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Molecular analysis of the psa permease complex of Streptococcus pneumoniae
Author(s) -
McAllister Lauren J.,
Tseng HsingJu,
Ogunniyi A. David,
Jennings Michael P.,
McEwan Alastair G.,
Paton James C.
Publication year - 2004
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/j.1365-2958.2004.04164.x
Subject(s) - biology , mutant , operon , permease , locus (genetics) , virulence , gene , streptococcus pneumoniae , microbiology and biotechnology , genetics , bacteria
Summary The psaBCA locus of Streptococcus pneumoniae encodes a putative ABC Mn 2+ ‐permease complex. Downstream of the operon is psaD , which may be co‐transcribed and encodes a thiol peroxidase. Previously, there has been discordance concerning the phenotypic impact of mutations in the psa locus, resolution of which has been complicated by differences in mutant construction and the possibility of polar effects. Here, we constructed unmarked, in frame deletion mutants Δ psaB , Δ psaC , Δ psaA , Δ psaD , Δ psaBC , Δ psaBCA and Δ psaBCAD in S. pneumoniae D39 to examine the role of each gene within the locus in Mn 2+ uptake, susceptibility to oxidative stress, virulence, nasopharyngeal colonization and chain morphology. The requirement for Mn 2+ for growth and transformation was also investigated for all mutants. Inductively coupled plasma mass spectrometry (ICP‐MS) analysis provided the first direct evidence that PsaBCA is indeed a Mn 2+ transporter. However, this study did not substantiate previous reports that the locus plays a role in choline‐binding protein pro‐duction or chain morphology. We also confirmed the importance of the Psa permease in systemic virulence and resistance to superoxide and hydrogen peroxide, as well as demonstrating a role in nasopharyngeal colonization for the first time. Further evi‐dence is provided to support the requirement for Mn 2+ supplementation for growth and transformation of Δ psaB , Δ psaC , Δ psaA , Δ psaBC , Δ psaBCA and Δ psaBCAD mutants. However, transformation, as well as growth, of the Δ psaD mutant was not dependent upon Mn 2+ supplementation. We also show that, apart from sensitivity to hydrogen peroxide, the Δ psaD mutant exhibited essentially similar phenotypes to those of the wild type. Western blot analysis with a PsaD antiserum showed that deleting any of the genes upstream of psaD did not affect its expression. However, we found that deleting psaB resulted in decreased expression of PsaA relative to that in D39, whereas deleting both psaB and psaC resulted in at least wild‐type levels of PsaA.