Center for Biofilm Engineering
Abstract:
"Role of RpoS and AlgT in Pseudomonas Aeruginosa Biofilm
Resistance to Hydrogen Peroxide and Monochloramine"
00-009 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.
Cochran, W., S.-J. Suh, G. McFeters, and P. Stewart, "Role of RpoS and AlgT in Pseudomonas Aeruginosa Biofilm
Resistance to Hydrogen Peroxide and Monochloramine," J. Appl. Micro.
88:546-553. (2000)
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