EFFECT OF HEAT AND PLATING MEDIUM ON SURVIVAL OF ESCHERICHIA COLI AFTER TREATMENT WITH RADIOMIMETIC CHEMICALS

Zampieri, Antonio (Palo Alto Medical Research Foundation, Palo Alto, Calif.), and Joseph Greenberg. Effect of heat and plating medium on survival of Escherichia coli after treatment with radiomimetic chemicals. J. Bacteriol. 89:931-936. 1965.-Survival of Escherichia coli strain S and its radioresistant mutant R(4) after treatment with mitomycin C, azaserine, nitrogen mustard, 1-methyl-3-nitro-1-nitrosoguanidine, nitrofurazone, and proflavine was studied. With all agents except proflavine, R(4) was more resistant than was S. Survival of strain S was greater on minimal glucose-salts medium than on Penassay (Difco), and greater on the latter than on Tryptone (Difco) agar; survival of S was greater when posttreatment incubation temperature was 45 C than when it was 37 C. Post-treatment plating medium or temperature had no effect on survival of R(4). Visible light did not affect survival of S or R(4). The survival curves of R(4) were exponential; those of S exhibited decreasing sensitivity with time of exposure. With proflavine, photoactivation by visible light was demonstrable, but there was no difference in survival between S and R(4). Survival of either strain was not affected by post-treatment plating medium or incubation temperature.

SYSTEMIC WEBER-CHRISTIAN DISEASE

A patient suffering from Weber-Christian panniculitis was found at necropsy to have similar lesions in the visceral adipose tissue. When the lesions occur internally, diagnosis during life is complicated by the difficulty of examining visceral adipose tissue and the disease may often go unrecognized, but patients suffering from Weber-Christian panniculitis should be investigated bearing in mind the possibility of internal lesions. Only 11 cases confirmed by necropsy appear to have been reported hitherto. The aetiology remains obscure. It is suggested that the name ;systemic Weber-Christian disease' be applied when the lesions occur in adipose tissue other than the panniculus adiposus and that the term ;Weber-Christian panniculitis' be used when the lesions are confined to the subcutaneous adipose tissue.

NITROUS ACID REACTIVATION OF ULTRAVIOLET-IRRADIATED TRANSFORMING DNA FROM HEMOPHILUS INFLUENZAE

Partial recovery of ultraviolet-damaged denatured or native transforming DNA from Hemophilus influenzae, has been obtained by exposing the irradiated DNA in the denatured form to nitrous acid. Some factors that affect this recovery are described. An erythromycin marker (E₂₀) was not reactivated. The UV damage reactivable by nitrous acid is different from that repaired by the photoreactivating enzyme from bakers' yeast. The pretreatment with nitrous acid affords a slight protection for denatured C₂₅ DNA and Sm₂₅₀ DNA against ultraviolet irradiation, but this pretreatment sensitized the E₂₀ DNA to this irradiation.

OPTIMAL CONDITIONS FOR THE TRANSFORMATION OF STREPTOCOCCI

Perry, Dennis (Northwestern University Medical School, Chicago, Ill.) and Hutton D. Slade. Optimal conditions for the transformation of streptococci. J. Bacteriol. 85:636-642. 1963.-A study of the properties of the streptococcal transforming system, employing streptomycin resistance as a marker, resulted in a 1,000- to 10,000-fold increase in the rate of transformation. In some cases, as high as 0.5% transformants have been obtained. Certain aspects of the system differed markedly from those of other bacterial transforming systems, particularly with regard to the time for the appearance of competence. When a group H strain was exposed to deoxyribonucleic acid after various periods of incubation, the time at which cells were most competent was about 2 hr. Similar experiments with a different group H strain and an ungroupable strain showed that competence for both occurred after 1 hr of growth. It is significant that the period of optimal competence, though attained at different times, took place at the beginning of the logarithmic phase of growth. The temperature optimum for transformation was about 37 C. Cells preincubated in sheepblood broth exhibited a higher level of transformation than cells preincubated in plain or human serum broth. That some correlation exists between the attainment of competence and growth is evident. In contrast, human serum was most effective in the transforming media. The few preparations of bovine albumin (fraction V) employed did not appreciably support transformation. Data are also presented which show that some relationship exists between transforming efficiency and serological classification, in that homologous transformation showed a 100- to 10,000-fold greater efficiency over heterologous transformation. Antibodies to deoxyribonuclease, as well as other inhibitors of deoxyribonuclease, failed to bring about transformation in group A streptococci.

ALTERATIONS IN THE MOUSE VIRULENCE OF SALMONELLA TYPHIMURIUM BY GENETIC RECOMBINATION

Krishnapillai, V. (Walter Reed Army Institute of Research, Washington, D.C.), and L. S. Baron. Alterations in the mouse virulence of Salmonella typhimurium by genetic recombination. J. Bacteriol. 87:598-605. 1964.-The genetic basis of mouse virulence was investigated with an avirulent strain of Salmonella abony as chromosomal donor and a virulent strain of S. typhimurium as recipient in recombination experiments. In these genetic crosses, the transfer of partial avirulence was found to segregate among the hybrids that were examined. At least two determinants controlling avirulence were depicted to account for the partial avirulence of the hybrids. One of these determinants is indicated as being in the region of the locus for streptomycin sensitivity or resistance, and the other was adjacent to the locus for inositol utilization. Moreover, both determinants were essential for the phenotypic expression of complete avirulence in a hybrid. This was established by the results of experiments in which an initial, partially avirulent hybrid was backcrossed with the S. abony donor so that it further received the additional determinant.

STUDIES OF THE ENZYME ACTIVITY OF BACT. LACTIS AEROGENES. (AEROBACTER AEROGENES). II. THE EFFECTS OF VARIOUS ADAPTATIONS ON THE ENZYME BALANCE

A study has been made of the changes in enzyme balance accompanying the adaptation of Bact, lactis aerogenes to resist various drugs or to utilize lactose. Enzymes directly responsible for the breakdown of the source of carbon and energy prove, in general, to be expanded in cells resistant to streptomycin or crystal violet. Training to these drugs appears to transfer metabolism to anaerobic routes requiring more of the carbon source and thus needing a greater activity of the degradative enzymes. Training to both drugs jointly, however, leaves these enzyme activities unchanged or actually reduces them. After adaptation to resist proflavine, the oxidative and catabolic processes are less active than before, whereas asparagine deaminase, representing part of the amino-acid metabolism, is expanded, perhaps in compensation. The activities of enzymes normally latent in the cell and capable of degrading carbon sources which the cell has not previously used are usually, but not invariably decreased by drug training. In the development of a new cellular economy these enzymes may apparently have to be partially sacrificed. Training to chloramphenicol does not alter the activities of the enzymes studied. Catalase shows little change during training to most of the drugs. During adaptation to utilize lactose the activity of every enzyme studied changes in a way which suggests a co-ordinated pattern. Those enzymes responsible for the breakdown of lactose are expanded and the activities of the non-induced enzymes all show a complex pattern linked with this. Catalase activity falls but asparagine deaminase activity rises.

URINARY TRACT INFECTIONS DUE TO COAGULASE-NEGATIVE STAPHYLOCOCCI

A survey of Staphylococcus albus urinary infections is reported from a general hospital. The infection followed urethral instrumentation in 75% of the patients, and was usually caused by organisms already present in the urethra. Novobiocin-resistant strains caused infections in four out-patients with no predisposing lesions or instrumentation of the urinary tract.

NITROFURAN DERIVATIVES AS RADIOMIMETIC AGENTS: CROSS-RESISTANCE STUDIES WITH ESCHERICHIA COLI

Mutants of Escherichia coli B selected on the basis of resistance to nitrofurazone, NFT, or ultraviolet light proved to be resistant to all three of these agents. Further tests showed that these mutants are also resistant to three other nitrofuran derivatives, nitrofurantoin, nihydrazone, and furazolidone, but not to nifuroxime. The mutants are also resistant to the chemically dissimilar radiomimetic agent, proflavin. Strain B and all the mutants derived from it are equally sensitive to streptomycin, a non-radiomimetic antibiotic. E. coli strain B/r (resistant to radiation and radiomimetic chemicals) shows the same resistance pattern as the new mutant strains. The results are discussed in terms of what is known concerning the basis for the resistance of strain B/r to ultraviolet light. It is concluded that radiomimetic nitrofurans probably exert their effect on E. coli through damage to DNA.