Abstract
Relative quantification of algC gene expression was evaluated in the multidrug resistant strain Acinetobacter baumannii AIIMS 7 biofilm (3 to 96 h, on polystyrene surface) compared to the planktonic counterparts. Comparison revealed differential algC expression 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 indicated algC gene product as the bifunctional enzyme phosphomannomutase/phosphoglucomutase (PMM/PGM) of ∼53 kDa size, which augmented biofilms significantly in algC clones compared to controls (lacking algC gene), 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 in P. aeruginosa (synthesis of alginate and lipopolysaccharide core) and involved in constitution of biofilm EPS (extracellular polymeric substances). Our observation on differential expression pattern of algC having 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 of A. baumannii AIIMS 7 biofilm development on inanimate surfaces.
Highlights
In recent years, Acinetobacter baumannii has been listed as one of the most important nosocomial pathogens [1,2,3]
We identified the algC gene in the multidrug resistant (MDR) strain of A. baumannii AIIMS 7 genome and characterized its quantitative gene expression patterns in growing biofilm cells compared to the planktonic cells using the relative quantification (ΔΔCt method) in real-time PCR
An initial genetic characterization of the algC gene and its association with biofilm formation is reported in the MDR strain AIIMS 7 of A. baumannii, which depicts differential expression of algC gene during the biofilm development
Summary
Acinetobacter baumannii has been listed as one of the most important nosocomial pathogens [1,2,3]. The pathogen has become a universal challenge to treatment, owing to its multidrug resistant (MDR) nature and a plethora of virulence attributes [2, 4, 5]. A. baumannii infection and colonization often involve biofilm formation [7] on either abiotic [8, 9] or biotic surfaces [10, 11]. Biofilm formation is a virulence trait in A. baumannii which is of multifactorial nature [4, 12]. The extracellular matrices of bacterial biofilm comprise of proteins, nucleic acids, and polysaccharides [14] which are often considered as ideal start-points to further investigation towards effective treatment measures against biofilmassociated pathogens, such as MDR A. baumannii
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