| Antimony(Sb)pollution is one of the most serious pollution in China and is also one of the global dilemmas.Increasing demand for antimony-containing(Sb)product in social activities inevitably cause antinomy pollution.When Sb enters the environment,it will cause serious toxic effects on plants,animals,microorganisms and human,and also pose potential threat to the ecosystem.Studying the mechanism of microbial resistance to Sb is of great significance for elucidating the biogeochemical cycle of Sb.Exploring the Sb resistance mechanism of microbes can also provide theoretical support for microbial-based environmental pollution control.Sb(?)is of highly toxic and is the common form of antimony in the contaminated sites.In the present study,a bacterial strain,Acinetobacter.johnsonii JH7 with high Sb(?)-resistant ability was isolated from antimony mine tailings.The resistance of this strain to Sb(?)and other heavy metals and organic flotation agents was determined;physiological and biochemical characteristics was measured;genomic scanning sequencing technology was employed to obtain the genome sequence of Acinetobacter.johnsonii JH7,genes related to Sb(?)-resistance of Acinetobacter.johnsonii JH7 were screened by gene annotation and functional prediction;acute toxicity test,chemical analysis,adsorption batch test and other means were combined to explain the mechanism Sb(?)oxidation and surface adsorption by Acinetobacter.johnsonii JH7;finally,comparable proteomic study(i TRAQ method)was established to probe the Sb(?)-resistance mechanisms of Acinetobacter.johnsonii JH7 at protein expression level.From research mentioned above,present study has reached following conclusions:(1)The lowest inhibition concentration of Sb(?)to A.johnsonii JH7 reached 365.25 mg/L(3 m M)and it also possess resistant ability to a variety of heavy metals and organic flotation reagents.(2)Results of physiological and biochemical characterization and genomic mapping showed that A.johnsonii JH7 can utilize a wide range of carbon sources.The genome of A.johnsonii JH7 codes metal/metalloid resistance protein genes,multidrug-resistance protein genes,chaperone genes and oxidative stress protein genes,which together provide molecular basis of Sb(?)resistance.(3)A.johnsonii JH7 is an Sb(?)oxidizing bacterium.It oxidized Sb(?)to less toxic Sb(V)by enhancing intracelluar radical oxygen species.Analyses of Sb(?)distribution revealed that surface adsorption inhibited Sb(?)entry into JH7 cells.Our results indicated that biosorption and oxidation of Sb(?)were likely to contribute to the decreased toxicity of Sb(?).(4)Proteomic analysis revealed that ars operon proteins up-regulated significantly(p ? 0.05)under Sb(?)stress,which would mediate the extrude of Sb(?)and reduces the toxicity of sb(?)to cells.The activities of GSH-Px,Gst,SOD and CAT also witness an significant increased(p ? 0.05)under the stress of Sb(?).Other than enhance the expression of stress response proteins,A.johnsonii JH7 also increased the protein expression that involved in TCA cycle,oxidative phosphorylation,sulfer metabolism,coenzyme synthesis and ribosome construction,which together provided material and energy for the survival and formation of Sb(?)resistance of A.johnsonii JH7.At last,some proteins which have been proved to be able to mediate Cu and Cd resistance were probed to be highly expressed under the Sb(?)stress,indicating these proteins have potential correlation with the ability of A.johnsonii JH7 to resist Sb(?).The present study successfully isolated a Sb(?)-resistance bacterium A.johnsonii JH7 and revealed the Sb(?)-resistance mechanisms of A.johnsonii JH7 comprehensively using toxicology determination,chemistry analysis,genomics mapping and proteomics analysis.The mechanisms revealed in the present study successfully filled the gap of bacterial Sb(?)-resistance mechanisms of Acinetobacter spp.,proposed new potential functional proteins for Sb(?)-resistance,and provides a solid theoretical basis for microbial treatment of Sb(?)pollution. |
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