title: Role of RpoS and AlgT in Pseudomonas aeruginosa biofilm resistance to hydrogen peroxide and monochloramine.
abstract: The role of two sigma factors, AlgT and RpoS, in mediating Pseudomonas aeruginosa biofilm resistance to hydrogen peroxide and monochloramine was investigated. Two knock out mutant strains, SS24 (rpoS-) and PAO6852 (algT-), were compared with a wild type, PAO1, in their susceptibility to monochloramine and hydrogen peroxide. When grown as biofilms on alginate gel beads (mean untreated areal cell density 3.7 +/- 0.27 log cfu cm-2) or on glass slides (mean untreated areal cell density 7.6 +/- 0.9 log cfu cm-2), wild type bacteria exhibited reduced susceptibility to both antimicrobial agents in comparison with suspended cells. On alginate gel beads, all strains were equally resistant to monochloramine. rpoS- and algT- gel bead biofilms of 24-hour-old were more susceptible to hydrogen peroxide disinfection than were biofilms formed by PAO1. Biofilm disinfection rate coefficients for the two mutant strains were statistically indistinguishable from planktonic disinfection rate coefficients, indicating complete loss of biofilm resistance. While 48-hour-old algT- biofilm cells became resistant to hydrogen peroxide, 48-hour-old rpoS- biofilm cells remained highly susceptible. With the thicker biofilms formed on glass coupons, all strains were equally resistant to both hydrogen peroxide and monochloramine. It is concluded that while RpoS and AlgT may play a transient role in protecting thin biofilms from hydrogen peroxide, these sigma factors do not mediate resistance to monochloramine and do not contribute significantly to the hydrogen peroxide resistance of thick biofilms.
authors.affiliation: Center for Biofilm Engineering, Department of Microbiology, Montana State University, Bozeman 59717, USA.
authors.forename: W L
authors.initials: WL
authors.lastname: Cochran
authors.forename: S J
authors.initials: SJ
authors.lastname: Suh
authors.forename: G A
authors.initials: GA
authors.lastname: McFeters
authors.forename: P S
authors.initials: PS
authors.lastname: Stewart
mesh_terms: D000464:Alginates; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D002700:Chloramines / Q000494:pharmacology*; D004203:Disinfection; D004352:Drug Resistance, Microbial; D005816:Genetic Complementation Test; D005898:Glass; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008863:Microspheres; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: C079619:AlgU protein, Pseudomonas aeruginosa; D000464:Alginates; D001426:Bacterial Proteins; D002700:Chloramines; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D006861:Hydrogen Peroxide; C030816:chloramine