DC1, a podoviridae with a putative cepacian depolymerase enzyme

Plaques formed by DC1 on B. cepacia LMG 18821 and B. cenocepacia PC184 are surrounded by large and expanding halos when production of the exopolysaccharide (EPS) cepacian is induced. This plaque morphology indicates that DC1 putatively carries an EPS depolymerase enzyme. Plaque halos were absent when DC1 infected a PC184 cepacian knockout mutant and a non-mucoid LMG 18821 mutant, constructed using plasposon mutagenesis. The virulence of these mutants compared to wildtype PC184 and LMG 18821 was determined using the Galleria mellonella infection model. No major changes to virulence were observed for the LMG 18821 mutant. But, the PC184 cepacian knockout mutant was attenuated for virulence suggesting that this carbohydrate pathway may play a role in pathogenesis. The gene(s) involved in halo formation remain unknown although attempts were made to determine the gene(s) involved by cloning and expressing DC1 fragments in E. coli and assaying for EPS degradation.