Lipopolysaccharides from Commensal and Opportunistic Bacteria: Characterization and Response of the Immune System of the Host Sponge Suberites domuncula

Abstract

Marine sponges harbor a rich bacterioflora with which they maintain close relationships. However, the way these animals make the distinction between bacteria which are consumed to meet their metabolic needs and opportunistic and commensal bacteria which are hosted is not elucidated. Among the elements participating in this discrimination, bacterial cell wall components such as lipopolysaccharides (LPS) could play a role. In the present study, we investigated the LPS chemical structure of two bacteria associated with the sponge Suberites domuncula: a commensal Endozoicomonas sp. and an opportunistic Pseudoalteromonas sp. Electrophoretic patterns indicated different LPS structures for these bacteria. The immunomodulatory lipid A was isolated after mild acetic acid hydrolysis. The electrospray ionization ion-trap mass spectra revealed monophosphorylated molecules corresponding to tetra- and pentaacylated structures with common structural features between the two strains. Despite peculiar structural characteristics, none of these two LPS influenced the expression of the macrophage-expressed gene S. domuncula unlike the Escherichia coli ones. Further research will have to include a larger number of genes to understand how this animal can distinguish between LPS with resembling structures and discriminate between bacteria associated with it.

Diversity and function of prevalent symbiotic marine bacteria in the genus Endozoicomonas

“…In the Caribbean, the giant barrel sponge ( Xestospongia muta ) not only contained Endozoicomonas bacteria, but evidence of their transcriptional activity was also detected (Fiore et al 2015 ). Sponges in Brazil (Rua et al 2014 ), Japan (Nishijima et al 2013 ), and several other European seas also contain Endozoicomonas symbionts (Esteves et al 2013 ; Gardères et al 2015 ). In addition, tunicates, which are basal chordates, have a microbiome that consistently contains a substantial proportion of Endozoicomonas , suggesting that these symbionts are core members of the tunicate microbiome (Dishaw et al 2014 ).…”

Spotlight on Antimicrobial Metabolites from the Marine Bacteria Pseudoalteromonas: Chemodiversity and Ecological Significance

“…Few studies completely defined LPS structures of Pseudoalteromonas species [ 149 ]. However, it appears that most Pseudoalteromonas LPS known to date are composed of a pentaacylated Lipid A instead of a hexaacylated one [ 149 , 150 , 151 , 152 , 153 , 154 ]. Such a structural difference may provide an advantage to evade PRRs-mediated recognition.…”

“…Such a structural difference may provide an advantage to evade PRRs-mediated recognition. Indeed, LPS from various Pseudoalteromonas strains were shown to elicit a low immune response and are capable of modulating immune responses in their hosts [ 150 , 153 ].…”

The Lipid A Structure from the Marine Sponge Symbiont Endozoicomonas sp. HEX 311

“…As a Gram‐negative species, Endozoicomonas sp. HEX311 exhibits LPS on its surface; thus it can be recognized by SLIP and, consequently, can elicit an inflammatory process . On the contrary, Endozoicomonas sp.…”