- Volume 45, Issue 2, 1966
Volume 45, Issue 2, 1966
- Article
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The Adaptation of Aerobacter Aerogenes to the Stress of Sublethal Doses of Formaldehyde
More LessSUMMARY: This paper deals with some biochemical events that occur when a population of Aerobacter aerogenes is treated with a sublethal dose of formaldehyde. It was discovered that during the bacteriostatic period there was a change in the base ratio of the non-ribosomal RNA. Along with this change there was the appearance of induced enzymes capable of metabolizing the formaldehyde at an increased rate. As soon as the formaldehyde concentration had been decreased by metabolism, growth resumed and the base ratio of the RNA returned to a normal value.
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Continuous Culture of Torulopsis utilis: A Kinetic Study of Oxygen Limited Growth
More LessSUMMARY: A small single-phase continuous fermentor system for convenient longterm operation at steady state with small population densities is described. A method by which the effect of extracellular limiting nutrient on growth rate can be evaluated from the resulting data is discussed. This method was used for Torulopsis utilis to determine the Michaelis constants for growth with oxygen and glycerol; these were found to be 1·4×10−5 m and 4·9×10−5 m. Size of organisms and yields were found to decrease with growth rate. Average volume of organisms decreased from 60 to 41 μ3 and the yield decreased from 1·8 to 1·2 g. dry wt./organism/g. oxygen consumed. An endogenous metabolism rate constant determined from yields at growth rates above 30% maximum was 0·056 g. oxygen used/g. dry wt. organism/hr.
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Continuous Culture of Torulopsis utilis: A Kinetic Study of Oxygen Limited Growth
More LessSUMMARY: A small single-phase continuous fermentor system for convenient longterm operation at steady state with small population densities is described. A method by which the effect of extracellular limiting nutrient on growth rate can be evaluated from the resulting data is discussed. This method was used for Torulopsis utilis to determine the Michaelis constants for growth with oxygen and glycerol; these were found to be 1·4×10−5 m and 4·9×10−5 m. Size of organisms and yields were found to decrease with growth rate. Average volume of organisms decreased from 60 to 41 μ3 and the yield decreased from 1·8 to 1·2 g. dry wt./organism/g. oxygen consumed. An endogenous metabolism rate constant determined from yields at growth rates above 30% maximum was 0·056 g. oxygen used/g. dry wt. organism/hr.
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Diurnal Changes in the Concentrations of Micro-organisms in the Rumens of Sheep Fed Limited Diets Once Daily: WITH AN APPENDIX ON THE KINETICS OF RUMEN MICROBES AND FLOW
More LessSUMMARY: The pattern of change of concentration of different groups of microorganisms in the rumen was found to be characteristic of the group and little affected by the time of day, the nature of the diet, or the host animal. The dilution rate of rumen liquor and the rate of change of concentration of several groups of micro-organisms were measured at intervals following feeding; this allowed calculation of the apparent specific growth rate. The changes in concentration of the ophryoscolecid ciliate protozoa, the selenomonads and the oval organism described by Eadie could be explained as the resultant of the changes in dilution rate due to the act of eating and in growth rate in response to incoming nutrients. Rates of change in concentration greater than could be accounted for on the basis of growth and dilution alone were found with the peptostreptococci, the polymastigate flagellate protozoa and the holotrich ciliate protozoa. It is suggested that the peptostreptococci underwent lysis or engulfment by other organisms and that the polymastigates became sequestered, probably close to the rumen wall. The concentration changes of the holotrichs were more difficult to understand, but it would appear that little division took place for some 18 hr after feeding, followed by several divisions in quick succession. The oscillospirae showed two peaks in concentration; no explanation can be offered for this.
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Periodic Changes in the Concentrations of Micro-organisms in the Rumen of a Sheep Fed a Limited Ration every Three Hours
More LessSUMMARY: A sheep was given small amounts of feed at 3-hr intervals and the concentrations of several groups of micro-organisms in the rumen were measured at intervals over 28 hr. A 3-hr rhythm of concentration change was seen for most micro-organisms. Superimposed on this was a gradual decline in concentration of several groups of micro-organisms, presumably due to removal of nutrients by repeated sampling from the rumen.
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Diurnal Changes in the Concentrations of Micro-organisms in the Rumens of Sheep Fed to Appetite in Pens or at Pasture
More LessSUMMARY: The concentrations of the various groups of micro-organisms in the rumens of sheep when feeding on a roughage diet to appetite or grazing a mixed pasture, changed with time in patterns very similar to those previously found in sheep fed restricted diets once daily. It is postulated that these patterns will be present wherever the daily eating behaviour of the animal includes a major fairly continuous period during which all or most of the ration is eaten, and long periods during which little or no feed is consumed.
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Adansonian Classification of Mycobacteria
More LessSUMMARY: An Adansonian classification of mycobacteria has been done by using 94 characters. Fifty-nine strains of slowly growing mycobacteria were classified into five groups: (1) Mycobacterium tuberculosis and M. bovis (2) M. kansasii; (3) M. avium, 16 strains of non-photochromogens from human sources, 6 strains of non-photochromogenic mycobacteria from soil sources, and scotochromogens from human sources (M. aquae); (4) 2 strains of non-photochromogens from human sources; (5) 1 strain of non-photo-chromogen from human source.
The third group seemed to consist of three subgroups: (3, i) non-chromogens from soil sources; (3, ii) Mycobacterium avium and some non-photochromogens, which were inseparable from M. avium; (3, iii) some non-photochromogens from human sources resembling M. avium (but separable from it) and scotochromogens from human sources.
Slowly growing non-photochromogenic mycobacteria from soil sources (subgroup 3, i) were considered to form a new species, M. terrae. A description of this species is given.
Seventy-eight strains of rapidly growing mycobacteria were classified into seven groups: (6) 6 strains of miscellaneous species, Mycobacterium marinum, M. balnei, M. platypoecilus, M. ranae and M. piscium; (7) M. thermoresistibile (sp.nov.); (8) M. phlei; (9) M. aurum (sp.nov.); (10) M. fortuitum and group IV rapid growers; (11) M. parafortuitum; (12) M. smegmatis. These groups seemed to form independent species. Mycobacterium thermoresistibile is a new species capable of growing at 52°. Mycobacterium aurum is a new species consisting of rapidly growing scoto-chromogenic mycobacteria with urease, nicotinamidase and pyrazina-midase and some strains also with acetamidase and allantoinase.
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Bacterial Survival in Suspension in Polyethylene Glycol Solutions
More LessSUMMARY: The % survivals of Escherichia coli (B, Jepp, commune), Serratia marcescens (uk8) and Aerobacter aerogenes (Hinshelwood), in the presence of polyethylene glycol were studied as a function of molecular weight and % polyethylene glycol. Polyethylene glycol is shown to cause a loss of viability; experiments are described which suggest loci for its action.
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The Survival of Escherichia coli in Nitrogen Atmospheres under Changing Conditions of Relative Humidity
More LessSUMMARY: The consequence of relative humidity (RH) changes before collection of bacterial aerosols are described; it is shown how Escherichia coli (B, commune), but not E. coli Jepp, gave good survival over the range 100--20% RH provided that the following conditions applied: (1) a pure nitrogen atmosphere; (ii) a protective agent in the spray fluid; (iii) sucrose in the collecting fluid; (iv) an RH change to 100% or to a nominal 30% (depending upon the experimental conditions) before collection of the aerosol. Differences in survival of E. coli commune sprayed from suspension in solutions of raffinose into an atmosphere of nitrogen which were previously attributed to the effect of raffinose concentration in the spray fluid were found to be caused by the use of variant organisms.
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Automatic Control of Dissolved Oxygen Concentration in Stirred Microbial Cultures
More LessSUMMARY: Equipment was developed for the automatic control of dissolved oxygen concentration in microbial cultures, by using the Mackereth electrode as a sensing probe. Factors affecting the choice of components are discussed and the performance of the equipment is described during typical batch and continuous culture runs. The equipment provided precise and reliable control over a wide range of dissolved oxygen concentrations, and retained a high degree of stability over long periods of continuous use.
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Biochemical Studies of Lethal Processes in Aerosols of Escherichia coli
More LessSUMMARY: The effects of holding time and relative humidity on the survival of populations recovered from aerosols of Escherichia coli strain B was examined. β-Galactosidase was chosen as a convenient model of a bacterial protein in this organism. Populations recovered from aerosols of E. coli strain B were shown: (i) to have suffered no detectable damage to β-galactosidase; (ii) to have suffered a temporary and severe loss of ability to synthesize β-galactosidase. The significance of these results in identifying lethal mechanisms in bacterial aerosols is discussed. For these studies a method was developed for the determination of total bacterial numbers recovered from aerosols by labelling the organisms directly with [14C]. Bacillus globigii was shown to be unsuitable as a tracer for the determination of total numbers in biological aerosols.
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Reducing Compounds and the Growth of Phytophthora infestans
More LessSUMMARY: An investigation into the effect of light on the growth of Phytophthora infestans revealed that whereas exposure to light caused diminished growth on pea medium, growth on several other media was not decreased. This diminished growth was an indirect effect of light caused by an alteration of the medium. All the P. infestans tested reacted similarly, but most other fungi examined were unaffected. Germination of zoospores of P. infestans appeared to be especially sensitive. This inhibitory effect was not removed by heat and peroxides were not, therefore, considered as the immediate cause of the inhibition. Nevertheless, following exposure to light, peroxide formation and the appearance of the inhibitory effect were closely associated. Addition of several reducing compounds to pea medium overcame the effect of exposure to light on zoospore germination. Mycelial growth was also improved by similar additions to a defined medium. This was particularly marked following the addition of glutathione (10−3 M) and L-ascorbic acid (1·0 g./l). The decrease in reducing potential during illumination might, in the light of experiments conducted with defined media, explain the observed effects of illumination.
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Characteristics of Bovine Mammillitis Virus
More LessSUMMARY: A virus isolated from cattle in Scotland does not seem to have been described previously as existing in Europe. The virus has been provisionally designated bovine mammillitis virus (BMV). It grows in tissue cultures, particularly of bovine origin, giving rise to large multinucleate cells which have type A inclusions in many of their nuclei. Baby mice injected with it develop skin lesions, but only a limited number of passages can be made. The BMV particle has a nucleocapsid of about 80 mμ diameter which, in complete particles, is surrounded by a loose envelope. The virus is sensitive to ether and chloroform, and contains DNA with a base composition of 64% G+C and a band-width molecular weight of 34×106. BMV shows antigenic similarity, in neutralization tests and double-diffusion tests in agar, to the group II viruses (prototype Allerton) of lumpy skin disease (Alexander, Plowright & Haig, 1957). All these features place it in the family of the herpesviruses.
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The Nutritional Requirements of some Pasteurella Species
More LessSUMMARY: The nutritional requirements for growth on agar media at 28° and at 37° were investigated for strains representative of Pasteurella pseudotuberculosis, P. pestis and Pasteurella strain ‘X’ (Yersinia enterocolitica). At 28°, strains of P. pseudotuberculosis either required no growth factors or were dependent on thiamine or pantothenate. Most strains of P. pestis required cystine, methionine and phenylalanine but some strains could dispense with methionine or phenylalanine while others required additional factors. Strains of Pasteurella ‘X’ either were thiamine-dependent or required no factors. At 37° all strains showed additional requirements. Most strains of P. pseudotuberculosis could then grow with any 3 of the 4 factors glutamic acid, thiamine, cystine and pantothenate; other strains specifically required all 4 factors and nicotinamide. Strains of P. pestis grew reliably on media supplemented with cystine, methionine, phenylalanine, glycine, valine, isoleucine, glutamic acid and thiamine when incubated in CO2-enriched air. All strains of Pasteurella ‘X’ required thiamine and either cystine or methionine; some substrains showed additional requirements. Virulent and avirulent representative strains of P. pestis had similar calcium requirements for growth on defined media.
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Observations on the Adsorption of Caulobacter Bacteriophages containing Ribonucleic Acid
More LessSUMMARY: Caulobacter bacteriophages containing ribonucleic acid have been found to attach to pili of their hosts. Only when the phage is actually lytic for a given host can the phage+pilus complexes be observed; non-specific complexes are not formed. Removal of the pili from the host by shear treatment before phage adsorption resulted in effective inhibition of phage adsorption. While swarmer caulobacters frequently possessed pili which were located at the flagellated pole of the organism, stalked caulobacters were almost always devoid of these structures. Adsorption experiments with segregated populations of caulobacters indicated that stalked caulobacters adsorbed RNA phages very poorly, while in swarmer populations and unsegregated cultures the RNA phages were efficiently adsorbed.
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Some Criteria for the Recognition of Nocardia madurae (Vincent) Blanchard
More LessSUMMARY: A combination of characters for the description and identification of strains of Nocardia madurae, based on the examination of 44 strains, is presented. Although nearly all the 44 strains were received from medical laboratories, a few were isolated from soil. Some of the distinguishing properties of N. madurae are compared with those of N. asteroides, N. caviae, N. brasiliensis, N. pelletieri and Streptomyces somaliensis.
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The Relationship of F type Piliation and F phage Sensitivity to Drug Resistance Transfer in R+F− Escherichia coli K12
More LessSUMMARY: Resistance factors (R factors), of the kind which confer sensitivity to F specific phage as well as promoting conjugation in enterobacteria determine the production of a pilus similar to the specific pilus seen on F− bacteria. R factors, however, unlike F, also determine the production of a repressor of function: this means that in an established R+ culture, only a small proportion of the bacteria can conjugate, be infected with F phage, or produce the pilus. Under conditions where repression is lifted, the three characters, conjugation, F phage sensitivity and production of the pilus, are coordinately de-repressed.
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Morphological Features of the Pili Associated with Escherichia coli K12 Carrying R Factors or the F Factor
More LessSUMMARY: Strains of Escherichia coli K12 carrying various R factors or the F factor were examined with the electron microscope. The F specific RNA phage MS 2 was added to differentiate the specific F type pili, which adsorbed the phage, from common pili, which did not. Even when phage was not added it was possible to identify F type pili because they were wider and generally longer than common pili. F type pili, but never common pili, often possessed terminal knobs whose presence on attached pili has not been previously described. The F type pili formed by E. coli carrying the different R factors or HfrH could not be morphologically distinguished from each other. Only one morphological type of common pilus was observed.
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