16
D. E. MAHONY
orange), non-toxigenic bacteria were converted to toxin production.
Further evidence supporting the role of phage in toxin production
was provided by Inoue and Iida (1971) when they showed that a lysate
from a type C strain could convert a non-toxigenic type D strain into a
type C toxin-producing strain. Eklund et al. (1971) demonstrated the
existence of two phages carried by C. botulinum type C , only one of which
had converting ability. Toxin-producing strains lost toxigenicity upon
addition of phage antisera. I n 1972, Eklund et al. in quantitating C.
botulinum phages found the composition of the soft agar overlays to be
important. This consisted of trypticase, peptone, yeast extract, glucose,
0.7% agar, 2.5% NaCl and 0.5% lactalysate as well as catalase and cysteine
hydrochloride. The association of phage and toxigenicity in type D strains
was also confirmed. Oguma et al. (1973) produced further evidence for
phage conversion when phage lysates from already converted strains could
convert non-toxic strains of types C and D.
Eklund and Poysky (1974) could interconvert non-toxigenic type C and
D strains with phages from toxigenic type C and D and postulated that
toxigenic types C and D might lose their prophage in their natural environment and could then be converted to either type C or D toxin-producers by
specific phages. However, C. botulinum might lose prophages and still
produce toxins. In such strains either prophages remain non-induced or
not all toxin production in C. botulinum is phage-controlled. Of even greater
interest, perhaps, was the demonstration of interspecies conversion (Eklund
et al., 1974) where a non-toxigenic mutant of C. botulinum type C could be
converted not only to toxigenic type C or D by respective phages, but also
to C. novyi type A by a phage from that organism.
Hariharan and Mitchell (1976) observed that all toxigenic strains of C.
botulinum type C which they examined were infected with one or two types
of phages and, that in highly toxigenic strains, the phage-bacterium relationship was characterised by a stable lysogenic type of association. When
Oguma (1976) examined the stability of toxigenicity in C. botulinum types
C and D, he found that most converted strains lost toxigenicity upon serial
transfer with or without phage antiserum, suggesting that pseudolysogeny
rather than true lysogenic conversion was occurring. He also suggested
that non-converting mutants of the phages may have arisen and that this
type of phage would render the bacteria phage-resistant but non-toxigenic,
thus explaining the loss of toxigenicity commonly observed in some type C
and D strains of C. botulinum.
Oguma et al. (1976, 1977) reported that haemagglutinin production in
C. botulinum types C and D seemed to be controlled by bacteriophages
and that this property could be transmitted separately or concomitantly
with toxin production.
D. E. MAHONY
orange), non-toxigenic bacteria were converted to toxin production.
Further evidence supporting the role of phage in toxin production
was provided by Inoue and Iida (1971) when they showed that a lysate
from a type C strain could convert a non-toxigenic type D strain into a
type C toxin-producing strain. Eklund et al. (1971) demonstrated the
existence of two phages carried by C. botulinum type C , only one of which
had converting ability. Toxin-producing strains lost toxigenicity upon
addition of phage antisera. I n 1972, Eklund et al. in quantitating C.
botulinum phages found the composition of the soft agar overlays to be
important. This consisted of trypticase, peptone, yeast extract, glucose,
0.7% agar, 2.5% NaCl and 0.5% lactalysate as well as catalase and cysteine
hydrochloride. The association of phage and toxigenicity in type D strains
was also confirmed. Oguma et al. (1973) produced further evidence for
phage conversion when phage lysates from already converted strains could
convert non-toxic strains of types C and D.
Eklund and Poysky (1974) could interconvert non-toxigenic type C and
D strains with phages from toxigenic type C and D and postulated that
toxigenic types C and D might lose their prophage in their natural environment and could then be converted to either type C or D toxin-producers by
specific phages. However, C. botulinum might lose prophages and still
produce toxins. In such strains either prophages remain non-induced or
not all toxin production in C. botulinum is phage-controlled. Of even greater
interest, perhaps, was the demonstration of interspecies conversion (Eklund
et al., 1974) where a non-toxigenic mutant of C. botulinum type C could be
converted not only to toxigenic type C or D by respective phages, but also
to C. novyi type A by a phage from that organism.
Hariharan and Mitchell (1976) observed that all toxigenic strains of C.
botulinum type C which they examined were infected with one or two types
of phages and, that in highly toxigenic strains, the phage-bacterium relationship was characterised by a stable lysogenic type of association. When
Oguma (1976) examined the stability of toxigenicity in C. botulinum types
C and D, he found that most converted strains lost toxigenicity upon serial
transfer with or without phage antiserum, suggesting that pseudolysogeny
rather than true lysogenic conversion was occurring. He also suggested
that non-converting mutants of the phages may have arisen and that this
type of phage would render the bacteria phage-resistant but non-toxigenic,
thus explaining the loss of toxigenicity commonly observed in some type C
and D strains of C. botulinum.
Oguma et al. (1976, 1977) reported that haemagglutinin production in
C. botulinum types C and D seemed to be controlled by bacteriophages
and that this property could be transmitted separately or concomitantly
with toxin production.