Abstract
As a stage of life cycle, larval settlement and metamorphosis are critical processes for persistence of many marine invertebrate populations. Bacterial biofilms (BFs) could induce larval settlement and metamorphosis. Pseudoalteromonas, a widely distributed genus of marine bacteria, showed inductive effects on several invertebrates. However, how Pseudoalteromonas BFs induce settlement and metamorphosis of Mytilus coruscus remains unclear. Pseudoalteromonas marina BFs with the highest inducing activity were further investigated to define inductive cues. Surface-bound products of P. marina BFs could induce larval settlement and metamorphosis. P. marina BFs treated with formalin, antibiotics, ultraviolet irradiation, heat and ethanol significantly reduced inductive effects and cell survival rates. The confocal laser scanning microscopy and the biovolume analysis showed the dominance of α-polysaccharides on P. marina BFs. Treatment of BFs with amylases, proteases and lipase led to the decrease of inducing activity, suggesting that inductive cues of P. marina BFs may comprise of molecular domains of polysaccharides, proteins, and lipids. Finding inductive cues of BFs could put forward further studies about the mechanism of larval settlement and metamorphosis of marine invertebrates.
Highlights
Natural BFs were proposed as one of biotic cues to stimulate larval settlement and metamorphosis[8,9,10]
The significant correlations were observed between bacterial cell densities and the inducing activity of P. marina, Pseudoalteromonas sp. 15, and Pseudoalteromonas sp. 17 BFs (Table 1)
Bacteria belonging to Pseudoalteromonas genus have been commonly observed in marine BFs17
Summary
Natural BFs were proposed as one of biotic cues to stimulate larval settlement and metamorphosis[8,9,10]. Multispecies BFs and monospecies BFs of bacteria can induce larval settlement and metamorphosis[13,14]. It has been shown that BFs of Pseudoalteromonas, Vibrio, Shewanella and Tenacibaculum can induce larval settlement and metamorphosis[3,14,15,16]. BFs of some Pseudoalteromonas species were reported as inducers[14,19,20] or inhibitors[21,22,23,24] of larval settlement. The water-soluble and -insoluble cues were involved in larval settlement and metamorphosis of marine invertebrates, respectively[29]. Inducing activity of Pseudoalteromonas BFs on larval settlement and metamorphosis of M. coruscus. How EPS and its components affected inductiveness of Pseudoalteromonas BFs remain unclear
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