Jacob Kristin M, Reguera Gemma
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA.
Biofilm. 2022 Jan 18;4:100067. doi: 10.1016/j.bioflm.2022.100067. eCollection 2022 Dec.
The identification of a diverse microbiome in otic secretions from healthy young adults challenged the entrenched dogma of middle ear sterility and underscored previously unknown roles for oral commensals in the seeding of otic biofilms. We gained insights into the selective forces that enrich for specific groups of oral migrants in the middle ear mucosa by investigating the phylogeny and physiology of 19 strains isolated previously from otic secretions and representing otic commensals () or transient migrants ( and actinobacterial and ). Phylogenetic analyses of full length 16S rRNA sequences recovered from partially sequenced genomes resolved close relationships between the isolates and (peri)oral commensals. Physiological functions that facilitate mucosal colonization (swarming motility, surfactant production) and nutrition (mucin and protein degradation) were also widespread among the cultivars, as was their ability to grow in the presence or absence of oxygen. Yet, streptococci stood out for their enhanced biofilm-forming abilities under oxic and anoxic conditions and ability to ferment host-derived mucosal substrates into lactate, a key metabolic intermediate in the otic trophic webs. Additionally, the otic streptococci inhibited the growth of common otopathogens, an antagonistic interaction that could exclude competitors and protect the middle ear mucosa from infections. These adaptive traits allow streptococcal migrants to colonize the otic mucosa and grow microcolonies with syntrophic anaerobic partners, establishing trophic interactions with other commensals that mirror those formed by the oral ancestors in buccal biofilms.
在健康年轻成年人的耳部分泌物中发现了多样的微生物群，这挑战了中耳无菌的固有观念，并突显了口腔共生菌在耳部生物膜定植中此前未知的作用。通过研究先前从耳部分泌物中分离出的19株菌株（代表耳部共生菌（）或短暂迁移菌（和放线菌及））的系统发育和生理学，我们深入了解了在中耳黏膜中富集特定口腔迁移菌群的选择压力。从部分测序基因组中回收的全长16S rRNA序列的系统发育分析解析了这些分离株与（口周）口腔共生菌之间的密切关系。促进黏膜定植（群体游动、表面活性剂产生）和营养摄取（黏蛋白和蛋白质降解）的生理功能在这些培养菌株中也很普遍，它们在有氧或无氧条件下生长的能力也是如此。然而，链球菌在有氧和无氧条件下增强的生物膜形成能力以及将宿主来源的黏膜底物发酵成乳酸（耳部营养网络中的关键代谢中间体）的能力方面表现突出。此外，耳部链球菌抑制常见耳病原体的生长，这种拮抗相互作用可以排除竞争者并保护中耳黏膜免受感染。这些适应性特征使链球菌迁移菌能够在耳部黏膜定植，并与厌氧共生伙伴形成微菌落，与其他共生菌建立营养相互作用，这与口腔祖先在颊部生物膜中形成的相互作用相似。
