A Role for Exopolysaccharides in the Protection of Microorganisms from Desiccation

Abstract

Mucoid strains of Escherichia coli, Acinetobacter calcoaceticus , and Erwinia stewartii were significantly more resistant to desiccation than corresponding isogenic nonmucoid mutants (survival rates of up to 35% in mucoid strains and between 0.7 and 5% in nonmucoid variants), even in colonies containing both cell types. Desiccation was found to bring about an induction of β-galactosidase in Lon - strains of E. coli K-12 carrying transcriptional lac fusions in the capsule biosynthetic ( cps ) regulon. This induction was dependent on the transcriptional activators RcsA and RcsB. Induction was lower in cells carrying mutations in the membrane sensor protein RcsC.