ABSTRACT: Heterotrophic bacteria play a key role in ecosystem processes, but little is known about the factors that shape bacterial community structure in aquatic biofilms, especially in lakes. We used molecular techniques (16S rRNA) to evaluate resource controls on biofilm bacterial community structure in an oligotrophic subalpine lake. We manipulated nutrients (nitrogen and phosphorus; NP) and glucose (G) on inorganic (rock) and organic (wood) substrates under light and dark conditions (i.e. with and without autotrophy, respectively) in a full factorial design using nutrient diffusing substrates in situ for 20 d. Distinct patterns of separation in community structure between treatments with nutrients (NP, NP+G) and without nutrients (control, G-only) indicated that community structure was more strongly influenced by nutrients than organic matter irrespective of substrate type or light availability. Further separation in community structure between treatments with nutrients only (NP) and nutrients with glucose (NP+G) on both organic and inorganic substrates indicated that once nutrient limitation was alleviated, organic matter quality played an important role in shaping community structure. Differences in the relative abundance of 6 phyla, 3 classes, and 19 genera among treatments revealed (1) contrasting taxa-specific resource requirements, (2) the influence of interspecific interactions on composition, and (3) the potential for individual taxa to participate in the decomposition of recalcitrant organic matter. Our findings provide insight into the role that nutrients and organic matter quality play in shaping bacterial community structure, which is a critical step in bridging the knowledge gap between microbial composition and ecosystem function within aquatic environments.

中文翻译：

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湖泊生物膜中的养分有效性和有机质质量塑造细菌群落结构

摘要：异养细菌在生态系统过程中起着关键作用，但对于影响水生生物膜（尤其是湖泊）中细菌群落结构的因素知之甚少。我们使用分子技术（16S rRNA）来评估贫营养型亚高山湖泊生物膜细菌群落结构的资源控制。我们在明亮和黑暗条件下（分别有自养和无自养作用）在无机（岩石）和有机（木材）基质上处理营养素（氮和磷； NP）和葡萄糖（G），采用全营养设计，其中包括原位20 d。在使用营养物（NP，NP + G）和不使用营养物（对照，仅G）的处理之间，群落结构的不同分离模式表明，无论底物类型或光可利用性如何，群落结构受营养物质的影响均大于有机质。在有机和无机基质上，仅使用营养素（NP）的处理与使用葡萄糖营养素（NP + G）的处理之间的进一步分离表明，一旦缓解了养分限制，有机质就将在塑造社区结构中发挥重要作用。处理之间6个门，3个类别和19个属的相对丰度的差异表明（1）特定分类单元资源需求的差异，（2）种间相互作用对组成的影响，（3）个体分类单元参与顽固有机物分解的潜力。我们的发现提供了对营养物质和有机物质质量在塑造细菌群落结构中所起的作用的深入了解，这是弥合水生环境中微生物组成与生态系统功能之间的知识鸿沟的关键步骤。