Visscher P T, Taylor B F
Division of Marine and Atmospheric Chemistry, Rosenstiel School of Marine and Atmospheric Science, Miami, Florida 33149-1098.
Appl Environ Microbiol. 1993 Nov;59(11):3784-9. doi: 10.1128/aem.59.11.3784-3789.1993.
Aerobic degradation of dimethyl sulfide (DMS), previously described for thiobacilli and hyphomicrobia, involves catabolism to sulfide via methanethiol (CH3SH). Methyl groups are sequentially eliminated as HCHO by incorporation of O2 catalyzed by DMS monooxygenase and methanethiol oxidase. H2O2 formed during CH3SH oxidation is destroyed by catalase. We recently isolated Thiobacillus strain ASN-1, which grows either aerobically or anaerobically with denitrification on DMS. Comparative experiments with Thiobacillus thioparus T5, which grows only aerobically on DMS, indicate a novel mechanism for aerobic DMS catabolism by Thiobacillus strain ASN-1. Evidence that both organisms initially attacked the methyl group, rather than the sulfur atom, in DMS was their conversion of ethyl methyl sulfide to ethanethiol. HCHO transiently accumulated during the aerobic use of DMS by T. thioparus but not with Thiobacillus strain ASN-1. Catalase levels in cells grown aerobically on DMS were about 100-fold lower in Thiobacillus strain ASN-1 than in T. thioparus T5, suggesting the absence of H2O2 formation during DMS catabolism. Also, aerobic growth of T. thioparus T5 on DMS was blocked by the catalase inhibitor 3-amino-1,2,4-triazole whereas that of Thiobacillus strain ASN-1 was not. Methyl butyl ether, but not CHCl3, blocked DMS catabolism by T. thioparus T5, presumably by inhibiting DMS monooxygenase and perhaps methanethiol oxidase. In contrast, DMS metabolism by Thiobacillus strain ASN-1 was unaffected by methyl butyl ether but inhibited by CHCl3. DMS catabolism by Thiobacillus strain ASN-1 probably involves methyl transfer to a cobalamin carrier and subsequent oxidation as folate-bound intermediates.
先前已报道硫杆菌属和生丝微菌属可对二甲基硫醚（DMS）进行需氧降解，该过程涉及通过甲硫醇（CH3SH）将其分解代谢为硫化物。甲基通过DMS单加氧酶和甲硫醇氧化酶催化结合O2依次以HCHO的形式被去除。在CH3SH氧化过程中形成的H2O2被过氧化氢酶破坏。我们最近分离出硫杆菌属菌株ASN-1，它可以在DMS上进行需氧生长或通过反硝化作用进行厌氧生长。与仅在DMS上进行需氧生长的嗜硫硫杆菌T5进行的对比实验表明，硫杆菌属菌株ASN-1对DMS进行需氧分解代谢存在一种新机制。这两种微生物最初攻击DMS中的甲基而非硫原子的证据是它们将乙甲基硫醚转化为乙硫醇。在嗜硫硫杆菌需氧利用DMS的过程中，HCHO会短暂积累，但硫杆菌属菌株ASN-1不会。在DMS上进行需氧生长的细胞中，硫杆菌属菌株ASN-1中的过氧化氢酶水平比嗜硫硫杆菌T5低约100倍，这表明在DMS分解代谢过程中不存在H2O2的形成。此外，嗜硫硫杆菌T5在DMS上的需氧生长被过氧化氢酶抑制剂3-氨基-1,2,4-三唑阻断，而硫杆菌属菌株ASN-1则不受影响。甲基丁基醚而非CHCl3阻断了嗜硫硫杆菌T5的DMS分解代谢，可能是通过抑制DMS单加氧酶，也许还有甲硫醇氧化酶。相比之下，硫杆菌属菌株ASN-1的DMS代谢不受甲基丁基醚影响，但受CHCl3抑制。硫杆菌属菌株ASN-1的DMS分解代谢可能涉及甲基转移至钴胺素载体并随后作为与叶酸结合的中间体进行氧化。
