Showing papers in "Microbiology in 1974"

Abstract: SUMMARY: R factors of the compatibility class P were transferred between strains of Escherichia coli k12 and Rhizobium leguminosarum. These R factors were stable in R. leguminosarum and conferred similar levels of antibiotic resistance to those in the corresponding R+ E. coli k12 hosts, with the exception of carbenicillin resistance which was greatly reduced. Transfer between R. leguminosarum strains was by conjugation and was stimulated by conditions favouring spheroplast formation. R factor mediated recombination could not be demonstrated.

Abstract: Cultural conditions for forming and stabilizing protoplasts of Streptomyces griseus and S. venezuelae were studied by reference to the number of protoplasts formed, leakage from protoplasts and reversion rate. Effective formation and stabilization of the protoplasts was accomplished by using a hypertonic medium containing 10 mM-MgCl2 and 25 mM-CaCl2. Electron microscopy showed that the protoplasts of S. griseus, when prepared in the above medium, formed vesicles on the cytoplasmic membrane or out of the protoplasts, but when prepared in a medium with 3 mM-MgCl2 and 3 mM-CaCL they provided few such vesicles. The reversion of protoplasts to the normal filamentous state was examined by the growth on various synthetic agar media. A high reversion rate was obtained by incubating the protoplasts on a hypertonic agar medium containing 20 or 50 mM-MgCl2, 50 or 20 mM-CaCl2, 0·44 or 0·22 mM-phosphate and 0·01 % Casamino acids. Combinations of appropriate concentrations of MgCl2 and CaCl2 were significantly effective in the reversion as well as in the stability of protoplasts. The concentration of phosphate should be adjusted to 0·44 or 0·22 mM. Casamino acids enhanced both growth and reversion rates. The reversion of protoplasts of Streptomyces griseus was followed by using phase-contrast microscopy. The protoplasts incubated on medium R1 enlarged to about 40 μ and then generated filamentous hyphae from the periphery.

Abstract: Summary: We have analysed the pattern of concentric waves visible at the onset of aggregation of amoebae of Dictyostelium discoideum and have shown that each wave consists of a light band of elongated, moving cells, and a darker interband zone of rounded cells. Our analysis supports earlier suggestions that aggregation occurs in response to chemotactic signals emanating from a centre and which are propagated outwards through the field by a relay mechanism. The width of each band of moving cells corresponds to the distance the signal is propagated during the time that the cells remain elongated after stimulation, and does not vary with signal frequency. The width of the interbands of non-moving cells depends upon the distance the signal is propagated between signalling events, and varies with the signal frequency which increases during aggregation. The velocity of signal propagation decreases slightly with increase in the density of the monolayer of aggregating cells. We have shown by time-lapse films taken at high magnification that the signal is relayed radially outwards in steps of approximately 57 μm (relay zones) and that the response of each successive zone occurs approximately 12 s after the previous one (relay time). We have attempted to demonstrate the existence of a refractory period for chemotactic responsiveness. Our results indicate that such a refractory period, if it exists, cannot be more than 12 s.

Abstract: Growth of Mucor hiemalis, Geotrichum candidum, Aspergillus nidulans, Neurospora crassa and Penicillium chrysogenum was studied by time lapse photography. The total hyphal length of the mycelium of each species increased at an exponential rate; in M. hiemalis exponential growth continued until the mycelium had a total hyphal length in excess of 10 mm. After spore germination there was an initial phase of discontinuous tip production followed by a phase of ‘continuous’ tip production. The hyphal length and number of tips possessed by a mycelium increased exponentially at approximately the same specific growth rate. The amplitude of the oscillations in the length of the hyphal growth unit of a mycelium decreased progressively during mycelial growth and eventually the growth unit attained a more or less constant value. The results support the hypothesis that mycelial growth involves the duplication of a ‘growth unit’ which consists of a tip and a certain mean length of hypha.

Abstract: The incidence of mycorrhizas in the roots and Endogone spores in rhizosphere soil of 52 xerophytes, 21 halophytes and 16 hydrophytes from Pakistan was investigated. Vesicular-arbuscular mycorrhizas were of general occurrence in all plants examined except hydrophytes and members of the families Urticaceae, Casuarinaceae, Nyctaginaceae, Portulaceae, Caryophyllaceae, Amaranthaceae, Chenopodiaceae, Capparaceae, Oleaceae, Elaeagnaceae, Zygophyllaceae, Tamaricaceae, Euphorbiaceae and Palmae. Mycorrhizas were found mainly in the surface and subsurface horizons of the soil, and they were much less abundant in the deeper layers, although the abundance of Endogone spores did not decrease with depth. Endogone spores were rare in permanently waterlogged soils, which suggested that soil moisture affected spore number. Most other soil samples contained Endogone spores, including some from rhizospheres of non-mycorrhizal plants. In some soils an increase in spore numbers was recorded in the autumn and winter and a decrease in the spring and summer.

Abstract: SUMMARY: Most invasive strains of Escherichia coli from man and domestic animals were lethal for chickens and mice. The lethal characteristic was not, in general, transferred when invasive strains were grown in mixed culture with non-pathogenic strains of E. coli, although two transmissible plasmids coding for pathogenic properties were discovered. One plasmid, designated Vir, was found in an E. coli strain causing bacteraemia in a lamb. It transferred at high rate to several strains of E. coli, including a rec A-KI2 strain, to Salmonella typhi, Salm. typhimurium and Shigella sonnei. Culture filtrates and, especially, bacterial ultrasonicates of Vir+ strains were toxic for chickens, mice and rabbits. The toxin was heat-sensitive, acid-sensitive and non-diffusible. Organisms producing it were agglutinated by specific Vir+ antisera; their toxic activity was not neutralized. The transfer factor of the Vir plasmid was fi+ and could transfer antibiotic-resistance determinants in addition to the Vir determinant. The other plasmid was first discovered in an E. coli strain F120, isolated from an outbreak of bacteraemia in chickens. Organisms of E. coli K12 and of other E. coli strains acquiring this plasmid during mixed culture with FI20 were increased in lethality for chickens and mice; this was associated not with toxic activity but with greater ability to survive in blood and peritoneal fluids. Strain FI20 possessed transmissible ColV and Collb plasmids; increased lethality was closely associated with the ColV plasmid. When the ColV plasmids of another six wild strains of E. coli of varied origin were transferred to organisms of E. coli KI2, the lethality increase was similar to that for ColV transfer from FI20. No lethality change accompanied transfer of other Col plasmids. It was concluded that colicine V itself might be responsible for the increased lethality. Strains of E. coli associated with bacteraemia in man and animals commonly produced colicine V.

Abstract: SUMMARY: All of 108 strains of Escherichia coli that synthesized K88 antigen caused mannose-resistant and eluting (m.r.e.) haemagglutination of guinea-pig erythrocytes in a microhaemagglutination test; none of 23 representative strains did so in a tile haemagglutination test which requires firmer binding. It was concluded that the K88 antigen was the m.r.e. haemagglutinin since (i) only K88-positive strains caused m.r.e. haemagglutination (ii) K88-positive strains grown at 18°C failed to produce both haemagglutinin and K88 antigen (iii) haemagglutinating activity was not detected in K88-negative mutants of a K88-positive enteropathogenic strain, and (iv) extracts of K88 antigen possessed haemagglutinating activity which could not be separated from the K88 antigen by the fractionation and serological procedures examined. Haemagglutination appears to resemble the attachment of K88-positive bacteria to the gut wall in enteric disease and the haemagglutination test may assist in characterizing this mechanism.

Abstract: Summary: Three Pseudomonas aeruginosa phages specific for bacteria harbouring the P-group plasmid RP1 have been isolated, and their properties compared with those of a previously described sex-specific phage, PRR1 (Olsen & Shipley, 1973). These phages are distinguishable from each other by various criteria, although in terms of host range to FP+ and RP+ lines of P. aeruginosa pao they comprise broadly two groups. Thus all the phages infect bacteria harbouring any of a group of plasmids with similar properties to those of RP1, but whereas the filamentous phage Pf3 is specific for this group, the host ranges of PRR1, PR3 and PR4 are considerably wider. Nevertheless, with one exception, this does not extend to plasmids isolated outside the United Kingdom, which suggests that all these plasmids share a common ancestry even though by other criteria they constitute three fairly discrete subgroups. Of the plasmids that fail to allow phage propagation, three, when present in the same cell as RP1, reduce its susceptibility to phage infection. This inhibition may reflect a relationship between these elements, similar to that found among plasmids of Enterobacteria. A correlation is observed between the susceptibility of bacteria to phage infection and their ability to mediate plasmid transfer, such that these phages can conveniently be used to isolate both derepressed or transfer-defective mutants of various R factors.

Abstract: SUMMARY: Eighteen cariogenic streptococcal strains identified as members of Streptococcus mutans (Clarke, 1924) were compared on the basis of biochemical tests, mannitol-i-phosphate dehydrogenases, DNA base compositions and DNA base sequence homologies. Some slight biochemical differences were found which correlated with the large differences in DNA base composition and sequence heterology which exist among these strains. All strains could be assigned to one of four groups based on these biochemical and genetic differences. Furthermore, these four groups correlated with four serological groups described by Bratthall (1970). It is proposed to divide S. mutans into four subspecies: S. mutans subsp. mutans, the type subspecies, has a guanine-cytosine (G-C) of 36 to 38 mol % and belongs to Bratthall serological group c; S. mutans subsp. rattus subsp. nov. has 41 to 43 mol % G-C, belongs to Bratthall group b, and can be distinguished from the other subspecies by its production of ammonia from arginine; S. mutans subsp. cricetus subsp. nov. has 42 to 44 mol % G-C, belongs to Bratthall group a, and can be distinguished by its lack of growth in air: S. mutans subsp. sobrinus subsp. nov. has 44 to 46 mol % G-C, belongs to Bratthall group d, and can be distinguished by its failure to ferment raffinose.

Abstract: SUMMARY Escherichia coli, C-M7, a His+Nif+ hybrid obtained by intergeneric mating with a Klebsiella pneumoniae donor strain, also inherited the unselected markers gnd and rfb. The R factor, R144drd3, which had been used to confer fertility on the donor, was present, detectable as covalently closed circular DNA of molecular weight 69 x lo6 daltons. No other species of supercoiled DNA were isolated and the elimination of R144drd3 did not result in the loss of Klebsiella genes. Segregation analysis of donor markers indicated that the Klebsiella DNA was integrated at the his region of the E. coli chromosome in the probable order his-gnd-nif-rfb. Strain C-M7 produced a nitrogenase physiologically identical to that of K. pneumoniae, but synthesized a heteromeric species of gluconate-6-phosphate dehydrogenase.

Abstract: The wall structure of the fission yeast Schizosaccharomyces pombe, examined by enzymic techniques, consists of a galactomannan, an α-glucan and β-glucan. The structures of the α-glucan and galactomannan were investigated by methylation. The wall structure is discussed in relation to the taxonomic position of the genus Schizosaccharomyces.

Abstract: The addition of amphotericin methyl ester (AME) to suspensions of Candida albicans is followed by a progressively increasing rate of release of K+ from within the cell. The time taken for a given rate of release to be reached depends upon the AME concentration (the product of AME concentration and time being approximately constant), the pH and concentration of buffer, the temperature, the suspension density, and the phase of growth of the organisms. The sensitivity of C. albicans to AME decreases during the growth of a batch culture, rapid decrease occurring after the organisms have reached the stationary phase of growth. The induction of K- release does not occur at 0 °C and shows a high temperature coefficient over the range 15 to 30 °C. Suspensions of mouse LS cells are 10 to 30 times less sensitive than Candida albicans towards AME, amphotericin B and nystatin; the two types of cell display little difference in sensitivity towards perimycin and candicidin, while mouse LS cells are more sensitive than C. albicans towards filipin. Addition of sterols at the same time as AME increases the time taken for the release of K+ to reach a given rate; of the sterols tested, zymosterol was the most effective in antagonizing AME, while ergosterol was approximately twice as effective as cholesterol on a molar basis. When organisms were exposed to AME for a short time, removed and resuspended in the absence of drug, the rate of K+ release continued to increase; this increase was prevented by ergosterol: 2 x 10-5 M-ergosterol prevented further damage after organisms had been exposed to 10-6 M AME.

Abstract: SUMMARY: In Candida utilis, the amount of glutamine synthetase is finely attuned to the availability of ammonia in the culture medium, and any change in ammonia availability results in a compensatory adjustment to enzyme level. In yeast growing with different sources of nitrogen there was a good inverse correlation between the rate of enzyme synthesis and the size of the cell pool of glutamine: glutamine and not ammonia appeared to act as a co-repressor of the formation of glutamine synthetase. Sudden changes in ammonia availability or carbon supply could lead to the inactivation of glutamine synthetase. This was shown to be associated, under some conditions, with a marked increase in the pool of glutamine and it is possible that it was brought about by sudden changes in the relative cell concentrations of glutamine and glutamate. However, the process is clearly more complex than this and catabolism of carbon substrates is also involved. The specific activity of the NAD-specific (deaminating) glutamate dehydrogenase also varied with the availability of ammonia, but neither it nor glutamine synthetase was subject to parallel regulation.

Abstract: SUMMARY: The cell volume and macromolecular composition, in terms of DNA, RNA and cell mass, were examined in Anacystis nidulans at different growth rates of the organism. Both DNA and RNA increased exponentially with increasing growth rate, as has been found in several heterotrophic bacteria. However, in this blue-green alga the ratio of DNA to RNA was independent of growth rate. Cell mass and volume also increased exponentially with growth rate though at a slower rate than RNA and DNA. These results also indicate a constant ratio of tRNA and rRNA to DNA in contrast to the situation in heterotrophic bacteria so far studied. The variation of cell volume in this organism can be related to the control of cell division, and indicates that the commencement of DNA replication and the processes of cell division are associated with the achievement of a critical cell volume, as has been demonstrated for Escherichia coli.

Abstract: SUMMARY: Plasmids determining I pili show a variety of intricate compatibility relationships. None the less, all I plasmids tested showed a ‘core’ of common DNA sequences of approximately 30 x 106 daltons. Plasmids of the O compatibility group do not appear to specify for the synthesis of I-like pili and yet they held about 20 % of their sequences in common with all tested I plasmids, suggesting a common phylogenetic origin. Members of the I complex (including group O) do not hold a significant proportion of their sequences in common with representative plasmids of other compatibility groups. We propose that the regions of similar polynucleotide sequences of the different I complex plasmids are due to phylogenetic homology between genes governing pili biosynthesis and/or transfer functions. The regions determining compatibility of the I complex plasmids in some cases may be either unrelated to or have diverged from a common ancestor.

Abstract: SUMMARY Increases in turbidity of Escherichia coli strain K12 due to added non-permeant salts (NaCl and MgCl2) and sucrose are strictly dependent on medium osmotic pressure, when correction is made for changes in medium refractive index. The volume of the whole cell and the fraction of the intact cell bounded by the cyto-plasmic membrane have been measured by dextran and [14C]sucrose exclusion spaces. Increases in medium osmotic pressure due to non-penetrant medium solutes cause outflow of water across the cytoplasmic membrane and contraction away from the cell wall (plasmolysis), corresponding to the increases in turbidity. In addition salts (NaCl and MgCl2) cause appreciable contraction in volume of the whole cell, presumably due to ionic interaction with the wall; sucrose causes only marginal decreases in whole cell volume. Electron micrographs of cells plasmo-lysed by NaCl or MgCl2, but not by sucrose, show numerous adhesion points between the wall and the cytoplasmic membrane. Glycerol penetrates the cell to the same extent as water, but because of its slower rate of penetration, transient decreases in volume occur which can be measured in a stopped-flow spectrophotometer due to concomitant increases in turbidity. In cells grown on glucose-containing medium the rate of glycerol penetration is non-saturating. In cells grown on glycerol an additional saturating-facilitated diffusion system is induced. Mutants deleted in the facilitator (F-) are available and do not show facilitated diffusion when grown on glycerol. Water exit and glycerol penetration in glucose-grown cells show transition points in Arrhenius plots corresponding to phase changes of the membrane lipids.

Abstract: Of more than 100 R factors transferred from naturally occurring Providence strains, approximately 60 % belonged to the A-C compatibility complex. Plasmids of groups F1, J, N, P and X, and the prototype of a new group G were also transferred. The Providence R factor set differs from those of Proteus rettgeri and P. morganii most strikingly in the abundance of plasmids of the A-C group and the infrequency of N group plasmids.

Abstract: SUMMARY: Drug resistant mutants of the slime mould Dictyostelium discoideum useful for mitotic genetic analysis have been studied. Mutations to acriflavin resistance are recessive and have been assigned to two genes (acrA, acrB) located in different linkage groups. One of these (acrA) confers resistance to the unrelated compounds methanol and thiabendazole. Ability to grow axenically (in the absence of bacteria) is determined by genes on two linkage groups, one carrying acrA and the other an established temperature sensitive mutation. Preliminary results for two linkage groups show that the sequence of genes on a linkage group can be determined by analysis of homozygous drug resistant diploids, obtained by drug selection from diploids heterozygous for recessive drug resistance markers.

Abstract: SUMMARY Mineralization of a cycloparaffinic hydrocarbon in soil has been demonstrated. Addition of [U-14C]cyclohexane to marine mud, followed by incubation at 26 °C, resulted in the evolution of 14CO2. All attempts in our laboratory to isolate organisms from soil which utilize cycloparaffins as a sole source of carbon and energy have proved unsuccessful. However, several hydrocarbon-utilizing bacteria oxygenated cycloparaffins to ketone derivatives that serve as the energy and carbon source for numerous other soil micro-organisms. The concerted attack of a mixed microbial population on cyclohexane has been demonstrated, suggesting that both co-metabolism and commensalism are associated with microbial degradation of cycloparaffinic hydrocarbons.

Abstract: SUMMARY: We tested 151 strains representing the genera Nocardia and Gordona, the taxon ‘Mycobacterium’ rhodochrous and a collection of strains isolated from bagasse for their in vitro susceptibility to 52 antimicrobial agents by using the impregnated filter-paper disc method. The ‘bagasse’ isolates were resistant to most of the antimicrobial agents but the nocardiae, gordonae and rhodochrous groups formed a series with increasing sensitivity. The nocardiae were inhibited by low concentrations of a number of antibiotics, notably erythromycin, miconazole, gentamycin and tobramycin, which may be of value in treating Nocardia infections. Certain antibiotics, at suitable concentrations, provided data of value for the classification and identification of nocardioform bacteria.

Abstract: SUMMARY: Methionine is a substrate for ethylene formation in Mucor hiemalis, but glucose is also required for maximal ethylene production. The formation of ethylene from these substrates in a defined mineral salts medium was studied both with sealed shaken flasks and with a chemostat. Oxygen promoted growth and ethylene production per unit weight of organism. That anaerobic conditions appear to be necessary to observe ethylene accumulation in the soil is probably because soil anaerobiosis mobilizes the substrates required for ethylene biosynthesis.

Abstract: SUMMARY: A co-operative taxonomic study has been performed on slowly growing non-pigmented mycobacteria (Runyon's group III). Phenetic data on 89 strains, studied in 18 laboratories, were collected and analysed by a numerical taxonomic method. A variety of immunological properties, lipid analyses and measures of pathogenicity were analysed independently to establish correlation with numerical classification. Mycobacterium gastri, M. nonchromogenicum, M. terrae, M. avium and M. xenopi were recognized by almost all participants as distinct species. Mycobacterium novum was considered to be synonymous with M. terrae. A clearcut distinction could not be made between M. avium and M. intracellulare; the majority of participants in the study recommend that M. intracellulare be reduced to a synonym of M. avium. A minority of authors cannot agree with this proposal.

Abstract: SUMMARY: A methane-oxidizing bacterium, isolated from soil, was capable of fixing nitrogen. Nitrogenase activity could be assayed by acetylene reduction when the bacterium was growing on methanol but not when growing on methane, although 15N2 was fixed. Bacteria growing on methane co-oxidized ethylene but methanol-growing cells did not. The organism was extremely sensitive to oxygen when dependent on N2 as nitrogen source, a consequence of the sensitivity of its nitro-genase towards oxygen.

Abstract: Fifty-nine strains labelled Corynebacterium parvum were investigated by cell-wall agglutination tests using antisera to Propionibacterium acnes and P. granulosum. Fifty-two strains appeared to be serologically identical with P. acnes and three with P. granulosum; these identifications were confirmed by the results of fermentation and other metabolic tests. Of the remaining four strains, three were identified as P. avidum by fermentation tests, and by DNA/DNA homology determinations against reference strains of P. avidum, P. acnes and P. granulosum. One strain was identified as Actinomyces, probably A. naeslundii. These results indicate that C. parvum should be regarded as a synonym of P. acnes.

Abstract: SUMMARY A lysine bradytroph of Penicillium chrysogenum Wis. 54-1255 was isolated. The mutant (L1) grew with α-aminoadipic acid and excreted homocitrate. In vivo accumulation of homocitrate, which did not require protein synthesis, was markedly reduced by lysine. These results indicate that lysine diminution of penicillin production is caused by feedback inhibition of homocitrate synthase, thus limiting the supply of α-aminoadipic acid available for penicillin biosynthesis.

Abstract: SUMMARY: Naphthalene oxygenase was induced in several pseudomonads when these were grown on salicylate as a carbon and energy source, or when salicylate was added to cultures growing on succinate. The enzyme was not induced in Pseudomonas strain NCIB9816 when this was grown in the presence of catechol, although after the addition of this compound to cultures growing on succinate the levels of catechol 1,2-oxygenase and catechol 2,3-oxygenase were similar to those observed after the addition of salicylate. Furthermore, two structural analogues of salicylate, 2-aminobenzoic acid and 2-hydroxybenzyl alcohol, induced naphthalene oxygenase gratuitously. Therefore salicylate is probably the inducer of naphthalene oxygenase.

Abstract: Summary: Only small numbers of fungi were found in the rumen fluid of cattle cultured on agar plates at 39°C, the counts being up to 3500 yeast colonies/ml, with a similar number of mould colonies. However, considerably larger numbers of yeast colonies appeared on plates incubated at 25°C. Nine species of yeasts were isolated belonging to Candida (including corresponding species of Pichia), Trichosporon, Torulopsis, Kluyveromyces, Saccharomycopsis, and Hansenula. The predominating species were Candida krusei, Trichosporon cutaneum and Trichosporon capitatum. The most common moulds were members of the Mucoraceae, of which Absidia corymbifera, A. ramosa, and Mucor pusillus were identified. Aspergillus fumigatus was isolated frequently. The fungal content of rumen fluid seemed to be dependent on the diet of the animal, and no particular fungal flora could be associated with the rumen per se. The predominating Candida krusei, and also the rarely-isolated species Torulopsis pintolopesii and Kluyveromyces bulgaricus, could reproduce under anaerobic conditions in vitro, but another commonly occurring yeast, Trichosporon capitatum, was unable to grow under the same conditions. The majority of yeast cells were obviously destroyed during passage through the alimentary tract, whereas large quantities of moulds could be excreted in a viable state.

Abstract: Summary: The production of bacitracin by Bacillus licheniformis closely paralleled growth in a synthetic medium without glucose. Glucose inhibited bacitracin production during the first hours of growth, whereas growth was not affected. Bacitracin was produced mainly during the later stages of growth. Formation of bacitracin was apparently not under catabolite repression control by glucose since the inhibitory effect of glucose upon the early bacitracin production was prevented by neutralizing the culture fluid with CaCO3. The inhibitory effect of glucose may be due to the low pH created by its metabolism. Addition of 0.5% glucose markedly increased the maximum titre of bacitracin. This stimulation could also be due to the effect of glucose metabolism upon the pH of the medium. The observation that peptide antibiotics are produced mainly after growth is not always true; in appropriate media they might also be produced during the phase of rapid growth.

Abstract: Summary: A survey of phenol-water extracts of 17 different Fusobacterium and Bacteroides species, including subspecies, and of Leptotrichia buccalis has been carried out using colorimetric and chromatographic techniques to demonstrate the presence of heptose and 2-keto-3-deoxy-octonate. Both sugars were found in the water phase of the extracts from Fusobacterium strains and Leptotrichia buccalis. Neither heptose nor 2-keto-3-deoxy-octonate were detected in the water or the phenol phase of extracts from strains classified as Bacteroides.

Abstract: Summary: Examination of thin sections of sporulating wild-type colonies revealed new structural details of the development of the sporulation-septum walls. Spores with very thick (about 75 nm) three-layered walls were seen in spore preparations. Of the sporulation defective (whi) mutants examined, whiDI6 was defective in spore-wall thickening while whiF99 was defective in rounding up and produced rod-shaped, thick-walled spores. A third mutant (whi-92) showed occasional abnormality in sporulation-septum spacing and produced immature as well as mature spores. One mutant (whi-53) produced only a few spores, all structurally normal. In two whiE mutants, structural abnormalities in spores were absent or rare.