Figure 6: VCBP-C affects in vitro biofilm formation differentially in five gut bacterial isolates recovered from C. intestinalis.

(a) Stationary cultures of a Bacillus sp. isolated from the Ciona gut forms biofilms within 3–5 days. Biofilm formation is enhanced in the presence of recombinant VCBP-C (6.5 μg ml⁻¹); a similar effect is noted for gut isolates of (b) Shewanella sp. and (c) Pseudoalteromonas sp. (d) Vibrio isolate 6251 (laboratory-assigned number) exhibits a significant increase only with the addition of VCBP-C plus chitin; (e) no significant difference is seen with Vibrio isolate 6269. (f) E. coli biofilms are increased in the presence of SIgA; VCBP-C at similar concentrations does not influence E. coli biofilms. Biofilms were stained with crystal violet, dried, re-dissolved in acetic acid and absorbance (Abs) was read at OD₅₅₀. Increased absorbance reflects the increased surface biofilm. Each experiment was performed in triplicate a minimum of four separate times; results shown represent one triplicate experiment. s.d. is shown by black error bars. Significant differences from control samples were calculated by using analysis of variance with post hoc Dunnett’s test. *P<0.05; **P<0.01; CTL, control; VCBP, VCBP-C; V/C, VCBP-C plus hydrolysed chitin.