Ramachandran Arthi, Walsh David A
Department of Biology, Concordia University, 7141 Sherbrooke St West, Montreal, Quebec, H4B 1R6, Canada.
Department of Biology, Concordia University, 7141 Sherbrooke St West, Montreal, Quebec, H4B 1R6, Canada Canadian Institute for Advanced Research, Integrated Microbial Biodiversity Program, Canada Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Montreal, Quebec Canada
FEMS Microbiol Ecol. 2015 Oct;91(10). doi: 10.1093/femsec/fiv105. Epub 2015 Aug 30.
The diversity and distribution of methylotrophic bacteria have been investigated in the oceans and lakes using the methanol dehydrogenase mxaF gene as a functional marker. However, pelagic marine (OM43) and freshwater (LD28 and PRD01a001B) methylotrophs within the Betaproteobacteria lack mxaF, instead possessing a related xoxF4-encoded methanol dehydrogenase. Here, we developed and employed xoxF4 as a complementary functional gene marker to mxaF for studying methylotrophs in aquatic environment. Using xoxF4, we detected OM43-related and LD28-related methylotrophs in the ocean and freshwaters of North America, respectively, and showed the coexistence of these two lineages in a large estuarine system (St Lawrence Estuary). Gene expression patterns of xoxF4 supported a positive relationship between xoxF4-containing methylotroph activity and spring time productivity, suggesting phytoplankton blooms are a source of methylotrophic substrates. Further investigation of methanol dehydrogenase diversity in pelagic ecosystems using comparative metagenomics provided strong support for a widespread distribution of xoxF4 (as well as several distinct xoxF5) containing methylotrophs in marine and freshwater surface waters. In total, these results demonstrate a geographical distribution of OM43/LD28-related methylotrophs that includes marine and freshwaters and suggest that methylotrophy occurring in the water column is an important component of lake and estuary carbon cycling and biogeochemistry.
利用甲醇脱氢酶mxaF基因作为功能标记，对海洋和湖泊中甲基营养菌的多样性和分布进行了研究。然而，β-变形菌纲中的远洋海洋甲基营养菌（OM43）和淡水甲基营养菌（LD28和PRD01a001B）缺乏mxaF基因，而是拥有一种相关的由xoxF4编码的甲醇脱氢酶。在此，我们开发并采用xoxF4作为mxaF的互补功能基因标记，用于研究水生环境中的甲基营养菌。利用xoxF4，我们分别在北美洲的海洋和淡水中检测到了与OM43相关和与LD28相关的甲基营养菌，并表明这两个谱系在一个大型河口系统（圣劳伦斯河口）中共存。xoxF4的基因表达模式支持了含xoxF4的甲基营养菌活性与春季生产力之间的正相关关系，表明浮游植物大量繁殖是甲基营养底物的一个来源。利用比较宏基因组学对远洋生态系统中甲醇脱氢酶多样性的进一步研究，为含xoxF4（以及几种不同的xoxF5）的甲基营养菌在海洋和淡水表层水中的广泛分布提供了有力支持。总的来说，这些结果证明了与OM43/LD28相关的甲基营养菌的地理分布包括海洋和淡水，并表明水柱中发生的甲基营养作用是湖泊和河口碳循环及生物地球化学的一个重要组成部分。
