Abstract:
OBJECTIVE: Catabolism of dimethylsulfoniopropionate (DMSP) by marine bacteria has important impacts on the global sulfur cycle and climate. However, whether and how members of most oligotrophic bacterial groups participate in DMSP metabolism in marine environments remains largely unknown. In this study, by characterizing culturable strains, we have revealed that bacteria of the SAR92 clade, an abundant oligotrophic group of Gammaproteobacteria in coastal seawater, can catabolize DMSP through the DMSP lyase DddD-mediated cleavage pathway and/or the DMSP demethylase DmdA-mediated demethylation pathway to produce climate-active gases dimethylsulfide and methanethiol. Additionally, we found that SAR92 clade bacteria capable of catabolizing DMSP are widely distributed in global oceans. These results indicate that SAR92 clade bacteria are potentially important DMSP degraders and sources of climate-active gases in marine environments that have been overlooked, contributing to a better understanding of the roles and mechanisms of the oligotrophic bacteria in oceanic DMSP degradation.
摘要:
二甲基磺丙酸酯(DMSP)是地球上最丰富的有机硫分子之一,它们可以被海洋细菌分解代谢,通过裂解和/或去甲基化途径释放气候活性气体。海洋SAR92进化枝是沿海海水中丰富的寡营养型γ变形菌,但是它们分解DMSP的能力尚未测试。在这项研究中,从沿海海水中分离出的三种SAR92进化枝菌株和SAR92代表性菌株HTCC2207均显示出分解代谢DMSP作为碳源。所有SAR92进化枝菌株均表现出DMSP裂解酶活性,产生二甲基硫醚(DMS),其基因组编码已批准的DddDDMSP裂解酶。相比之下,只有HTCC2207和两个分离的菌株包含DMSP脱甲基酶dmdA基因,并且可能同时将DMSP脱甲基和裂解以产生甲硫醇(MeSH)和DMS。在具有dddD和dmdA的SAR92进化枝菌株中,这些基因的转录可被DMSP底物诱导。生物信息学分析表明,含有和转录DddD和DmdA的SAR92进化枝细菌在全球海洋中广泛分布,尤其是在极地地区。这项研究强调了SAR92的寡营养细菌进化枝作为DMSP的潜在重要分解者以及海洋环境中气候活性气体MeSH和DMS的来源,特别是在极地地区。海洋细菌对二甲基磺丙酸酯(DMSP)的重要代谢对全球硫循环和气候具有重要影响。然而,大多数贫营养细菌群的成员是否以及如何参与海洋环境中的DMSP代谢仍在很大程度上未知。在这项研究中,通过表征可培养的菌株,我们已经发现了SAR92进化枝的细菌,沿海海水中丰富的γ变形菌的贫营养群,可以通过DMSP裂解酶DddD介导的裂解途径和/或DMSP去甲基酶DmdA介导的去甲基化途径分解代谢DMSP,以产生气候活性气体二甲基硫醚和甲硫醇。此外,我们发现能够分解代谢DMSP的SAR92进化枝细菌广泛分布在全球海洋中。这些结果表明,SAR92进化枝细菌是潜在的重要的DMSP降解剂和海洋环境中的气候活性气体的来源,但却被忽视了。有助于更好地了解贫营养细菌在海洋DMSP降解中的作用和机制。