Lanthanide-dependent cross-feeding of methane-derived carbon is linked by microbial community interactions
Lanthanide-dependent cross-feeding of methane-derived carbon is linked by microbial community interactions
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DOI：
10.1073/pnas.1619871114
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发表时间：
2017-01-10
影响因子：
11.1
通讯作者：
Lidstrom, Mary E.
中科院分区：
文献类型：
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作者：
Krause, Sascha M. B.;Johnson, Timothy;Lidstrom, Mary E.
甲烷是一种强效温室气体，其利用是当地和全球碳循环的重要组成部分，其特点是利用甲烷（甲烷氧化菌）和非甲烷氧化菌之间的紧密联系。有人认为，甲烷氧化菌通过交叉喂养来维持这些非甲烷氧化菌，因为甲烷氧化途径的后续产物，例如甲醇，代表了替代碳源。我们在微观模型系统中建立了共培养，以确定在环境中观察到的交叉喂养的机制和基质。镧是一种稀土元素，因其在甲基营养中的重要性日益增加而被应用。我们使用了从华盛顿湖沉积物中分离出来的参与甲烷利用的共生菌株：一种甲烷氧化菌和两种非甲烷氧化型甲基营养菌。基因表达谱和突变体分析表明，甲醇是甲烷氧化菌为支持非甲烷氧化菌生长提供的主要碳和能源。然而，在非甲烷氧化菌存在的情况下，主要甲醇脱氢酶（MDH）的基因表达从镧系元素依赖性MDH（XoxF）型转变为钙依赖性MDH（MxaF）型。相应地，仅当甲烷氧化菌表达MxaF型MDH时，甲醇才会释放到培养基中。这些结果表明了一种交叉喂养机制，其中非甲烷氧化菌伙伴诱导甲烷氧化菌MDHs表达的变化，导致其生长释放甲醇。这种由伴侣引起的基因表达变化有利于伴侣，这是在纯培养物研究中无法观察到的微生物相互作用的范例，强调了合成微生物群落方法对于了解环境微生物组的重要性。
The utilization of methane, a potent greenhouse gas, is an important component of local and global carbon cycles that is characterized by tight linkages between methane-utilizing (methanotrophic) and nonmethanotrophic bacteria. It has been suggested that the methanotroph sustains these nonmethanotrophs by cross-feeding, because subsequent products of the methane oxidation pathway, such as methanol, represent alternative carbon sources. We established cocultures in a microcosm model system to determine the mechanism and substrate that underlay the observed cross-feeding in the environment. Lanthanum, a rare earth element, was applied because of its increasing importance in methylotrophy. We used co-occurring strains isolated from Lake Washington sediment that are involved in methane utilization: a methanotroph and two nonmethanotrophic methylotrophs. Gene-expression profiles and mutant analyses suggest that methanol is the dominant carbon and energy source the methanotroph provides to support growth of the nonmethanotrophs. However, in the presence of the nonmethanotroph, gene expression of the dominant methanol dehydrogenase (MDH) shifts from the lanthanide-dependent MDH (XoxF)-type, to the calcium-dependent MDH (MxaF)-type. Correspondingly, methanol is released into the medium only when the methanotroph expresses the MxaF-type MDH. These results suggest a cross-feeding mechanism in which the nonmethanotrophic partner induces a change in expression of methanotrophMDHs, resulting in release of methanol for its growth. This partner-induced change in gene expression that benefits the partner is a paradigm for microbial interactions that cannot be observed in studies of pure cultures, underscoring the importance of synthetic microbial community approaches to understand environmental microbiomes.