Cymbiomics: multipartite interactions and a large-scale approach to pinpointing symbiotic competence of cyanobacteria

蓝细菌和真核宿主之间的共生相互作用对这个星球上的生命进化产生了深远的影响。它是一种蓝藻共生体，最终变成了叶绿体，用于碳固定。然而，在共生中还有另一种突出的蓝藻（蓝藻）。在这里，相互作用围绕着氰基生物进行固氮的能力。在某些情况下，这些氰基生物紧密地整合到宿主体内，但尚未被驯化成细胞器。这种现存的相互作用在陆地植物（胚状体）中得到了最好的描述，但也有真菌地虹吸管，它是少数几个已知的自然种群之一，在哥廷根附近蓬勃发展。共生蓝细菌的多样性，其中许多仍然能够生活在一起，并远离他们的主机，值得的问题是，是什么让他们有资格共生摆在首位。在所有的蓝藻共生体中，宿主、蓝藻和相关的微生物群落之间存在多组分的相互作用。因此，我们假设能够成为蓝藻的蓝藻必须不仅具有与宿主交流的能力，而且还具有在多生物生物膜中发挥作用甚至形成多生物膜的能力。在这里，我们将探讨两个问题：i）是什么体现了这些蓝藻谱系的共生能力？和ii）蓝藻伴侣的能力是否由招募功能正确的微生物组的能力决定？我们将采取三管齐下的办法。首先，我们将利用哥廷根的SAG收集和从共生和非共生条件下分离的蓝藻菌株的序列;与公开的基因组相结合，这些数据将与全基因组关联研究和比较基因组学相结合，以确定所有蓝藻共同的遗传因素，这些蓝藻显然能够共生。其次，我们将从Geosiphon的多个个体和含氰基生物体的植物Gunnera，Azolla和Anthoceros中采集天然存在的氰基生物体及其微生物组。第三，我们将使用Anthoceros实验室系统对测序的蓝藻菌株进行表型分析，以获得共生能力，并确定蓝藻接种后Anthoceros-蓝藻共生的微生物组。总之，我们的数据将确定与蓝藻的共生能力相关的因素，无论是在自然和培养的蓝藻。可能的后续研究将包括在确定的候选基因中敲除的蓝藻的产生。

The symbiotic interaction between cyanobacteria and eukaryotic hosts had a profound impact on the evolution of life on this planet. It was a cyanobacterial symbiont that eventually was turned into the chloroplasts for carbon-fixation. Yet, there is another prominent type of cyanobacteria in symbiosis (cyanobionts). Here, the interaction revolves around the ability of cyanobionts to perform nitrogen-fixation. In several cases, these cyanobionts are tightly integrated into the host body but have not (yet) been domesticated into an organelle. Such extant interactions are best-described in land plants (Embryophyta), but also the fungus Geosiphon—for which one of the few known natural populations thrives close to Göttingen. The manifold occurrence of symbiotic cyanobacteria, many of which are still capable of living together and apart from their host, warrants the question what made them eligible for a symbiosis in the first place. In all cyanobacterial symbioses, multipartite interactions between the host, the cyanobiont, and an associated microbial community occur. We therefore hypothesize that the cyanobacteria capable to be cyanobionts must have the ability to not only communicate with their hosts but also to function in—and perhaps even shape—a multi-organism biofilm. Here we will explore two questions: i) What manifests the symbiotic competence of these cyanobacterial lineages? and ii) Is the competence of the cyanobacterial partner determined by the capacity to recruit the functionally correct microbiome? We will carry out a three-pronged approach. First, we will leverage the SAG collection in Göttingen and sequence cyanobacterial strains isolated from symbiotic and non-symbiotic conditions; contextualized with publicly available genomes, these data will be combined with genome-wide association studies and comparative genomics to pinpoint genetic factors that is common to all cyanobacteria that are clearly capable of symbiosis. Second, we will sample naturally occurring cyanobionts and their microbiome from multiple individuals of Geosiphon and the cyanobiont-bearing plants Gunnera, Azolla and Anthoceros. Third, we will use the Anthoceros lab system to phenotype the cyanobacterial strains sequenced for symbiotic competency and determine the microbiome of the Anthoceros–cyanobacteria symbiosis after cyanobacterial inoculation. Altogether, our data will determine factors linked to the symbiotic capabilities of the cyanobacteria—both in natural and cultivated cyanobionts. Possible follow-up studies will include generation of cyanobacteria that are knocked out in the identified candidate genes.