Screening Of Manganese Resistance Microorganism And Their Physio-biochemical Characteristics,Identify

Accounted for by its advantage of low cost and high efficiency, the bio-technology using microorganisms to remove manganese has received much attention since 1980s. As the key functional component, various identified species of microorganisms have played important roles in ecological restoration of heavy metal polluted areas.In the present study soil samples were collected from Koelreuteria paniculata Laxm recovery site of manganese mining area in Heling Town of Xiangtan City. Manganese-resistance strains were screened out using the soil samples by gradually increasing Mn2+ ion concentration in the culture. The growth curve, tolerance and physio- and bio-chemical characteristics of the screened microorganisms were further investigated. The results are summarized as follows:(1) Three manganese-resistant strains (No.2,3 and 80) were isolated from the soil samples by adding a definite amount of Mn2+ ions in the medium. The results showed that the presence of Mn2+ ions enhanced the growth of the strains at low Mn2+ ion concentration levels but inhibit that at high concentration levels. In comparison, No.80 tolerated higher Mn2+ ion concentration than the other two strains.(2) At the lowest tested Mn2+ concentration level (16 mg/L), strain No.3 gave the highest Mn2+ ion removal rate (82.6%), followed by No.2 (72.3%) and No.80 (64.1%). At the highest Mn2+ concentration level (about 2000 mg/L), No.80 gave the highest removal rate (41.0%), followed by No 2 (22.0%) and No.3 (18.3%). The highest Mn2+ ion removal rate (>90%) was obtained at the Mn2+ ion concentration level of about 200 mg/L in both individual and mixed strain samples.(3) Based on colony morphology observation, gram staining analysis and 16s rDNA molecular identification, strains No 2,3 and 80 were identified as bacillus megaterium, klebsiella oxytoca and citrobacter freundii, respectively.(4) All isolated strains reached their peak growth within 16 hours to 18 hours and the strain growth remained stable for a relatively long period. No 80 grew slower than the other two strains. The growth of the all isolated microorganisms enhanced the pH in the culture medium, which provided a favorable condition for oxidation of Mn2+ ion into oxidized precipitates. Three strains grew well within a relatively wide pH range (5-9). The optimum temperature for Nos.2,3 and 80 were found to be 35,37 and 33℃, respectively, within the tested temperature range 28～37℃. The scanning electron micrograph of three strains grown in the medium containing 1000 mg/L of Mn2+ ion showed that the function of the microorganisms to transform Mn2+ ions into oxidized precipitates could be one of the main mechanisms to remove Mn2+ ions from the liquid phase of the culture medium. Antibiotic resistance experiment indicated that No 3 could resistant to ampicillin,even it could grow when the concentration reach 200ug/ml,but the strain was sensitive to kanamycin sulfate and chloramphenicol.No 2 an 80 were both sensitive to the three antibiotics.(5) For purpose of application strain inoculants of the isolated bacteria were made using peat soil as carrier.