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Journal of Bacteriology, September 1999, p. 5389-5394, Vol. 181, No. 17
Channing Laboratory1
and Division of Infectious Diseases,2
Department of Medicine, Brigham & Women's Hospital and Harvard Medical
School, Boston, Massachusetts 02115
Received 8 March 1999/Accepted 23 June 1999
Group B Streptococcus (GBS) is the leading cause of
bacterial sepsis and meningitis among neonates. While the capsular
polysaccharide (CPS) is an important virulence factor of GBS, other
cell surface components, such as C proteins, may also play a role in
GBS disease. CPS production by GBS type III strain M781 was greater
when cells were held at a fast (1.4-h mass-doubling time
[td]) than at a slow (11-h
td) rate of growth. To further investigate
growth rate regulation of CPS production and to investigate production
of other cell components, different serotypes and strains of GBS were
grown in continuous culture in a semidefined and a complex medium.
Samples were obtained after at least five generations at the selected
growth rate. Cells and cell-free supernatants were processed
immediately, and results from all assays were normalized for cell dry
weight. All serotypes (Ia, Ib, and III) and strains (one or two strains
per serotype) tested produced at least 3.6-fold more CPS at a
td of 1.4 h than at a
td of 11 h. Production of beta C protein
by GBS type Ia strain A909 and type Ib strain H36B was also shown to
increase at least 5.5-fold with increased growth rate (production at a
td of 1.4 h versus 11 h). The
production of alpha C protein by the same strains did not significantly
change with increased growth rate. The effect of growth rate on other cell components was also investigated. Production of group B antigen did not change with growth rate, while alkaline phosphatase decreased with increased growth rate. Both CAMP factor and beta-hemolysin production increased fourfold with increased growth rate. Growth rate
regulation is specific for select cell components in GBS, including
beta C protein, alkaline phosphatase, beta-hemolysin, and CPS production.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Regulation of Cell Component Production by Growth
Rate in the Group B Streptococcus
*
Corresponding author. Mailing address: Channing
Laboratory, 181 Longwood Ave., Boston, MA 02115. Phone: (617) 525-0726. Fax: (617) 731-1541. E-mail: rross{at}channing.harvard.edu.
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