Morrison Jessica M, Murphy Chelsea L, Baker Kristina, Zamor Richard M, Nikolai Steve J, Wilder Shawn, Elshahed Mostafa S, Youssef Noha H
Department of Microbiology and Molecular Genetics, Oklahoma State University , Stillwater , OK , USA.
Grand River Dam Authority , Vinita , OK , USA.
PeerJ. 2017 Jan 10;5:e2803. doi: 10.7717/peerj.2803. eCollection 2017.
Algae encompass a wide array of photosynthetic organisms that are ubiquitously distributed in aquatic and terrestrial habitats. Algal species often bloom in aquatic ecosystems, providing a significant autochthonous carbon input to the deeper anoxic layers in stratified water bodies. In addition, various algal species have been touted as promising candidates for anaerobic biogas production from biomass. Surprisingly, in spite of its ecological and economic relevance, the microbial community involved in algal detritus turnover under anaerobic conditions remains largely unexplored.
Here, we characterized the microbial communities mediating the degradation of (Chlorophyta), sp. strain IWP1 (Charophyceae), and kelp (phylum Phaeophyceae), using sediments from an anaerobic spring (Zodlteone spring, OK; ZDT), sludge from a secondary digester in a local wastewater treatment plant (Stillwater, OK; WWT), and deeper anoxic layers from a seasonally stratified lake (Grand Lake O' the Cherokees, OK; GL) as inoculum sources. Within all enrichments, the majority of algal biomass was metabolized within 13-16 weeks, and the process was accompanied by an increase in cell numbers and a decrease in community diversity. Community surveys based on the V4 region of the 16S rRNA gene identified different lineages belonging to the phyla Bacteroidetes, Proteobacteria (alpha, delta, gamma, and epsilon classes), Spirochaetes, and Firmicutes that were selectively abundant under various substrate and inoculum conditions. Within all kelp enrichments, the microbial communities structures at the conclusion of the experiment were highly similar regardless of the enrichment source, and were dominated by the genus , or family within the Firmicutes. In all other enrichments the final microbial community was dependent on the inoculum source, rather than the type of algae utilized as substrate. Lineages enriched included the uncultured groups VadinBC27 and WCHB1-69 within the Bacteroidetes, genus and the uncultured group SHA-4 within Spirochaetes, , , , , and within the Firmicutes, and genera , , and and within the Gamma-Proteobaceteria order Enterobacteriales.
Our results represent the first systematic survey of microbial communities mediating turnover of algal biomass under anaerobic conditions, and highlights the diversity of lineages putatively involved in the degradation process.
藻类包含广泛的光合生物，广泛分布于水生和陆地生境。藻类物种常在水生生态系统中大量繁殖，为分层水体中更深的缺氧层提供大量的本地碳输入。此外，各种藻类物种被认为是生物质厌氧生产沼气的有前途的候选者。令人惊讶的是，尽管其具有生态和经济相关性，但在厌氧条件下参与藻类碎屑周转的微生物群落仍 largely 未被探索。
在这里，我们使用来自厌氧泉（俄克拉荷马州佐尔特奥内泉；ZDT）的沉积物、当地污水处理厂二级消化池的污泥（俄克拉荷马州斯蒂尔沃特；WWT）以及季节性分层湖泊（俄克拉荷马州切诺基人的大湖；GL）的更深缺氧层作为接种源，对介导绿藻（绿藻门）、IWP1 菌株（轮藻科）和海带（褐藻门）降解的微生物群落进行了表征。在所有富集培养中，大部分藻类生物量在 13 - 16 周内被代谢，并且该过程伴随着细胞数量增加和群落多样性降低。基于 16S rRNA 基因 V4 区域的群落调查确定了属于拟杆菌门、变形菌门（α、δ、γ和ε类）、螺旋体门和厚壁菌门的不同谱系，它们在各种底物和接种条件下选择性丰富。在所有海带富集培养中，实验结束时的微生物群落结构无论富集源如何都高度相似，并且以厚壁菌门中的属或科为主导。在所有其他富集培养中，最终的微生物群落取决于接种源，而不是用作底物的藻类类型。富集的谱系包括拟杆菌门中未培养的 VadinBC27 和 WCHB1 - 69 组、螺旋体门中的属和未培养的 SHA - 4 组、厚壁菌门中的、、、、和、以及γ - 变形菌门肠杆菌目中的属、、和。
我们的结果代表了对厌氧条件下介导藻类生物量周转的微生物群落的首次系统调查，并突出了可能参与降解过程的谱系的多样性。
