diversity than that in marine sediment, and Geobacter sp. is detected both in marine sediment and on the surface of anode of BMFC by PCR-DGGE and 16S rDNA sequencing. The effect of enriched B. cereus (LYX03, HQ202561), A. faecimaris (LYX05) and DNA of strain LYX05 on the performance of BMFC and bacterial community is studied. The addition of A. faecimaris leads to the reduction of output voltage (about 20% of the original value) and the disappearance of Roseobacter sp. The addition of B. cereus and DNA of B. cereus have no significant influence on the bacterial community and output voltage of BMFC. The effects of carbon source (glucose and LB medium) on the performance of BMFC and bacterial community is also examined. The addition of LB medium lead to the reduction of output voltage significantly (about 40% of the original value). LB medium may promote the growth of aerobic bacteria and consequently inhibit the growth of electricigens. Glucose has no significant effect in bacterial community and output voltage. Interestingly, Chryseobacterium sp. is easily influenced by the addition of exogenous bacteria and carbon source to the surface of anode of BMFC, no change of output voltage is observed.The bacterial community on the surface of anode may play an important role on the performance of BMFC and be easily effected by ingredients of organic matter in sediment. Therefore, the study on bacterial community on the surface of anode and the interaction relationship between electrogenesis and other bacteria are necessary for the stable operation of BMFC. |
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