Prevention of loss of Streptomycin production on repeated transfer of Streptomyces griseus

The streptomycin-producing capacity of submerged cultures of Streptomyces griseus 107 was nearly lost during repeated transfers on synthetic nutrient medium. This effect did not occur on the same nutrient medium from which Fe(++) was omitted. The physiological reason for this effect was discussed from the point of the relationship of iron-containing porphyrin enzymes to the process of streptomycin biosynthesis.

Inhibition by antibiotics of the growth of bacterial and yeast protoplasts

Shockman, Gerald D. (Temple University School of Medicine, Philadelphia, Pa.) and J. Oliver Lampen. Inhibition by antibiotics of the growth of bacterial and yeast protoplasts. J. Bacteriol. 84:508-512. 1962.-The characteristics and requirements for growth of bacterial (Streptococcus faecalis) and yeast (Saccharomyces cerevisiae) protoplasts were established and the effect of a variety of antibacterial and antifungal antibiotics determined. A clear differentiation was obtained between such inhibitors of bacterial cell wall synthesis as penicillin and cycloserine, which did not prevent protoplast growth, and all others, antibacterial and antifungal, which inhibited protoplasts and intact organisms at the same range of concentration. Novobiocin, previously reported to inhibit bacterial wall synthesis, was also effective against a reaction(s) essential to the growth of S. faecalis protoplasts. The antibacterial action of streptomycin, neomycin, and kanamycin was essentially eliminated by the high salt concentration needed to maintain the protoplasts. Removal of the cell wall did not significantly increase antibiotic susceptibility of a resistant species. Protoplasts of Bacillus megaterium were insensitive to the antifungal agent, nystatin, and did not bind it to any detectable degree. Thus, the yeast or bacterial cell wall does not appear to play a major role in determining relative antibiotic susceptibility by masking internal sensitive target sites. A variety of antifungal antibiotics tested on the growth of log-phase yeast cells failed to produce osmotically fragile forms.

Genotypic alterations associated with avirulence in streptomycin-resistant Pasteurella pestis

Brubaker, Robert R. (Fort Detrick, Frederick, Md.) and Michael J. Surgalla. Genotypic alterations associated with avirulence in streptomycin-resistant Pasteurella pestis. J. Bacteriol. 84:615-624. 1962.-Avirulence in Pasteurella pestis, as indicated by the existence of a new genotype, was associated with the genetic loss of Ca(++) dependence rather than with the usual concomitant loss of ability to produce virulence antigens. Strains of the new type exhibited all four of the known virulence factors of P. pestis but were avirulent for mice and guinea pigs (ld(50) > 10(8) cells). In addition to producing virulence antigens, the new strains formed rough colonies at 37 C when grown on Ca(++)-deficient medium, as opposed to typical avirulent strains which formed smooth colonies on this medium and failed to produce virulence antigens. Growth of the new strains in a corresponding Ca(++)-deficient broth medium was slow, as compared with that of typical avirulent strains, but was more rapid than that of virulent strains. The new strains were obtained (i) at 26 C by selecting for resistance to streptomycin or (ii) at 37 C by isolation from rough colonies growing on a Ca(++)-deficient agar medium plated with either a virulent streptomycin-sensitive or -resistant culture. Usually, isolates obtained at 26 C exhibited a marked reduction in ability to form colonies upon primary plating at 37 C. Of 108 streptomycin-resistant isolates obtained from six virulent strains, 20% were of the new type. In addition, five isolates were of reduced virulence (mouse ld(50) approximately 10(4) cells) but differed in being Ca(++)-dependent; they possessed all of the known virulence properties. Certain streptomycin-resistant strains failed to give rise to avirulent colonies when plated on a Ca(++)-deficient agar medium containing streptomycin. The significance of this phenomenon, which was not exhibited by the five strains of reduced virulence, is discussed, as are some apparent differences between isolates from a glycerol-fermenting strain and similar isolates obtained from five nonglycerol-fermenting strains.

Influence of streptomycin on nucleotide excretion in Escherichia coli

Tzagoloff, Helen (Rutgers, The State University, New Brunswick, N.J.) and W. W. Umbreit. Influence of streptomycin on nucleotide excretion in Escherichia coli. J. Bacteriol. 85:49-52. 1963.-The action of streptomycin in causing nucleotide excretion is not the cause of the killing effect of streptomycin, because, in certain strains, streptomycin may kill the cells without evidence of nucleotide excretion. In readily excreting strains, most of the cells are killed before nucleotide excretion is evident.

KINETICS OF MATING OF FP+ AND FP- STRAINS OF PSEUDOMONAS AERUGINOSA

Loutit, J. S. (University of Otago, Dunedin, N.Z.), and L. E. Pearce. Kinetics of mating of FP(+) and FP(-) strains of Pseudomonas aeruginosa. J. Bacteriol. 90:425-430. 1965.-Recently, we reported the variability of the FP(+) x FP(-) mating in Pseudomonas aeruginosa, and the increase in efficiency when the cells were mated after dilution. The present work shows that when standardized cells were mated after a dilution of 10(-2) for FP(-) and 2 x 10(-3) for FP(+), there was less variability in the system. Investigation of pairing between FP(+) and FP(-) cells, as measured by genetic transfer, revealed that none took place during 24 hr in liquid media in which growth of both parents was possible. Transfer in liquid minimal medium was not investigated, because the single marker in the male was insufficient to control back mutation in 24 hr. No transfer occurred on solid media which allowed full growth of both FP(+) and FP(-) cells. Transfer took place very slowly on minimal agar, requiring 19 to 20 hr. It is thought that this represents growth of microcolonies with eventual transfer when internal nutrients were exhausted.

PLAQUE ASSAY FOR PSITTACOSIS VIRUS IN MONOLAYERS OF CHICK EMBRYO FIBROBLASTS

Piraino, F. (City of Milwaukee Health Department, Milwaukee, Wis.), and C. Abel. Plaque assay for psittacosis virus in monolayers of chick embryo fibroblasts. J. Bacteriol. 87:1503-1511. 1964.-A tissue culture system for the assay of 6BC psittacosis virus by plaque production on chick embryo fibroblast cells is described. Experiments are given which characterize the specificity of the reaction and identify factors found to cause variations in plaque counts. The statistical data obtained indicate this assay to be a precise and highly reliable procedure for the detection of 6BC virus and antibody.

STREPTOMYCIN AS AN ANTIVIRAL AGENT: MODE OF ACTION

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.

INTRASPECIFIC AND INTERSPECIFIC TRANSFORMATION IN STREPTOCOCCI

Perry, Dennis (Northwestern University Medical School, Chicago, Ill.), and Hutton D. Slade. Intraspecific and interspecific transformation in streptococci. J. Bacteriol. 88:595-601. 1964.-Interspecific transformation reactions, employing streptomycin resistance as a marker, were performed with eight strains of streptococci belonging to three serological groups (F, H, and O) and one ungroupable (UG) strain. Generally, autotransformation (within the same strain) was most efficient. Homotransformation (between different strains of the same serological group), however, was sometimes as efficient or slightly better. Heterotransformation (between different serological groups) yielded the least number of transformants or none at all. The rate of transformation of different strains varied from 2.0 x 10(-7) to 7.6 x 10(-3). Group H streptococci exhibited the highest rate of autotransformation, followed by groups F and O, and strain UG. The results of heterotransformation reactions revealed that a genetic relationship exists between various strains of different serological groups. No transformation, however, occurred between F and O strains, indicating a lack of genetic homology between these serological groups of streptococci. Deoxyribonucleic acid (DNA), isolated by physical and enzymatic methods from a group O and a UG strain, failed to induce transformation. DNA from these strains, however, significantly inhibited the transforming ability of other DNA preparations. Heat and mechanical shear resulted in a marked decrease in this inhibitory property.

GENETIC LINKAGE OF MUTATIONAL SITES AFFECTING SIMILAR CHARACTERS IN PNEUMOCOCCUS AND STREPTOCOCCUS

Ravin, Arnold W. (University of Rochester, Rochester, N.Y.), and Joscelyn D. H. De Sa. Genetic linkage of mutational sites affecting similar characters in pneumococcus and streptococcus. J. Bacteriol. 87:86-96. 1964.-By interspecific transformation, deoxyribonucleic acid (DNA) determinants conferring resistance to high levels of streptomycin in pneumococcus were found to be allelic with DNA determinants conferring low levels of streptomycin resistance in the Challis and NBSI strains of streptococcus. The reciprocal transformation (low resistance pneumococcus x high resistance streptococcus) led to the same conclusion. In addition, determinants controlling resistance to erythromycin in pneumococcus and the Challis strain of streptococcus were found to become closely linked after interspecific transformation. Modifier genes influencing the phenotype conferred by mutations at the streptomycin-resistance locus differentiate species to a certain extent. The results demonstrate that transformations between pneumococcus and streptococcus are not due to episomes, but involve recombinational events in which genetic material of the host species is replaced by homologous material that performed a similar function in the donor species.