铅锌污染耕地中重金属耐受细菌调查

Heavy-metal-tolerant bacteria in agricultural soils contaminated by Pb and Zn

对铅锌矿冶炼厂周围耕地中的细菌总数和抗性细菌群体数进行了调查。结果表明 ,随着污染的加重 ,土壤中可培养的细菌数量急剧减少 ,抗性细菌的比例增加。但是 ,细菌对Pb、Zn胁迫的适应进化反应不一样。经过长期的选择作用后 ,多数细菌群体能够耐受低浓度的Pb污染 (<2mmol·L-1) ,部分群体对低浓度Pb(0 .5mmol·L-1)有依赖性 ,但没有观察到能够耐受Pb浓度大于 4mmol·L-1的群体 ;0 .5mmol·L-1的Zn对细菌有抑制作用 ,但在所调查的样品中都存在能够耐受 4～ 6mmol·L-1Zn污染的群体 ,有的群体甚至能耐受 8mmol·L-1的Zn污染。能同时耐受Pb、Zn 2种重金属污染的群体数量较少 ,且耐受水平也较低 ,仅达到 2mmol·L-1。

Heavy-metal-tolerant bacteria in the agricultural soils around a lead-zinc smeltery were investigated. The results show that with increase in pollution, the number of culturable bacteria dropped drastically whereas the proportion of heavy-metal-tolerant bacteria rose. The adaptabilities of bacteria to Pb and Zn stresses vary. After a long time of screening, most strains of bacteria became able to stand low concentration of Pb ( < 2 mmol·L -1 ) and some grew dependent on low concentration of Pb (0.5 mmol·L -1 ). No strains, however, were found tolerant to concentration higher than 4 mmol·L -1 Pb. Zn contamination, when reaching 0.5 mmol·L -1 in concentration, began inhibiting bacteria activity. But in all the samples investigated, bacteria were found tolerant to Zn, ranging from 4 to 6 in mmol·L -1 concentration and some even to Zn of 8 mmol·L -1 in concentration. The number of strains tolerant to both Pb and Zn was very limited, so was their tolerance to 2 mmol·L -1 and below only.