某典型铬盐厂污染场地Cr(VI)还原菌的筛选、鉴定及还原特性

从河南省义马市某典型铬盐厂污染场地3个典型区域获得污染土壤，以K2Cr2O7为供试物，用固体平板法筛选出8株菌，并进行Cr（VI）还原菌耐受性实验，挑选出耐受性较高的2株菌作为Cr（VI）的优势还原菌株，对这2株菌进行生长曲线的测定，用16S rRNA基因测序技术对其进行菌种鉴定，并研究了其在不同初始浓度、接种量、pH、温度条件下的还原特性，获得最佳还原条件。结果表明：YM4和YM7等2株菌对Cr（VI）具有高耐受性，其对50 mg·L-1和75 mg·L-1 Cr（VI）浓度的还原率均能达到97%以上。但Cr（VI）浓度提高到100 mg·L-1，YM4和YM7对Cr（VI）的还原率下降到了60%，说明100 mg·L-1 Cr（VI）对YM4和YM7产生了抑制作用。基因测序鉴定出YM4为芽孢杆菌，YM7为微小杆菌。在20～75 mg·L-1 范围内YM4和YM7均对Cr（VI）有较好去除效果。YM4的最佳还原条件是接种量为5%、pH为7.0～8.0、温度为35 ℃，YM7的最佳还原条件是接种量为5%、pH为7.0、温度为40 ℃。基于2株菌对Cr（VI）还原特性的研究，YM4和YM7可以用来作为微生物修复铬污染土壤的备选菌种。

Screening,identification and reduction characteristics of Cr(VI)-reducing bacteria from a typical site contaminated by chromium plant

Chromium contaminated soil was collected from three typical site contaminated by chromate plants in Henan, and strains were screened using solid plate method in which potassium dichromate was added as test material. Eight Cr（VI） reducing bacteria stains were screened out and resistance experiments were conducted. Two strains of higher tolerance were picked up and their growth curves were determined. 16S rRNA gene sequencing technology was adopted for primary identification, then their reduction characteristics were studied with different initial concentrations, inoculation amounts, pH, and temperature, and then it further obtained their optimal reduction conditions. Results showed that YM4 and YM7 were advantage strains for Cr（VI） reduction. The reduction rate of YM4 and YM7 for Cr（VI） with concentration of 50 mg·L-1 and 75 mg·L-1 were above 97%, but the reduction rate was decreased to 60% as its concentration increased to 100 mg·L-1, Therefore Cr（VI） with concentration of 100 mg·L-1 was inhibited to YM4 and YM7. As revealed by the gene sequencing, YM4 was identified as Bacillus and YM7 was identified Exiguobacterium. YM4 and YM7 all had great reduction effect for Cr（VI） with concentration of 20 to 75 mg·L-1. The optimal conditions for the reduction of Cr（VI） by strain YM4 were inoculation amount of 5%, initial pH of 7.0 to 8.0, and temperature of 35 ℃. The optimal conditions for the reduction of Cr（VI） by strain YM7 were inoculation amount of 5%, initial pH of 7.0, and temperature of 40 ℃. Based on the research of reduction characteristics of above two strains,YM4 and YM7 can be used as alternative bacteria for microbial remediation chromium contaminated soil.