Abstract
A sponge-associated bacterium, which was identified as Psychrobacter sp. in this study, was found with high activity against biofilm formation of benthic diatoms, including Amphora sp., Nitzschia closterium, Nitzschia frustulum, and Stauroneis sp. The activity against diatom biofilm formation by the tested strain was confirmed mostly in the culture supernatant and could be extracted using organic solvents. Treatment with its supernatant crude extract significantly reduced the cells of Stauroneis sp. forming biofilm and slightly increased the cells floating in the culture medium, which results in the ratio of biofilm cell/floating cell altering from 0.736 in control to 0.414 in treatment. Use of the supernatant crude extract led to increased production of extracellular polymeric substances (EPSs) by diatom Stauroneis sp. from 16.66 to 41.59 (g/g cell dry weight). The increase in EPS production was mainly contributed by soluble EPS (SL-EPS) and followed by the EPS that was tightly bound to biofilm cells (BF-TB-EPS). In addition, the supernatant crude extract caused significant changes in the monosaccharides composition of the EPS of Stauroneis sp. Specifically, glucuronic acid (Glc-A) and N-acetyl-D-glucosamine (Glc-NAc) in BF-TB-EPS were 55% fold decreased and 1219% fold increased, respectively. Based on our findings, we proposed that these changes in monosaccharides composition might lead to a decreased biofilm formation efficiency of diatom.
Highlights
Biofouling of ship hulls by biofilms of algae and bacteria and by larger organisms, for example, barnacles and mussels, causes large economic losses worldwide [1]
Photoautotrophic biofilms are composed of cells that are embedded in extracellular polymeric substances (EPSs) [10]
EPS acts as a type of glue that is primarily used by benthic diatoms for aggregation and Scientifica gripping to substrates and is involved in the motility system and substratum adhesion of diatoms [15,16,17]. erefore, EPS is proposed to be a key component for diatom cells to form biofilms on the substratum beneath water [16]
Summary
Biofouling of ship hulls by biofilms of algae and bacteria and by larger organisms, for example, barnacles and mussels (macrofouling), causes large economic losses worldwide [1]. Benthic diatoms, which are capable of forming biofilm even on the most fouling resistant surfaces, play a key role in the biofilm development [7]. Erefore, interruption of diatom biofilm formation is an essential and challenging step for resolving the biofouling problem [8, 9]. Photoautotrophic biofilms are composed of cells that are embedded in extracellular polymeric substances (EPSs) [10]. Marine benthic diatoms secrete large amounts of EPSs into the surrounding environment, as much as approximately 30–60% of photoassimilated carbon [11, 12]. Erefore, EPS is proposed to be a key component for diatom cells to form biofilms on the substratum beneath water [16] EPS acts as a type of glue that is primarily used by benthic diatoms for aggregation and Scientifica gripping to substrates and is involved in the motility system and substratum adhesion of diatoms [15,16,17]. erefore, EPS is proposed to be a key component for diatom cells to form biofilms on the substratum beneath water [16]
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