The Journal of Medical Microbiology, Vol 21, Issue 1 69-74, Copyright © 1986 by Society for General Microbiology
Surface proteins in the transduction of groups A and G streptococci
S. A. Skjold and L. W. Wannamaker
Four pairs of M+SOR+ and M-SOR- variants of group-A type-49 streptococci
were compared as receptor strains in transduction of a
streptomycin-resistance marker. The yield of transductants was 5-9-fold
greater with the M-SOR- variants than with the corresponding M+SOR+
variants. Treatment of M+SOR+ variants of type-49 streptococci with trypsin
enhanced the rate of transduction by 16-35-fold whereas trypsin treatment
of corresponding M-SOR- variants resulted in minimal enhancement (5-fold or
less). With trypsin treatment the numbers of transductants were
approximately equal in pairs of M+SOR+ and M-SOR- variants. Enhanced
transduction (10-26-fold) of streptomycin resistance was obtained by
trypsin treatment of another seven M+SOR+ type-49 strains, of diverse phage
subtypes and from various geographical locations. A wide range of
enhancement (5-46-fold) was found in eight of nine M+ strains of group-A
type-6 streptococci. With trypsin treatment, three of 10 transducible
group-G strains showed enhanced transduction (10-13-fold) of a plasmid
containing a determinant for erythromycin resistance. Transductional
enhancement is proteolytic in nature, being enhanced by trypsin,
chymotrypsin, papain, pronase and streptococcal proteinase. Although
interference with phage adsorption by surface proteins would appear to be
the most obvious explanation for these findings, further studies are
required to define more clearly the mechanism of trypsin enhancement.
