- Volume 28, Issue 3, 1962

SUMMARY: Agglutinogens and precipitinogens have been detected in the spores of many species of aerobic and anaerobic spore-formers and these antigens are distinct from those of the vegetative growth phases of the corresponding organisms. Spore antigens are heat resistant and antibody response is elicited by the injection of autoclaved spores into rabbits. Injection of living spores leads to the development of antibodies reacting with vegetative cell antigens in addition to spore antibodies.

Agglutinogens tend to show subspecies distribution in some aerobic species but spore precipitinogens appear to be mainly species specific in aerobes. Less information is available about anaerobes where a similar pattern of specificity is suggested. Data about the antigenic structure of the spore and the antigenic changes accompanying sporulation and germination are scant; it is in these aspects of the subject that the most significant progress is to be anticipated.

SUMMARY: The influence of casein hydrolysate and certain amino acids on the uptake and utilization of tryptophan and other precursors of nicotinic acid biosynthesis by a mutant of Neurospora crassa which can grow on tryptophan or nicotinic acid was investigated. Whereas casein hydrolysate and certain amino acids inhibited the growth of the organism when tryptophan, kynurenine, or 3-hydroxykynurenine was present in the medium, they had no effect in the presence of other precursors, i.e. 3-hydroxyanthranilic acid or nicotinic acid. Studies have been made with wild strain and the mutant on the amount of tryptophan taken up from the medium at different periods of growth of the organism.

SUMMARY: The existence of haploid and diploid Dictyostelium discoideum amoebae has been confirmed. Strains were isolated which displayed widely different ploidal compositions. These appear to fall into three general classes: stable haploid, stable diploid and metastable strains. Their ploidal compositions are clonally inherited. Procedures are described by which strains of differing ploidal composition can be isolated, one from the other. The ploidal composition of a clone is correlated with differences in spore and amoeboid size distributions as well as other morphological and morphogenetic properties.

SUMMARY: In four strains of Escherichia coli B/r (ORNL), B (ORNL), B (Hill), Bs (Hill) protection by β-mercaptoethylamine (MEA) exceeded that observed for oxygen removal by nitrogen bubbling. Although only a slight decrease of protection was found with strain Bs (Hill) when oxygen was removed by nitrogen bubbling, the protection afforded by MEA in excess of that achieved by nitrogen bubbling was similar with all four strains. The data suggest that at least two mechanisms for protection by MEA may operate simultaneously in some bacteria and that one of these is a removal of oxygen equivalent to that achieved by nitrogen gas bubbling.

SUMMARY: The effect of thirty-seven different steroids on the growth of Trichophyton rubrum is reported. The effects varied from complete inhibition of growth to stimulation. Highly inhibitory compounds included androstan-3, 17-dione, testosterone, 11-deoxycorticosterone, progesterone and 7-dehydro-cholesterol. 17α-Hydroxypregnenolone was stimulatory but all other compounds with the 17α-hydroxyl group were inactive. Structural requirements for activity are discussed.

SUMMARY: Growth curves were determined for a single strain of Actinomyces israelii grown in systematic modifications of the partially defined medium of Howell & Pine (1956). These determinations resulted in a progressive simplification of the Howell & Pine medium and in the elucidation of a completely defined medium containing 335 μg. total-N/ml. instead of 948 μg. total-N/ml. in the original medium; the yield of organism was increased concomitantly from 55 μg. total-N/ml. of medium to 80 μg. total-N/ml. of medium. This simplified medium contained no ammonium sulphate, purine or pyrimidine bases but twenty amino acids (of which L-cysteine and L-tryptophan were found to be essential) and sixteen growth factors.

SUMMARY: A defined medium HP6/B used by Christie & Porteous (1962) for the cultivation of a single strain (Wills) of Actinomyces israelii contained sixteen growth factors. By using the quantitative inoculation technique of Christie & Porteous (1960) and a semi-quantitative method for assessing growth it has now been found that the Wills strain will grow in the presence of only five of the sixteen growth factors. These growth factors are: biotin, inositol, nicotinic acid, pyridoxal, riboflavin.

SUMMARY: The induction of penicillinase in Staphylococcus aureus resistant to benzyl penicillin has been investigated. Inducers tested included several new penicillins derived from 6-aminopenicillanic acid, benzyl penicillin amide and cephalosporin C. Fifteen strains of S. aureus were examined, one in detail and the others using only two or three inducers. All strains possessed basal penicillinase and all were inducible, although maximum enzyme levels varied somewhat from one strain to another.

Hydrolysis of the penicillins by staphylococcal penicillinase was investigated by using supernatant fluid from a cephalosporin C-induced culture of Staphylococcus aureus 524 as the source of enzyme. Under these conditions all the penicillins except methicillin were inactivated, although at different rates. Hydrolysis of methicillin was only detectable at much higher enzyme concentrations. Hydrolysis of cephalosporin C was not observed.

The use of penicillins for the treatment of staphylococcal infections is discussed in the light of these results.

SUMMARY: There are now at least three main types of antibacterial activity shown by different penicillins-the ordinary penicillin G type, the type shown by methicillin active against penicillinase-producing staphylococci and the ‘broad spectrum’ type of activity shown by α-aminobenzylpenicillin.

The inducing capacity of different penicillins can be measured by the concentration required for maximal or half maximal induction, which gives the Michaelis (induction) constant, or by the total amount of enzyme eventually produced. But either of these methods of determining inducing capacity may give misleading results with penicillins which may be easily hydrolysed during the induction process.

Of the penicillins used methicillin is by far the best inducer-but it is uncertain how much this is due to a true ‘inducing affinity’ and how much a result of its resistance to hydrolysis.

SUMMARY: Two non-allelic suppressors have been isolated which suppress non-allelic, leaky, methionine-requiring mutants blocked either between cysteine and cystathionine or between cystathionine and homocysteine. Strains carrying either suppressor gene in the presence of the me + allele were stimulated by either cysteine or methionine, whereas the suppressed methionine-requiring mutants (me su) although stimulated by methionine were inhibited by cysteine. S-methylcysteine supported the growth of leaky methionine-requiring mutants when it was present as the sole sulphur source and it also stimulated the growth of suppressed methionine-requiring mutants inhibited by cysteine. Sulphate or cysteine inhibited the growth response of certain methionine-requiring mutants to S-methylcysteine. The incorporation of radioactive sulphate into protein methionine was inhibited to a greater extent by S-methylcysteine than was its incorporation into protein cysteine. The results suggest that the sulphur of S-methylcysteine is converted to methionine without prior conversion to cysteine and that the suppressors act by retarding the formation of an inhibitor which accumulates as a result of the primary mutation to methionine requirement.

SUMMARY: The uptake of radioactivity from 14C-streptomycin, in a form which cannot be displaced from the organisms by unlabelled streptomycin, was determined in several species of bacteria and one yeast growing under standard conditions. This uptake showed a good correlation with the sensitivity of the organism to streptomycin, and in streptomycin-resistant organisms was about 1 % of that in a highly sensitive organism, Bacillus megaterium. The quantity of streptomycin taken up when growth ceased represented an intracellular concentration 10- to 50-fold higher than that in the growth medium. Environmental factors, such as anaerobiosis or presence of carbon monoxide, which increased the resistance of Staphylococcus aureus to streptomycin also resulted in decreased rates of uptake of 14C-streptomycin. When Bacillus subtilis grew in medium containing the streptomycin antagonist 2-n-heptyl-4-hydroxyquinoline N-oxide, the rate of uptake of radioactivity was reduced to about 30 % of that in absence of the antagonist; the rate at which harvested organisms oxidized succinate and malate was reduced to a similar extent.

SUMMARY: More than 90 % of the radioactivity taken up by Bacillus megaterium growing in medium containing inhibitory concentrations of 14C-streptomycin appeared to be identical with streptomycin, as shown by its behaviour on an ion-exchange resin and by recrystallization with streptomycin derivatives. Streptomycin was not removed from the organisms by washing in growth medium with or without addition of unlabelled streptomycin, or in distilled water. It could be extracted with inorganic acids and trichloroacetic acid, but not by some other commonly used extraction procedures. When the organisms were converted to protoplasts and these lysed and fractionated, up to 99 % of the streptomycin in the organisms was recovered in the material sedimented from the cytoplasmic fraction by centrifugation at 105,000 g. Very small amounts of streptomycin were found in the fraction containing protoplast ‘ghosts’, but these may have represented contaminating cytoplasmic material. This distribution may not, however, be a true indication of the location of streptomycin before fractionation, since a similar distribution was found when streptomycin was added to lysed protoplasts immediately before fractionation. The uptake of streptomycin was decreased at pH values below 7. Uptake depended on continued synthesis of cell material, and environmental conditions which prevented growth and bactericidal action also considerably decreased uptake of streptomycin. The quantity of streptomycin finally taken up was proportional to the concentration of streptomycin in the growth medium, and at the lowest growth-inhibitory concentrations was about 5 x 104 molecules of streptomycin per bacterium.

SUMMARY: The ‘negative contrast method’ was used to study by electron microscope four previously described Bacillus cereus bacteriophages. The main features of the structure of these phages are described and the observations corrected with similar work on phages associated with other genera.

SUMMARY: The number of micro-organisms present in soil located at a distance of 4 cm. from a 60Co-source 1 m. above ground declined considerably after 24 hr. of exposure. Respirometric determination showed no decrease in oxygen uptake at this time. The distance at which the effect of irradiation could be demonstrated increased with increasing duration of exposure; after 396 days a reduction of the oxygen uptake as well as of the number of microbes could be detected at a distance of more than 3 m. and at a depth of 10 cm. as well as at the surface.

There appeared to be no significant difference between the effects of chronic irradiation on spore-forming and on non-spore-forming bacteria, respectively.

The plot of microbial count showed a better fit to a double-logarithmic than to a semi-logarithmic diagram according to Lea’s formula. Possible explanations of this fact are discussed.

SUMMARY: Studies on the kinetics of diphtheria toxin formation in iron-free culture media by variants of the PW no. 8 strain of Corynebacterium diphtheriae labelled with 14C-phenylalanine or 35S-methionine, showed that the toxin protein was synthesized de novo from amino acids by growing organisms. Release of toxin into the extracellular medium occurred without lysis of more than a minor proportion of the bacterial population.

SUMMARY: The growth rate and the time schedule of the mitotic cycle of the lepto-monads of Leishmania donovani, the Kala-azar parasite, were studied. The numbers of cells in the different division stages were estimated by photomicroscopy after Feulgen staining. The observed time intervals of resting, prophase, metaphase, anaphase, telophase and binucleate condition were 15.2, 1.1, 3.9, 1.1, 0.9 and 1.8 hr., respectively; the total generation time was 24 hr.

SUMMARY: Cultures of the giant bacterium Caryophanon latum Peshkoff, among them our own isolates from cow dung, were studied. A method for isolation is described. A fluid medium containing acid-hydrolysed casein, thiamine, biotin, sodium acetate, sodium butyrate and dipotassium phosphate, at pH 7.8, was devised which, without added colloids, allowed luxuriant growth of C. latum when sufficient aeration was provided. C. latum has been found to utilize acetic, butyric and β-hydroxybutyric acids. A variety of other carbon sources did not appear to be readily utilized by C. latum. The organism produced a carotenoid-like yellow pigment, the synthesis of which was inhibited by diphenylamine. A large amount of poly-β-hydroxybutyric acid (PHB) was synthesized by C. latum growing in the fluid medium described above. Much of the PHB was liberated as free granules. C. latum was found to be Gram-positive, in contrast to previously published reports.

SUMMARY: At minimal bacteriostatic concentrations, bacitracin had four distinct actions on Staphylococcus aureus: (a) prevention of growth; (b) induction of lysis; (c) suppression of induced enzyme synthesis; (d) stimulation of the reduction of 2,3,5-triphenyltetrazolium chloride. In contrast, penicillin and cycloserine had activities (a) and (b) but neither (c) nor (d), and chloramphenicol had activities (a) and (c) but neither (b) nor (d). With bacitracin, properties (a) and (b) but neither (c) nor (d) were enhanced by Zn2+; other metal ions were inactive. Sequential inactivation of bacitracin by autoclaving revealed that the bacteriostatic property was quite labile whereas the other three activities were more heat resistant. Thus, although several distinct mechanisms have been demonstrated whereby bacitracin can injure bacterial cells, the present data do not indicate which of these, if any, is associated with the primary biochemical lesion that results in suppression of growth.