Castle Lake Biofilm Microbiom Targeted loci environmental. Castle Lake Biofilm Microbiom

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 in light and dark conditions (i.e., with and without autotrophy, respectively) in a full factorial design using nutrient diffusing substrates in-situ for 20 days. 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.

异养细菌（Heterotrophic bacteria）在生态系统过程中发挥关键作用，但目前对调控水生生物膜细菌群落结构的因素仍所知甚少，尤其是湖泊生境中的此类群落。本研究采用分子技术（16S rRNA），针对一座贫营养亚高山湖泊，探究资源因子对其生物膜细菌群落结构的调控作用。研究采用原位营养扩散底物（nutrient diffusing substrates）的全因子实验设计，在光照（即存在自养作用）与黑暗（即无自养作用）条件下，于无机（岩石）和有机（木材）基质上设置营养物（氮、磷，简称NP）与葡萄糖（简称G）的添加处理，实验周期为20天。添加营养物组（NP、NP+G）与无营养物组（对照组、仅G组）间的群落结构呈现显著分离模式，表明无论基质类型与光照条件如何，营养物对群落结构的调控作用均强于有机质。进一步分析发现，在有机与无机基质上，仅添加营养物组（NP）与添加营养物+葡萄糖组（NP+G）的群落结构仍存在分离，这表明当营养限制被解除后，有机质质量会对群落结构塑造起到重要作用。不同处理组间6个门、3个纲以及19个属的相对丰度存在显著差异，由此揭示三点结论：1）不同类群具有差异化的资源需求；2）种间相互作用对群落组成具有调控影响；3）部分类群具备参与难降解有机质分解的潜力。本研究结果阐明了营养物与有机质质量在调控水生生物膜细菌群落结构中的作用，为填补水生环境中微生物组成与生态功能间的认知空白提供了关键依据。