Enhanced expression of catechol 1,2 dioxygenase gene in biofilm forming Pseudomonas mendocina EGD-AQ5 under increasing benzoate stress

•Pseudomonas mendocina EGD-AQ5 utilised benzoate and accumulated catechol differentially under biofilm and planktonic mode.•Extent of catechol accumulation was low in biofilm associated cells.•Bacteria underwent shift in their phenotype to biofilm under benzoate stress.•Different catechol cleavage genes were expressed in planktonic and biofilm associated cells.

In natural settings, microbes often associate closely with surfaces and interfaces called biofilms and adhere in an extracellular matrix. The biofilm provide diverse microenvironments and high resistance to environmental stress on the constituent cells that aid to generate cellular heterogeneity and phenotypic variability. The work presented here examines for the first time the capability of Pseudomonas mendocina EGD-AQ5 biofilm-associated cells, compared with that of planktonic cells to utilize toxic intermediate catechol under benzoate degradation conditions in liquid culture systems. Both planktonic and biofilm-associated cells utilized benzoate to the same extent but accumulated catechol differently. This differential catechol accumulation activity of the Pseudomonas mendocina EGD-AQ5 could be accredited to the cells adapted as a biofilm. Further experiments with transcriptome implicated to increased expression of genes like pelA (involved in biofilm formation) cat1,2D (ortho pathway) and decreased expression of cat2,3D (meta pathway) in biofilm harvested cells than free suspended cells. Whole genome sequence analysis of Pseudomonas mendocina EGD-AQ5 (Genbank Accession No AVQF00000000) deciphered catechol ortho and meta-pathways for benzoate utilization and pelABCDEFG as involved in biofilm formation. These results suggest that Pseudomonas mendocina EGD-AQ5 biofilms should facilitate bioaugmentation to be more resilient and efficient bioremediation technology than free suspended planktonic cells.