Bacterial extracellular polymeric substances and their effect on settlement of zoospore of Ulva fasciata

The extracellular polymeric substances (EPSs) secreted by Bacillus flexus (GU592213) were estimated to have the molecular weight of approximately 1528 and 33,686 kDa with the elemental composition of Na, P, Mg, C, O, Cl and S. The 1H NMR and FT-IR analysis of EPS confirmed the presence of different aliphatic and aromatic groups. The EPS was amorphous in nature with an average particle size of 13.969 μm (d 0.5) and roughness of 193 nm. The GC–MS analysis has revealed different monosaccharides such as fucose, ribose, xylose, galactose, mannose and glucose. Oligo and polysaccharides were detected with MALDI TOF–TOF MS. The bacterial EPS for the first time tested as a natural substratum for settle of zoospores of Ulva fasciata by incubating for various durations ranging from 2 h to 48 h. The zoospore settlement on EPS coated cover slips progressively increased with incubation time in axenic cultures over controls. The EPS, thus investigated in this study was found to facilitate the primary settlement of spores that play crucial role in recruitment of macroalgal communities in coastal environment including intertidal regions.