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Infect Immun, July 1998, p. 3170-3178, Vol. 66, No. 7
Department of Microbiology and Immunology,
University of Arkansas for Medical Sciences, Little Rock, Arkansas
72205;1
Department of Microbiology,
Molecular Genetics and Immunology, University of Kansas Medical
Center, Kansas City, Kansas 661602; and
Laboratory of Bacteriology and Immunology, Rockefeller
University, New York, New York 100213
Received 2 October 1997/Returned for modification 14 January
1998/Accepted 9 February 1998
To determine whether the ability of Staphylococcus
aureus to bind collagen involves an adhesin other than the
collagen adhesin encoded by cna, we examined the collagen
binding capacity (CBC) of 32 strains of S. aureus. With
only two exceptions, a high CBC corresponded with the presence of
cna. Both exceptions involved cna-positive
strains with a low CBC. The first was a single strain (ACH5) that
encoded but did not express cna. The second were the mucoid
strains Smith diffuse and M, both of which encoded and expressed
cna but bound only minimal amounts of collagen. Analysis of
capsule mutants suggests that the reduced CBC observed in the mucoid
strains was due to masking of the collagen adhesin on the cell surface
and that this masking effect is restricted to heavily encapsulated
strains. Differences in the CBC of the remaining cna-positive strains were correlated to variations in the
level of cna transcription and were independent of the
number of B domain repeats in the cna gene. In all
cna-positive strains other than ACH5, cna
transcription was temporally regulated, with cna mRNA levels being highest in cells taken from exponentially growing cultures
and falling to almost undetectable levels as cultures entered the
post-exponential growth phase. The CBC was also highest with cells
taken from exponentially growing cultures. Mutation of agr
resulted in a slight increase in cna transcription and a
corresponding increase in CBC during the exponential growth phase but
did not affect the temporal pattern of cna transcription. Mutation of sar resulted in a more dramatic increase in CBC
and a delay in the post-exponential-phase repression of cna
transcription. Mutation of both sar and agr had
an additive effect on both CBC and cna transcription. We
conclude that (i) cna encodes the primary collagen-binding
adhesin in S. aureus, (ii) sar is the primary regulatory element controlling expression of cna, and (iii)
the regulatory effects of sar and agr on
cna transcription are independent of the interaction
between sar and agr.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Factors Affecting the Collagen Binding Capacity of
Staphylococcus aureus
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Slot 511, University of Arkansas for
Medical Sciences, 4301 W. Markham, Little Rock, AR 72205. Phone: (501) 686-7958. Fax: (501) 686-5359. E-mail:
smeltzermarks{at}exchange.uams.edu.
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