| Bacteria that could oxidized Mn (Ⅱ) (the following are collectively termed as manganese-oxidizing bacteria) were isolated in zonal soils.The types of these bacteria were determined with 16S rDNA analyses, and the genetic distances of these manganese oxidizing bacteria were analyzed with application of phylogenetic tree. In addition, the oxidizing abilities of these bacteria at different manganese concentrations (1mM, 10mM) were measured and the basic physiology and biochemistry properties were characterized. Typical manganese oxidizing bacteria No.27,63,79 were selected as materials in manganese oxidizing ability studies at different initial pHs and various ionic compounds at different concentrations. The products yielded by manganese oxidizing bacteria, and the transformation of these products to other manganese oxides were also investigated. The main results are as follows:1. At different manganese concentration,34 strains of manganese oxidizing bacteria were isolated from four zonal soils in China, among which 29 strains were identified. For those been idedntified,19 trains were separated from the brunisolic soil of Tai’an in Shandon,3 strains were from cinnamon soil of Zaoyang in Hubei,2 strains were from yellow brown soil of Wuhan in Hubei,5 strains were from drab soil of Guiyang in Hunan o. With 16S rDNA analyses of these bacteria,11 kinds of bacteria were identified, among which 9 kinds belonged to Shandong,3 kinds belonged to Zaoyang in Hubei,2 kinds belonged to Wuhan in Hubei,5 kinds belonged to Guiyang in Hunan. With analysis of phylogenetic tree, these strains could be attributed to 2 phylogenetic groups,3 family (Firmicutes, Flavobacteria, Alphaproteobacteria),11 kinds, among which 7 kinds belonged to firmicutes,3 kinds belonged to alphaproteobacteria,1 kind belonged to flavobacteria.2. Mn2+oxidiation by the manganese-oxidizing bacteria is a processing of both chemical and biological mediations. It is not a simple biological oxidation (direct oxidation), nor simple chemical oxidation (indirect oxidation), but the growth of microorganism that regulates the solution redox environment, promotes the manganese oxide formation.3. Growth curves of manganese-oxidizing bacteria under the condition of adding and non-adding Mn2+(1mM) were measured. Adding Mn2+delayed logistic growth periods of the bacteria. However, adding Mn2+to the LB medium when the bacteia were activated promoted the oxidation of Mn. It was indicated that, the manganese oxidation amounts were increased by 10.7%,45.6%,287% respectively when Mn2+ was added during bacteria activiation period.4. It was showed that initial pH values (5,7 and 8) of the LB medium play an important role in manganese(II) oxidation by the bacteria. Both bacterium 27 and 63 strains with increasing pH values, oxidation amounts were decreased. Especially strain 63, at pH 8 the decreases of oxidation amount were greatest. It can be explained that high initial pH value is not conducive to the growth of bacterium 27 and 63. However, with increasing pH, the oxidation amount of the bacterium 79 increased. At pH 5, the oxidation amount was low; at pH 7 and 8, the oxidation sharply rose, but from 7 to 8, rose slowly. Therefore, high initial pH was in favor of growth of bacterium 79.5. The effects of different anion-cations (cations:Na+, K+, Mg2+, Ca2+; anions:Cl-; NO3-; SO42-) at different concentrations (10 mM and 30 mM) on Mn2+oxidation capacity of the bacteria were significant. The most suitable salt condition to strain 27 was 10 mM potassium sulfate and magnesium sulfate. For strain 63 it was 30 mM of potassium sulfate. For strain 79, it was 30 mM of magnesium sulfate.6. In the process of manganese-oxidizing bacteria cultivated in the LB culture medium, pH increase might be caused due to low C/N in the medium. Nutrition was so rich that bacteria produce a large amount of ammonia during metabolism. Even adding N-2-hydroxyethylpi perazine-N-ethane-sulphonic acid (hereinafter referred to as HEPES) buffer in the medium, pH value still increased and were stabilized at about 9. In the higher C/N Leptothrix growth medium, the system could be stabled at pH 7, however Mn oxide was not yielded by the bacteria.7. During the process of Mn2+oxidation, oxidation amount gradually rose, but after 13 days of oxidation, the oxide amount stayed contanst. In the contrast, if a certain amount of manganese was added after 5 days of oxidation, oxidation amount significantly increased, after 13 days oxidation reached new equilibrium again. It showed that the manganese concentration was not enough for oxidation by the bacteria after 5 days, the oxidation stabilities of the manganese-oxidizing bacteria were still strong.8. Manganese oxides formed by the bacteria was identified by XRD, which were disordered weak crystalline manganese oxides. The biogenic manganese oxides could not transform to other phases after exchanging with 1 M magnesium chloride solution, washed and refluxed at 110℃. |
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