Showing papers in "Microbiology in 1957"

The application of computers to taxonomy.

Abstract: SUMMARY: A method is described for handling large quantities of taxonomic data by an electronic computer so as to yield the outline of a classification based on equally weighted features. This enables Similarity to be expressed numerically, and would allow taxonomic rank to be measured in terms of it. An example in bacteria is given, and the results compared with the conventional classification. The method is to count the number of similar and of dissimilar features between strains and to sort the strains into groups whose members have a high percentage of similarities.

The Infection of Clover Root Hairs by Nodule Bacteria Studied by a Simple Glass Slide Technique

Abstract: SUMMARY: A simple glass slide technique has been devised for the continuous microscopical observation of growth and infection of root hairs of clover seedlings. The method involves an aseptic cultivation of seedlings on microscope slides which are partly immersed in a mineral salts medium. The roots are protected by a cover-slip. By this procedure, the root hairs of white clover inoculated with nodule bacteria were studied. The earliest infection was observed to take place within 48 hr. of inoculation, on 4-day-old seedlings. In branched hairs the growth of the thread from a lateral branch towards the hair tip is tentatively explained as an effect of the position of the hair nucleus relative to the site of infection.

Some thoughts on bacterial classification.

Abstract: SUMMARY: Scientific classification is virtually a branch of mathematics which describes the overall similarities of organisms. Catalogues do not do this. Many schemes of bacterial taxonomy are not classifications but catalogues. Similarity is best measured by the number of features in common between two strains, while division into taxa is based on correlated features. Other criteria for these two basic ideas are unsatisfactory and cause confusion, and there seems to be no logical reason why any one feature should be given greater weight in classification than any other. Hierarchical systems are a practical necessity, and simple mathematical methods are useful in bacterial classification. It is not necessary to know the evolutionary history of organisms in order to classify them in a scientific manner.

Autolytic Release and Osmotic Properties of ‘Protoplasts’ from Staphylococcus aureus

Abstract: SUMMARY: The cell wall of exponential phase Staphylococcus aureus (strain Duncan) loses its tensile strength in c. 2 hr. when the organisms are incubated at 25° in 1·2 m-sucrose at pH 5·8 and ionic strengtin 0·3. The ‘protoplasts’ thus released from the mechanical protection of the cell wall are stable in 1·2 m-sucrose but lyse in media of lower osmotic pressure. The mean internal osmotic pressure of the ‘protoplasts’ is c. 20 atmospheres; they are permeable to glycerol but not to sucrose or NaCl. The rate of ‘protoplast’ release varies with the rate of growth of the organisms at harvesting. After osmotic explosion of ‘protoplasts’ released from slowly growing organisms the plasma membranes may be recovered as spherical shells which disintegrate and condense into small particles on washing, and 75% of the weight of the cell walls may be recovered as hemispherical shells.

The summer air-spora at Rothamsted in 1952.

Abstract: SUMMARY: The air over an arable field at Rothamsted Experimental Station, Harpenden, was sampled from 1 June to 25 October 1952 at 2 m. above ground with an automatic volumetric spore trap. Each day's slide was scanned and all the spores counted on an area representing a sample volume of 41 1. of air. Spores were classified in 20 morphological groups and a miscellaneous one. Seasonal periodicities are presented as 6-day running means of the daily average number of spores/m.3 air, and then related to meteorological data. Cladosporium conidia accounted for 46% of the total catch; hyaline basidiospores (chiefly Sporobolomyces) for 31%; and pollen only 1%. The relative frequency of various spore types differs from that recorded by earlier workers because the suction trap catches spores of all sizes with almost equal efficiency and is little influenced by external conditions. The results which should be representative of large rural areas of central and south England show that the major changes of spore concentration depend on the weather and the phenology of the local vegetation and its associated fungal flora. During 24 days in late June and July comparable estimates of spore concentration were made with another trap 24 m. above ground. The spore concentration of the twelve commonest groups at 24 m. totalled 82% of that at 2 m.

The Occurrence and Distribution of Bacterial Types on Flatfish

Abstract: SUMMARY: An investigation of the bacterial flora of the representative flatfish, skate and lemon sole, was carried out by direct counts of special groups of bacteria and by the analysis of over 1700 strains of bacteria isolated from the fish. Luminous and agar-digesting bacteria occurred seasonally on fish. Luminous strains occurred mainly in the gut contents. A group of sea-water-loving Pseudomonas spp. which seem to require sea water for growth on initial isolation was present on the flatfish in variable numbers throughout the year. A more or less distinct intestinal flora was present in North Sea flatfish in which a homogeneous group of micro-organisms provisionally labelled Gut Group vibrios predominates; this group includes luminous bacteria. The bacterial populations of skin and gills were similar in both the fish studied and were composed principally of Gram-negative rods of the Pseudomonas and Achromobacter genera. The composition of the bacterial flora of the two flatfish, as calculated from an analysis of strains isolated from sea-water agar plates, was: Lemon sole: Pseudomonas 60%, Achromobacter 14%, Alcaligenes 8%, Flavobacterium 5%, corynebacteria 1%, cocci 1%, Gut Group vibrios 9%, miscellaneous 2%. Skate: Pseudomonas 53%, Achromobacter 13%, Alcaligenes 6%, Flavobacterium 9%, corynebacteria 2%, cocci 3%, Gut Group vibrios 12%, miscellaneous 2%.

Some Hypotheses on the Aetiology of Fatal Infections in Partially Resistant Hosts and their Application to Mice Challenged with Salmonella paratyphi-B or Salmonella typhimurium by Intraperitoneal Injection

Abstract: SUMMARY: Some hypotheses are considered which describe the aetiology of a fatal infection in a partially resistant host; i.e. a host which does not invariably die after inoculation with one bacterium. The hypothesis of independent action postulates that the mean probability per inoculated bacterium of multiplying to cause (or help to cause) a fatal infection is independent of the number of bacteria inoculated and, for a partially resistant host, is less than unity (1>p>0). It predicts: (1) that the slope, b, of the probit-mortality/log-dose curve will be 2·0 or less at the LD 50 point; (2) that, while hosts dying after inoculation with many LD50 die as a result of the multiplication of many of the inoculated bacteria, most of those dying from 1 LD50 or less do so following the multiplication of only one of the inoculated bacteria, regardless of the total number of bacteria inoculated. When a mixture of several equally virulent, distinguishable variants of a given pathogen are inoculated, fatal infections caused by the growth of one bacterium should result in the predominance of only one variant at post mortem. The hypotheses of maximum and of partial synergism postulate that inoculated bacteria co-operate so that the value of p increases as the size of the dose increases. They predict: (1) that the slope of the dose-response curve may be more than 2·0 at the LD50 point; (2) that all observed fatal infections will be initiated by more than one bacterium and that consequently the inoculation of a mixed inoculum will lead to the predominance of several variants at post mortem. Variants of Salmonella paratyphi-B which carried one of the three flagellar antigens, b, i, or e, h, were prepared by transduction. Variants of S. typhimurium which either fermented or did not ferment xylose were also prepared. In each case, the variants did not differ detectably in growth rate in vivo, or in virulence. The value of b was 1·8 for mice inoculated with S. paratyphi-B by intraperitoneal injection (LD50 = 7·7 × 106 organisms). As predicted by the hypothesis of independent action, the relative frequencies of the variants in samples of heart blood obtained post mortem varied greatly from mouse to mouse when the dose was 1 LD50 or less, and became progressively more uniform (and similar to the inoculum) as the size of the dose increased. The value of b was 0·66 for mice challenged by S. typhimurium by subcutaneous injection (LD50 = 2 × 103 organisms); and challenge with a mixed inoculum gave similar results. Despite this general conformity with prediction, far fewer mice than expected yielded only one variant at post mortem. This discrepancy possibly resulted from a terminal breakdown in resistance, which was demonstrated by experiment. It is concluded that these results are most economically explained by the hypothesis of independent action and that this hypothesis is probably applicable to many other infective systems.

The aerobic breakdown of uric acid by certain pseudomonads.

Abstract: SUMMARY: Four pseudomonad isolates which could use uric acid aerobically as a sole C, N and energy source were isolated from poultry house deep-litter, droppings, and nearby soil. Organisms harvested from media containing uric acid can degrade uric acid completely, with the formation of CO3 and NH3. Allantoin, allantoic, glyoxylic and formic acids were completely oxidized.

The Water and Solid Content of Living Bacterial Spores and Vegetative Cells as Indicated by Refractive Index Measurements

Abstract: SUMMARY: Refractive index measurements were made on the spores and vegetative cells of strains of Bacillus cereus, B. cereus var. mycoides and B. megaterium by phase contrast and interference microscopy with protein immersion. The refractive indices of the spores were found to be very high and comparable with that of dehydrated protein, suggesting that they contained very little water. Those of the vegetative cells were much lower, and indicated a solid content of about 30%, w/v.

The oxygen requirement of growing cultures of an Aerobacter species determined by means of the continuous culture technique.

Abstract: SUMMARY: A formula for calculating the oxygen demand of a growing culture is derived. The fate of substrate-glucose in cultures of Aerobacter cloacae was found to depend on the amount of available oxygen and the oxygen demand of the organisms. Anaerobically, cell synthesis and CO2 production are at their minimum levels and most of the glucose-carbon is converted into ethanol, formic acid, 2:3-butanediol, acetoin and acetic acid. A small supply of oxygen suppresses the formation of ethanol and formic acid but still permits the production of butanediol and acetoin and increases the proportion of glucose-carbon converted to acetic acid, cells and CO2. A larger supply of oxygen suppresses the formation of butanediol and acetoin and still further increases the yields of cells and CO2. With an excess of oxygen available, provided the growth rate of the organism is not too near its maximum value, acetic acid production is suppressed and complete conversion of the glucose-carbon into cell and CO2 occurs. At growth rates very close to the maximum a part of the glucose is converted into acetic acid even with an excess of available oxygen. The metabolism in a batch culture with excess oxygen resembles the metabolism with excess oxygen in a continuous cultures in which the organisms are growing at a rate close to the maximum. Means of recognizing and preventing an oxygen deficiency are discussed.

The mode of action of phenanthridines: the effect of ethidium bromide on cell division and nucleic acid synthesis.

Abstract: SUMMARY: The action of 2:7-diamino-9-phenyl-10-ethyl phenanthridinium bromide (ethidium bromide) on the parasitic flagellate Strigomonas oncopelti has been studied. The drug is irreversibly active only against growing organisms. Addition of the drug to cultures of organisms in the logarithmic phase of growth did not result in an immediate inhibition of growth but in a progressive decrease in growth rate; at least a doubling in number of organisms always occurred before multiplication finally ceased. During the period of growth in the presence of drug the deoxyribonucleic acid content of the organisms fell to half its normal value whilst the ribonucleic acid remained approximately constant. Conditions have been determined which permit the synthesis of nucleic acids and proteins by washed suspensions of S. oncopelti and the effect of ethidium bromide on these processes has been studied. The drug rapidly inhibits DNA synthesis whereas RNA and protein synthesis continue for a period of 2–3 hr. after the addition of drug. A study has been made of the uptake of 14C-labelled ethidium bromide by organisms under conditions which will or which will not permit nucleic acid synthesis. The uptake of drug is of two types: (i) an initial rapid uptake which occurs in the absence of nucleic acid synthesis and which does not affect the subsequent growth of organisms; (ii) an additional uptake by growing organisms which appears to follow the course of RNA synthesis and which results, eventually, in an inhibition of growth.

An Agar-Diffusion Method for Titrating Bacillus anthracis Immunizing Antigen and its Application to a Study of Antigen Production

Abstract: SUMMARY: An agar-diffusion method is described for the titration of Bacillus anthracis immunizing antigen and antibody. It is a sensitive and simple method that can be used for determining antigen concentrations in culture filtrates and for titrating antisera from animals and humans which have been immunized with the antigen. Marked improvements in yields of antigen in a defined medium and a hydrolysed casein - amino acids (Casamino) medium have been achieved with the aid of this assay method.

The Kinetics of the Mating Process in Escherichia coli

Abstract: SUMMARY: When broth cultures of donor (HfrH) and recipient (F-) strains of Escherichia coli K-12 are mixed, zygotes are formed by the transfer of part of the donor chromosome to the recipient cell. The donor parent thus becomes dispensable as soon as transfer is accomplished. The kinetics of zygote formation can therefore be studied by treating samples, removed at intervals from a parental mixture, with virulent bacteriophage to which only the donor parent is susceptible. Only zygotes already formed at the time of treatment can segregate a recombinant ceil. A lag of 8-10 min. precedes a linear rise in the number of zygotes when selection is made for inheritance of the donor nutritional markers T + L + only. The formation of zygotes inheriting the marker Lac+ as well as T + L + shows a lag of about 18 min. These lag periods represent the times required for the genes T + L + and Lac +, respectively, to enter the F- cells and confirm the finding of Wollman & Jacob (1955) that chromosome transfer is an oriented process and that the donor genes penetrate the F- cell in the same order as their arrangement on the chromosome. The process of zygote formation in the equivalent F + × F- cross has also been studied by the phage method. Although the yield of T + L + recombinants is c. 2 × 104 times less than in the Hfr × F- cross under the same conditions, the times of entry of the donor genes T + L + and Lac + are the same in both crosses. In the Hfr × F- cross, significant zygote formation does not occur in unsupplemented buffer but requires the presence of both glucose and sodium aspartate. Zygote formation is a temperature-dependent process which occurs in the absence of multiplication of either parent and is unaffected by the presence of deoxyribonuclease. The number of zygotes (and therefore of recombinants) formed in a given time is a function of two independently variable factors: (i) the frequency and intimacy of chance concacts; (ii) the speed of chromosome transfer which is related to energy production. Decrease of temperature from 37° to 32° about doubles the time required for any given Hfr gene to be transferred to an F- cell. Alteration of the parental population density, or the pH values of the medium (Fisher, 1957b), does not affect the times of entry of Hfr genes into the F- cells but does modify the rate of effective contact formation. Segregation of haploid recombinant cells from Hfr × F- zygotes, at 37°, takes place in nutrient broth at about 140 min., and on minimal agar at about 160 min., after mixing the parental suspensions. The phenotypic expression of resistance to sodium azide, inherited from the Hfr parent, commences shortly after the zygotes are formed and becomes complete just before segregation; resistance to phage T1, however, is not expressed at all until the time of segregation, and requires four generations of the recombinant segregants for completion.

The active agent in nascent phage lysis of streptococci.

Abstract: SUMMARY: A powerful lytic factor has been obtained in phage lysates of group C streptococci, which is active against streptococci of groups A, C and E and under some conditions group H. It is the factor responsible for ‘nascent’ phage lysis. The lytic activity remains unaltered by the removal of the phage by high-speed centri-fuging, and also in the presence of phage antiserum. It is active against young and old cell suspensions, live, or killed by chloroform. The activity diminishes in the absence of reducing agents and it is destroyed by protcolytic enzymes. Heat-killed cocci when attacked by the lytic factor become Gram-negative but do not lyse. The addition of a proteolytic enzyme completes lysis. Efforts to demonstrate the release of proteinases from streptococcal suspensions have failed. After lysis the group polysaccharide is free as a hapten and some cell-wall structure remains. M antigen is also present in group A lysates.

A cell-wall lytic enzyme associated with spores of Bacillus species.

Abstract: SUMMARY: Aqueous extracts of disintegrated spores of Bacillus cereus and non-virulent B. anthracis contained an enzyme which produced visible lysis of the isolated cell walls of vegetative B. cereus. Optimum activity occurred at pH 7-8 in the presence of cobalt or manganese ions (10 p.p.m.) at 58°. Activity was destroyed during heating at 100° for 15 min. The lytic preparation released non-dialysable components containing αe-diaminopimelic acid (DAP), glutamic acid, alanine, amino sugars and glucose. Although lysis was less obvious, the enzyme preparation released similar material from cell walls of other Bacillus species, spore coats of B. megaterium and coats of autoclaved B. cereus spores. Extracts of freshly harvested B. cereus spores were more active than those from spores which had been stored for several weeks at 2°. Extracts from disintegrated spores of B. megaterium had no enzymic activity; the enzyme system was associated with the insoluble spore coat fraction. The action of the enzyme differed from that of lysozyme or glucosaminidase; the reaction products did not give a significant reaction for N-acetylhexosamine and visible lysis proceeded more rapidly with cell walls of B. cereus than with B. megaterium. Possible functions of the enzyme may be to release ‘spore peptide’ from the spore coat during germination and to lyse the sporangium and free the spore during sporulation.

The development and testing of a method of counting rumen ciliate protozoa.

Abstract: SUMMARY: The limitations of methods previously used for counting rumen ciliates, and the value of developing a method of known accuracy, are discussed. Two counting-chambers, one based on the Sedgwick-Rafter cell, the other on the MacMaster eelworm-counting cell, were constructed and tested. A MacMaster-type cell was adopted. The preparations of suitable suspensions for counting organisms from washed suspensions and from rumen contents are described. The counting technique adopted was found to be reliable; its accuracy depends upon the number of organisms counted. In one sheep on a constant diet, day-to-day differences in rumen ciliate population were far greater than the differences found throughout the rumen at any one time, or the variations due to technique.

Dose-response curves of toxic and infective actions of adenovirus in HeLa cell cultures.

Abstract: SUMMARY: Study of the dose-response curves in titrations of adenovirus type 5 in cultures of HeLa cells suggests two different mechanisms of cytopathic effect. A late effect, caused by relatively small virus doses, is considered to be a manifestation of virus infectivity and is in good agreement with the hypothesis of independent action of virus units in the initiation of infection. The early effect, on the other hand, requires large virus doses and is considered to be of a toxic nature. Infective and toxic properties of adenovirus type 5 are distinguished by the greater sensitivity of the latter to inactivation by ultraviolet light.

The pathway of breakdown of 2:4-dichloro- and 4-chloro-2-methyl-phenoxyacetic acid by bacteria.

Abstract: SUMMARY: The metabolism of 2:4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid by a strain of Flavobacterium peregrinum and an Achromobacter sp., respectively, has been studied. Bacteria from young cultures were more active than those from older ones in oxidizing these substrates. Evidence is presented that adapted organisms dissimilate 2:4-dichlorophenoxyacetic acid through 2:4-dichlorophenol and 4-chlorocatechol, and that 4-chloro-2-methylphenoxyacetic acid is dissimilated through 5-chloro-2-cresol. Bacteria grown on 2:4-dichlorophenoxyacetic acid do not oxidize any of the other five possible isomers, but can oxidize 2:4-dibromo-, 4-bromo-2-chloro-, 4-chloro-, and, to a small extent, 2-chlorophenoxyacetic acids.

Cell-wall lytic enzymes at sporulation and spore germination in Bacillus species.

Abstract: SUMMARY: When washed sporulating cells of Bacillus cereus were incubated in buffer at 37°G in the presence of toluene, a partial autolysis occurred resulting in the freeing of mature and immature spores. The autolysate contained lytie enzymes which attacked vegetative cells and cell-wall preparations, releasing hexosaminecontaining peptides of characteristic constitution. The most active enzyme preparations were obtained from sporulating cells incubated for 1-2 hr. in buffer at pH 5-0-6-0. Two water-soluble lytic systems, enzyme V and enzyme S with pH optima near 4-5 and 8-0 respectively, were separated from the autolysate. Enzyme S is probably identical with the lytic system present in spores of B. cereus and other Bacillus species and further observations on this system are described. When non-sporulating cells of B. cereus were incubated under similar conditions no obvious lysis or sporulation occurred and no cell-wall lytic activity could be demonstrated. In growing cultures of Bacillus cereus, considerable amounts of hexosamine-containing peptides were released into the medium during the period between the appearance of intracellular spores and free spores. It is suggested that enzyme V may be mainly concerned with the release of free spores from sporangia and enzyme S with the lytic processes which accompany spore germination.

Nutritional requirements and biosynthetic capabilities of the parasitic flagellate Strigomonas oncopelti.

Abstract: SUMMARY: A study of the nutritional requirements of the trypanosomid flagellate Strigomonas (Herpetomonas) oncopelti has led to the development of a chemically defined growth medium containing methionine, thiamine, nicotinamide, p-amino-benzoic acid, glucose, salts and trace metals. Fractionation and analysis of organisms grown in this defined medium supplemented with trace amounts of various 14C-labelled substrates has thrown light upon the ability of growing organisms to utilize carbon derived from glucose, acetate, a number of amino acids, purines and pyrimidines for the synthesis of cellular components.

Yeasts from the bovine caecum.

Abstract: SUMMARY: From the caeca of 252 adult bovines 131 yeast strains were isolated, distributed as shown (in brackets) among the following species: Saccharomyces cerevisiae (12), S. chevalieri (3), S. drosophilarum (3), S. fragilis (1), Pichia bovis (1), P. membranaefaciens (3), P. fermentans (3), Cryptococcus diffluens (1), Torulopsis glabrata (4), Torulopsis sp. (2), Candida tropicalis (45), C. parapsilosis (3), C. krusei (33), C. macedoniensis (1), C. utilis (1), C. bovina (1), Trichosporon cutaneum (5). Candida albicans was not isolated. The apparent absence of C. albicans from the bovine intestinal tract may explain the rareness of oral and intestinal moniliasis in bovines. Infection in certain forms of yeast mastitis (caused neither by C. albicans nor by Cryptococcus neojormans) may be derived from the intestinal tract. Descriptions and Latin diagnoses of Pichia bovis n.sp. and Candida bovina n.sp. are given.

Acriflavine-resistant mutants of Aspergillus nidulans.

Abstract: SUMMARY: In three independently obtained mutant strains of Aspergillus nidulans, resistant in different degrees to acriflavine, resistance is due, in each case, to mutation in a single gene. Two of the mutant alleles, ACR1 and ACR3, are semi-dominant and either allele confers a high degree of resistance. These alleles are located about 23 units distal to the w (white conidia) locus and are presumably allelic. A cross involving these two alleles in repulsion gave 0.1% sensitives. A third mutant allele (acr2) is also located on the w chromosome, but on the other arm about 25 units distal to the ad1 locus and over 100 units distant from the ACR1 and ACR3 loci. This allele, which confers relatively slight resistance, is almost completely recessive. Diploid strains which carry any allele for resistance in heterozygous condition give, by vegetative segregation, haploid and homozygous diploid resistant types which are preferentially selected on medium with acriflavine. The use of this technique for the automatic selection of vegetative segregants provides an additional tool for analyses through the parasexual cycle.

The nutritional requirements of Clostridium perfringens.

Abstract: SUMMARY: The requirements for growth factors, amino acids and inorganic constituents were determined for three strains of Clostridium perfringens (Veillon & Zuber) Holland. A number of substances were tested as energy sources for this organism, and the influence of pH value and temperature on growth was determined. The minimal medium evolved contained: alanine, arginine, aspartic acid, eystine, glutamic acid, histidine, isoleueine, leueine (methionine), phenylalanine, threonine, tryptophan, tyrosine and valine; ammonium chloride, magnesium chloride, ferrous chloride, sodium-potassium phosphate buffer; glucose; adenine, biotin, calcium pantothenate and pyridoxine. For maximal growth the presence of lysine, glycine and serine was necessary. Maximal growth was affected by the balance of amino acids in the medium; the balance of sodium and potassium ions was also important. Certain strain differences were noticed with respect to amino acid and vitamin requirements. Methionine was needed by one strain only; none of the strains required serine (reported essential for strain BP6K of Boyd, Logan & Tytell, 1948b), whereas aspartic acid was essential for all strains tested but not for BP6K. Riboflavine, an essential growth factor in BP6K, had no effect on growth of the strains tested. One of the strains showed a need for added nicotinamide when transferred to a nicotinamide-free medium after several transfers in peptone water.

Studies on the antigens of Paramecium aurelia with the aid of fluorescent antibodies.

Abstract: SUMMARY: Preparations of Paramecium aurelia, which had been immobilized by placing the organisms in a solution containing antiserum conjugated with fluorescein (conjugated antiserum), were examined by fluorescence microscopy. Unfixed paramecia accumulated fluorescent antibody in a thin layer around the entire surface of the organisms, and in globules at the clumped tips of the cilia, but not in the cilia themselves. No fluorescence was seen in the nuclei or the cytoplasm, but the food vacuoles became brightly fluorescent when the paramecia remained in conjugated antiserum for a few hours. Paramecia, which had been fixed with osmic acid and subsequently treated with fluorescent antibody, showed a faint fluorescence along the whole lengths of the cilia. When transformation from one serotype to another took place, the change in ability to take up a given kind of fluorescent antibody was seen to occur uniformly over the whole surface of the organism. It is concluded that the immobilization antigen is a fluid substance which covers the whole surface of the paramecia and is exuded into the medium under certain conditions, especially when homologous antibody is present.

The metabolism of inorganic polyphosphate in mycobacteria.

Abstract: SUMMARY: Cell-free extracts of Mycobacterium smegmatis contain an inorganic polyphosphatase and a ‘polyphosphate-AMP-phosphotransferase’. The latter enzyme, which synthesizes adenosine triphosphate from adenosine-5-monophosphate and inorganic polyphosphate, has a pH optimum of about 6.3, and is stimulated by Mg. It does not appear to be attached to cell particles, and a slight purification may be effected by ammonium sulphate precipitation. With a tracer technique it was shown that cellular inorganic polyphosphate is probably not the sole precursor either of lipid phosphorus or of nucleic acid phosphorus in M. smegmatis. The rapid accumulation of insoluble polyphosphate caused in M. smegmatis and M. phlei but not M. tuberculosis, by a number of organic substances, particularly alcohols, was studied. This accumulation takes place even after inoculation into a fresh nitrogenous medium, when polyphosphate normally decreases.

The applicability of the hypothesis of independent action to fatal infections in mice given Salmonella typhimurium by mouth.

Abstract: SUMMARY: Mice were challenged by mouth with a suspension containing equal numbers of streptomycin-sensitive (Str-) and streptomycin-resistant (Str+) variants of Salmonella typhimurium. These variants were of equal virulence but the Str+ variant grew more slowly in vivo than the Str- variant. The LD50 dose contained c. 5 x 105 bacteria. Heart blood obtained from mice dying from many LD50 doses nearly always contained a great excess of the Str- variant, but blood from mice dying from less than one LD50 dose contained either Str-, Str-, or a mixture of Str- and Str+ variants. The appearance of the Str+ variant alone in the latter mice strongly suggests that these fatal infections were initiated by a very small number of organisms or possibly by a single organism. It is therefore concluded that these organisms were acting independently. In this system, it is likely that any bacterium which enters the tissues from the gut can initiate a fatal infection and that the probability of effecting such an entrance almost entirely determines the probability of an inoculated bacterium causing a fatal infection.

An electron microscope study of the spores of some species of the genus Bacillus using carbon replicas.

Abstract: SUMMARY: A method for the preparation of carbon replicas of Bacillus spores is described. Micrographs of these replicas reveal much more of the surface detail than direct electron micrographs. Rib formations were found on five different species and the micrographs obtained suggest that the sculpturing varies according to the species.

Some general properties of a psychrophilic pseudomonad: the effects of temperature on some of these properties and the utilization of glucose by this organism and Pscudomonas aeruginosa.

Abstract: SUMMARY: A psychrophilic species of the genus Pseudomonas was found to be capable of growth in a simple defined medium with any one of a number of carbon sources The growth requirements were the same at 0 and 20 The organism vigorously oxidized glucose to gluconic and 2-ketogluconic acids Rates of O2 uptake were measured over the range 0–40 and compared with similar measurements on P aeruginosa Under the experimental conditions values of Q o2 for the psychrophile were higher than those for P aeruginosa at all temperatures, including those above 30 at which temperatures the psychrophilic organism does not grow The values of Q o2 and their temperature coefficients were dependent on conditions of cultivation It is concluded that the systems involved in the oxidation of glucose and gluconic acid by the two organisms may not be greatly different in those physical properties which determine their temperature relations