Research On Electrical Characteristics Of Cable Bacteria Based On Atomic Force Microscopy

Cable bacteria are a kind of filamentous multicellular electrochemically active bacteria from Desulfobulbaceae family discovered in recent years,which have high electron transfer efficiency.Cable bacteria run through the aerobic zone and anaerobic zone of sediments,and can transport electrons in centimeter-level long distance along the growth dimension of bacteria,thus coupling the oxidation half reaction and reduction half reaction in different spaces,and transporting the electrons generated by anodic sulfide oxidation to the cathode for oxygen reduction reaction.According to the literature,the long-distance electron transmission of cable bacteria is an efficient electron transmission mode,and the current density is basically the same as that of copper wire in long-distance electron transmission,and the current loss is very small in the process of electron transmission.The electrons transfer of cable bacteria is very efficient.Compared with other electrochemically active bacteria,the conductivity of cable bacteria is 1-2 orders of magnitude stronger than that of ordinary electricity-producing bacteria.It has been 10 years since the discovery of cable bacteria,but the relationship between the electrical properties and the structure of its conductive structures is still unclear.For this reason,the conductive structures and electrical properties of cable bacteria on micro-nano scale were researched by atomic force microscope in this paper,so as to further understand and explore the conductive structures and the relationship between its functions and structures.The research contents and main research progress of this paper are as follows:(1)Enrichment culture and metagenome sequencing analysis of cable bacteria.According to the collected sludge,the cable bacteria were enriched and cultured,and then the successfully enriched cable bacteria filaments were extracted and identified by SEM and AFM.The results showed that the unique morphological structures with "ridge" structures and junctions were detected.Taking the cable bacterial microbial community obtained by enrichment culture as the research object,combined with high-throughput technology,the cable bacterial microbial community metagenome sequencing analysis was carried out on the sludge rich in cable bacterial filaments,and the species diversity and metabolic relationships of the cable bacterial microbial community were researched.The results showed that the cable bacterial microbial community had certain species diversity,and the metabolic relationships between them were complicated,and there were various types of interactions between the cable bacterial and its coexisting microorganisms,so as to increase the understanding of the gene functions and interaction mechanism of the cable bacterial microbial community.(2)Research on surface potential of cable bacteria based on SKPM.Taking the dried intact hyphae and fiber sheaths of cable bacteria as the research objects,the in-situ surface potential of the intact hyphae and fiber sheaths of cable bacteria and the intact hyphae and fiber sheaths of cable bacteria with the surface insulating protein layer scraped off were researched by scanning Kelvin probe microscope,and the electron transmission ability of cable bacterial conductive structures was explored.The experimental results showed that the conductive fibers of cable bacteria fiber sheaths have higher surface potential and weaker electron binding ability,that is,stronger electron transmission ability.The intact hyphae and fiber sheaths of cable bacteria and the intact hyphae and fiber sheaths of cable bacteria with the surface insulating protein layer scraped off were injected with electric charges,and the changes of their surface potential were researched to explore the charge behavior of the conductive structures of cable bacteria.The results showed that the surface potential decreased after the electric charges were injected,indicating that cable bacteria have the function of charge storage.(3)Research on Young’s modulus of cable bacteria based on AM-FM.Taking the intact hyphae and fiber sheaths of cable bacteria as the research objects,the Young’s modulus of intact hyphae and fiber sheaths of cable bacteria before and after scraping were researched by using amplitude modulation-frequency modulation mode,and the change of rigidity and elasticity of cable bacteria were explored.The experimental results showed that the Young’s modulus of the edge of cable bacteria with scraping were lower than that without scraping,which may be due to the structures that are more easily deformed by force inside cable bacteria.The changes of Young’s modulus of fiber sheaths scraping surface protein and more structures including conductive fibers were researched,and the change of rigidity and elasticity of conductive structures of fiber sheaths were explored.The experimental results showed that the Young’s modulus of fiber sheaths decreased after scraping surface insulating protein layer,and it is easier to be deformed by force.The fiber sheaths continued to scrap off more structures including conductive fibers,and the Young’s modulus were higher than that of conductive fibers.The experimental results showed that the conductive fibers of cable bacterial fiber sheaths were less rigid,more elastic and more prone to tensile deformation.