ABSTRACT
Bioelectrochemical systems (BESs) are unique devices that harness the metabolic activity of electroactive microorganisms (EAMs) to convert chemical energy stored in organic substrates into electrical energy. Enhancing electron transfer efficiency between EAMs and electrodes is the key to practical implementation of BESs. Considering the role of outer membrane vesicles (OMVs) in mediating electron transfer of EAMs, a genetic engineering strategy to achieve OMVs overproduction was explored to enhance electron transfer efficiency and the underlying mechanisms were investigated. This study constructed a mutant strain of Geobacter sulfurreducens that lacked the ompA gene encoding an outer membrane protein. Experimental results showed that the mutant strain produced more OMVs and possessed higher electron transfer efficiency in Fe(III) reduction, dye degradation and current generation in BESs than the wild-type strain. More cargoes such as c-type cytochromes, functional proteins, eDNA, polysaccharides and signaling molecules that might be favorable for electron transfer and biofilm formation were found in OMVs produced by ompA-deficient anodic biofilm, which possibly contributed to the improved electron transfer efficiency of ompA-deficient biofilm. The results indicate that overproduction of OMVs in EAMs might be a potential strategy to enhance BESs performance.
Subject(s)
Biosensing Techniques , Geobacter , Oxidation-Reduction , Ferric Compounds , Electrons , Electron Transport , Geobacter/geneticsABSTRACT
Three bacterial strains, designated as AS18T, AS27 and AS39, were obtained from mangrove sediment sampled in Futian district, Shenzhen, PR China. Cells of these strains were Gram-negative rods with no flagella. They were able to grow at 10-42 °C (optimum, 37 °C), at pH 5-9 (optimum, pH 6) and in 1-11â% (w/v) NaCl (optimum, 2â%). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the new isolates were clustered within the genus Mangrovimonas, closely related to Mangrovimonas yunxiaonensis (95.1â% similarity) and Mangrovimonas spongiae (94.7â% similarity). Phylogenomic analysis based on multiple core genes revealed that the three strains were located in a different cluster from other closely related strains of the genus Mangrovimonas. Digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity values calculated from genome sequences between isolates and type strains were lower than 25, 75 and 72â%, respectively. The dominant fatty acids were iso-C15â:â0 and iso-C15â:â1 G. The main respiratory quinone was identified as MK-6. The major polar lipids contained phosphatidylethanolamine, two unidentified aminolipids and five unidentified lipids. The results of multiphase taxonomy suggested that the three strains should be assigned to a novel species of the genus Mangrovimonas, for which the name Mangrovimonas futianensis sp. nov. is proposed, with the type strain AS18T (=GDMCC 1.2739T=JCM 34871T).
