A Novel Deep-sea Iron Reducing Bacteria And The Influence Of Hydrostatic Pressure On The Free Energy Production In The Process Of Iron Dissimilation Reduction

Microbial dissimilatory iron reduction is an important biogeochemical process that plays an important role in the global material and energy cycles.Of all the terminal electron acceptors,Fe(III)is the most naturally abundant in many subsurface environments.From a thermodynamic point of view,Fe(III)reduction is energetically favorable compared with sulfate reduction and methanogenesis but yields less free energy than O2 and nitrate reduction.In most anaerobic environments,Fe(III)reduction occurs before sulfate reduction and methanogenesis but is inhibited in the presence of nitrate.Under anaerobic conditions,dissimilatory iron-reducing microorganisms use Fe(III)as terminal electron acceptor of the respiratory chain to for energy production under the catalysis of iron reductase.Fe(III)reduction may have been the first from of microbial respiration,it is helps us to better understand the origin and evolution of life.Redox reactions of Fe with C,N,O,and S drive the global biogeochemical cycles.Previous studies have examined a variety of dissimilatory iron reduction microbial,including isolation and purification of microorganisms,the mechanisms of microbial electron transport to the insoluble Fe(III)oxides by Fe(III)-reducing microbes,biomineralization and biological remediation of environment.Yet the effect of hydrostatic pressure on microbial metabolic activities and energy production in biogeochemical cycles has not been fully studied.The deep-sea piezosphere accounts for approximately 75% of the total ocean volume and hosts 62% of the global biosphere.The deep-sea piezosphere encompasses the volume of the deep sea at the depth of 1000 m and greater,the pressure increases with the increase of depth,and the average hydrostatic pressure is 38 MPa.Deep sea is an extreme environment of darkness,high pressure,oligotrophic and low temperature(the temperature of submarine hydrothermal vent can reach 400? or even higher).And hydrostatic pressure is one of the important thermodynamic parameters affecting microbial physiology,metabolism and activity in pressured environments on Earth,such as the deep ocean and the deep biosphere.Yet the effect of hydrostatic pressure on microbial metabolic activities and energy production in biogeochemical cycles has not been fully studied.Here,this study from the perspective of varying hydrostatic pressure,and investigate the effect of hydrostatic pressure on the physiological activity and free energy production of dissimilatory iron reduction microbial.Meanwhile,the iron reduction capability of Bacillus M1132 from Mariana Trench was characterized.In this study,iron reduction and substrates and fermented products of a fermentative dissimilatory iron-reducing bacterium,Orenia metallireducens Z6,were systematically examined at different hydrostatic pressure(0.1,10,20,30,40 and 50MPa).The results indicate that the growth range of strain Z6 was 0-40 MPa,and the optimum growth pressure was 20 MPa.At the same time,the thermodynamic analysis of Fe(III)reduction process of strain Z6 under the pressure of 0.1-30 MPa was carried out,and the free energy was calculated.The results showed that the free energy was the highest at 20 MPa,which was coupled with the highest Fe(?)reduction efficiency and the fastest substrate utilization of strain Z6 at 20 MPa.The free energy of strain Z6 under different pressures was consistent with the adaptability of strain Z6 to pressure.Meanwhile,the iron reduction capability of Bacillus sp.M1132,Gram-positive-bacteria,from Mariana Trench sediment was characterized.