不同淹水时间水稻土微生物群落的Fe(Ⅲ)还原能力及其与脱氢酶活性的关系

Relationships between Fe(Ⅲ) Reduction and Dehydrogenase Activity of Microbial Communities in Paddy Soil during Different Flooding Periods

为探讨淹水水稻土中微生物Fe(Ⅲ)还原机理,采用厌氧恒温培养方法,比较了水稻土微生物群落在淹水演替过程中,分别以葡萄糖、丙酮酸盐和乳酸盐为底物时的脱氢酶活性变化及Fe(Ⅲ)还原特征.结果显示,不同淹水时间的土壤微生物群落均可以葡萄糖为优势碳源还原Fe(OH)3,最大反应速率对应时间(TVmax)与脱氢酶活性峰值出现时间比较一致,为厌氧培养的6—8d;以丙酮酸盐或乳酸盐为碳源时,脱氢酶活性的半饱和常数Ks表现为淹水30d<12d<1d,Fe(Ⅲ)还原过程和脱氢酶活性均随淹水时间延长而显著增强;Fe(Ⅱ)生成量在91—345mg/L时,土壤脱氢酶具有最大活性.本试验表明,利用葡萄糖的脱氢过程主要发生在厌氧培养初期,脱氢酶活性是影响水稻土中Fe(Ⅲ)还原过程的重要因素;脱氢酶活性峰值出现时间与Fe(Ⅲ)还原最大反应速率Vmax呈显著负相关关系,与TVmax则为显著正相关.

To investigate the mechanism of microbial Fe(Ⅲ)reduction in flooding paddy soil,the dehydrogenase activity(DHA)and Fe(Ⅲ)reduction characteristics were studied during the succession of bacterial communities.The method of anaerobic incubation at isothermic temperature regime was adopted with amendment of glucose,pyruvate and lactate as the carbon source,respectively.Solutions extracted from paddy soil in different flooding period were used as inoculums.Results showed that,glucose was used as the dominant carbon source in all flooding treatments,and Fe(Ⅲ)reduction characteristics TVmax was consistent with the peak time of DHA,appearing at 6—8d in anaerobic incubation.When pyruvate or lactate was added,flooding time had significant effects on DHA kinetic characteristics Ks,with the order of 30d<12d<1d,and microbial Fe(Ⅲ)reduction and DHA both increased with the flooding time.Maximum DHA was observed when Fe(Ⅱ)accumulation were 91—345mg/L.It showed that dehydrogenation occurred mainly in the early incubation stage when glucose was fed,and DHA significantly effected on the microbial Fe(Ⅲ)reduction.The peak time of DHA was positively correlated with TVmax and negatively correlated with Vmax.