University of Hawaii, Kewalo Marine Laboratory, Honolulu, 96813, United States.
Sci Rep. 2017 Feb 14;7:42557. doi: 10.1038/srep42557.
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.
通过定居的浮游幼虫进行招募对于底栖海洋种群的持续存在至关重要。对于许多底栖无脊椎动物来说，幼虫的定居是对表面微生物膜的反应。管居环节动物 Hydroidess elegans 的幼虫可以被单一的细菌物种诱导定居。到目前为止，只有 Pseudoalteromonas luteoviolacea 已经接受了详细的遗传和机制研究。为了确定来自噬菌体尾基因组装的复杂结构，称为尾菌素，是否存在于所有诱导细菌中，对诱导的 Cellulophaga lytica、Bacillus aquimaris 和 Staphylococcus warneri 菌株进行了基因组比较。结果表明，这些其他细菌中缺乏尾菌素的基因组装。负染色 TEM 图像证实了尾菌素的缺失，并在所有三种细菌的定居诱导部分中发现了大量的细胞外囊泡。TEM 成像证实，对于 C. lytica，囊泡是从细胞表面出芽形成的，这与外膜囊泡的产生方式一致。发现多种细菌定居线索突出了进一步研究细菌细胞外囊泡在引发底栖海洋幼虫定居和变态中的作用的重要性。
