Genomic basis of Baikal sponge tissue degradation caused by a free-living <i>Flavobacterium</i> with host-glycan-targeting polysaccharide utilization loci

Panova, Yulia; Belikov, Sergei; Chernogor, Lubov

doi:10.31951/2658-3518-2025-A-6-1313

Authors

Panova Yu.A. ^{1, 2}
Belikov S.I. ¹
Chernogor L.I. ¹

¹

²

DOI:

https://doi.org/10.31951/2658-3518-2025-A-6-1313

Keywords:

Flavobacterium sp. PLB03, freshwater sponges, CAZymes, PULs, Type IX secretion system, genomic islands, opportunistic pathogenicity

Abstract

Here we present the complete genome sequence of the Flavobacterium sp. strain PLB03 isolated from the primmorphs cell culture of the Lubomirskia baikalensis sponge and compare it with pathogenic free-living members of the genus Flavobacterium. Strain Flavobacterium sp. PLB03 exhibits pronounced lytic activity towards sponge cells and causes death of symbiotic microalgae (the Trebouxiophyceae). The Flavobacterium sp. PLB03 genome has 5,925,828 bp and a GC content of 34.3%. An average nucleotide identity (ANI) of 98.9% revealed that strain Flavobacterium sp. PLB03 has the highest similarity to Flavobacterium CSZ. Comparative genomic analysis of the strain and phylogenetically related Flavobacterium indicated that Flavobacterium sp. PLB03 has a large genome size characteristic of the environmental genus Flavobacterium, and the peptidase (PEP) to glycoside hydrolase (GH) gene ratio is 1.8, suggesting that strain PLB03 exhibits characteristics similar to nonpathogenic strains.