Induction of Invertebrate Larval Settlement; Different Bacteria, Different Mechanisms?

Abstract

Recruitment via settlement of pelagic larvae is critical for the persistence of benthic marine populations. For many benthic invertebrates, larval settlement occurs in response to surface microbial films. Larvae of the serpulid polychaete Hydroides elegans can be induced to settle by single bacterial species. Until now, only Pseudoalteromonas luteoviolacea had been subjected to detailed genetic and mechanistic studies. To determine if the complex structures, termed tailocins, derived from phage-tail gene assemblies and hypothesized to be the settlement cue in P. luteoviolacea were present in all inductive bacteria, genomic comparisons with inductive strains of Cellulophaga lytica, Bacillus aquimaris and Staphylococcus warneri were undertaken. They revealed that the gene assemblies for tailocins are lacking in these other bacteria. Negatively stained TEM images confirmed the absence of tailocins and revealed instead large numbers of extracellular vesicles in settlement-inductive fractions from all three bacteria. TEM imaging confirmed for C. lytica that the vesicles are budded from cell surfaces in a manner consistent with the production of outer membrane vesicles. Finding multiple bacteria settlement cues highlights the importance of further studies into the role of bacterial extracellular vesicles in eliciting settlement and metamorphosis of benthic marine larvae.

Natural products and morphogenic activity of γ-Proteobacteria associated with the marine hydroid polyp Hydractinia echinata

“…P1-9, because of its moderately anti-fungal activity and the presence of several genes assigned to NRPS within the genome. 13 Strain P1-9 was cultivated on a 50 L scale using modified SWCL medium (stirring, 30 ° C). Culture supernatant was extracted using XAD16 resin and the resulting crude extract was fractionated using an established C18-SPE purification protocol.…”

“…In another study, Hadfield and co-workers reported that amongst other not yet identified chemical signals, 13 phage tail-like bacteriocins derived from Pseudoalteromonas luteoviolacea induce larval settlement in the marine invertebrate Hydroides elegans . 14,15 As a third example, Clardy and co-workers elucidated the absolute structure of a rosette-inducing factor (RIF-1, 7 ) produced by the prey bacterium Algoriphagus machipongonensis of the choanoflagellate Salpingoeca rosetta .…”

High bacterial diversity in nearshore and oceanic biofilms and their influence on larval settlement by Hydroides elegans (Polychaeta)

“…). Metamorphosis of H. elegans is also triggered by taxonomically distant strains of Cellulophaga lytica , Bacillus aquimaris and Staphylococcus warneri , suggesting that there might be conserved mechanisms that induce settlement and metamorphosis (Freckelton et al ., ). This is also the case for other marine organisms such as macroalgal zoospores (e.g.…”

Cobble community DNA as a tool to monitor patterns of biodiversity within kelp forest ecosystems

“…The diversity and taxonomic resolution of cobble communities using metabarcoding illustrate the potential of WRMS to detect DNA profiles of specific species and explore community interactions between member species at a small scale. Many marine invertebrates experience dispersive larval stages in which they settle on surfaces in response to environmental cues (Freckelton, Nedved, & Hadfield, ). These surfaces play a pivotal role in larval habitat selection and can influence postsettlement survival (Harrington, Fabricius, De'Ath, & Negri, ).…”