Diversity And Mn(?) Oxidation Characteristics Of Manganese-oxidizing Bacteria From Beidaihe Intertidal Zone Sediment

Manganese-oxidizing bacteria,existing widely in soil,fresh water and marine environments,can oxidize the environmental manganese ions to form manganese oxide precipitation.They play a very important role on the geochemical cycle of manganese.Due to the biogenic manganese oxides have a large specific surface area and a high adsorption capacity,make it can adsorb most of the heavy metals in the environment.Thus,it has a potential application in bioremediation of heavy metals in the polluted environments.Diversity,distribution,species and characteristics of manganese-oxiding bacteria isolated from the sediments of Xinhe estuarine delta,Beidaihe were studied in this research.The results indicated that the total number of bacteria in surface sediment of the intertidal zone was higher than that of in the bottom.The total number of bacteria in the surface sediment decreased gradually from the high tidal zone to the low tidal zone,whereas the total number of bacteria in the bottom sediment along the sampling sites from the high tidal zone to the low tidal zone was no obvious difference observed.A total of 149 strains of manganese-oxidizing bacteria were screened out from 720 strains of bacteria.Based on 16 S rRNA sequence analysis of manganese-oxidizing bacteria and the retrieved results performed BLAST research in the GenBank database,13 OTUs of the sequences were observed,which belong to 6 genus as Bacillus,Lysinibacillus,Brevibacillus,Celluosimicrobium,Ochrobactrum and Acinetobacter.The manganese-oxidizing bacteria affiliated to Bacillus,Lysinibacillus and Ochrobactrum are the dominant groups,which accounted for 47.79%,20.83% and 27.08% of the total bacteria.The strains shown strong oxidizing property on manganese are mainly belong to the genus of Bacillus and Lysinibacillus.Bacillus pumilus B-4S-13,a strong manganese oxidization bacterium,were chosen to perform further studies of the influence of different initial pH and manganese iron concentration on the manganese oxidization.The results showed that when the initial pH was ranged from 5 to 9,the manganese removal rate by B-4S-13 could reach above 83.75% after 14 days incubation.When the pH was 7,the manganese removal rate reached as high as 94.63%.When the initial concentration of manganese was 1 mM,the removal rate of manganese reached as highest as 94.6% when compared with other initial manganese concentration used.Manganese oxides produced by B-4S-13,using the incubation conditions at initial pH 7.0 and 1 mM manganese concentration were performed minerals and morphorology analyses.The result obtained by X-ray diffraction?XRD?analysis shows that minerals of the manganese oxides were mainly composed of Manganite?MOOH?,Birnessite??-MnO₂?,Hausmannite?Mn3O4?and so on.Morphorologies of the minerals observed by scanning electron microscopy?SEM?showed that the minerals were mainly in shapes of flocculent,lamellar and octahedron.Element composition of the manganese composition analyzed by Energy Dispersive X ray spectroscopy?EDX?showed that elements of the manganese oxides mainly includiong of carbon,oxygen and manganese etc.