Bacteria of the phylum Verrucomicrobia are ubiquitous in marine environments and can be found as free‐living organisms or as symbionts of eukaryotic hosts. Little is known about host‐associated Verrucomicrobia in the marine environment. Here we reconstructed two genomes of symbiotic Verrucomicrobia from bacterial metagenomes derived from the Atlanto‐Mediterranean sponge Petrosia ficiformis and three genomes from strains that we isolated from offshore seawater of the Eastern Mediterranean Sea. Phylogenomic analysis of these five strains indicated that they are all members of Verrucomicrobia subdivision 4, order Opitutales. We compared these novel sponge‐associated and seawater‐isolated genomes to closely related Verrucomicrobia. Genomic analysis revealed that Planctomycetes‐Verrucomicrobia microcompartment gene clusters are enriched in the genomes of symbiotic Opitutales including sponge symbionts but not in free‐living ones. We hypothesize that in sponge symbionts these microcompartments are used for degradation of l‐fucose and l‐rhamnose, which are components of algal and bacterial cell walls and therefore may be found at high concentrations in the sponge tissue. Furthermore, we observed an enrichment of toxin–antitoxin modules in symbiotic Opitutales. We suggest that, in sponges, verrucomicrobial symbionts utilize these modules as a defence mechanism against antimicrobial activity deriving from the abundant microbial community co‐inhabiting the host.

中文翻译：

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海绵相关Verrucomicrobia的表征：基于微室的糖利用和增强的毒素-抗毒素模块是宿主相关Opitutales的特征。

Verrucomicrobia门的细菌在海洋环境中无处不在，可以作为自由生物或真核宿主的共生体找到。对海洋环境中与宿主相关的疣状微生物病知之甚少。在这里，我们从Atlanto -Mediterranean海绵Petrosia ficiformis衍生的细菌基因组中重建了两个共生Verrucomicrobia基因组，并从我们从东地中海近海海水中分离的菌株中重建了三个基因组。这五个菌株的系统生物学分析表明，它们都是Verrucomicrobia细分4的成员，顺序为对立。我们将这些新颖的海绵相关基因和海水分离基因组与紧密相关的Verrucomicrobia进行了比较。基因组分析表明，浮霉菌门，疣微菌门微区基因簇在共生的基因组中富含Opitutales包括海绵共生体，但不是在自由生活的人。我们假设，在海绵共生体中，这些微隔室可用于降解藻糖和细菌细胞壁的l-岩藻糖和l-鼠李糖，因此在海绵组织中可能以高浓度被发现。此外，我们观察到共生立异体中毒素-抗毒素模块的富集。我们建议，在海绵中，疣疣共生体利用这些模块作为防御机制，抵御源自宿主共同居住的丰富微生物群落的抗菌活性。