Carbonyl sulfide (COS) is the most abundant sulfur compound in the atmosphere, and, thus, is important in the global sulfur cycle. Soil is a major sink of atmospheric COS and the numerical distribution of soil microorganisms that degrade COS is indispensable for estimating the COS-degrading potential of soil. However, difficulties are associated with counting COS-degrading microorganisms using culture-dependent approaches, such as the most probable number (MPN) method, because of the chemical hydrolysis of COS by water. We herein developed a two-step MPN method for COS-degrading microorganisms: the first step for chemoorganotrophic growth that supported a sufficient number of cells for COS degradation in the second step. Our new MPN analysis of various environmental samples revealed that the cell density of COS-degrading microorganisms in forest soils ranged between 106 and 108 MPN (g dry soil)–1, which was markedly higher than those in volcanic deposit and water samples, and strongly correlated with the rate of COS degradation in environmental samples. Numerically dominant COS degraders that were isolated from the MPN-positive culture were related to bacteria in the orders Bacillales and Actinomycetales. The present results provide numerical evidence for the ubiquity of COS-degrading microbes in natural environments.

中文翻译：

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用最可能数法计数化学有机营养羰基硫 (COS) 降解微生物

羰基硫 (COS) 是大气中含量最丰富的硫化合物，因此在全球硫循环中很重要。土壤是大气 COS 的主要汇，降解 COS 的土壤微生物的数量分布对于估算土壤的 COS 降解潜力是必不可少的。然而，由于 COS 被水化学水解，使用依赖培养的方法（例如最可能数 (MPN) 方法）计数降解 COS 的微生物存在困难。我们在此开发了一种用于 COS 降解微生物的两步 MPN 方法：化学有机营养生长的第一步，在第二步中支持足够数量的细胞进行 COS 降解。我们对各种环境样品的新 MPN 分析表明，森林土壤中 COS 降解微生物的细胞密度介于 106 和 108 MPN (g 干土)–1 之间，明显高于火山沉积物和水样中的细胞密度，并且强烈与环境样品中 COS 的降解速率相关。从 MPN 阳性培养物中分离出的数字显性 COS 降解物与芽孢杆菌目和放线菌目中的细菌有关。目前的结果为自然环境中 COS 降解微生物的普遍存在提供了数值证据。从 MPN 阳性培养物中分离出的数字显性 COS 降解物与芽孢杆菌目和放线菌目中的细菌有关。目前的结果为自然环境中 COS 降解微生物的普遍存在提供了数值证据。从 MPN 阳性培养物中分离出的数字显性 COS 降解物与芽孢杆菌目和放线菌目中的细菌有关。目前的结果为自然环境中 COS 降解微生物的普遍存在提供了数值证据。