Affiliation:
1. New Zealand Dairy Research Institute, Palmerston North, New Zealand
Abstract
A method was tested for protecting a
Streptococcus lactis
strain, ML3, used as a starter in the manufacture of Cheddar cheese, against the lytic activity of its homologous phage, ml
3
. At a concentration of 10
−2
m
, a naturally occurring polyamine, spermine, in the form of its hydrochloride, protected ML3 against lysis-from-without and lysozyme activity and against lysis by the phage when added at the time of infection or up to 21 min after infection. It was found that the latter protective effect could be accounted for in terms of the spermine preventing the formation of mature particles rather than preventing the escape of viable phage. Single colonies selected from a culture of ML3 cells that had been previously infected with phage ml
3
, in the presence of spermine, were all found to have acquired resistance to phage ml
3
. They retained this resistance during a 3-month period of daily subculture in broth and, in the absence of spermine, could not be induced to liberate phage or phage components either by the techniques normally used for inducing lysogens or by artificial disruption of the cells. It is concluded that when spermine is added to ML3 cells before a certain critical stage of the phage infection cycle, the process of phage synthesis is irreversibly halted and the cells retain the infecting phage as a defective prophage that confers on the cells immunity to infection by the homologous phage. Phage-resistant cultures did not inherit reduced starter activity in association with their acquired resistance characteristic.
Publisher
American Society for Microbiology
Subject
General Pharmacology, Toxicology and Pharmaceutics,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
Reference14 articles.
1. Adams M. H. 1959. Bacteriophages. Interscience Publishers Inc. New York.
2. Campbell A. M. 1968. In K. Maramorosch and H. Koprowski (ed.) Methods in virology vol. 4. Academic Press Inc. New York.
3. Polyamines and ribosomal structure;Cohen S. S.;J. Biol. Chem.,1960
4. Effect of spermnidine treatment on amino acid availability in amino acid-starved Escherichia coli;Ezekiel D. H.;J. Mol. Biol.,1968
5. Inhibition of protein synthesis by spermine in growing cells of Staphylococcus aureus;Friedman M. E.;J. Bacteriol.,1966