Docherty Kathryn M, Young Katherine C, Maurice Patricia A, Bridgham Scott D
Department of Biological Sciences, University of Notre Dame, PO Box 369, Notre Dame, IN 46556, USA.
Microb Ecol. 2006 Oct;52(3):378-88. doi: 10.1007/s00248-006-9089-x. Epub 2006 Jun 10.
Past studies have suggested that the concentration and quality of dissolved organic matter (DOM) may influence microbial community structure. In this study, we cross-inoculated the bacterial communities from two streams and a dystrophic lake that varied in DOM concentration and chemistry, to yield nine fully crossed treatments. We measured dissolved organic carbon (DOC) concentration and heterotrophic microbial community productivity throughout a 72-h incubation period, characterized DOM quality by molecular weight, and determined microbial community structure at the initial and final time points. Our results indicate that all bacterial inoculate sources had similar effects upon DOC concentration and DOM quality, regardless of the DOM source. These effects included an overall decrease in DOM M (W) and an initial period of DOC concentration variability between 0-24h. In contrast, microbial communities and their metabolic rates converged to profiles that reflected the DOM source upon which they were growing, regardless of the initial bacterial inoculation. The one exception was that the bacterial community from the low-concentration and low-molecular-weight DOM source exhibited a greater denaturing gradient gel electrophoresis (DGGE) band richness when grown in its own DOM source than when grown in the highest concentration and molecular weight DOM source. This treatment also exhibited a higher rate of productivity. In general, our data suggest that microbial communities are selected by the DOM sources to which they are exposed. A microbial community will utilize the low-molecular-weight (or labile) DOM sources as well as parts of the high-molecular-weight (refractory) DOM, until a community develops that can efficiently metabolize the more abundant high-molecular-weight source. This experiment examines some of the complex interactions between microbial community selection and the combined factors of DOM quality and concentration. Our data suggest that the roles of aerobic aquatic heterotrophic bacteria in carbon cycling, as well as the importance of high-molecular-weight DOM as a carbon source, may be more complex than is conventionally recognized.
以往的研究表明，溶解有机物（DOM）的浓度和质量可能会影响微生物群落结构。在本研究中，我们对来自两条溪流和一个腐殖质湖的细菌群落进行了交叉接种，这些水体的DOM浓度和化学性质各不相同，从而产生了九种完全交叉的处理方式。在72小时的培养期内，我们测量了溶解有机碳（DOC）浓度和异养微生物群落生产力，通过分子量表征DOM质量，并在初始和最终时间点确定微生物群落结构。我们的结果表明，无论DOM来源如何，所有细菌接种源对DOC浓度和DOM质量都有相似的影响。这些影响包括DOM M（W）总体下降以及0 - 24小时内DOC浓度的初始变异性。相比之下，微生物群落及其代谢率会趋向于反映它们所生长的DOM来源的特征，而与初始细菌接种无关。唯一的例外是，来自低浓度和低分子量DOM来源的细菌群落在其自身的DOM来源中生长时，比在最高浓度和分子量的DOM来源中生长时表现出更高的变性梯度凝胶电泳（DGGE）条带丰富度。该处理方式也表现出更高的生产力。总体而言，我们的数据表明微生物群落是由它们所接触的DOM来源选择的。微生物群落将利用低分子量（或易分解）的DOM来源以及部分高分子量（难分解）的DOM，直到形成一个能够有效代谢更丰富的高分子量来源的群落。本实验研究了微生物群落选择与DOM质量和浓度综合因素之间的一些复杂相互作用。我们的数据表明，好氧水生异养细菌在碳循环中的作用以及高分子量DOM作为碳源的重要性可能比传统认识的更为复杂。
