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Autorepressor PsrA is required for optimal Legionella pneumophila growth in Acanthamoeba castellanii protozoa
Author(s) -
Graham Christopher I.,
Patel Palak G.,
Tanner Jennifer R.,
Hellinga Jacqueline,
MacMartin Teassa L.,
Hausner Georg,
Brassinga Ann Karen C.
Publication year - 2021
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14760
Subject(s) - biology , rpos , legionella pneumophila , microbiology and biotechnology , virulence , legionella , protozoa , virulence factor , gene , genetics , bacteria , gene expression , promoter
Legionella pneumophila possesses a unique intracellular lifecycle featuring distinct morphological stages that include replicative forms and transmissive cyst forms. Expression of genes associated with virulence traits and cyst morphogenesis is concomitant, and governed by a complex stringent response based‐regulatory network and the stationary phase sigma factor RpoS. In Pseudomonas spp., rpoS expression is controlled by the autorepressor PsrA, and orthologs of PsrA and RpoS are required for cyst formation in Azotobacter . Here we report that the L. pneumophila psrA ortholog, expressed as a leaderless monocistronic transcript, is also an autorepressor, but is not a regulator of rpoS expression. Further, the binding site sequence recognized by L. pneumophila PsrA is different from that of Pseudomonas PsrA, suggesting a repertoire of target genes unique to L. pneumophila . While PsrA was dispensable for growth in human U937‐derived macrophages, lack of PsrA affected bacterial intracellular growth in Acanthamoeba castellanii protozoa, but also increased the quantity of poly‐3‐hydroxybutyrate (PHB) inclusions in matured transmissive cysts. Interestingly, overexpression of PsrA increased the size and bacterial load of the replicative vacuole in both host cell types. Taken together, we report that PsrA is a host‐specific requirement for optimal temporal progression of L. pneumophila intracellular lifecycle in A . castellanii .