A novel protein quality control mechanism contributes to heat shock resistance of worldwide‐distributed P seudomonas aeruginosa clone C strains

Summary P seudomonas aeruginosa is a highly successful nosocomial pathogen capable of causing a wide variety of infections with clone C strains most prevalent worldwide. In this study, we initially characterize a molecular mechanism of survival unique to clone C strains. We identified a  P . aeruginosa clone C ‐specific genomic island ( PACGI ‐1) that contains the highly expressed small heat shock protein sHsp 20c, the founding member of a novel subclass of class B bacterial small heat shock proteins. sHsp 20c and adjacent gene products are involved in resistance against heat shock. Heat stable sHsp 20c is unconventionally expressed in stationary phase in a wide temperature range from 20 to 42°C. Purified  sHsp 20c has characteristic features of small heat shock protein class B as it is monodisperse, forms sphere‐like 24‐meric oligomers and exhibits significant chaperone activity. As the  P . aeruginosa  clone C population is significantly more heat shock resistant than genetically unrelated P . aeruginosa strains without sHsp20c, the horizontally acquired shsp20c operon might contribute to the survival of worldwide‐distributed clone C strains.