水稻根际耐镉细菌的筛选与鉴定

为获得稻田土壤镉污染修复的微生物,采用培养基加镉平板法,从水稻根际土壤分离耐镉细菌。本研究分离得到3株耐镉菌株,经16S rDNA测序、比对,鉴定为假单胞菌属细菌。对菌株细胞形态的电镜观察、菌株生长曲线的测定结果表明,在镉处理浓度为100 mg L 1条件下,菌株生长未受明显抑制,但菌株形态发生了适应性的变化;在镉处理浓度超过300 mg L 1时,菌株生长受到明显抑制;在镉处理浓度700 mg L 1条件下,菌株仍能生长,但生长延滞期延长,对数期后的生长量亦低;对菌体镉含量分析表明,在100 mg L 1镉处理下,3株菌株菌体中的镉含量分别为9.04 mg g 1、4.96 mg g 1和28.58 mg g 1,富集系数依次为90.4、49.6和285.8。可见,分离得到的3株菌株具有较强镉耐性和镉吸收能力,将为稻田土壤重金属镉污染的修复提供重要微生物资源。

Screening and identification of cadmium-tolerant bacteriafrom rhizosphere soils under rice

To identify the bacteria for remediation of cadmium contaminated paddy soils, a plate method (with cadmium in culture medium) was used to screen cadmium tolerant bacterial strains in rhizosphere soils of rice. Three cadmium-tolerant strains were screened and classified as Pseudomonas sp. by using 16S rDNA sequence analysis. While microbial cell morphology observations (using electronic microscope) and growth curve determinations indicated no significant inhibition effects on growth rates of the three strains under 100 mg?L^?1 cadmium treatment, some adaptive morphological changes were noted. For over 300 mg?L^?1cadmium treatments, growth rates of the strains were obviously inhibited. Nevertheless, the three strains were tolerant to cadmium concentra-tions as higher as 700 mg?L^?1 for long periods up to stationary phase. However, growth rates lowered after logarithmic growing phase. Chemical analysis showed that cadmium contents in the bacterial strains under 100 mg?L^?1 cadmium concentration were 9.04 mg?g^?1, 4.96 mg?g^?1 and 28.58 mg?g^?1 by dry-weight. The corresponding enrichment coefficients were 90.4, 49.6 and 285.8, respectively. It then suggested that all the three strains had stronger tolerance and absorption abilities of cadmium. This was an important potential microbial resource for remediation of paddy soils contaminated with cadmium.