We isolated four novel Pseudoalteromonas strains lived in close association with Hexacorallians.
Interactions between hexacorallians and microalgae from the Symbiodiniaceae family or bacteria from the Endozoicomonas genus are well studied. Hexacorallians also lived in close association with other bacteria including members of other genera such as Pseudoalteromonas, but their functional roles and the molecular bases of these interactions are less understood. As a consequence, we isolated four novel Pseudoalteromonas strains from hexacorallians. We then performed genomic analyses with five additional Pseudoalteromonas strains previously isolated from hexacorallians, as well as 13 strains originating from other marine hosts. A phylogenomic reconstruction showed that (i) the 22 strains were divided into six species, (ii) the Hexacorallia-associated Pseudoalteromonas (HAP) belonged to four species, and (iii) most HAP (six out of nine) belonged to the Pseudoalteromonas piscicida species. Pan- and coregenome analyses were then computed at the scale of the Pseudoalteromonas piscicida species to identify specific characteristics of HAP. First, pangenome analyses revealed the absence of a HAMP domain-containing histidine kinase in the HAP genomes. In contrast, several proteins were HAP specific, among them proteins involved in the biosynthesis of surface polysaccharides, as well as a phytochrome-like protein and a type II secretion system (T2SS) protein. Moreover, coregenome analyses also highlighted signatures of molecular adaptation or diversification in two other phytochrome-like and T2SS proteins. Lastly, specific characteristics of HAP corresponded to significant enrichments of (i) accessory genes affiliated to COG M (cell wall/membrane/envelope biogenesis), COG U (intracellular trafficking, secretion, and vesicular transport) as well as the outermembrane localization, and (ii) fast evolving genes linked to cellular energy (ATP synthase) and the cytoplasmic-membrane localization. These genomic analyses brought new insights into the molecular bases of interactions between Pseudoalteromonas strains and their hexacorallian hosts, and they particularly highlighted links with HAMP domain-containing histidine kinase, phytochrome-like and T2SS proteins, ATP synthase subunits, as well as proteins involved in the biosynthesis of surface polysaccharides.
Interactions between hexacorallians and microalgae from the Symbiodiniaceae family or bacteria from the Endozoicomonas genus are well studied. Hexacorallians also lived in close association with other bacteria including members of other genera such as Pseudoalteromonas, but their functional roles and the molecular bases of these interactions are less understood. As a consequence, we isolated four novel Pseudoalteromonas strains from hexacorallians. We then performed genomic analyses with five additional Pseudoalteromonas strains previously isolated from hexacorallians, as well as 13 strains originating from other marine hosts. A phylogenomic reconstruction showed that (i) the 22 strains were divided into six species, (ii) the Hexacorallia-associated Pseudoalteromonas (HAP) belonged to four species, and (iii) most HAP (six out of nine) belonged to the Pseudoalteromonas piscicida species. Pan- and coregenome analyses were then computed at the scale of the Pseudoalteromonas piscicida species to identify specific characteristics of HAP. First, pangenome analyses revealed the absence of a HAMP domain-containing histidine kinase in the HAP genomes. In contrast, several proteins were HAP specific, among them proteins involved in the biosynthesis of surface polysaccharides, as well as a phytochrome-like protein and a type II secretion system (T2SS) protein. Moreover, coregenome analyses also highlighted signatures of molecular adaptation or diversification in two other phytochrome-like and T2SS proteins. Lastly, specific characteristics of HAP corresponded to significant enrichments of (i) accessory genes affiliated to COG M (cell wall/membrane/envelope biogenesis), COG U (intracellular trafficking, secretion, and vesicular transport) as well as the outermembrane localization, and (ii) fast evolving genes linked to cellular energy (ATP synthase) and the cytoplasmic-membrane localization. These genomic analyses brought new insights into the molecular bases of interactions between Pseudoalteromonas strains and their hexacorallian hosts, and they particularly highlighted links with HAMP domain-containing histidine kinase, phytochrome-like and T2SS proteins, ATP synthase subunits, as well as proteins involved in the biosynthesis of surface polysaccharides.
Station Biologique de Roscoff, France