- Volume 121, Issue 1, 1980
Volume 121, Issue 1, 1980
- Articles
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Peptide Uptake in Candida albicans
More LessTransport of radioactively labelled peptides has been used to characterize a common transport system for di- and tripeptides in Candida albicans. This permease is energy-dependent and has a requirement for l-amino acid residues, an α-linkage between residues and a free amino terminus. Transport was followed by the accumulation inside the cell of intact peptides and component amino acids. After transport of glycyl-[U-14C]phenylalanine the radioactive material was accumulated inside the cell and subsequently leaked into the medium under certain conditions.
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Selection of Pseudomonas putida Strains with Elevated Dehalogenase Activities by Continuous Culture Growth on Chlorinated Alkanoic Acids
More LessA continuous-flow culture selection experiment was designed to obtain mutants of Pseudomonas putida strain PP3 capable of growing on 2-monochlorobutanoic acid (2MCBA), normally unable to act as a carbon and energy source for P. putida PP3. The experiment involved continuous exposure of P. putida PP3 to 2MCBA whilst the population's growth was supported by the metabolizable substrate, 2-monochloropropionic acid. The system failed to select for mutants able to grow on 2MCBA alone. However, the procedure resulted in the selection of two different strains of P. putida, namely, PP309 and PP310, both stably maintained as a mixed culture having excluded the parent strain. The two mutants differed significantly from P. putida PP3 with respect to their dehalogenating system since it was found that major changes in both dehalogenase specific activities and overall activity ratios had occurred. The dehalogenase system in P. putida strains PP309 and PP310 was inducible as in the parent strain. The results obtained were explained in terms of elevated production of fraction I dehalogenase compared with fraction II dehalogenase in the mutant strains in contrast to the parent strain. The results demonstrate that mutants may be selected showing altered enzyme activities in the absence of acquiring the capacity to grow solely on a novel substrate which provided the selection pressure.
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Antigenic Heterogeneity Associated with Pilus Aggregation and Autoagglutinability in Neisseria gonorrhoeae
More LessA type-specific antigen of Neisseria gonorrhoeae was previously demonstrated by two-dimensional immunoelectrophoresis, and was produced by strains adapted to growth in subcutaneous chambers in guinea pigs. This antigen was also present in ‘smooth’ (non-autoagglutinating) variants selected directly from the first agar cultures of three clinical isolates, without chamber passage. The type-specificity of this antigen paralleled the reactions of pili in immune electron microscopy, suggesting that the type-specific antigens were pili. However, ‘rough’ (autoagglutinating) variants lacking this type-specific antigen were nevertheless pilated. Examination of one strain by immune electron microscopy showed that the pili of the rough variant differed antigenically from those of the smooth variant. Pili on the rough variant tended to form extensive parallel aggregates, whereas pili on the smooth variant radiated individually from the gonococci. This physical difference might relate to the behaviour of the gonococci in suspension. The significance of pilus variation in immunity to gonococcal infection is discussed.
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Generalized Transduction in Bacillus thuringiensis var. berliner 1715 using Bacteriophage CP-54Ber
More LessA phage isolated from lysates of phage CP-54 grown on Bacillus cereus 569 and selected on the basis of its ability to infect Bacillus thuringiensis var. berliner 1715 (serotype I) was designated CP-54Ber. Phages CP-54Ber and CP-54 were similar in size, morphology, cryosensitivity and stabilization by dimethyl sulphoxide. They showed significant differences with regard to inactivation by specific antiserum, adsorption to the berliner strains and host range. Phage CP-54Ber was able to mediate generalized transduction in the host strain berliner 1715 with frequencies ranging between 1×10−5and 1×10−6. Cotransduction of markers was demonstrated. Cross-transduction occurred between strains belonging to serotype I whereas it was more difficult to observe when lysates were prepared on strains from other serotypes.
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Mutation Induction in the Cyanobacterium Gloeocapsa alpicola
More LessThe lethal and mutagenic effects of ultraviolet light (u.v.), ethyl methanesulphonate (EMS), methyl methanesulphonate (MMS), N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) and mitomycin C on the unicellular cyanobacterium Gloeocapsa alpicola have been investigated. Mitomycin C and EMS did not significantly increase the frequency of streptomycin-resistant mutants above the spontaneous level. MNNG and MMS produced increases of 10 to 30 times the spontaneous frequency. Contrary to previous reports on mutation induction in cyanobacteria, u.v. was the most effective mutagen, increasing the spontaneous mutation frequency 4000-fold. However, since photoreactivating light eliminated most of this mutagenic response it was necessary to rigorously exclude light of wavelengths < 550 nm during post-irradiation growth. Caffeine failed to increase the mutation frequency of u.v.-irradiated cultures, but cells were more sensitive to u.v. killing in the presence of caffeine.
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Evidence for More Than One Mechanism of Plasmid-determined Tetracycline Resistance in Escherichia coli
More LessThe basis of tetracycline resistance mediated by TetA determinants and joint resistance to tetracycline and minocycline coded by TetB determinants was investigated. The TetA class of determinants was represented by those carried on plasmids pSC101, RP1 and pIP7 and TetB by Tn10. The relationships between expression of tetracycline and minocycline resistance and accumulation of these antibiotics suggest that there are three mechanisms of plasmid-determined resistance conferring (1) about a 10- to 20-fold increase in resistance to tetracycline that is not associated with decreased antibiotic accumulation, (2) a 4- to 7-fold increase in resistance to tetracycline that is associated with decreased drug accumulation, and (3) about a 2- to 3-fold increase in resistance to both tetracycline and minocycline that is not associated with decreased accumulation of either antibiotic. Mechanism 1 was coded by the tetracycline resistance determinant of pSC101 (TetA), mechanisms 1 and 2 by the determinants in RP1 and pIP7 (TetA) and all three mechanisms by Tn10 (TetB).
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DNA Content of Germinating Spores, Individual Hyphal Cells and Resting Structure Cells of Verticillium spp. Measured by Microdensitometry
More LessUsing microdensitometry, the cell cycle was investigated in large populations (500) of Feulgen-stained nuclei in conidia, hyphae and resting structures of various strains (all haploid) of Verticillium albo-atrum and V. dahliae as well as a stable diploid strain, V. dahliae var. longisporum. When uninucleate conidia, harvested from 3 d Roux bottle agar cultures, were incubated in stationary liquid complete medium at 24 C in the dark, they exhibited partial synchrony for germ-tube emergence (50% emergent at about 7 h, reaching 95% at 10 to 12 h), DNA replication (50% increase at about 7.5 h) and mitosis (50% at about 10 h, reaching 95% at 12 h); the second nuclear division occurred at 21 to 24 h. Significant amounts of DNA replication were not detected until 6 h; maximum levels, i.e. a doubling of DNA content (in nuclei not yet divided), occurred at 10 h. There was a 3 h G1 phase between the first and second nuclear divisions; the S and G2 phases were estimated at about 30 and 90 min duration, respectively. The absolute DNA content per nucleus for ungerminated conidia of one strain of V. dahliae was found to be 0.025 to 0.030 pg. In growing hyphae, only the apical cell(s) contained two or more nuclei; DNA levels approximated to those for ungerminated conidia (G1) but a small number of nuclei had begun the S phase. In hyphal tip regions comprising up to 10 cells, a synchronous nuclear division was observed, and nuclei in the apical cells often had higher DNA values than other nuclei in the same hypha. Cells of young microsclerotia (6 to 8 d-old) of V. dahliae and resting mycelium (9 to 12 d-old) of V. albo-atrum were haploid and uninucleate with a small minority of the nuclei in the S phase; no evidence for diploidy or endopolyploidy was found at these sampling levels.
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- Short Communication
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Genetic Evidence for a Second Asparaginase in Aspergillus nidulans
More LessThe apnA1 mutation strongly reduces l-asparagine utilization in Aspergillus nidulans. The ahr A1 mutation, leading to loss of an l-asparaginase (Drainas et al., 1977), eliminates residual l-asparagine utilization in double mutant strains also carrying apnA1. This additivity suggests that A. nidulans, like Saccharomyces cerevisiae (Jones, 1977; Dunlop et al., 1978), has two l-asparaginases specified by apnA and ahrA, respectively. apnA has been mapped to a position on the left arm of linkage group II, in the sequence adH-acrA-apnA-wA-methA-palcA-(centromere).
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Identification of Mycobacterium leprae: Use of Wall-bound Mycolic Acids
More LessA simple method for extraction and analysis of wall-bound mycolic acids from small samples of mycobacteria is described. Separation of mycolic acid classes according to their functional groups by thin-layer chromatography showed a difference between Mycobacterium leprae and a number of strains of acid-fast bacilli cultured from leprosy biopsies in vitro. This technique is proposed as a convenient preliminary test in the identification of possible cultures of M. leprae.
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Plasmid-specified Sucrose Fermentation in Salmonella arizonae
More LessThirty cultures of Salmonella arizonae 47:r:253 (Ar 23:24–25) were isolated over 7 months from the faeces of a captive reptile. All were unusual in their inability to produce a positive o-nitrophenyl-β-d-galactosidase reaction, and in their ability to ferment sucrose. These S. arizonae carried a plasmid having a molecular mass of 72 megadaltons which specified tetracycline resistance and a plasmid of 5 megadaltons which coded for the ability to ferment sucrose. The small size of this sucrose plasmid clearly distinguishes it from others which have been reported.
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Transposable Gentamicin Resistance in IncW Plasmids from Hammersmith Hospital
More LessA transposon, Tn733, encoding the gentamicin acetyltransferase AAC(3) was found on two gentamicin R plasmids of IncW at Hammersmith Hospital. Transposon Tn733 has a molecular mass of 5·8 megadaltons and gives a characteristic 2·4 megadalton fragment on digestion with Eco RI. The appearance of gentamicin resistance on a transposon will increase the chances of spread of this gene.
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Transfer of Plasmids among Bacilli
More LessPlasmids were transferred from Staphylococcus aureus to Bacillus subtilis and between B. subtilis and several other species of Bacillus by protoplast fusion and regeneration. The plasmids replicate and express themselves normally in all bacilli examined.
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A Serological Study of a β-d-Fructofuranosidase from Sphacelia sorghi McRae
More LessAntibodies raised against a purified β-d-fructofuranosidase from Sphacelia sorghi were cross-reacted with a purified β-d-fructofuranosidase from Claviceps purpurea. An immunodiffusion test indicated a high degree of serological identity between the S. sorghi and C. purpurea enzymes. A complement fixation test confirmed this result, the similarity in titres indicating a very close structural similarity between the enzymes.
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Yeasts in the Rumen Contents of Musk Oxen
More LessThe yeast flora of 16 samples of rumen contents of musk oxen (Ovibos moschatus) from East Greenland was examined. Variable numbers of yeast colonies developed on agar plates incubated at 25°C, the counts being up to 136000 per g (wet wt). Of the 41 strains isolated, the majority belonged to Candida and Cryptococcus; others were species of Trichosporon, Rhodotorula, Torulopsis and Pichia. Very few colonies appeared on plates incubated at 37°C, and only one species of Candida was isolated. Samples of rumen contents kept at about 5°C for about 3 years contained a much greater number of yeasts, up to several million per g (wet wt) being counted on agar plates incubated at 25, 15 and 5°C. The 30 strains isolated were of only three species of Candida, and none were obligate psychrophils.
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