1.International Research Center for Marine Biosciences, Ministry of Science and Technology, Shanghai Ocean University; 2.Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai Ocean University; 3.National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University
Abstract: Cellulose is prevalent in the environment, and a single point mutation in the AT00_08765 gene in Pseudoalteromonas lipolytica results in excessive cellulose production and biofilms formed by mutant represses larval settlement and metamorphosis of larvae of mussel Mytilus coruscus. However, little is known that how cellulose impacts the formation of biofilms of different bacterial species, and how these above biofilms regulate mussel settlement. In this study, after the formation of a single biofilm of P.lipolytica and Shewanella loihica exhibiting high and middle settlement-inducing activity, the slides were taken out, washed with autoclaved filtered seawater (AFSW), and put into a sterile culture dish, and then cellulose was added, add a certain amount of AFSW was added to a constant volume of 20 mL, so that the final concentration of cellulose was 0, 0.02, 0.2, 2, 20, and 200 mg/L. Twenty of eyespot larvae were reared in a sterile culture dish with the biofilm above under avoid light at 18 ℃, and number of settlement metamorphosis individuals was recorded at 12, 24, 48, and 96 h to evaluate the effects of cellulose on biofilm characteristics and attachment of mussel larvae. The results showed that both biofilms during bacterial adhesion with the addition of cellulose and biofilms treated with cellulose led to reduce in inducing the larval settlement and metamorphosis in comparison to the control(P<0.05), though there was no significant effect of sole cellulose on the larval settlement and metamorphosis(P>0.05). Further analysis showed that cell densities and thickness of biofilms of S.loihica and P.atlantica were decreased during biofilm formation with the addition of the cellulose, indicating that cellulose inhibited bacterial adhesion. Major components of extracellular matrix in biofilms were also decreased in number with the addition of cellulose compared with the control biofilms. Similarly, biofilms treated by cellulose also resulted in the decrease in biofilm bacterial density, biofilm thickness and major components of extracellular matrix. The findings indicate that cellulose can inhibit larval settlement via regulation of the contents of exopolymeric substances and biofilm biomass.
2020, Vol. 35 
