- Volume 28, Issue 4, 1962

SUMMARY: Determinations of the cellular content of RNA, total protein and dry weight of Euglena gracilis at different times during logarithmic growth indicated that these parameters did not reflect the constant reproductive rate of these organisms during this period of growth. During exponential growth, the RNA content was reduced by 37 %, the total protein by 45 % and the dry weight by about 76 %. In addition, the RNA and protein content of Euglena showed a similar pattern of decline as growth progressed; the DNA content, however, remained constant throughout the logarithmic growth phase.

SUMMARY: By direct observation of individual organisms in a micro-culture chamber and by viable plate counts, a study has been made of the function of sugar/colloid mixtures in promoting the survival of Gram-negative bacteria on drying. The high death rate after drying in sugar alone was due mainly to cell-wall damage caused during rehydration by the temporary osmotic pressure set up by the sugar within the cell, leading to the formation of spheroplasts not capable of division. Spheroplast formation was largely prevented and survival greatly enhanced by controlled rehydration, showing that the sugar component was the primary protective agent. The complementary role of the protein or ‘protective colloid’ appears to lie in its ability to compress the cell wall against the contracted plasma membrane in plasmolysed cells, thus decreasing the volume of the interspace between the two membranes and so limiting the sugar trapped therein to a safe amount. These observations were corroborated by cell volume measurements in the ultracentrifuge.

SUMMARY: Cells of Rhodopseudomonas spheroides cannot increase their specific photopigment content in the absence of protein synthesis. The significance of this finding for an understanding of the structure of the photosynthetic apparatus in bacteria is discussed.

SUMMARY: The magnitude of self-shading in light-grown cultures of Rhodopseudomonas spheroides has been estimated. When a culture of R. spheroides is transferred from bright light to dim light there is preferential synthesis of bacteriochlorophyll and carotenoid pigments relative to net protein synthesis. Protein turnover does not account for this.

The kinetics of the synthesis of bacteriochlorophyll relative to the incorporation of amino acids into protein have been estimated under a variety of conditions. On the basis of these findings a mechanism for the cellular control of pigment synthesis is presented.

SUMMARY: A technique for sectioning fixed preparations of Paramecium aurelia suitable for subsequent treatment with fluorescent antisera is described. Following application of specific fluorescein and rhodamine conjugates of paramecium antisera to sectioned paramecia, fluorescence was observed both on the surface structures (pellicle and cilia) and in the cytoplasm, but not in the macronucleus. Fluorescence of the cytoplasm was prevented by pretreating the sections with non-homologous, non-fluorescent antiserum. It was concluded that the immobilizing antigens were substances covering only the pellicle and cilia, and that the internal cytoplasmic antigens were relatively invariant in paramecia of diverse immobilization antigen type. Study of transforming organisms showed that new antigen appeared first on the pellicle, and later on the cilia. All the cilia of a given cell bore the same antigen or mixtures of antigen.

SUMMARY: The killing of conidia of Verticillium albo-atrum by ultraviolet irradiation followed first-order kinetics; about 0.5 % of the conidia which survived a 97 % lethal dose were nutritionally deficient mutants. This percentage of mutants among survivors was constant for different wild-type isolates for the first-, second- and third-order irradiations. This regularity implies that most conidia exposed at the first irradiations contained a single haploid nucleus. Adenine-requiring mutants formed pionnotes when grown on an agar medium containing low concentrations of adenine, and the extent of pionnotal formation depended on the position at which adenine synthesis had been blocked by the irradiation. 4-Aminoimidazole-5-carboxamide apparently did not act as an extracellular intermediary in adenine synthesis. An acriflavine-resistant mutant arose spontaneously in one of the mutants selected for nutritional deficiency, but mutants resistant to certain other growth inhibitors were not found.

SUMMARY: In the preparation of taxonomic data for computer analysis, some new methods are proposed which compensate for certain inadequacies in present techniques without violating the essential Adansonian axiom that all properties of organisms are of equal significance in the creation of taxa. A modified scoring technique is presented for use with tests wherein two or more alternative responses (none necessarily negative) are possible. The proposed method might well be extended to the scoring of all data; one is never sure of the significance of a ‘negative’ result, and it could be considered that at least two alternatives of equal value in classification may exist for any determinable property of an organism. It is suggested that computed relationships among organisms might better be expressed in terms of distance, which is a logarithmic function of the similarity ratio in current use. A new diagnostic parameter, P, is defined as a quantitative estimate of the proportion of organisms in any group (taxon) which possess a given property. Computer programs based on such values could be devised for diagnosis of organisms whose identitv is unknown.

SUMMARY: The systematic relationships among 54 strains of bacteria, representing principally the genera Achromobacter, Aerobacter, Alcaligenes, Escherichia, Mima, Pseudomonas, Serratia and Streptococcus, were examined by computer methods. Seventy-one properties of these organisms were determined, and the resulting data scored in different ways (according to various proposed techniques) before being submitted to an appropriate computer program for calculation of similarity (S) values. These comparative studies indicated that better division of organisms into mutually similar groups can be achieved when data about properties which may have several alternative expressions are handled in the manner proposed by Beers & Lockhart (1962). The number of comparisons which contribute to individual similarity values should be held constant by adequate treatment of quantitative data and by adoption of scoring methods which permit comparisons between ‘negative’ properties. It may be useful to employ distance (D = log2I/S) rather than similarity as the primary measure of relationships among groups of organisms.

SUMMARY: Growth of Rhizobium trifolii in a defined medium reflected the supply of Ca2+ and Mg2+ (subsequently Ca and Mg, respectively) in distinctive fashion. Deficiency of Ca, in the presence of sufficient Mg, caused reduction in growth rate, the level of maximum growth and the proportion of viable cells. Such Ca-deprived cells were markedly swollen and vacuolated. On the other hand, although shortage of Mg (Ca sufficient) was without effect on growth rate down to the lowest concentration at which growth occurred, maximum growth and the proportion of viable organisms were markedly decreased. Mg-deficient organisms were appreciably elongated. Signs of Ca deficiency became apparent at less than 0.025 mM, and Mg deficiency at less than 0.1 mM, most markedly in the range below 0.5 mM. Additionally there was a need for total divalent cations of the order of 0.4-0.6 mM. This could be met by either Ca or Mg provided both were sufficient for their maximum specific effect.

SUMMARY: Streptomyces lavendulae was studied in a defined medium. When tyrosine was added to the medium a brown-black pigment was synthesized; without tyrosine, only a trace of this pigment was detected. Growth was the same with or without tyrosine. The addition of (2-14C) DL-tyrosine to the medium resulted in synthesis of a radioactive pigment, and tyrosinase activity was demonstrated in extracts of disrupted organisms. Of 15 amino acids added to the medium only tyrosine and tryptophan were used for pigment formation. Pigment production was inhibited by p-benzyloxy-phenol, an inhibitor of mammalian melanogenesis. In yeast+ glucose medium a pH range of 6.8-8.2 was optimal for pigment synthesis; more pigment was formed at 200 than at 280 in spite of the fact that there was twice as much growth at the latter temperature. The pigment was precipitated from culture media by a method described for precipitating melanin from urine and in every way tested was identical with a synthetic dihydroxyphenylalanine-melanin. The data indicate that the brown-black pigment synthesized by S. lavendulae is melanin.

SUMMARY: Ability to produce colicines I, E1, E2, K or B was transferred to Salmonella typhimurium strain LT2 by growth in broth with suitable colicinogenic strains of Escherichia coli or Shigella sonnei. When LT2 (colI), i.e. carrying the colicine I factor, or LT2 (colB) were grown overnight in broth with LT2 col − (non-colicinogenic), c. 50 % of the latter became colicinogenic; LT2 (colE2) and LT2 (colK) did not transmit; LT2 (colE1) transmitted to only c. 0.1 % of the acceptor population. But LT2 carrying either colI or colB in addition to colE2, colK or colE1, transmitted both factors.

When overnight broth cultures of LT2 (colI) and LT2 col − were mixed and incubated c. 40 % of the latter acquired colI by 20 hr. (when the viable count had doubled); but only c. 0.02 % acquired colI in 3 hr. The low initial transfer results from the fact that in a stock culture of LT2 (colI) only c. 1/5000 bacteria are ‘competent donors’, able to transmit colI. The later large increase in the proportion of colicinogenic bacteria probably results from ‘epidemic spread’ of the colI factor amongst the acceptor population, initiated by the few acceptor bacteria which originally receive it. It is supposed that most bacteria which have just acquired colI become competent donors. In a doubly colicinogenic strain most competent donors transmit both colicine factors.

Aeration by shaking during incubation interfered with transmission of colicinogeny, probably by abolishing the prolonged phase of slow growth of unaerated cultures. Growth in the presence of acriflavine did not ‘cure’ LT2 (colI) or LT2 (colI) (colE2) of colicinogeny, nor of ability to transmit.

LT2 (colE1) and LT2 (colE2) supported the epidemic spread of colI or colB about as well as did LT2 col −; but in LT2 (colK) the spread of colI was greatly reduced and that of colB somewhat reduced. The prior presence in an acceptor strain of one of the readily transmissible factors, colI or colB, did not interfere with the epidemic spread of the other. But LT2 (colI) did not become a competent donor on accepting colE2 and, by inference, colI from LT2 (colI) (colE2).

SUMMARY: Improved methods are described for growing about 108 to 109 synchronized single generations of ordinary-colourless (OC) cells of the aquatic fungus Blastocladiella emersonii in submerged liquid 1200 ml. cultures at 240. The stimulatory effect of white light on the synthesis of the internal pool of soluble protein and soluble polysaccharide, and on the dry wt./cell during ontogeny was assessed. Soluble protein was characterized by fractionation on DEAE-cellulose into a number of components: the quantities/cell were affected differentially by illumination. Light caused a sharp decrease in total glucose-6-phosphate dehydrogenase activity/cell during the last stages of growth, when the light-induced formation of soluble polysaccharide/cell was most pronounced.

SUMMARY: When grown under certain conditions some group D streptococci did not yield HCl extracts which would react serologically with group D antisera. By varying the composition of the medium, it was shown that the optimum yield of group D antigen was obtained when the organisms were grown in an unbuffered medium containing 5-10 g. glucose/l. where the ultimate pH of the culture was 4.0 to 4.2. In a buffered medium containing a low glucose concentration the final pH value of the culture remained above 6.0 and poor yields of group D antigen in the acid extract were obtained with Streptococcus faecium, S. durans, and S. bovis.

SUMMARY: The transfer of a cytoplasmic component from λ-lysogenic F+ to non-lysogenic F− cells of Escherichia coli K-12 was demonstrated; similar transfer from λ-lysogenic Hfr to non-lysogenic F− cells was not detected. The component transferred confers on the recipient cell temporary immunity against maturation of the bacteriophage λ. The relevance of these observations to the mechanism of conjugation is discussed.

SUMMARY: Microsporum canis utilized several single amino acids as nitrogen source during growth on a defined medium; ammonia was also used but not nitrate or methionine. Several extractants for releasing cytoplasmic contents were examined. With acetic acid (100 g./l.) as extractant the content of α-amino nitrogen, pentose, ammonia and phosphate in the extracts was studied. A marked increase in orthophosphate with age of the mycelium was found. The free amino acid pool was examined chromatographically, qualitatively and quantitatively, during growth. Glutamic acid, glutamine, alanine and proline were the principal components of this pool at all stages of growth; proline formed 40 % of this fraction at the end of the logarithmic phase of growth. Phenylalanine and tyrosine were present only in trace amounts; tryptophan was not detected in the free amino acid fraction. These three amino acids were present in mycelial protein. Glucosamine was present in increasing amounts in mycelial hydrolysates as the mould aged.