Toggle Main Menu Toggle Search

Open Access padlockePrints

Characterization of an isogenic mutant of Streptococcus pyogenes Manfredo lacking the ability to make streptococcal acid glycoprotein

Lookup NU author(s): Dr Beverley Degnan, Dr Jeong-Jin Lee, Professor Michael Kehoe


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


An isogenic mutant of Streptococcus pyogenes Manfredo that lacks the ability to make streptococcal acid glycoprotein (SAGP) has been constructed by inserting a deletion in the sagp gene using the method of allelic exchange. An assay of cell extracts (CE) prepared from the wild-type and mutant Manfredo strains for the enzyme arginine deiminase (AD) showed that significant activity was present in wild-type CE but none could be detected in mutant CE. These findings confirm our earlier conclusion that SAGP has AD activity (B. A. Degnan, J. M. Palmer, T. Robson, C. E. D. Jones, M. Fischer, M. Glanville, G. D. Mellor, A. G. Diamond, M. A. Kehoe, and J. A. Goodacre, Infect. Immun. 66:3050-3058, 1998). Wild-type CE but not mutant CE potently inhibited human peripheral blood mononuclear cell proliferation in response to phytohemagglutinin, and this inhibition was overcome by the addition of L- arginine to proliferation assay mixtures. Invasion assays showed that the isogenic mutant organisms lacking SAGP, and thus AD activity, were between three and five times less able to enter epithelial cells (Hep-2C and A549) than were the wild-type streptococci. Both wild-type and mutant S. pyogenes bacteria were extremely sensitive to low pH. However, L-arginine (1 mM or above) significantly increased the viability of the wild type but not the isogenic mutant organisms under acidic conditions. The difference in acid susceptibility between wild-type and mutant bacteria may explain the reduced capacity of the isogenic mutant bacteria to invade and survive intracellularly.

Publication metadata

Author(s): Degnan BA; Kehoe MA; Lee JJ; Fontaine MC; Doebereiner AH; Mastroeni P; Dougan G; Goodacre JA

Publication type: Article

Publication status: Published

Journal: Infection and Immunity

Year: 2000

Volume: 68

Issue: 5

Pages: 2441-2448

ISSN (print): 0019-9567

ISSN (electronic): 1098-5522

Publisher: American Society for Microbiology


DOI: 10.1128/IAI.68.5.2441-2448.2000

PubMed id: 10768929


Altmetrics provided by Altmetric