(Per)chlorate-reducing bacteria can utilize aerobic and anaerobic pathways of aromatic degradation with (per)chlorate as an electron acceptor.
(Per)chlorate-reducing bacteria can utilize aerobic and anaerobic pathways of aromatic degradation with (per)chlorate as an electron acceptor.
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DOI：
10.1128/mbio.02287-14
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发表时间：
2015-03-24
期刊：
影响因子：
6.4
通讯作者：
Coates JD
中科院分区：
文献类型：
--
作者：
Carlström CI;Loutey D;Bauer S;Clark IC;Rohde RA;Iavarone AT;Lucas L;Coates JD
芳香族化合物在高氯酸盐和氯酸盐[统称为(PER)氯酸盐]还原条件下的氧化途径知之甚少。以前的研究表明，这些都是加氧酶依赖的途径，涉及氯酸盐呼吸过程中生物产生的O2。最近，我们描述了SeDimticola SelenatiReducens Cuz和Dechloromarinus Clouphilus NSS，它们分别氧化芳香化合物分解代谢的两个关键中间体苯乙酸酯和苯甲酸酯，并结合高氯酸盐或氯酸盐的还原和硝酸盐的还原。菌株CUZ也能以氧为电子受体氧化苯甲酸和苯乙酸酯，而菌株NSS即使在很低的氧气浓度(1%，Vol/Vol)下也只氧化后者。菌株CUZ和NSS含有类似的厌氧和好氧混合途径的基因，但编码好氧途径环氧酶的关键基因(PaaABCD)在两个基因组中都没有发现。通过使用转录组学和蛋白质组学，以及通过监测代谢中间产物，我们研究了厌氧和有氧-杂交途径在不同电子受体上的利用。对于CUZ菌株，结果表明利用了以高氯酸盐和硝酸盐为电子受体的厌氧途径和有氧条件下的好氧-杂交途径。相反，蛋白质组学结果表明，当菌株NSS在苯乙酸酯和氯酸盐上生长时，可能使用厌氧和有氧-杂交途径的组合。虽然微生物(PER)氯酸盐还原通过亚氯酸盐(ClO2−)的歧化产生分子氧，但这项研究表明，这些新生物仍然可以利用厌氧途径降解芳香族化合物。金黄色葡萄球菌和嗜氯杆菌分别是氯酸盐和氯酸盐还原细菌，它们的基因组编码苯乙酸酯和苯甲酸酯的厌氧和好氧混合降解途径。先前的研究表明，(PER)氯酸盐还原细菌和氯酸盐还原细菌(CRB)可以利用好氧途径在其他缺氧环境中通过捕获亚氯酸盐歧化产生的氧气来氧化芳香化合物。相反，我们证明了S.siselenatiReducens CUZ是第一个已知的利用以高氯酸盐为电子受体的厌氧芳香降解途径的高氯酸盐还原剂，并且它优先于好氧-混合途径，无论亚氯酸盐歧化产生任何氧气。另一方面，嗜氯杆菌NSS可能同时进行厌氧和好氧-混合过程。以前还没有关于其他CRB或任何微生物同时使用厌氧和好氧途径的报道，这些微生物编码类似的苯乙酸酯或苯甲酸酯降解途径，并且在低氧环境中可能是有利的。
The pathways involved in aromatic compound oxidation under perchlorate and chlorate [collectively known as (per)chlorate]-reducing conditions are poorly understood. Previous studies suggest that these are oxygenase-dependent pathways involving O2 biogenically produced during (per)chlorate respiration. Recently, we described Sedimenticola selenatireducens CUZ and Dechloromarinus chlorophilus NSS, which oxidized phenylacetate and benzoate, two key intermediates in aromatic compound catabolism, coupled to the reduction of perchlorate or chlorate, respectively, and nitrate. While strain CUZ also oxidized benzoate and phenylacetate with oxygen as an electron acceptor, strain NSS oxidized only the latter, even at a very low oxygen concentration (1%, vol/vol). Strains CUZ and NSS contain similar genes for both the anaerobic and aerobic-hybrid pathways of benzoate and phenylacetate degradation; however, the key genes (paaABCD) encoding the epoxidase of the aerobic-hybrid phenylacetate pathway were not found in either genome. By using transcriptomics and proteomics, as well as by monitoring metabolic intermediates, we investigated the utilization of the anaerobic and aerobic-hybrid pathways on different electron acceptors. For strain CUZ, the results indicated utilization of the anaerobic pathways with perchlorate and nitrate as electron acceptors and of the aerobic-hybrid pathways in the presence of oxygen. In contrast, proteomic results suggest that strain NSS may use a combination of the anaerobic and aerobic-hybrid pathways when growing on phenylacetate with chlorate. Though microbial (per)chlorate reduction produces molecular oxygen through the dismutation of chlorite (ClO2−), this study demonstrates that anaerobic pathways for the degradation of aromatics can still be utilized by these novel organisms. S. selenatireducens CUZ and D. chlorophilus NSS are (per)chlorate- and chlorate-reducing bacteria, respectively, whose genomes encode both anaerobic and aerobic-hybrid pathways for the degradation of phenylacetate and benzoate. Previous studies have shown that (per)chlorate-reducing bacteria and chlorate-reducing bacteria (CRB) can use aerobic pathways to oxidize aromatic compounds in otherwise anoxic environments by capturing the oxygen produced from chlorite dismutation. In contrast, we demonstrate that S. selenatireducens CUZ is the first perchlorate reducer known to utilize anaerobic aromatic degradation pathways with perchlorate as an electron acceptor and that it does so in preference over the aerobic-hybrid pathways, regardless of any oxygen produced from chlorite dismutation. D. chlorophilus NSS, on the other hand, may be carrying out anaerobic and aerobic-hybrid processes simultaneously. Concurrent use of anaerobic and aerobic pathways has not been previously reported for other CRB or any microorganisms that encode similar pathways of phenylacetate or benzoate degradation and may be advantageous in low-oxygen environments.