Department of Microbiology, University of Georgiagrid.213876.9, Georgia, USA.
Department of Marine Sciences, University of Georgiagrid.213876.9, Athens, Georgia, USA.
Microbiol Spectr. 2022 Dec 21;10(6):e0319122. doi: 10.1128/spectrum.03191-22. Epub 2022 Oct 27.
Dimethylsulfoniopropionate (DMSP) is an abundant organic compound in marine surface water and source of dimethyl sulfide (DMS), the largest natural sulfur source to the upper atmosphere. Marine bacteria either mineralize DMSP through the demethylation pathway or transform it to DMS through the cleavage pathway. Factors that regulate which pathway is utilized are not fully understood. In chemostat experiments, the marine Roseobacter Ruegeria pomeroyi DSS-3 was exposed to oxidative stress either during growth with HO or by mutation of the gene encoding catalase. Oxidative stress reduced expression of the genes in the demethylation pathway and increased expression of those encoding the cleavage pathway. These results are contrary to the sulfur demand hypothesis, which theorizes that DMSP metabolism is driven by sulfur requirements of bacterial cells. Instead, we find strong evidence consistent with oxidative stress control over the switch in DMSP metabolism from demethylation to DMS production in an ecologically relevant marine bacterium. Dimethylsulfoniopropionate (DMSP) is the most abundant low-molecular-weight organic compound in marine surface water and source of dimethyl sulfide (DMS), a climatically active gas that connects the marine and terrestrial sulfur cycles. Marine bacteria are the major DMSP consumers, either generating DMS or consuming DMSP as a source of reduced carbon and sulfur. However, the factors regulating the DMSP catabolism in bacteria are not well understood. Marine bacteria are also exposed to oxidative stress. RNA sequencing (RNA-seq) experiments showed that oxidative stress induced in the laboratory reduced expression of the genes encoding the consumption of DMSP via the demethylation pathway and increased the expression of genes encoding DMS production via the cleavage pathway in the marine bacterium Ruegeria pomeroyi. These results support a model where DMS production in the ocean is regulated in part by oxidative stress.
二甲基巯基丙酸酯（DMSP）是海洋表面水中一种丰富的有机化合物，也是二甲基硫（DMS）的来源，DMS 是大气上层最大的天然硫源。海洋细菌通过去甲基化途径或通过裂解途径将 DMSP 转化为 DMS。目前尚不完全清楚调节哪种途径被利用的因素。在恒化器实验中，海洋罗尔斯通氏菌 Ruegeria pomeroyi DSS-3 在生长过程中或通过编码过氧化氢酶的基因突变暴露于氧化应激下。氧化应激降低了去甲基化途径基因的表达，增加了裂解途径基因的表达。这些结果与硫需求假说相反，该假说认为 DMSP 代谢是由细菌细胞的硫需求驱动的。相反，我们发现了强有力的证据，证明在生态相关的海洋细菌中，DMSP 代谢从去甲基化向 DMS 产生的转换受氧化应激的控制，而不是受硫需求的控制。二甲基巯基丙酸酯（DMSP）是海洋表面水中最丰富的低分子量有机化合物，也是二甲基硫（DMS）的来源，DMS 是一种活跃于气候的气体，将海洋和陆地的硫循环联系起来。海洋细菌是 DMSP 的主要消耗者，它们要么产生 DMS，要么将 DMSP 作为碳和硫的还原来源消耗。然而，调节细菌中 DMSP 分解代谢的因素尚不清楚。海洋细菌也会受到氧化应激的影响。RNA 测序（RNA-seq）实验表明，实验室诱导的氧化应激降低了通过去甲基化途径消耗 DMSP 的基因的表达，并增加了通过裂解途径产生 DMS 的基因的表达，在海洋细菌罗尔斯通氏菌中。这些结果支持了一种模型，即海洋中二甲基硫的产生部分受氧化应激的调节。
