Fig. 4

Detection of cellulase production by vib1 mutants on AZCL-HE-Cellulose. Comparison of vib1 deletion (−vib1) and overexpression (+vib1) strains of a QM9414, b Rut-C30, and c QM9978 on minimal medium supplemented with glucose or lactose (1% w/v) and AZCL-HE-Cellulose (0,1% w/v). Blue halos on the agar plates result from degradation of the AZCL-HE-Cellulose substrate releasing a blue dye into the agar. Pictures were taken from the bottom side of the plates. The high enzyme production of Rut-C30 on glucose is due to the bigger colony size of this strain on glucose. For a comparison of colony size to enzyme production see Additional file 1: Figure S1, depicting the same plates from above. Pictures were taken after 4 days of incubation. For each strain, two biological replicates (individual clones) were assayed and one is shown representatively