Characterization of thealgCGene Expression Pattern in the Multidrug ResistantAcinetobacter baumanniiAIIMS 7 and Correlation with Biofilm Development on Abiotic Surface

Abstract

Relative quantification ofalgCgene expression was evaluated in the multidrug resistant strainAcinetobacter baumanniiAIIMS 7 biofilm (3 to 96 h, on polystyrene surface) compared to the planktonic counterparts. Comparison revealed differentialalgCexpression pattern with maximum 81.59-fold increase in biofilm cells versus 3.24-fold in planktonic cells (P<0.05). Expression levels strongly correlated with specific biofilm stages (scale of 3 to 96 h), coinciding maximum at initial surface attachment stage (9 h) and biofilm maturation stage (48 h). Cloning, heterologous expression, and bioinformatics analyses indicatedalgCgene product as the bifunctional enzyme phosphomannomutase/phosphoglucomutase (PMM/PGM) of ∼53 kDa size, which augmented biofilms significantly inalgCclones compared to controls (lackingalgCgene), further localized by scanning electron microscopy. Moreover, molecular dynamics analysis on the three-dimensional structure of PMM/PGM (simulated up to 10 ns) revealed enzyme structure as stable and similar to that inP. aeruginosa(synthesis of alginate and lipopolysaccharide core) and involved in constitution of biofilm EPS (extracellular polymeric substances). Our observation on differential expression pattern ofalgChaving strong correlation with important biofilm stages, scanning electron-microscopic evidence of biofilm augmentation taken together with predictive enzyme functions via molecular dynamic (MD) simulation, proposes a new basis ofA. baumanniiAIIMS 7 biofilm development on inanimate surfaces.