- Volume 65, Issue 2, 1971

SUMMARY: A comparison was made between streptococcal competence factors (CF) elaborated by strain CHALLIS in a chemically defined medium and in a complex medium (defined medium containing neopeptone and horse serum). The CF preparations acted similarly in that: (i) both CFs maximally activated the normally non-transformable streptococcal strain WICKY to the competent state when the WICKY cells were incubated for 40 to 100 min. in phase 2; (ii) both CF preparations had to react with WICKY cells for about 20 min. before the cells would take up deoxyribonucleic acid (DNA); (iii) the rates of DNA uptake in WICKY populations were identical when either CF preparation was used; (iv) both CFs activated different concentrations of WICKY cells so that a fixed proportion of the total population transformed to dihydro-streptomycin resistance; and (v) upon dilution both CF preparations behaved as if they contained more than a single component.

The CF preparations behaved differently in that: (i) WICKY cells activated to the competent state with CF made in the complex medium generally yielded frequencies of transformation two to eight times higher than CF prepared in the defined medium, and (ii) CF prepared in the complex medium occurred in culture filtrates at an apparently higher concentration than CF prepared in the defined medium. This observation may be one reason for the high frequencies of transformation observed with CF made in the complex medium.

SUMMARY: The genetic properties of transformable (SR 5a) and non-transformable (SR30) streptomycin-resistant streptococci were examined. In mutant SR30, the very high resistance (VHR) phenotype appeared to be due to at least two factors; a high resistance (HR) mutation and an enhancing modifier gene. In mutant SR 5a, resistance was due to a single VHR mutation which is allelic to the HR mutation of mutant SR 30. The transfer of non-trans-formability (Ntr) by SR 30 DNA revealed that this factor is separable from the streptomycin resistance marker and the enhancing modifier. Results indicate co-transfer of Ntr with the HR marker.

SUMMARY: Radioactively labelled transforming DNA is rapidly and irreversibly adsorbed by competent Haemophilus influenzae bacteria. Upon incubation, about 20% is degraded within 15 min. to acid-soluble products. Thereafter there is little change. Degradation products were identified by Dowex column chromatography as inorganic phosphate, nucleosides, small and large oligo-nucleotides. Mononucleotides were not observed. These products were always found in the medium while little, if any, was observed in the cells. It is concluded that the degradation process may take place outside the cells. It involves at least an endonuclease and a phosphatase.

SUMMARY: Radioactively labelled coliphage λ DNA is rapidly and irreversibly bound by competent bacteria of certain cultures of Haemophilus influenzae. The extent of adsorption in the presence of excess cells was always between 30 and 40% of the DNA added. Bound DNA was rather resistant against degradation to acid-soluble products but the biological activity was completely lost after 60 min. incubation. Reisolated phage λ DNA always banded in CsCl gradient centrifugation at a position characteristic for double stranded λ DNA. It sedimented with normal or slightly reduced velocity in sucrose density gradients. Production of λ phage or of infectious phage λ DNA was not observed.

SUMMARY: A strain of Rhizobium cowpea transformed interspecifically and intra-specifically for the gelatinase marker showed maximum competence in the early log phase of growth which was increased further by the addition of Casamino acids and Mg2+ to the competence medium at pH 7.0. Ferric ions inhibited transformation and this effect was partially reversed by addition of EDTA. The DNA concentration for maximum frequency of transformation was about 20 μg./ml. The frequency of intraspecific transformation was ten times higher than that of interspecific transformation although the G + C mole per cent of the donor and recipient was very similar, 64.0 and 64.5 respectively. A surface-bound nuclease specific for the transforming DNA could have resulted in the high donor DNA requirement.

SUMMARY: Fimbriae (pili) were demonstrated in three of four Neisseria species (Neisseria catarrhalis, N. perflava, N. subflava) by electron microscopy. Only one of three N. catarrhalis strains examined exhibited these non-flagellar appendages. Haemagglutination occurred with all strains bearing such surface structures, but different species reacted in different ways. Neisseria catarrhalis and N. perflava agglutinated mouse and rabbit red cells at 0 and 37°; N. subflava reacted similarly only with rabbit erythrocytes, and with human O cells at 0°. No reactions were observed with guinea pig, goat or sheep red cells. Prior heating of the organisms destroyed all obvious haemagglutination activity; addition of D-mannose did not inhibit haemagglutination.

SUMMARY: Escherichia coli isolates grew poorly in a phosphate-deficient medium. The presence of inorganic phosphate repressed the formation of alkaline phos-phatase enzyme but did not affect the formation of acid phosphatase enzyme.

Twenty-two non-enteropathogenic Escherichia coli isolates exhibited 16 esterase isoenzyme patterns while 15 enteropathogenic isolates exhibited three patterns. No relationship was found between enteropathogenicity and acid or alkaline phosphatase isoenzyme patterns.

SUMMARY: Tetrad analysis has shown that haploid forms arising from spores of a single ascus of Saccharomyces cerevisiae gave smooth and rough strains in the ratio I: I. These rough and smooth strains fermented the same sugars but differed in their morphology, mode of l-lysine assimilation and lipid content. Immunochemical studies, periodate oxidation and methylation analyses showed that both strains formed the same kind of mannan.

SUMMARY: A ribonuclease found in preparations of streptolysin S, unlike the strepto-coccal nucleases so far described, does not degrade DNA. It is only produced in significant amounts when RNA is present in the medium and is therefore an inducible enzyme. Unlike the previously described streptococcal enzymes it does not require divalent cations for activity. The molecular weight of the enzyme is about 14,000, its isoelectric point is 9.5 and it is highly heat-stable.

SUMMARY: Growth rates of Neisseria sicca in batch cultures were controlled by changing aeration rates. Organisms cultured at high aeration rates grew more rapidly and had a greater proportion of lipopolysaccharide (LPS) than had organisms grown at low aeration rates. The LPS isolated from bacteria grown at a rapid rate had higher hexosamine and 3-deoxyoctulosonic acid (KDO) contents and higher galactosamine to glucosamine ratios than LPS from bacteria grown at a slower rate. These results indicated that environmental conditions affected the content and composition of the bacterial LPS. The LPS of organisms from highly aerated cultures had a larger percentage of unsaturated fatty acids than had that from organisms grown under conditions of low aeration, suggesting that oxygen-dependent desaturation of fatty acids had occurred.

SUMMARY: Subcellular fractionation of the ciliate protozoon Tetrahymena pyriformis has been carried out using sucrose density gradients in zonal rotors. Fractions containing mitochondria, peroxisomes, ‘microsomes’ and organelles containing acid hydrolases have been characterized. Specific activities of acid phosphatase, DNase and N-acetyl glucosaminidase in whole homogenates increase during the growth cycle, while those of mitochondrial enzyme systems (succinoxidase and 2-oxoglutarate oxidase) as well as those of NADH- and NADPH-cytochrome c oxidoreductases decrease. Increased sedimentability of DNase and N-acetylglucosaminidase is manifest in homogenates of cells grown for 6 days but the density distributions of the sedimentable portions of these enzymes and also that of acid phosphatase is notaltered. Marked changes in density distributions of lysosomal enzymes occur on starvation. Resolution of the heterogeneous lysosomal population into several discrete populations with different enzyme complements has been achieved. No significant alteration of mitochondrial density occurs in the stationary phase of growth or on starvation, whereas the median buoyant density of peroxisomes is increased under both these conditions.

SUMMARY: Wall formation at different stages in the life-cycle of members of the Saprolegniales is accompanied by formation of membrane-bounded vesicles concentrated in the adjacent cytoplasm. The staining characteristics of these vesicles varies with the fixative used but suggest that their contents are intermediate between those of the Golgi cisternae and the cell walls. The origin and function of the vesicles are discussed.

SUMMARY: Fine structure studies have shown that in oosphere development the protoplast of the oogonium of Saprolegnia furcata is cleaved by the formation of large vesicles which extend from the centre to join the plasmalemma. The origin and behaviour of the central vesicles is indicated by the presence in them of special granules which are identical with those in smaller cyto-plasmic vesicles and in the space formed in the oogonium at cleavage. The cytoplasmic vesicles also contain dense (osmiophilic) bodies, mostly about 0.3 μm in diameter, and in some fixations show proliferation of membranes. The contents of the vesicles often show lamellation as do those in vesicles in zoosporangia of S. ferax, where cytoplasmic cleavage occurs in the same way. The appearance of this material in sporangia coincides with an increase in the quantity of phosphatidyl choline.

The vesicles in germinating zoospores of Saprolegnia ferax are also produced by fusion of dense-body vesicles.

The presence of vesicles of the dense-body type in many Oomycetes and other micro-organisms is recorded and their functions are discussed.

SUMMARY: The formation of kojic acid and aflatoxins by a toxigenic and a non-toxigenic strain of Aspergillus flavus was investigated using still and shake cultures on a glucose salts medium (AM medium) and a sucrose yeast extract medium (YES medium). YES medium supported better growth of both the strains and still cultures on this medium yielded the largest levels of kojic acid with both the strains. With the toxigenic strain, still cultures on this medium also produced the maximum amount of aflatoxins. The ratio of aflatoxins B to G and the ratio of aflatoxins in the mycelium to those in the medium were very low in YES medium still cultures. The significance of these data is discussed.