Cho Jang-Cheon, Stapels Martha D, Morris Robert M, Vergin Kevin L, Schwalbach Michael S, Givan Scott A, Barofsky Douglas F, Giovannoni Stephen J
Department of Microbiology, Oregon State University, Corvalis, OR, USA.
Environ Microbiol. 2007 Jun;9(6):1456-63. doi: 10.1111/j.1462-2920.2007.01264.x.
Ecological studies indicate that aerobic anoxygenic phototrophic bacteria (AAP) that use bacteriochlorophyll to support phototrophic electron transport are widely distributed in the oceans. All cultivated marine AAP are alpha-3 and alpha-4 Proteobacteria, but metagenomic evidence indicates that uncultured AAP Gammaproteobacteria are important members of ocean surface microbial communities. Here we report the description of obligately oligotrophic, marine Gammaproteobacteria that have genes for aerobic anoxygenic photosynthesis. Three strains belonging to the OM60 clade were isolated in autoclaved seawater media. Polymerase chain reaction assays for the pufM gene show that these strains contain photosynthetic reaction centre genes. DNA sequencing and phylogenetic analysis indicate that the pufM genes are polyphyletic, suggesting multiple instances of lateral gene transfer. Peptide sequences from six photosynthesis genes (pufL, pufM, pufC, pufB, pufA and puhA) were detected by proteomic analyses of strain HTCC2080 cells grown aerobically in seawater. They closely match predicted peptides from an environmental seawater bacterial artificial chromosome clone of gammaproteobacterial origin, thus identifying the OM60 clade as a significant source of gammaproteobacterial AAP genes in marine systems. The cell yield and rate of growth of HTCC2080 in autoclaved, aerobic seawater increased in the light. These findings identify the OM60 clade as a source of Gammaproteobacteria AAP genes in coastal oceans, and demonstrate that aerobic, anoxygenic photosynthetic metabolism can enhance the productivity of marine oligotrophic bacteria that also grow heterotrophically in darkness.
生态学研究表明，利用细菌叶绿素支持光合电子传递的需氧不产氧光合细菌（AAP）广泛分布于海洋中。所有已培养的海洋AAP均为α-3和α-4变形菌，但宏基因组学证据表明，未培养的AAPγ-变形菌是海洋表层微生物群落的重要成员。在此，我们报告了具有需氧不产氧光合作用基因的专性贫营养海洋γ-变形菌的描述。从高压灭菌海水培养基中分离出三株属于OM60进化枝的菌株。对pufM基因的聚合酶链反应分析表明，这些菌株含有光合反应中心基因。DNA测序和系统发育分析表明，pufM基因是多系的，表明存在多个横向基因转移实例。通过对在海水中需氧生长的HTCC2080菌株细胞进行蛋白质组学分析，检测到来自六个光合作用基因（pufL、pufM、pufC、pufB、pufA和puhA）的肽序列。它们与来自γ-变形菌起源的环境海水细菌人工染色体克隆的预测肽紧密匹配，从而确定OM60进化枝是海洋系统中γ-变形菌AAP基因的重要来源。HTCC2080在高压灭菌的需氧海水中的细胞产量和生长速率在光照下增加。这些发现确定OM60进化枝是沿海洋域中γ-变形菌AAP基因的一个来源，并证明需氧不产氧光合代谢可以提高在黑暗中也能异养生长的海洋贫营养细菌的生产力。
