The Potency of Nascent Streptococcus Bacteriophage B

The Bacteriophages of Streptococcus pyogenes

The bacteriophages of Streptococcus pyogenes (group A streptococcus) play a key role in population shaping, genetic transfer, and virulence of this bacterial pathogen. Lytic phages like A25 can alter population distributions through elimination of susceptible serotypes but also serve as key mediators for genetic transfer of virulence genes and antibiotic resistance via generalized transduction. The sequencing of multiple S. pyogenes genomes has uncovered a large and diverse population of endogenous prophages that are vectors for toxins and other virulence factors and occupy multiple attachment sites in the bacterial genomes. Some of these sites for integration appear to have the potential to alter the bacterial phenotype through gene disruption. Remarkably, the phage-like chromosomal islands (SpyCI), which share many characteristics with endogenous prophages, have evolved to mediate a growth-dependent mutator phenotype while acting as global transcriptional regulators. The diverse population of prophages appears to share a large pool of genetic modules that promotes novel combinations that may help disseminate virulence factors to different subpopulations of S. pyogenes. The study of the bacteriophages of this pathogen, both lytic and lysogenic, will continue to be an important endeavor for our understanding of how S. pyogenes continues to be a significant cause of human disease.

619. Host-phage relationships of cheese starter organisms: II. Effect of phage activity on heterologous strains of lactic streptococci

A reaction closely resembling the nascent phage phenonomenon was studied. When lysing the homologous strains ofStr. lactis, two phage races were found to be capable of simultaneously inducing lysis of a heterologous strain and of other phage-resistant homologous strains. Seitz filtered potent lysates of the homologous strains also caused lysis. Subjecting the lysates to a temperature of 60°C. for 5 min. destroyed the lytic activity on heterologous strains but did not inactivate the phage.

These two phage races produced haloes around their plaques while a third phage, unable to induce lysis of heterologous cultures, showed no haloes. Addition of I3-to the medium suppressed the appearance of haloes, providing further evidence that they are due to the production of bacterial lysins.

Evidence was obtained to show that several other possible mechanisms were not responsible for the observed lysis, and it was concluded that a heat-labile lysin or lysins capable of destroying the heterologous strain was produced during lysis of the homologous strain. The relationship of this to the nascent phage and other similar phenomena observed elsewhere is discussed.

500. The so-called ‘nascent’ bacteriophage phenomenon

The apparent lytic effect of a newly formed (‘nascent’) streptococcal bacteriophage on streptococcal strains not normally lysed by the phage was shown to be actually an inhibitory action produced by high concentrations of the phage. The inhibitory effect was exhibited by stock preparations of the phage, used in sufficient concentration, and there was no need to postulate a special potency for the phage in its ‘nascent’ form. The inhibitory effect of phages on heterologous organisms was found to be a widespread phenomenon among strains ofStreptococcus cremorisandStr. lactis. It became apparent only when larger proportions of phage than the traces normally used for lytic tests were employed.

295. The problem of bacteriophage in cheese making: Part I. Observations and investigations on slow acid production

That bacteriophage is the cause of much loss to the cheese-making industry of New Zealand has been shown by Whitehead(1). In New Zealand in recent years, cheese has been made almost entirely from flash-pasteurized milk with the aid of starters prepared from single-strain cultures of lactic acid streptococci (Str. cremoris). The use of such starters has been accompanied by the occasional failure of the bulk starter to clot, or, if clotted, by failure to produce the required amount of acid in the cheese vat—the latter condition being described by Whitehead as ‘pack up’. Whitehead has traced the cause of sudden failure to air-borne infection of the bulk starter by specific bacteriophage (2), the most probable source of infection being the spray from whey separators. When adequate protection from phage contamination was provided slowness in cheese making disappeared.

688. Phage-organism relationships among strains ofStreptococcus cremoris: the selection of strains as cheese starters

The relationships between nineteen strains ofStr. cremorisand nineteen phage races were investigated. It was found that in addition to clear-cut lytic reactions there were other actions between some phage races and bacterial strains whereby in some cases a phage could show adaptation to a strain and become changed in host range, and in other cases could inhibit growth of a strain without any phage multiplication.

There is some evidence to indicate that bacterial strains and phage races fall into family groups within which most of the phages act in one way or another on most of the strains. The suggestion is made that the strains and races in a group may have originated from a parent bacterial strain and parent phage race.

The selection of strains ofStr. cremorisfor use as cheese starters is discussed in the light of the findings reported in the present paper. The diffculty of isolating a large number of strains unrelated in every respect is indicated.

Lysis and lysogenization of groups A, C, and G streptococci by a transducing bacteriophage induced from a group G Streptococcus

A temperate bacteriophage, designated GT-234, was isolated from a group G Streptococcus after ultraviolet irradiation. After several single-plaque passages in a group G indicator strain, this phage formed plaques in 3 of 14 group A strains, in 3 of 15 group C strains, and in 4 of 13 group G strains-but not in some representatives of several other serogroups. After propagation in each of the sensitive strains, the progeny from each was shown to be the same phage by (i) adsorption and plaque formation in each of the other groups, (ii) lysogenization in each of the other groups, (iii) high titers on infection of each serogroup, regardless of the group of propagating strain, and (iv) neutralization of infection in each of the other groups by antiserum against the phage propagated in group G. Phage GT-234 is serologically related to virulent group A phage A25, from which it is morphologically indistinguishable. Like A25, it is a transducing phage. Other studies showed that A25, as well as a group A temperate transducing phage (AT-298), could also infect strains of group C and G. These results indicate a need for reassessment of group specificity and phage receptors among streptococci of groups A, C, and G and raise possibilities for intergroup transduction.

Studies on bacteriophages of hemolytic streptococci. I. Factors influencing the interaction of phage and susceptible host cell

The host ranges of bacteriophages for group A, types 1, 6, 12, and 25 and group C streptococci have been determined. The findings indicate that the susceptibility to these phages is primarily a group-specific phenomenon, although it is modified by several factors such as the hyaluronic acid capsule, lysogeny, and possibly the presence of surface proteins. Phage antibody studies indicate that while the group A phages are antigenically related, they are distinct from the group C phage. This is in agreement with the observation that group A phages are not specific for their homologous streptococcal types. The purified group C carbohydrate inactivates group C phage but not the group A phages, thus suggesting that the carbohydrate, a component of the cell wall, may serve as the phage receptor site. It has not been possible to inactivate the group A phages with group A carbohydrate. Phage lysis of groups A and C streptococci is accompanied by fragmentation of the cell wall since the C carbohydrate has been identified serologically and chemically in the supernate of centrifuged lysates. The immediate lysis of groups A and C hemolytic streptococci and their isolated cell walls by an accesory heat-labile lytic factor in fresh group C lysates is also described.

STUDIES WITH BACILLUS POLYMYXA: II. BACTERIOPHAGE OF BACILLUS POLYMYXA IN RELATION TO THE 2,3-BUTANEDIOL FERMENTATION

A procedure is described that resulted in the isolation of a number of phages against various strains of Bacillus polymyxa. Out of 82 strains tested, 63 were lysed completely and 6 partially. The phages produced plaques that were separated into eight morphological groups. No special relationship between susceptibility to phage and yield of butanediol was noted.Temperature studies indicated that these phages were very sensitive, being inactivated by an exposure of 30 min. at 55 °C. They were shown to be transmitted through the bacterial spore and under these conditions resisted a temperature of 80 °C. for 60 min.Eight out of 50 strains tested were lysogenic.Phage was capable of almost completely stopping the fermentation of wheat mashes by susceptible strains. Certain resistant cultures gave good yields in the presence of active phage. Mixing resistant and susceptible strains resulted in lowered yields; however, a good fermentation was obtained in the presence of phage by combining three resistant strains. Even in the absence of phage, a mixture of five strains was not favourable, probably as a result of antibiotic effects among the individual strains. Secondary cultures differed markedly in nature of growth and spore-producing capacity from primary strains and were, on the whole, poorer diol producers.It was suggested that under ordinary conditions in the factory, proper sterilization of equipment and materials, aseptic technique, and use of well-tested non-lysogenic strains are adequate precautions against this bacterial virus.