The abundance and activity of methane-oxidizing bacteria (MOB) in the water column were investigated in three lakes with different contents of nutrients and humic substances. The abundance of MOB was determined by analysis of group-specific phospholipid fatty acids from type I and type II MOB, and in situ activity was measured with a 14CH4 transformation method. The fatty acid analyses indicated that type I MOB most similar to species of Methylomonas, Methylomicrobium, and Methylosarcina made a substantial contribution (up to 41%) to the total bacterial biomass, whereas fatty acids from type II MOB generally had very low concentrations. The MOB biomass and oxidation activity were positively correlated and were highest in the hypo- and metalimnion during summer stratification, whereas under ice during winter, maxima occurred close to the sediments. The methanotroph biomass-specific oxidation rate (V) ranged from 0.001 to 2.77 mg CH4-C mg−1 C day−1 and was positively correlated with methane concentration, suggesting that methane supply largely determined the activity and biomass distribution of MOB. Our results demonstrate that type I MOB often are a large component of pelagic bacterial communities in temperate lakes. They represent a potentially important pathway for reentry of carbon and energy into pelagic food webs that would otherwise be lost as evasion of CH4.
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机译：在三个养分和腐殖质含量不同的三个湖泊中，研究了水柱中甲烷氧化细菌（MOB）的丰度和活性。通过分析I型和II型MOB的基团特异性磷脂脂肪酸来确定MOB的丰度，并使用 14 CH4转化法测量原位活性。脂肪酸分析表明，与甲基单孢菌属，甲基微生物和甲基藻类最相似的I型MOB对细菌总生物量有很大贡献（高达41％），而II型MOB的脂肪酸浓度通常很低。 MOB的生物量和氧化活性呈正相关，在夏季分层时次金属和次金属离子中最高，而在冬季，在冰层下，最大值发生在沉积物附近。甲烷营养生物质比氧化率（V）为0.001至2.77 mg CH4-C mg -1 C day -1 ，与甲烷浓度呈正相关，表明甲烷的供应很大程度上决定了MOB的活性和生物量分布。我们的结果表明，I型MOB通常是温带湖泊中上层细菌群落的重要组成部分。它们代表了碳和能量重新进入远洋食物网的潜在重要途径，否则将因逃逸CH4而损失。
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