Department of Civil and Environmental Engineering, 4105 Seamans Center, The University of Iowa, Iowa City, IA, 52242, USA.
Appl Microbiol Biotechnol. 2022 Sep;106(18):6335-6346. doi: 10.1007/s00253-022-12147-y. Epub 2022 Sep 3.
Vinyl chloride (VC) is a common groundwater pollutant generated during anaerobic biodegradation of chlorinated solvents (e.g., trichloroethene (TCE) or tetrachloroethene (PCE)). Aerobic VC biodegradation by etheneotrophs can support anaerobic PCE and TCE bioremediation to achieve complete removal in situ. However, anaerobic bioremediation strategies necessitate biostimulation with electron donors that are fermented in situ, generating organic acids that could influence aerobic VC biodegradation processes. We examined the effect of organic acids (lactate, acetate, propionate, and butyrate) on aerobic VC biodegradation by VC-assimilating etheneotrophs Mycobacterium strain JS60 and Nocardioides strain JS614. Strain JS60 grew on all organic acids tested, while strain JS614 did not respond to lactate. VC-grown strain JS60 fed VC and one or more organic acids showed carbon catabolite repression (CCR) behavior where VC biodegradation occurred only after organic acids were depleted. In contrast, CCR was not evident in VC-grown strain JS614, which degraded VC and organic acids simultaneously. Acetate-grown JS60 showed similar CCR behavior when fed VC and a single organic acid, except that extended lag periods (5-12 days) occurred before VC oxidation ensued. Acetate-grown JS614 fed VC and either acetate or butyrate displayed 5-8 day lag periods before simultaneous VC and organic acid biodegradation. In contrast, acetate-grown JS614 degraded VC and propionate without a significant lag, suggesting a regulatory link between propionate and VC oxidation in JS614. Different global regulatory mechanisms controlling VC biodegradation in the presence of organic acids in etheneotrophs have implications for developing combined anaerobic-aerobic bioremediation strategies at chlorinated ethene-contaminated sites. KEY POINTS: • With organic acids present, VC utilization was repressed in JS60, but not in JS614 • Strain JS60 grew readily on lactate, while strain JS614 did not • Propionate alleviated lag periods for VC utilization in acetate-grown JS614.
氯乙烯（VC）是在氯代溶剂（如三氯乙烯（TCE）或四氯乙烯（PCE））的厌氧生物降解过程中产生的一种常见地下水污染物。乙烯营养型细菌的好氧 VC 生物降解可以支持厌氧 PCE 和 TCE 的生物修复，从而实现原位完全去除。然而，厌氧生物修复策略需要用在原地发酵的电子供体进行生物刺激，产生的有机酸可能会影响好氧 VC 生物降解过程。我们研究了有机酸（乳酸盐、醋酸盐、丙酸盐和丁酸盐）对氯乙烯同化乙烯营养型细菌分枝杆菌菌株 JS60 和诺卡氏菌菌株 JS614 进行好氧 VC 生物降解的影响。菌株 JS60 可以在所有测试的有机酸上生长，而菌株 JS614 对乳酸盐没有反应。以 VC 生长的菌株 JS60 以 VC 和一种或多种有机酸为食，表现出碳分解代谢阻遏（CCR）行为，只有在有机酸耗尽后才会发生 VC 生物降解。相比之下，在以 VC 生长的菌株 JS614 中，CCR 并不明显，该菌株可以同时降解 VC 和有机酸。以醋酸盐生长的 JS60 在以 VC 和单一有机酸为食时表现出类似的 CCR 行为，只是在 VC 氧化之前会出现延长的迟滞期（5-12 天）。以醋酸盐生长的 JS614 以 VC 和醋酸盐或丁酸盐为食时，在同时降解 VC 和有机酸之前会出现 5-8 天的迟滞期。相比之下，以醋酸盐生长的 JS614 可以在没有明显迟滞的情况下降解 VC 和丙酸盐，这表明在 JS614 中丙酸盐和 VC 氧化之间存在调节关系。在乙烯营养型细菌中存在有机酸时，控制 VC 生物降解的不同全局调控机制对开发氯代乙烯污染场地的联合厌氧-好氧生物修复策略具有重要意义。关键点： • 有有机酸存在时，JS60 中 VC 的利用受到抑制，但在 JS614 中则没有 • 菌株 JS60 很容易在乳酸盐上生长，而菌株 JS614 则不能 • 丙酸盐缓解了在以醋酸盐生长的 JS614 中利用 VC 的迟滞期。
