背景:海绵相关细菌在其宿主的生理过程中发挥重要作用,其招募过程对于维持共生关系至关重要。然而,淡水海绵中细菌群落的获取仍在探索中。海绵是一种在欧洲河流和湖泊中广泛分布的典型海绵,产生休眠囊肿(称为宝石)以进行无性繁殖,在冬天之前。通过体外实验,这项研究的目的是描述细菌群落的动态和他们的传播方式后孵化这些宝石。
结果:通过幼年海绵的本体观察到细菌β多样性的总体变化。这些时间差异可能有联系,首先是根茎采集和运河系统的发展,然后,小球藻样光共生体的定殖增加。发现具有无菌表面孵化的宝石具有更分散且多样性较少的微生物组,揭示了宝石表皮细菌对整个整体稳定性的重要性。建议这些上细菌从母体组织垂直传播到宝石表面。通过在宝石内部掺入细菌群落进行垂直传播,也被发现是一种主要的传输模式,尤其是固氮剂Terasakiellaceae。最后,我们发现自由生活社区和青少年之间几乎没有共享ASV,这表明横向招聘不太可能发生在发展的第一阶段。然而,过滤的自由生活的细菌可能被用作营养来源,允许富集已经存在于其微生物组中的共营养细菌。
结论:这项研究为更好地了解淡水海绵发育的第一阶段的微生物组获取带来了新的见解。我们展示了宝石上的表观细菌群落对于整个整体稳定性的重要性,并证明在第一阶段几乎没有招募自由生活的细菌。
BACKGROUND: Sponge-associated bacteria play important roles in the physiology of their host, whose recruitment processes are crucial to maintain symbiotic associations. However, the acquisition of bacterial communities within freshwater sponges is still under explored. Spongilla lacustris is a model sponge widely distributed in European rivers and lakes, producing dormant cysts (named gemmules) for their asexual reproduction, before winter. Through an in vitro experiment, this study aims to describe the dynamics of bacterial communities and their transmission modes following the hatching of these gemmules.
RESULTS: An overall change of bacterial β-diversity was observed through the ontology of the juvenile sponges. These temporal differences were potentially linked, first to the osculum acquisition and the development of a canal system, and then, the increasing colonization of the Chlorella-like photosymbionts. Gemmules hatching with a sterilized surface were found to have a more dispersed and less diverse microbiome, revealing the importance of gemmule epibacteria for the whole
holobiont stability. These epibacteria were suggested to be vertically transmitted from the maternal tissues to the gemmule surface. Vertical transmission through the incorporation of bacterial communities inside of the gemmule, was also found as a dominant transmission mode, especially with the nitrogen fixers Terasakiellaceae. Finally, we showed that almost no ASVs were shared between the free-living community and the juveniles, suggesting that horizontal recruitment is unlikely to happen during the first stages of development. However, the free-living bacteria filtered are probably used as a source of nutrients, allowing an enrichment of copiotrophic bacteria already present within its microbiome.
CONCLUSIONS: This study brings new insight for a better understanding of the microbiome acquisition during the first stages of freshwater sponge development. We showed the importance of epibacterial communities on gemmules for the whole
holobiont stability, and demonstrated the near absence of recruitment of free-living bacteria during the first stages.