Alterins, a new family of marine antibacterial cyclolipopeptides.

Five strains of Pseudoalteromonas, isolated from oyster haemolymph, have exhibited antibacterial activity against several Gram-negative bacteria. Bioactive compounds have been identified in their cell-free supernatant and characterised as alterins, which are cyclolipopeptides comprising a heptapeptidic ring connected to a fatty acid chain. Using ultra-performance liquid chromatography-high-resolution mass spectrometry, this paper describes 37 structural analogues differing from each other by one or more amino acid residue, the length of the fatty acid chain, its hydroxylation and the presence of unsaturation.

sp. nov., a new bacterial species harboured by the flat oyster .

Three bacterial strains, named h-66, h-124 and h-125, were isolated from the haemolymph of different specimens of the flat oyster collected in Concarneau bay (Finistère, France). These strains were characterized by a polyphasic approach, including (i) whole genome analyses with 16S rRNA gene sequence alignment and pangenome analysis, determination of the G+C content, average nucleotide identity (ANI), and DNA-DNA hybridization (DDH), and (ii) fatty acid methyl ester and other phenotypic analyses. Strains h-66, h-124 and h-125 were closely related to both type strains RA15 and PAMC 28425 with less than 93.

Alterins Produced by Oyster-Associated Are Antibacterial Cyclolipopeptides with LPS-Binding Activity.

Discovery after discovery, host-associated microbiota reveal a growing list of positive effects on host homeostasis by contributing to host nutrition, improving hosts' immune systems and protecting hosts against pathogens. In that context, a collection of oyster associated bacteria producing antibacterial compounds have been established to evaluate their role in non-host-derived immunity. Here, we described alterins; potent anti-Gram negative compounds produced by h-6 and h-42 isolated from different healthy oyster hemolymph.

Protective Efficacy of a Pseudoalteromonas Strain in European Abalone, Haliotis tuberculata, Infected with Vibrio harveyi ORM4.

The hemolymph of healthy marine invertebrates is known to harbor antibiotic-producing bacteria belonging to the genus Pseudoalteromonas. Such strains are potential probiotics to control infectious diseases in aquaculture. In the present study, we screened a collection of Pseudoalteromonas strains isolated from the hemolymph of oyster and mussel for antimicrobial activity against Vibrio harveyi, a pathogenic species responsible for high mortality in abalone.

Deep Subseafloor Fungi as an Untapped Reservoir of Amphipathic Antimicrobial Compounds.

The evolving global threat of antimicrobial resistance requires a deep renewal of the antibiotic arsenal including the isolation and characterization of new drugs. Underexplored marine ecosystems may represent an untapped reservoir of novel bioactive molecules. Deep-sea fungi isolated from a record-depth sediment core of almost 2000 m below the seafloor were investigated for antimicrobial activities.