Assessment of Anaerobic Toluene Biodegradation Activity by bssA Transcript/Gene Ratios
Assessment of Anaerobic Toluene Biodegradation Activity by bssA Transcript/Gene Ratios
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DOI：
10.1128/aem.01031-13
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发表时间：
2013-09-01
影响因子：
4.4
通讯作者：
Simon, Holly M.
中科院分区：
文献类型：
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作者：
Brow, Christina N.;Johnson, Reid O'Brien;Simon, Holly M.
苯甲基琥珀酸合成酶（bssA）基因与甲苯降解进行了分析，在硝酸盐还原条件下的地下水污染物羽，并检测到大量的整个羽。然而，地下水和岩芯沉积物样本之间的差异表明，微生物的运输，而不是当地的活动，是在下坡羽高拷贝数的根本原因。基因转录物和反应物浓度与这一假设是一致的。bssA基因的表达，诱导甲苯，但只有在硝酸盐的存在下，和转录丰度迅速下降后，去除甲苯或硝酸盐。去除甲苯后bssA转录物的下降可以用半衰期为1小时的指数衰减函数来描述。有趣的是，bssA转录从未完全消失，但总是在一定程度上检测到，如果诱导剂存在。因此，仅检测转录本可能不足以证明污染物降解。为了避免错误地将基础水平的基因表达与积极降解的微生物种群相关联，建议使用功能基因转录本与基因拷贝的比率的综合方法。这种方法最大限度地减少了微生物迁移对活性评估的影响，并允许从水样中获得可靠的微生物活性评估。
Benzylsuccinate synthase (bssA) genes associated with toluene degradation were profiled across a groundwater contaminant plume under nitrate-reducing conditions and were detected in significant numbers throughout the plume. However, differences between groundwater and core sediment samples suggested that microbial transport, rather than local activity, was the underlying cause of the high copy numbers within the downgradient plume. Both gene transcript and reactant concentrations were consistent with this hypothesis. Expression of bssA genes from denitrifying toluene degraders was induced by toluene but only in the presence of nitrate, and transcript abundance dropped rapidly following the removal of either toluene or nitrate. The drop in bssA transcripts following the removal of toluene could be described by an exponential decay function with a half-life on the order of 1 h. Interestingly, bssA transcripts never disappeared completely but were always detected at some level if either inducer was present. Therefore, the detection of transcripts alone may not be sufficient evidence for contaminant degradation. To avoid mistakenly associating basal-level gene expression with actively degrading microbial populations, an integrated approach using the ratio of functional gene transcripts to gene copies is recommended. This approach minimizes the impact of microbial transport on activity assessment and allows reliable assessments of microbial activity to be obtained from water samples.