Salinity-dependent impacts of ProQ, Prc, and Spr deficiencies on Escherichia coli cell structure.
ProQ is a cytoplasmic protein with RNA chaperone activities that reside in FinO- and Hfq-like domains. Lesions at proQ decrease the level of the osmoregulatory glycine betaine transporter ProP. Lesions at proQ eliminated ProQ and Prc, the periplasmic protease encoded by the downstream gene prc. They dramatically slowed the growth of Escherichia coli populations and altered the morphologies of E. coli cells in high-salinity medium. ProQ and Prc deficiencies were associated with different phenotypes. ProQ-deficient bacteria were elongated unless glycine betaine was provided. High-salinity cultures of Prc-deficient bacteria included spherical cells with an enlarged periplasm and an eccentric nucleoid. The nucleoid-containing compartment was bounded by the cytoplasmic membrane and peptidoglycan. This phenotype was not evident in bacteria cultivated at low or moderate salinity, nor was it associated with murein lipoprotein (Lpp) deficiency, and it differed from those elicited by the MreB inhibitor A-22 or the FtsI inhibitor aztreonam at low or high salinity. It was suppressed by deletion of spr, which encodes one of three murein hydrolases that are redundantly essential for enlargement of the murein sacculus. Prc deficiency may alter bacterial morphology by impairing control of Spr activity at high salinity. ProQ and Prc deficiencies lowered the ProP activity of bacteria cultivated at moderate salinity by approximately 70% and 30%, respectively, but did not affect other osmoregulatory functions. The effects of ProQ and Prc deficiencies on ProP activity are indirect, reflecting their roles in the maintenance of cell structure.
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
Craig H
CH
Kerr
Doreen E
DE
Culham
David
D
Marom
Janet M
JM
Wood
D001622:Betaine / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects; D002876:Chromosomes, Bacterial / Q000187:drug effects; D003470:Culture Media / Q000737:chemistry; D003546:Cysteine Endopeptidases / Q000172:deficiency*; D010450:Endopeptidases / Q000172:deficiency*; D004926:Escherichia coli / Q000166:cytology* / Q000187:drug effects* / Q000254:growth & development; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins / Q000172:deficiency*; D019897:Periplasm / Q000187:drug effects; D016601:RNA-Binding Proteins; D054712:Salinity; D012965:Sodium Chloride / Q000378:metabolism*
D003470:Culture Media; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; C118132:ProQ protein, E coli; D016601:RNA-Binding Proteins; D001622:Betaine; D012965:Sodium Chloride; D010450:Endopeptidases; C072135:C-terminal processing peptidase; D003546:Cysteine Endopeptidases; C532221:mepS protein, E coli