- Volume 4, Issue 3, 1950
Volume 4, Issue 3, 1950
- Article
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Viability of Dried Bacterial Cultures:With a Note on the Immediate Death-Rate
More LessSUMMARY: Cultures were dried in a vacuum over phosphorus pentoxide. At varying intervals up to 14 years tests were made on 2724 strains (representing over forty genera) and 83 % of cultures were found to be viable. Staphylococcus, Sarcina and Micrococcus were the genera most resistant to drying; Vibrio and Neisseria were among the least resistant.
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Further Observations on the Motility of Proteus vulgaris Grown on Penicillin Agar
More LessSUMMARY: The movement of the enormously enlarged filaments of Proteus vulgaris grown on penicillin agar ceased, or was slowed down, by screening the culture from the radiant heat of a microscope lamp. Organisms stimulated by heat after resting a short time in this way moved more rapidly than before. The increased activity was maintained for longer periods with longer rests, the increment in the period of activity increasing gradually as the resting period increased. In the condition of the test, rests of 60–120 sec. produced a maximal response.
Repeated heat stimulation rapidly exhausts the capacity of the organisms to maintain a steady rate of movement. Under constant stimulation organisms maintain a fairly constant rate for some hours and then slow considerably as though they or their Hagella were exhausted. A small decrease in radiant heat energy can induce a reversal in the direction of movement.
Active flagella attached to immobile organisms react to heat stimuli in the same way.
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Some Factors Affecting the Activation of Virus Preparations Made from Tobacco Leaves Infected with a Tobacco Necrosis Virus
More LessSUMMARY: Preparations of the Rothamsted tobacco necrosis virus were made by the ultracentrifugation of sap from infected tobacco leaves after a preliminary concentration by freezing. Not all the anomalous nucleoprotein in these preparations was infective, and the products were fractionated by differential ultracentrifugation at lower speeds and by precipitation at pH 4 in the presence of sedimentable protein from uninfected leaves. The more readily sedimentable and precipitable material carried with it most infectivity, whereas the other material had the greater sero-logical activity.
Preparations made quickly from freshly expressed sap were less infective than those made from sap that had been frozen or allowed to age for a few days. The extent of the activation produced by these treatments depended on the physiological condition of the infected leaves.
As much virus could be extracted from the leaf residues as occurred in the sap. The infectivity of this residual virus depended on the medium used for its extraction.
It is suggested that much of the infectivity of this virus in sap is acquired during or after extraction from the leaf, but the relationship between the particles with different sizes and properties remains uncertain.
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Some Effects of Freezing in the Leaf, and of Citrate in vitro, on the Infectivity of a Tobacco Necrosis Virus
More LessSUMMARY: Preparations of the Rothamsted tobacco necrosis virus made from tobacco leaves that have been frozen while intact are less infective than preparations made from unfrozen leaves. Freezing minced leaves or expressed sap does not destroy infectivity. The suggestion is made that much virus in the intact leaf becomes infective only by means of a mechanism that is set in action by mincing and is disordered by freezing.
The infectivity, but not the serological activity, of the virus is lost on exposure to 0·02–0·01 m neutral citrate; the extent of this inactivation is influenced by the temperature, pH, duration of exposure, concentration of virus and presence of salts and other substances. Similar processes could influence the infectivity of the virus in sap and may do so in the leaf.
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A Preliminary Study of Ammonia Production by Corynebacterium renale and some other Pathogenic Bacteria
More LessSUMMARY: Urease is a constituent enzyme of Corynebacterium renale and appears to account for the bulk of its ammonia production. C. renale also contains an arginase and some amino-acid deaminases, but the former has not been fully characterized. Bovine urine supports the growth of a small inoculum of C. renale for a limited time but after growth has reached a maximum it diminishes rapidly and the ammonia and pH values increase. C. renale also contains uricase but its precise significance has not yet been determined.
Of the other bacteria studied, C. ovis has urease activity similar to C. renale, and C. pyogenes a stronger initial arginase. C. equi contains no appreciable urease or arginase, although it tends to form ammonia from glutamine.
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Identification of Characteristic Extracellular Ninhydrin-Positive Substances Produced by some Bacteria
A. J. Woiwod and H. ProomSUMMARY: When certain species of bacteria are grown in an acid-hydrolysate of casein medium, ninhydrin-positive substances which were not present in the un-inoculated medium appear on chromatograms of the culture filtrates. Shigella paradysenteriae and Escherichia coli produce γ-aminobutyric acid by decarboxy-lation of glutamic acid. The substance produced by Serratia marcesens resists acid hydrolysis, gives a positive Sakaguchi reaction and matches arginine on two-dimensional chromatography. The substances produced by Clostridium sporogenes, Cl. bifermentans and Cl. sordellii, but not by any of the other species of Clostridia examined, are δ-aminopentanoic acid, probably derived from proline, and α- and γ-aminobutyric acids produced by unknown mechanisms. Proteus vulgaris and Clostridium tetani each produce two polypeptides containing a high proportion of amino-acids in the groups valine/methionine and leucine/isoleucine. These two pairs of polypeptides are similar in R F value and gross amino-acid composition. Staphylococcus aureus produces α-aminobutyric acid which may be derived from threonine.
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A Comparative Survey of the Nutrition and Physiology of Mesophilic Species in the Genus Bacillus
More LessSUMMARY: Two hundred and ninety-six strains of mesophilic species of the genus Bacillus were isolated from soil and examined for the characters described principally by Smith, Gordon & Clark (1946) as well as for some additional characters. Two hundred and forty-six belonged clearly to named species in the classification of Smith et al., thirty-two strains were clearly intermediate between two species and eight strains remained unallocated. In addition, eleven other strains appeared to represent a previously undescribed species (Proom & Knight, 1950).
Ability to grow under strictly anaerobic conditions, to give the Gibson & Abdel-Malek (1945) test and to produce typical (lecithinase-like) or ‘restricted’ reactions with egg-yolk emulsion were valuable diagnostic characters in this genus.
A survey was made of the nutritional requirements of some 200 strains which included many of the newly isolated ones and representative laboratory strains. Typical nutritional patterns characterizing the species were found, with an unexpected degree of uniformity with the groups of strains examined; the number of nutritionally aberrant strains in each species was very small.
The characteristic nutritional patterns were:
B. subtilis, B. licheniformis and B. megatherium grew with ammonia as nitrogen source and in the absence of added growth factors.
B. cercus and B. brevis grew in absence of added growth factors but required mixtures of amino-acids instead of ammonia only.
B. pumilus and B. polymyxa both grew with ammonia + biotin, and B. macerans grew with ammonia + biotin + aneurin.
B. alvei required amino-acids + aneurin; B. circulans and B. coagulans required amino-acids and usually both aneurin and biotin; some strains of B. circulans had more complex requirements.
Some strains of B. sphaericus required amino-acids + aneurin, others required biotin as well, and all of the strains of B. sphaericus var. fusiformis required amino-acids + aneurin + biotin.
The strains of B. pasteurii were the most heterogeneous in their nutritional requirements, the components ammonium ion, amino-acids, aneurin, biotin and nicotinic acid being involved. All strains required amino-acids and aneurin; in addition, biotin or nicotinic acid and sometimes ammonium ion were required, depending on the particular strain.
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Bacillus pantothenticus (n.sp.)
More LessSUMMARY: A new mesophilic species of the genus Bacillus was isolated from soil. Within the genus it most nearly resembles B. circulans but is clearly distinct in that it produces no motile colonies and no gas from glucose in the presence of an inorganic nitrogen source, hydrolyses casein, liquefies inspissated serum and gives a restricted egg-yolk reaction. It also differs from all other Bacillus spp. tested in that its growth is stimulated by 4% NaCl, and that pantothenic acid satisfies a nutritional requirement. The name Bacillus pantothenticus is proposed.
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