Pyomelanin And Cellulose Regulating The Formation Of Biofilms And Larval Settlement And Metamorphosis Of The Mussel Mytilus Coruscus

Most marine bacteria regulate the settlement and metamorphosis of marine invertebrate larvae by biofilms.Studies have shown that the biological properties of biofilms are important factors affecting the settlement and metamorphosis of marine invertebrate larvae,such as the density of biofilm,biofilm thickness and extracellular products?EPS?.It has important biological activity in the natural environment of pyomelanin and cellulose.It is found that deletion or mutation of hmg A gene in Pseudoalteromonas lipolytica leads to overproduction of pyomelanin,while one base in AT00₀8765 gene the point mutation causes excessive production of cellulose,and the biofilms by the two mutants has a significant inhibitory effect on the settlement and metamorphosis of the mussel Mytilus coruscus larvae.However,whether pyomelanin and cellulose affect the formation and characteristics of biofilms of other genus bacteria,and the mechanism of the effects on the settlement and metamorphosis of M.coruscus larvae have not been studied.In this paper,Pseudoalteromonas atlantica and Shewanella loihica,which have moderate induction activity and high induction activity for the settlement and metamorphosis of M.coruscus larvae,were selected to investigate the formation of pyomelanin and cellulose in the formation of two bacterial biofilms and biofilm formation.The effect on the properties of biofilms and the regulation of the settlement and metamorphosis of M.coruscus larvae.It mainly includes the following contents:1,Effects of different concentrations of pyomelanin on the biofilms formed by P.atlantica and S.loihica and the addition of pyomelanin in the formation of biofilms,and the effect on the settlement and metamorphosis of M.coruscus larvae.The pyomelanin and the marine bacteria P.atlantica form biofilms,and the induction rate of the settlement and metamorphosis of M.coruscus larvae by the two biofilms is counted.The initial bacterial density is 1×10⁷ cells/mL,when the concentration of pyomelanin was 2 mg/L,the biofilm was significantly lower than the P.atlantica bacterial biofilm.At the same time,the pyomelanin and the marine bacteria S.loihica formed the biofilms also showed different degrees of inducing activity on the settlement and metamorphosis of M.coruscus larvae,and the initial bacterial density was 1×10⁷ cells/mL and the pyomelanin concentration was 2 mg/L,10 mg/L,the induction activity is the lowest.The results showed that the pyomelanin can affect the characteristics of the biofilms during or after the formation of P.atlantica and S.loihica biofilms,and inhibit larval settlement and metamorphosis of M.coruscus larvae.2.Effects of different concentrations of cellulose on biofilms formed by P.atlantica and S.loihica,and biofilms formation after adding cellulose to the larval settlement and metamorphosis of M.coruscus larvae.Cellulose and marine bacteria P.atlantica form a biofilm,and the induction rate of the larval settlement and metamorphosis of M.coruscus larvae by two biofilms is counted,the initial bacterial density is 1×10⁷ cells/mL,and the cellulose concentration is 2 mg/L,20 mg/L,and 200 mg/L,the adhesion induction rate of the biofilms to the larvae of M.coruscus was significantly lower than that of the P.atlantica biofilms;At the same time,the biofilm formed by cellulose and marine bacteria S.loihica has different degrees of inducing activity on the larval settlement and metamorphosis of the M.coruscus,and the initial bacterial density was 1×10⁷ cells/mL,the inducing activity was the lowest when the cellulose concentration was 2 mg/L,20 mg/L,and 200 mg/L.The results indicate that cellulose can affect the characteristics of biofilms during the formation of P.atlantica and S.loihica biofilms,and inhibit the process of the larval settlement and metamorphosis of the M.coruscus.3.Analysis of related factors affecting the larval settlement and metamorphosis of M.coruscus in the regulation of biofilms by pyomelanin and cellulose.In order to explore the related feature impact of pyomelanin and cellulose on biofilms,the paper calculates and analyzes the density,changes in biofilm distribution,thickness and morphology were observed by laser scanning confocal microscopy and scanning electron microscopy.Secondly,the extracellular products of the biofilms,such as extracellular polysaccharide,extracellular lipid and extracellular protein,were dyeing analyzed.It was found through analysis that pyomelanin and cellulose have no effect on bacterial morphology,but can reduce the bacterial density,aggregation degree and biofilm thickness,compared with biofilm of P.atlantica and S.loihica and pyomelanin and cellulose,the biofilm formed by pyomelanin and cellulose,and the biofilm,pectin,and extracellular lipids added with pyomelanin and cellulose in the later stage were significantly reduced,while the extracellular protein content was not significantly different.Therefore,it is speculated that the reduction of extracellular polysaccharides and extracellular lipids in biofilms may be a key factor in inhibiting the larval settlement and metamorphosis of the M.coruscus.This paper provides a theoretical basis for further study of the settlement and metamorphosis mechanism of marine invertebrates and the marine biofouling treatment.