Fig. 4

Planktonic growth and biofilm formation in polypropylene tubes of the transposon mutants and 17978hm parent strain. Cells were cultured in Luria Bertani media without shaking at 37 °C in polypropylene tubes for 72 h. (a) Planktonic growth was assessed by removal of 1 mL of media and the optical density measured at OD₆₀₀. All three transposon insertion mutant strains showed a dramatic increase of planktonic growth; 4-fold greater than the 17978hm parent strain. Complementation of the cdpA mutation in the cpdA::Tn(0249) strain returned the phenotype to wild-type levels. (b) The level of biofilm produced was assessed by crystal violet staining. Transposon insertion mutant strains had an increased biomass of the surface/liquid biofilm by approximalty 30 % compared to that of the 17978hm parent. The cpdA::Tn(0249) mutant strain that contains a wild-type copy of the gene, restored the biofilm phenotype to that of the parent. Bars indicate the standard deviation of three separate experiments. Asterisks indicate significant difference: one denotes a p-value <0.05, two a p-value <0.01 and three a p-value <0.001, as determined by a student t-test