- Volume 21, Issue 1, 1959

Summary: In contrast to the failure of several previous workers to transduce streptomycin resistance, it was found that streptomycin indifference (one-step complete resistance) could quite reproducibly be transduced. For the expression of indifference after transduction, the infected bacteria must be allowed to divide at least once. This finding is assumed to reflect a segregation delay because of the recessive nature of the indifference locus. But from the fact that transduced indifference is phenotypically expressed from partial to complete resistance, the participation of a phenomic lag is also assumed.

In addition to the delay of phenotypic expression, several other aspects of transduction of indifference were studied and a close similarity of the behaviour of indifference to other chromosomal markers was found.

The transduction of one-step intermediate resistance into sensitive and into other one-step intermediate resistant recipients, however, was found to be difficult to demonstrate if it occurs at all. The difficulty of detecting resistant transductants is apparently not due to the killing of resistant bacteria in the presence of sensitive cells.

The difficulty of transducing intermediate resistance is assumed to be due to a selective disadvantage of the resistant, slow-growing transductants. The failure to find transductions even with slow-growing sensitive recipients may have been due to the fact that successful transductions yielded even slower growing resistant clones.

On the other hand, the transduction of second-step resistance into one-step resistant mutants was found to take place and the transduction of indifference into one-step resistant bacteria yielded slow-growing indifferent transductants.

Summary: The infection of slow-growing one-step intermediate streptomycin- resistant mutants with phage from wild-type bacteria, indifferent (one-step completely resistant) or other one-step intermediate resistant mutants gives rise to fastgrowing streptomycin-sensitive transductants. From this fact it is clear that both slow growth and streptomycin resistance are controlled by a single locus. The transductants are very easily detected on the poor background growth of the intermediate resistant recipient. With this technique it has become possible to cross one-step resistance with resistance, indifference and sensitivity. The results so far obtained indicate that one-step intermediate resistance is controlled by multiple loci. None of these loci is linked to the indifference locus. The fast-growing mutants which develop from the two-step resistant mutants are assumed from the transduction analysis to be due to reverse mutations at the first step loci.

SUMMARY: Results from studies of continuous cultures of Aerobacter aerogenes growing in chemically denned media indicate that specific growth rate (R) is a function of population density (P) as well as the concentration of the limiting nutrient (S). From these observations, and those of others, the following model for bacterial growth is derived:

where um and B are growth parameters that are constants under defined conditions. This model is believed to have general applicability and to account for bacterial growth in both batch and continuous cultures.

Summary: Megacin however highly bactericidal for sensitive organisms was not adsorbed by them. Its bactericidal action was markedly dependent on temperature. The viability of organisms exposed to megacin at 0° was not affected. When megacin was added to exponentially growing Bacillus megaterium there was cessation of growth followed by a gradual decrease in turbidity of the culture. The decrease in turbidity was, however, not associated with a total lysis of individual organisms; rather it. was the consequence of the escape of the dense intracellular material from the organisms. Intracellular components, i.e. substances which absorbed in the ultraviolet region escaped from the bacteria into the medium while cell wall remained essentially intact. When B. megaterium suspended in a medium containing lactose was exposed to megacin, μ-galactosidase appeared on the surface of bacteria.

Protoplast preparations made from Bacillus megaterium and Micrococcus aurantiacus (both sensitive to megacin) were converted into ghost-like structures on the addition of megacin. On the other hand, protoplasts made from insensitive species resisted megacin. Observations indicate that megacin causes a radical change in the osmotic barrier of sensitive organisms by attacking the cytoplasmic membrane. Data available suggest that megacin is either an enzyme which breaks down the osmotic barrier of sensitive cells, or is a substance capable of activating the intrinsic enzymes of cells which lead to an autolysis of cytoplasm.

Summary: Sodium selenite is toxic in low concentration to salmonellas as well as to other enterobacteria. The ability of salmonellas to grow in selenite broth appears to be due to binding of selenite by constituents of peptone (e.g. peptides). Reduction of selenite takes place after growth is established and the intensity of reduction is related to the profuseness of growth. The presence of a fermentable carbohydrate favours growth and intensity of selenite reduction. Many organisms, however, die as a result of the reducing conditions. Organisms differ in their ability to use different sulphur sources; there was evidence that cystine and pentathionate as highly preferred sulphur sources may be of special significance. Sodium selenite reacts with certain inorganic sulphur compounds to form seleno-polythionates. It is believed that the selectivity of selenite broth may be due to the presence of seleno-polythionates or other seleno-sulphur compounds which act as growth-inhibitory analogues of highly preferred sulphur sources.

Summary: An organism, resembling Microbacterium lacticum, was found to be stimulated by liver or yeast extract in a medium composed of glucose, amino acids, vitamins, adenine, guanine, uracil, ammonium formate, and mineral salts. These complex materials could be replaced by comparable concentrations of porphyrin-containing compounds and by extremely low concentrations of ferrichrome, coprogen, or terregens factor, which are thought to act as intracellular ‘iron transport factors’.

Summary: Hartmannella rhysodes Singh was cultivated under axenic conditions at 25–30° in a buffered physiological salt solution containing 1 % (w/v) proteose peptone and a suitable additional carbon source. Optimal growth and maximum cyst formation were obtained aerobically under constant agitation in vessels coated with silicone. The addition of a thickening agent did not improve growth. No cysts were formed at low oxygen tensions. This may reflect a fundamental metabolic block in cyst formation. Growth curves were obtained with a variety of carbon sources: glucose, maltose and mannose supported optimal growth; lactose supported unusual growth which resembled diauxie. By testing for reducing sugars, no utilization of glucose was detected. A specific chemical test for glucose revealed that glucose was utilized during growth and by resting suspensions. Through the use of uniformly labelled 14C glucose, it was possible to demonstrate that glucose was assimilated and also used as an energy source during growth. The osmotic concentration required for optimal growth was in itself not optimal when the total osmotic pressure was kept constant and the concentration of utilizable carbon sources was decreased.

Summary: Upon repeated subculture in media of gradually increasing pH value a strain of Bacillus cereus developed the ability to grow under strongly akaline conditions. Organisms with the highest alkali resistance could grow at pH 10·3, and stocks of intermediate resistance were also obtained. When growing on alkaline agar, resistant bacteria underwent marked morphological changes. In liquid media, the bacteria retained the ability to synthesize lecithinase. Resistance was not lost upon several transfers on a neutral medium.

Resistant bacteria when growing in alkaline media caused a rapid decrease in pH value. A similar pH decrease was caused by sensitive bacteria in media of the highest degree of alkalinity in which they could grow. The decline of pH value accompanied, but did not precede, growth; acid production by the resistant bacteria does not appear to be a primary mechanism of resistance.

Summary: The chromatin configurations of acid-Giemsa preparations of Spirillum anulus were followed sequentially, at 2 hr. intervals, for 48 hr. A series of broth cultures were inoculated with 0·1 ml. of a 7-day broth culture, incubated at 30° and centrifuged at 2 hr. intervals. The sedimented cells were used to inoculate agar plates for use in making smears by the agar block method. The smears were fixed in acid-alcohol, hydrolysed in n-HC1 solution at 60° for 8 or 15 min. and stained with Giemsa. Samples of living cells, taken from the sedimented cells at all time intervals, were examined by phase-contrast and darkfield microscopy.

The majority of the early cells (0–16 hr.) were resistant to acid hydrolysis, being undifferentiated by 15 min. of hydrolysis until the 12th hr. of growth. After the 16th hr. of the growth cycle the cells showed an abrupt change in their reaction toward acid hydrolysis; subsequent preparations were hydrolysed for 8 min. The early cells appeared undifferentiated by phase contrast until approximately the 14th hr. of growth; after this time inclusions could be observed in the cells. Transparent cells containing dark inclusions were observed in the living cells by the 16 hr. of growth and coincided with the abrupt change of the acid-Giemsa cells toward acid hydrolysis.

The pattern of the chromatin configurations found in the acid-Giemsa cells consisted in : (1) an axial filament which fragmented into thick bars, from which spherical bodies were formed; (2) the direct division of the spherical bodies into smaller spheres, from which bead-like granules were formed by means of intermediate X-, Y-, and V-forms or the direct formation of rings of bead-like granules from the spherical bodies; (3) the re-formation of the axial filaments from the bead-like granules with the aggregation of all the chromatin material of the cell at the centre of the cells; (4) the division of the aggregated chromatin material on cell division and the extension of the chromatin material in the form of an axial filament; and (5) the re-formation of the spherical bodies and bead-like granules as outlined in steps (1) and (2) from the axial filaments.

Essentially the same types of chromatin configurations were observed in living cells. The most exact correlation between the living and fixed images of the chromatin bodies of Spirillum anulus occurred between the 18th and 30th hr. of the growth cycle. The correlation between the living and fixed images of the chromatin bodies of S. anulus was less exact at other time intervals. Various theories concerned with the occurrence of axial filaments and chromatin aggregations in bacterial cells are discussed.

SUMMARY: Protoplasts of Bacillus cereus 569 and B. cereus 569/H were shown to be as competent as intact cells in the induced and constitutive formation of penicillinase, as well as in other biochemical activities. It was demonstrated that the cell- bound penicillinase was localized at or near the cell surface. The β-penicillinase fraction was released by digestion of the cell wall and by washing of the protoplast membrane. However, the γ-penicillinase was tightly bound to the cytoplasmic membrane. It was obtained in a soluble form by treating the membrane with sonic vibration or with fat solvents.

SUMMARY: Strains of Pasteurella pestis under certain conditions form a bacteriocin- like material, which has been named pesticin. Pesticin formation was induced by ultraviolet irradiation. A chemically defined medium composed of inorganic salts and amino acids supported the synthesis of pesticin by irradiated organisms. The minimal amino acid requirement for pesticin synthesis has been established. For the synthesis of pesticin at 37° the irradiated organisms required certain amino acids which they did not require at 27°. Bacteria in the stationary phase and actively dividing bacteria were equally able to produce pesticin upon irradiation. Concentrations of chloramphenicol lower than those required for bacteriostasis inhibited pesticin synthesis. Non-pesticin producing mutants of P. pestis were obtained by exposure of the bacteria to higher doses of u.v. irradiation than those required for the induction of pesticin formation. These mutants were sensitive to pesticin.

SUMMARY: In an attempt to elucidate the taxonomic relationship of Clostridium bifermentans and C. sordellii about sixty strains assigned to one or other of the two species were examined. Two groups of strains differing in their cultural and biochemical properties were recognized. One closely resembled the type culture of C. bifermentans (Tissier & Martelly, 1902), and the other, in which some strains were pathogenic, resembled the C. sordellii isolate ‘82’ of C. Sordelli. The former of these groups is clearly to be regarded as C. bifermentans and the latter as C. sordellii. It has been shown that the two species, although similar in many respects, are distinct and easily distinguishable. In view of this, the present practice of some bacteriologists of combining the two species under the name C. bifermentans is incorrect and should be discontinued.

SUMMARY: Antigens G and E of stock 28 variety 2 of Paramecium, aurelia show cross-reactions with their respective antisera in immobilization and gel diffusion tests. In immobilization tests the anti-E serum P, no. 132, shows the strongest cross-reaction; in gel diffusion tests the anti-G serum P, no. 130, cross reacts more strongly. During serotype transformation of type G protozoa to type E, the increase of the E antigen and the disappearance of the G antigen were followed by the gel diffusion technique. However, because of the peculiar cross-reactions of these two antigens, only the increase of the new (E) antigen was studied quantitatively by this technique. No reliable measurements of the loss of the old (G) antigen were obtained. The results indicate that during transformation the amount of the new antigen increased exponentially.

SUMMARY: Amino acid-requiring mutants of Salmonella typhimurium were examined for their ability to regenerate flagella when incubated with a source of nitrogen and of energy, but in the absence of the amino acid required for growth. The mutants fell into two major groups and one intermediate group. The major groups were: (a) mutants requiring for growth an amino acid (such as leucine or tyrosine) present in flagellin and unable to regenerate flagella in the absence of this amino acid, (b) mutants requiring for growth an amino acid (such as tryptophan or cysteine) not present in flagellin and able to regenerate flagella in the absence of this amino acid. The intermediate group (c) contained mutants requiring for growth an amino acid (such as histidine or methionine) present in small amount in flagellin and able to regenerate flagella in the absence of this amino acid. With all the mutants tested there was no significant net synthesis of RNA or protein in the absence of the amino acid required for growth, but DNA synthesis did occur.

SUMMARY: The growth of Tetrahymena piriformis W is inhibited by several steroids of mammalian origin. The degree of inhibition is related to the molecular configuration. All of the effective growth inhibitors were of the carbon-21 or pregnane series. Hydroxyl substitution at carbon-11 enhanced inhibition, while hydroxyl substitution at carbon-17 lowered the potency of inhibition. The inhibition of growth induced by these steroids was antagonized by stigmasterol or cholesterol. The mode of action of these compounds is discussed with regard to possible competitive inhibition with some metabolite essential for this organism.

SUMMARY: The recently isolated organism of the second phase of nitrification is identified as Nitrobacter winogradskyi Ruch. The organism reproduces by polar budding and possesses a distinct and easily demonstrated nucleus. The life cycle includes alternation of motile and non-motile stages. Motile cells possess a single flagellum which is 20 times longer than the cell body. The flagellum is laterally attached to the cell. The organism is related to the family Pasteuriaceae.

SUMMARY: A toxic protein has been isolated from Inaba and Ogawa strains of Vibrio cholerae and from water vibrios by dissolving the bacteria in 2·5m-urea and subsequent fractional precipitation with ammonium sulphate. This toxic protein accounted for the major portion of the toxicity of whole organism. Immunological and chemical data suggest that the toxic protein is the protein component of the Boivin antigen. The lipopolysaccharide endotoxins of the strains examined were relatively non-toxic as compared with the lipopolysaccharides from other Gramnegative bacteria, though in other biological and chemical properties they resembled the general class.

SUMMARY: Gram-negative bacilli could not be obtained from the Oxford strain of Staphylococcus aureus nor from 15 other strains of S. aureus in the presence of benzylpenicillin.

SUMMARY: It has not been found possible to repeat the work of Briggs et al. (1957) in which Gram-negative rods were isolated from cultures of staphylococci treated with penicillin, and staphylococci were subsequently recovered from cultures of these rods when the latter were grown in the absensce of penicillin. No flaw in technique has been revealed which would enable the earlier results to be readily explained in terms of contamination.