27. PhAMP-induced modulation of biofilm related mutants in Pseudomonas aeruginosa
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Abstract
Pseudomonas aeruginosa is an opportunist bacterium which grows at the infection site of immunocompromised patients and secretes virulence factors. It produces antibiotic resistant biofilms which are very hard to eradicate and a major problem for clinicians. Biofilm formation involves initial attachment to solid surface which require combined action of flagella and pili. These attached bacteria form sessile colonies by cell-cell attachment using fimbriae and by secreting exopolysaccharides and other proteins conferring resistance. Peganum harmala antimicrobial peptides (PhAMP) are known to inhibit the biofilm formation. In order to find out which component of biofilm formation is affected by PhAMP, transposon mutants of flagella, pili, fimbriae and exopolysaccharide production were used. We grew MPAO1 parent and its mutant strains (ΔflgK, ΔPilA, ΔcupA1 and ΔpslC) in the presence and absence of PhAMP. It was found that in the absence of PhAMP, the growth of planktonic cells was significantly affected in flagella and pili mutants and was not affected in fimbriae and exopolysaccharide mutants in comparison with MPAO1 strain while biofilm development was reduced in all mutants except ΔpslC. In the presence of PhAMP, the growth of both planktonic and biofilm cells was significantly reduced in all parent and mutant strains indicating that PhAMP effects bacterial growth even in the absence of a functional component. Gene expression analysis indicated that the transcriptional inhibition was observed in flgK, pilA, cupA1 and pslC genes by PhAMP. This study imparts important information about the molecular mechanism of action of PhAMP in bacterial biofilm production and bacterial growth.
Keywords: Antimicrobial peptides; Biofilm; Peganum harmala; Pseudomonas aeruginosa;
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