攀枝花矿区糙野青茅根际耐铬放线菌筛选及促生能力评价

从攀枝花矿区糙野青茅根际土中分离放线菌,筛选获得对重金属铬具有强耐受性、抗菌促生和产胞外酶能力的放线菌,为微生物-植物联合修复重金属污染提供菌种资源.采用稀释涂布法进行放线菌的分离,通过放线菌在不同铬浓度高氏一号培养基上的生长状况判断其对重金属铬的耐受性,进一步采用原子吸收分光光度法分析菌株对铬耐受性强的菌株耐铬及去铬能力;通过对菌株产铁载体、溶磷、产吲哚乙酸(IAA)、产纤维素酶、产淀粉酶、产木糖酶、产酪蛋白酶能力及抗菌活性的筛选,综合评价菌株抗菌促生能力.结果显示,分离获得的27株根际菌株,光学显微形态及扫描电镜结果均显示为放线菌,其中有14株能在含铬的培养基上生长,具有耐铬能力.16S rRNA基因测序结果显示,14株放线菌分属于链霉菌属(streptomyces)、小单孢菌属(Micromonospora)和冢村氏菌属(Tsukamurella).菌株SCAU9002和SCAU9008在铬浓度为300mg·L~(-1)的处理下培养6 d,去铬率分别达到81.17%和78.41%;菌株SCAU9002、SCAU9006、SCAU9008、SCAU9009、SCAU9013同时具有3种促生功能,盆栽实验结果进一步表明,在重金属胁迫下,经菌株处理后的玉米植株更高,生物量更大,根系更发达,促生效果较好.此外,菌株SCAU9006对6种病原菌具有拮抗作用,5株菌同时具有3种及以上产胞外水解酶的能力,4株菌能在7%的NaCl浓度下生长,13株菌在pH5.0~8.0的范围内均可生长.结果表明,根际放线菌在促进矿区植物生长和铬尾矿污染土壤的生物修复研究中具有很大潜力.

Chromium-resistant rhizosphere actinomycetes from Deyeuxia scabrescens in Panzhihua mine area: Isolation, screening and plant growth promoting

In order to provide strains possessed both heavy metal resistant and plant growth promoting ability, the rhizospheric actinobacteria of Deyeuxia scabrescens was isolated and screened. The chromium resistant strains were selected from GAUZE''s medium NO.1 with different chromium concentration. Atomic absorption spectrophotometry (AAS) was employed to analyze the chromium stress resistance and removal ability of isolates. The antimicrobial activity of isolates was tested by antagonistic experiment. The plant growth promoting activity including phosphate solubilizing ability, siderophore secreted, production of indole-3-acetic acid (IAA), chitinase, amylase, xylase and casease activity, as well as antimicrobial activity of isolates were also analyzed. The results showed a total of 27 strains were isolated from rhizosphere of Deyeuxia scabrescens. These strains were identified as actinobacteria by microscopic morphology analysis. Out of the 14 isolates could grow on medium with chromium and showed chromium resistant ability. The 16S rRNA gene sequences analysis showed that the isolates were belonged to 3 genus, including Streptomyces, Micromonospora and Tsukamurella. Among of 14 isolates, SCAU9002 and SCAU9008 possessed the high chromium removal rate with 81.17% and 78.41% in medium (300 mg Cr⁶⁺/L, 6 d incubation), respectively. Furthermore, strains SCAU9002, SCAU9006, SCAU9008, SCAU9009 and SCAU9013 harbored multiple plant growth promoting properties. Subsequently, pot experiment demonstrated that actinobacteria can improve both corn biomass and root growth under heavy metal stress. In additon, strains SCAU9006 have antimicrobial activities to six pathogens, five strains possessed capacity for producing at least three exoenzyme, four strains were able to tolerate 7% NaCl concentrations, 13 out of 14 strains can grow under pH between 5.0 to 8.0. The results revealed that the rhizosphere actinobacteria isolated from Deyeuxia scabrescens possessed potential application prospect in bioremediation for chromium contaminated soil.