- Volume 39, Issue 3, 1965
Volume 39, Issue 3, 1965
- Article
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Bacteriocinogeny and Lysogeny in the Genus Pseudomonas
More LessSUMMARYBacteriocinogeny and lysogeny have been investigated in strains of Pseudomonas aeruginosa, P. fluorescens and P. ovalis. The 39 strains of P. aeruginosa were all bacteriocinogenic and 32 were also lysogenic. No bacteriocine production was detected in 8 strains of P. fluorescens, although 3 were lysogenic. The one strain of P. ovalis studied was neither bacteriocinogenic nor lysogenic for P. aeruginosa or P. fluorescens. Typing of the bacteriocines of P. aeruginosa on the basis of their action spectra showed that 25 fall into four main groups; the bacteriocines of 6 strains could not be fitted into any definite group.
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Cycloheximide-producing and Fungicidin-producing Mutants of Streptomyces noursei
More LessSUMMARYStreptomyces noursei strain 52/152 produced compounds of the cyclo-heximide series and fungicidin. On the contrary its mutant strain 54/465 did not produce any compound of the cycloheximide series, and as compared with strain 52/152 produced about double the amount of fungicidin. This strain 52/152 was also insensitive to additions to the cultivation medium of fungicidin up to a concentration of 20,000 units/ml. In the strains studied, a direct proportionality was observed between fungicidin production and sensitivity to it. The interrelation of their production is discussed from the viewpoint of a common precursor for fungicidin and cycloheximide (malonyl-coenzyme A).
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The Atypical Ribosomal RNA Complement of Rhodopseudomonas spheroides
More LessSUMMARYRibosomes and phenol-purified RNA were prepared from Rhodopseudomonas spheroides and were characterized by sucrose density-gradient centrifugation and sedimentation-velocity centrifugation. The ribosomes extracted from R. spheroides correspond to the 30S, 50S and 70S ribosomes derived from other bacteria. Under appropriate conditions polyribosomes were extracted. The primary ribosomal RNA of R. spheroides corresponds to the 16S particle of other bacteria. Rhodopseudomonas spheroides was devoid of the 23S ribosomal RNA typically found in other bacteria. Preparations of phenol-purified R. spheroides RNA contain, in addition to 16S RNA, smaller amounts of an RNA component which sediments more slowly than the 16S unit, with a sedimentation coefficient of about 14–15S. Of several other Athiorhodaceae examined, only Rhodopseudomonas capsulata had an unusual RNA complement like that of R. spheroides.
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Lysogenic Conversion of Staphylococci to Loss of β-Toxin
More LessSUMMARYStaphylococci may produce β-toxin and staphylokinase (fibrinolysin). In clinical material there is a preponderance of strains which are β-toxin negative and kinase positive (β –K+), but β +K–, β –K– and β +K+ strains also occur. Strains which are β +K– can be converted by lysogenization with certain phages to loss of β-toxin and gain of kinase (β –K+). This is true conversion, since every lysogenized coccus carries the new characters. All the phages which produced this double conversion (β –K+ phages) belong to the serological group F. The conversion is due to two separate loci on the phage which are active in the prophage state. These loci have not been found in phages of other serological groups (β 0K0 phages). The β-toxic and fibrinolytic properties of staphylococci are not always phage-dependent; strains which do not carry detectable phages or carry only β 0K0 phages can be either β +K–, β –K+, β +K+ or β –K–, implying the occurrence of structural loci on the bacterial genome. Several strains with the phage-typing pattern 80/81 or a related pattern, which are β –K+, were found to carry converting phages. On loss of these phages the strains became β +K–. and showed a change of typing-pattern, gaining sensitivity for phages of group III.
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Reduction of Phenolindo-2,6-dichlorophenol in Dark and Light by the Blue-Green Alga, Anabaena variabilis
More LessSUMMARYThe reduction of phenolindo-2,6-dichlorophenol (PICP) by the blue-green alga Anabaena variabilis was examined in the dark and in the light. The two reductions differed in order with respect to PICP, in pH optimum, response to cyanide and iodoacetate, and in sensitivity to starvation and lysozyme treatment of the organism. The reduction in the dark was suppressed at light intensities of 300 ft.-candles. These results are discussed in relation to work on the photo-inhibition of respiratory processes in this and other micro-organisms.
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The Autolysis of Clostridium sporogenes
More LessSUMMARYWashed Clostridium sporogenes lysed during storage at 2° or on incubation at 37° in various buffered salt solutions. The lysis was accompanied by a marked increase in adenosine triphosphatase activity (ATPase), due to an enzyme bound to the cytoplasmic membrane. The lysis in buffered salt solutions was most rapid in young vegetative organisms and negligible in organisms from cultures incubated for 30 hr. No lysis occurred when organisms were incubated in buffered sucrose, but young organisms formed spheroplasts under these conditions. Both young and older organisms incubated in sucrose lysed when diluted in water. After lysis the residue of older organisms appeared structurally similar to cell-wall membranes prepared by crushing the organisms. Organisms incubated in EDTA or salt solutions containing sulphydryl compounds did not lyse during the incubation or on subsequent dilution with water. It is suggested that lysis was mainly due to changes in the composition or structure of the cell wall and not to alterations in the protoplasmic membrane.
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Magnesium-limited growth of Aerobacter aerogenes in a chemostat
More LessSUMMARYThe influence of Mg2+-limitation, compared with carbon-limitation, on bacterial concentration, and on protein, carbohydrate, RNA and DNA contents of Aerobacter aerogenes cultures (grown in the chemostat at several dilution rates) was determined. In both types of culture the bacterial protein, carbohydrate and DNA contents varied slightly, and the RNA content grossly, with changes in dilution rate. Bacterial yield varied with growth rate, and to a marked degree in the Mg2+-limited culture; this resulted from Mg2+ control of RNA synthesis. A growth-rate independent stoichiometry between RNA and Mg2+ was observed; 4 moles of RNA nucleotide were synthesized per mole of Mg2+ present in the culture. The protein and RNA distributions between cellular components varied with growth rate. The ribosomal fractions increased with increasing growth rate, as did the RNA:protein ratios in these fractions, in both cultures. Mg2+-limited bacteria contained little polysaccharide; washed suspensions of such organisms synthesized polysaccharide from glycerol at a low rate as compared with C-limited bacteria. Added Mg2+ stimulated polysaccharide synthesis by Mg2+-limited bacteria but not by C-limited bacteria. Washed suspensions of bacteria were induced to synthesize β-galactosidase. With cultures grown at three different dilution rates, the rates of enzyme synthesis in C-limited bacteria were twice those found with Mg2+-limited bacteria, though both had equal ribosome contents.
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Inhibition of Microbial Multiplication by Hypocholesteraemic Compounds
More LessSUMMARYThe hypocholesteraemic compounds benzmalecene and triparanol inhibited multiplication of certain bacteria (especially Gram-positive organisms), protozoa, algae and ascomycetes but not other higher fungi. Oleic acid (or methyl oleate) annulled the inhibition in bacteria, algae, protozoa and a yeast.
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Depolymerases for Bacterial Exopolysaccharides obtained from Phage-Infected Bacteria
More LessSUMMARYSeveral bacteriophages have been isolated which, in association with the host bacteria, produce enzymes that depolymerize the exopolysaccharide of Escherichia coli k12 and other slime polysaccharides of the same chemical type. Chemical analyses show the similarity of the polysaccharides produced by E. coli k12, by other E. coli strains and by Aerobacter cloacae nctc 5920 : all contain 28–33 % fucose, 16–19 % glucose, 25–28 % galactose, 14–22 % glucuronic acid. The action of the depolymerizing enzymes greatly decreases the viscosity of the polysaccharide solutions but does not liberate any fragments of low molecular weight. Partial purification of the enzymes was achieved by ammonium sulphate precipitation and chromatography on DEAE-cellulose. The enzymes are active against exopolysaccharides produced by bacteria in which the phages are unable to multiply. Evidence is presented to show that the structural genes for enzyme production are located on the phage genome rather than on the bacterial genome. One of the enzyme systems was unusual in that it was only produced following phage infection and lysis of mucoid host strains. Its production was induced by the polysaccharide substrate.
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The Effect of Ethylenediaminetetra-acetic Acid on the Cell Walls of Some Gram-Negative Bacteria
More LessSUMMARYA comparative survey of amino acid, amino sugar, sugar and lipid components of the cell walls of strains of Pseudomonas aeruginosa, Alcaligenes faecalis, Escherichia coli and Proteus mirabilis was made. The cell walls of P. aeruginosa and A. faecalis, against which ethylenediaminetetra-acetic acid (EDTA) has a potent bactericidal action, differed from those of the other organisms principally in their sugar components and in their high content of phosphorus. EDTA at alkaline pH selectively solubilized a high proportion of the carbohydrate and phosphorus present, apparently as lipopolysaccharides, in the walls of sensitive organisms. It is suggested that metal cations and lipopolysaccharides in the cell walls of P. aeruginosa and A. faecalis may be essential to the structural integrity of these organisms.
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A Model for Computer Identification of Micro-organisms
More LessSUMMARYSpecific groups (or taxa) of micro-organisms can be defined as to their location and extension in a space which is produced when the recorded characters are imagined as dimensions. Since a culture to be identified can be imagined as a point in this space, identification can be achieved by examining which group or taxon occupies the region where the ‘unknown’ lies.
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Taxonomic Characteristics of So-called ‘ Form 2 mycobacteria’
More LessSUMMARYTwo strains of rapidly growing spore-forming bacteria were obtained from cultures of Mycobacterium tuberculosis and identified as so-called ‘form 2 mycobacteria’ ( Csillag, 1961 ). The properties of these and of two similar strains received from Dr A. Csillag were investigated, and compared with those of NCTC strains of the genus Bacillus. All four ‘form 2’ strains were almost identical in character, and differed from M. tuberculosis in many respects, rendering it highly unlikely that they were genetically derived from the mycobacterial cultures in which they were found. They were identified as strains of Bacillus licheniformis. It is considered that ‘form 2’ organisms are not part of a complex mycobacterial life-cycle, as has been suggested, but are contaminants.
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Inheritance of Capsule and the Manner of Cell-Wall Formation in Bacillus anthracis
More LessSUMMARYDuring growth in broth, Bacillus anthracis strain 2160 s became capsulated only towards the end of exponential growth. An inoculum of fully capsulated organisms formed chains which were non-capsulated save at their tips and at occasional junctions between neighbouring cells. This appearance suggested that new non-capsulated wall was synthesized at the equator of each organism but not at the poles or throughout the existing wall.
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