Showing papers by "Thomas D. Brock published in 1963"
TL;DR: A survey has been made of bacteriocine production by a wide variety of well-characterized strains of group D streptococci, and five distinct bacteriOCines can be defined on the basis of spectrums and sensitivity to chloroform, heat, and proteolytic enzymes.
Abstract: Brock, Thomas D. (Indiana University, Bloomington), Barbara Peacher, and Deborah Pierson. A survey of the bacteriocines of enterococci. J. Bacteriol. 86:702–707. 1963.—A survey has been made of bacteriocine production by a wide variety of well-characterized strains of group D streptococci. On the basis of spectrums and sensitivity to chloroform, heat, and proteolytic enzymes, five distinct bacteriocines can be defined. Type 1 is produced by all Streptococcus zymogenes (S. faecalis var. zymogenes) strains, is active against a wide variety of gram-positive bacteria, and is also a hemolysin. Type 2 is produced by some S. liquefaciens (S. faecalis var. liquefaciens) strains, and acts on many enterococci as well as on certain other lactic acid bacteria. Type 3 is produced by certain strains of both S. faecalis and S. faecium, and inhibits a wide variety of group D streptococci, but is inactive against all other lactic acid bacteria tested except Leuconostoc citrovorum. Type 4 is produced by certain S. faecium strains and resembles in certain ways the type 3 activity, but differs from it in other ways. Type 5 has been found to be produced by only one proteolytic strain of S. zymogenes, and this bacteriocine has a very narrow spectrum. The strain that produces this bacteriocine also produces type 1 activity. No strain is sensitive to a bacteriocine of the type it produces.
139 citations
TL;DR: Two strains of Streptococcus zymogenes produce a bacteriocine which is active against lactic acid bacteria and most other grampositive bacteria, and both activities are stable when heated in agar.
Abstract: Brock, Thomas D. (Indiana University, Bloomington) and Joseph M. Davie. Probable identity of a group D hemolysin with a bacteriocine. J. Bacteriol. 86:708–712. 1963.—All strains of Streptococcus zymogenes (S. faecalis var. zymogenes) produce a bacteriocine which is active against lactic acid bacteria and most other grampositive bacteria. Mutants which have lost the hemolytic characteristic lose at the same time their bacteriocine-producing ability. A strain which was resistant to the bacteriocine but which was nonhemolytic and nonbacteriocinogenic was irradiated, and two hemolytic mutants were isolated from it. These mutants were also bacteriocinogenic. Thus, the two activities are gained or lost together by mutation. Both activities are destroyed by chloroform vapors and are antagonized by lecithin. Both activities are destroyed at the same rate by treatment at 45 C under mildly acid conditions, and both activities are stable when heated in agar. The two activities are produced in parallel during the growth cycle, and disappear in parallel. The possible ecological role of a substance which is both a hemolysin and a bacteriocine is discussed.
108 citations
TL;DR: In host bacteria resistant to the antibiotic, streptomycin inhibits phage replication by inhibiting the process of injection, and this effect is competitively reversed by certain divalent cations, polyamines, and streptidine.
Abstract: In host bacteria resistant to the antibiotic, streptomycin inhibits phage replication by inhibiting the process of injection. This effect is competitively reversed by certain divalent cations, polyamines, and streptidine. It is proposed that streptomycin inhibits injection by attaching to the phage DNA while it is still folded within the phage head, and in this way it prevents the unfolding which is essential for the injection process. The reversal agents probably function by displacing the antibiotic from the phage, but they also promote injection themselves.
27 citations
TL;DR: M protein synthesis in nongrowing cells may be a useful model system for obtaining a detailed understanding of protein synthesis and a survey of a large number of antibiotics and other potential inhibitors was made.
Abstract: Brock, Thomas D. (Western Reserve University, Cleveland, Ohio). Effect of antibiotics and inhibitors on M protein synthesis. J. Bacteriol. 85:527-531. 1963.-This work extends the observations of Fox and Krampitz on M protein synthesis in nongrowing cells of streptococci. A survey of a large number of antibiotics and other potential inhibitors was made. Some substances bring about inhibition of fermentation and inhibit M protein synthesis because they deprive the cell of the energy needed for this process. A second group of substances inhibit growth at concentrations tenfold or more lower than they inhibit M protein synthesis. These are the antibiotics which inhibit synthesis of cell wall or other structures in growing cells, but do not affect protein synthesis. A third group of substances inhibit growth and M protein synthesis at the same concentration. These substances probably inhibit growth because they inhibit general protein synthesis, and are therefore specific inhibitors of protein synthesis. In this class are chloramphenicol, erythromycin, and the tetracyclines. Several other antibiotics of previously unknown mode of action are in this class. A fourth group of substances had no effect on M protein synthesis. No substances were found which inhibited M protein synthesis at a lower concentration than that which inhibited growth. M protein synthesis in nongrowing cells may be a useful model system for obtaining a detailed understanding of protein synthesis.
23 citations
TL;DR: Analysis of the mode of action of the antibiotic in this system reveals that it probably has two effects, which are consistent with the hypothesis that the phage DNA exists transiently at a streptomycin-accessible site, and then moves to a site of replication which is inaccessible to the antibiotic.
Abstract: SUMMARY: Streptomycin is a specific antiviral agent for a variety of bacteriophages active against Streptococcus faecium, S. faecalis, S. liquefaciens and S. zymogenes since it inhibits bacteriophage growth even when the host is resistant to the antibiotic. An analysis of the mode of action of the antibiotic in this system reveals that it probably has two effects. If the antibiotic is present before adsorption, it inhibits injection of the phage DNA. This effect is readily reversible. If the antibiotic is added after adsorption, it appears that injection is not inhibited, but that the phage genome is inactivated. The antibiotic has no effect on replication of the phage once the genome has become established in the host cell. This is consistent with the hypothesis that the phage DNA exists transiently at a streptomycin-accessible site, and then moves to a site of replication which is inaccessible to the antibiotic. Streptomycin-resistant phages probably have a different injection mechanism from streptomycin-sensitive phages.
The senior author has reported similar findings for an RNA bacteriophage of Escherichia coli. The implications of this work for virus chemotherapy and for analysing the mode of penetration into the cell of virus nucleic acid are discussed.
17 citations