Isolation, Identification Of Manganese-oxidizing Bacterium And Its Manganes Oxidition Characteristics

The level of Manganese is the main component of the earth's crust. And it is justlittle than iron. Manganese is widespread in nature and is one of the necessary traceelements for the body, but if we intake excessive manganese, it can cause neurologicaldiseases, or even endanger our health. Here is drinking water requirement of ourcountry: The maximum allowable concentration of manganese is0.1mg/L. And in theuse of the domestic water and industrial water, the exceeded concerntration ofmanganese is also the major factor which can affect the quality of water, such as theimpact of water color and odor. In addition, the treatment of manganese by biologicalmethods is better than the treatment by traditional method of chemistry, for the result ofthe treatment is more stable and more economical. In recent years, biolgical removal ofiron and manganese has been widely used. The treatment of manganese by microbialoxidation is widely used and present in the aqueous phase and the soil environment,manganese bacteria has an important role in the biogeochemical cycling of manganeseand they can efficiently oxidize Mn (II) to Mn (IV). Some bacteria have a very strongmanganese oxiding ability, the oxidizing rate is about10times faster than the catalyticof chemistry. Therefore, manganese-oxidizing bacteria have a higher value in the studyof biological manganese removal; they can be used to deal with the high concerntrationof manganese in groundwater. However, the study of the mechanism of manganese-oxidizing progress and manganese-oxidizing bacteria is not deep enough.In this study, different environmental samples (soil, river sediment, etc) wereenriched by three different enrichment media.we tested the effect of the enrichment bythe indicator of LBB, and then the enrichment which of good effect is used for theisolution.The isolates are identified through the identification methods of physiologicaland molecular biology.Both the effect of inoclum, the concerntration of Mn2+, Ph on thegrowth curve of the isolates and the characteriastics of manganese oxidation aredetermined.PYCM medium, K medium and PC medium are used for the enrichment of soiland river sediment samples.The ability of the Mn (II) oxidation of the isolated10strainsof bacteria were tested by LBB, Analysis by MIDI microbial identification system,Biolog analysis, the analysis of physiological and biochemical and16S rDNAsequencing, identified that MB1is Bacillus licheniformis and MB2is Bacillusmegaterium.Initial pH (5-9) of the medium K can effect the growth of bacteria, and the curve of manganese oxidation rate of manganese.When MB1and MB2are at a pH of5.0-7.0,the cells may grow well in this range, when the pH value is7.0, the amount of the cellin the biological medium is maximum, for under the conditions the cells quickly adaptto the environment and enter the logarithmic growth phase quickly. As the pH of themedium changed to alkaline, the enhanced biomass gradually decreases.The growth ofthe bacteria is inhibited when the pH is9.0, which shows the physiological activities ofthe cells are affected by the alkaline environment. The effects of differentMn2+concentrations on cell growth, especially when the concentration is higherthan12mmol/L, MB1can't grow, indicating that Mn2+can inhibit the growth ofbacteria when the concentration is too high. Strain MB2can also grow betterwhen there is no Mn2+in the medium, but the concertration within12mmol/Lvaries little, indicating that MB2can tolerate Mn2+better than MB1.The optimalinoculum size of MB1is5%,.The optimal inoculum size of MB2is15%.The test of the manganese oxidation rate is through the use of atomic absorptionspectrometry Determination. After7days in K medium.The Manganese Oxidizing rateof Bacteria MB1was61.7%, the Manganese Oxidizing rate of MB2Bacteria was90%.Ander the conditions of pH6.0-8.0,the Mn2+oxidation rate is above35%, whenthe pH is7.0,the bio-oxidation rate of MB1and MB2can reach80%. When the pH is5.0or6.0, the Mn2+oxidation rate of the strain MB1and MB2are less than60%, It issuggested that, the acidic environment may affect the growth of manganese-oxidizing bacteria, or the composition of the medium was changed by an acidicenvironment, resulting in the decrease of the rate of oxidation.The analysis of themanganese resistant characteristics of bacteria MB1and MB2proves the oxidation ofmanganese-oxidizing bacteria contains two factors, biological and chemical oxidation ofMn2+are both included during the oxidation process.The Bacteria we isolated provide important species for further study andthe realization of strengthening the manganese oxidizing mechanisms.