Hydrogen oxidizing bacteria belonging to the plant growth promoting rhizobacteria,so the mechanism for the growth of exploration has become a focus attention at home and abroad,in which there are few researches on plant growth promoting of hydrogen oxidizing bacteria under heavy metals stress.In order to study whether the hydrogen oxidizing bacteria has growth promotion and protection to the Pak choi seedlings under heavy metal stress.We used two strains hydroxide bacteria and cabbage seedlings as the research materials.The strain species identification was determined by conventional and molecular biology method.Using NJ adj acent method to construct phylogenetic tree, ACC deaminase activity was estimated by 2,4-dinitrobenzene hydrazine method,the ability of IAA was determined by Salkowski reagent method,the plant root elongation promoting activity of the isolated hydrogen oxidizing bacteria was determined by the modified Belimov method.Wilkins method was used to test the resistance of Pak choi seed-lings tolerance index.The results showed that two hydrogen oxidizing bacteria respectively belong to Pseudomonas sp.zw-17 and Sphingobacterium sp.zw-35.The ACC deaminase activity was (17.87±0.58),(22.26±0.85)μmol a-KB•mg-1•h-1.The ability of IAA was (13.21±0.78)to (5.79±5.79)mg•L-1.Compared to the control group, inoculating hydroxide bacteria was benefit to the growth of the Pak choi seedlings root.Compared to the control group,tolerance index of Pak choi seedlings had significant increase when inoculated with zw-17,zw-35.The results of tolerance index and physiological indicators for Pak choi seedlings,obtained for chromium and lead for both hydro-gen oxidizing bacteria strains,showed that the development of plants inoculated with the hydrogen-oxidizing bacteria Pseudomonas sp.zw-1 7 strain favored the radical growth of Pak choi seedlings exposed to Pb and Pseudomonas sp.zw-3 5 strain in seedlings exposed to Cr;both strains keep the safe development of this species in the presence of the heavy metals at higher concentrations.This study would provide a theoretical basis for hydrogen oxidizing bacteria promoting and protecting plants,and enriched hydroxide bacteria species classification.%氢氧化细菌属于植物促生菌,其促生机制的探索已成为当前国内外关注的热点,目前对氢氧化细菌的研究主要集中在其促生活性物质的研究,对重金属胁迫下植物的促生研究较少.为了研究氢氧化细菌对重金属胁迫下的植物幼苗是否具有促生和保护作用,该研究以2株氢氧化细菌和白菜幼苗为材料,用常规鉴定和分子生物学鉴定法确定菌株的种属,采用NJ 邻近法构建系统发育树、2,4-二硝基苯肼法测定菌株 ACC脱氨酶活性、Salkowski reagent 法测定菌株分泌IAA的能力、Belimov法测定氢氧化细菌的植物促生根长活性、Wilkins法测定白菜幼苗的抗性指数.结果表明：2株氢氧化细菌分别属于Pseudomonas sp．zw-17和Sphin-gobacterium zw-35；ACC脱氨酶活力为(17．87±0．58)、(22．26±0．85)μmol a-KB•mg-1•h-1；产IAA的能力为(13．21±0．78)、(5．79±0．35)mg•L-1；与未接种氢氧化细菌的对照组的根长相比,接种氢氧化细菌有利于植物根的生长；与对照组相比,接种zw-17,zw-35的白菜幼苗抗性指数都有显著性的增长.在处于 Cr、Pb 的环境下,2株氢氧化细菌都能促进白菜幼苗增长,Pb 存在时Pseudomonas sp．zx-17的表现较显著,在 Cr 存在时Sphingobacterium sp．zx-35的表现较显著.在高浓度的重金属环境中,能保护白菜种子安全的生长.该研究结果可为氢氧化细菌对植物的促生和保护提供理论依据,同时丰富了氢氧化细菌的种群分类.
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