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Antimicrobial Agents and Chemotherapy Aug 1973Variations of inoculum, pH, and composition of the agar assay media each influenced the in vitro susceptibility of Nocardia organisms (30 strains of N. asteroides and 6...
Variations of inoculum, pH, and composition of the agar assay media each influenced the in vitro susceptibility of Nocardia organisms (30 strains of N. asteroides and 6 strains of N. brasiliensis) to one or more antimicrobial agents incorporated in solid agar and incubated at 37 C for 48 h. Among newer antimicrobial agents, doxycycline, minocycline, and 7-halogenated lincomycin analogues exhibited the most consistent in vitro inhibitory activity; among older agents, viomycin, erythromycin, and streptomycin exhibited more selective in vitro inhibitory activity, but against a significant percentage of strains tested. N. brasiliensis was conspicuously more susceptible to erythromycin and gentamicin and more resistant to viomycin and capreomycin than was N. asteroides. Cycloserine demonstrated no significant in vitro inhibitory activity when assayed in appropriately augmented alanine-free medium. The outstanding feature of this in vitro survey was the marked variation in susceptibility among individual strains of N. asteroides, which variation deserves more careful consideration in future clinical or experimental therapeutic trials.
Topics: Anti-Bacterial Agents; Culture Media; Methods; Microbial Sensitivity Tests; Nocardia; Species Specificity
PubMed: 4790942
DOI: 10.1128/AAC.4.2.85 -
Microbiology (Reading, England) Mar 1997A system for gene disruption and replacement based on a streptomycete temperate phage vector was developed to introduce DNA in the rapamycin-producing Streptomyces...
A system for gene disruption and replacement based on a streptomycete temperate phage vector was developed to introduce DNA in the rapamycin-producing Streptomyces hygroscopicus strain ATCC 29253. This will be useful in attempts to produce, through genetic manipulation, novel forms of the therapeutically important immunosuppressive drug rapamycin. Recombinant phages were constructed from the phi C31 phage derivative KC515 (C+ attp) carrying a thiostrepton or viomycin resistance gene along with segments of the S. hygroscopicus chromosome. Each of the cloned segments also contained the aphll neomycin/kanamycin resistance gene to enable gene replacement by loss of the phage-derived DNA. Specific deletion of the entire polyketide synthase (PKS) believed to govern rapamycin biosynthesis resulted in the loss of rapamycin production. In contrast, disruption or deletion of a region predicted to encode four PKS open reading frames, or another region predicted to encode another PKS plus a cytochrome P450 hydroxylase and ferredoxin, had no effect on the production of rapamycin or nigericin, a polyether antibiotic also produced by S. hygroscopicus. Therefore, S. hygroscopicus may have the capacity to produce polyketides additional to rapamycin and nigericin.
Topics: Bacteriophages; Cloning, Molecular; DNA, Bacterial; DNA, Recombinant; DNA, Viral; Gene Expression Regulation, Bacterial; Molecular Sequence Data; Polyenes; Sirolimus; Streptomyces
PubMed: 9084171
DOI: 10.1099/00221287-143-3-875 -
Microbiology and Immunology 1992Bacteriostatic and bactericidal activities of rifampicin, isoniazid, streptomycin, enviomycin and ethambutol against Mycobacterium tuberculosis, Mycobacterium avium--M.... (Comparative Study)
Comparative Study
Bacteriostatic and bactericidal activity of antituberculosis drugs against Mycobacterium tuberculosis, Mycobacterium avium-Mycobacterium intracellulare complex and Mycobacterium kansasii in different growth phases.
Bacteriostatic and bactericidal activities of rifampicin, isoniazid, streptomycin, enviomycin and ethambutol against Mycobacterium tuberculosis, Mycobacterium avium--M. intracellulare complex and Mycobacterium kansasii were studied in different growth phases. Bacteriostatic activities of the drugs were similar in different growth phases, except isoniazid. M. tuberculosis was much less susceptible to isoniazid in the lag phase than in the log and the stationary phases. In contrast, bactericidal activity was influenced by the growth phase. M. tuberculosis was killed by isoniazid, streptomycin and rifampicin. The bactericidal activity of isoniazid was strongest. The bactericidal activity of isoniazid and streptomycin was most marked in the log phase. M. avium complex and M. kansasii resisted the bactericidal activity, but some strains of M. avium complex were killed by streptomycin and enviomycin, and the activities of these two drugs were most marked in the lag phase.
Topics: Antitubercular Agents; Cell Division; Enviomycin; Ethambutol; Isoniazid; Microbial Sensitivity Tests; Mycobacterium; Mycobacterium avium Complex; Rifampin; Streptomycin
PubMed: 1406364
DOI: 10.1111/j.1348-0421.1992.tb02035.x -
Biochemistry Oct 2010The biosynthesis of many natural products of clinical interest involves large, multidomain enzymes called nonribosomal peptide synthetases (NRPSs). In bacteria, many of...
The biosynthesis of many natural products of clinical interest involves large, multidomain enzymes called nonribosomal peptide synthetases (NRPSs). In bacteria, many of the gene clusters coding for NRPSs also code for a member of the MbtH-like protein superfamily, which are small proteins of unknown function. Using MbtH-like proteins from three separate NRPS systems, we show that these proteins copurify with the NRPSs and influence amino acid activation. As a consequence, MbtH-like proteins are integral components of NRPSs.
Topics: Bacteria; Bacterial Proteins; Capreomycin; Multigene Family; Peptide Synthases; Viomycin
PubMed: 20845982
DOI: 10.1021/bi1012854 -
The Journal of Antibiotics Dec 1978
Topics: Aminoglycosides; Animals; Anti-Bacterial Agents; Brain Chemistry; Glycoproteins; In Vitro Techniques; Microtubules; Protein Binding; Swine; Tubulin; Viomycin
PubMed: 216659
DOI: 10.7164/antibiotics.31.1306 -
The British Journal of Venereal Diseases Oct 1975Motility of pathogenic T. pallidum was maintained in aerobic in vitro cultures for several weeks using a special medium. The latter consisted of McCoy's 5a medium...
Motility of pathogenic T. pallidum was maintained in aerobic in vitro cultures for several weeks using a special medium. The latter consisted of McCoy's 5a medium supplemented with glutathione, sodium pyruvate, HEPES buffer, gentamycin (garamycin), and fetal calf serum. The virulence of the organisms was lost in 5 to 6 days. No multiplication of the organisms was observed. Four antibiotics (viomycin, kanamycin, gentamycin (garamycin), and neomycin) were tested for their bactericidal action and possible toxicity to T. pallidum. Gentamycin proved to be superior to the other three antibiotics in being non-toxic to the treponemes and showing a possible stimulatory effect on their motility and longevity. Cultivation of T. pallidum in cultured cells in the presence of the enzymes, superoxide dismutase and catalase, in a special medium showed possibilities for future experimentation under monitored, reduced oxygen pressure with a continuous system to dismutate superoxide radicals.
Topics: Aerobiosis; Catalase; Cells, Cultured; Culture Media; Gentamicins; Kanamycin; Neomycin; Superoxide Dismutase; Treponema pallidum; Viomycin; Virulence
PubMed: 172190
DOI: 10.1136/sti.51.5.296 -
Microbiology and Immunology 1979
Topics: Cell-Free System; Crosses, Genetic; Drug Resistance, Microbial; Mutation; Mycobacterium; Peptide Biosynthesis; Phenotype; Recombination, Genetic; Ribosomes; Streptomycin; Viomycin
PubMed: 228160
DOI: 10.1111/j.1348-0421.1979.tb00499.x -
Molecular Microbiology Jul 2008The cytotoxin colicin E3 targets the 30S subunit of bacterial ribosomes and specifically cleaves 16S rRNA at the decoding centre, thereby inhibiting translation....
The cytotoxin colicin E3 targets the 30S subunit of bacterial ribosomes and specifically cleaves 16S rRNA at the decoding centre, thereby inhibiting translation. Although the cleavage site is well known, it is not clear which step of translation is inhibited. We studied the effects of colicin E3 cleavage on ribosome functions by analysing individual steps of protein synthesis. We find that the cleavage affects predominantly the elongation step. The inhibitory effect of colicin E3 cleavage originates from the accumulation of sequential impaired decoding events, each of which results in low occupancy of the A site and, consequently, decreasing yield of elongating peptide. The accumulation leads to an almost complete halt of translation after reading of a few codons. The cleavage of 16S rRNA does not impair monitoring of codon-anticodon complexes or GTPase activation during elongation-factor Tu-dependent binding of aminoacyl-tRNA, but decreases the stability of the codon-recognition complex and slows down aminoacyl-tRNA accommodation in the A site. The tRNA-mRNA translocation is faster on colicin E3-cleaved than on intact ribosomes and is less sensitive to inhibition by the antibiotic viomycin.
Topics: Colicins; Electrophoresis, Polyacrylamide Gel; Escherichia coli; Models, Biological; Protein Biosynthesis; RNA, Bacterial; RNA, Ribosomal, 16S; RNA, Transfer; Ribosomes
PubMed: 18485067
DOI: 10.1111/j.1365-2958.2008.06283.x -
RNA (New York, N.Y.) Jan 2016Here we report that the specificity of peptide release in the ribosome on a nonstop mRNA by ArfA and RF2 is achieved by an induced-fit mechanism. Using RF2 that is...
Here we report that the specificity of peptide release in the ribosome on a nonstop mRNA by ArfA and RF2 is achieved by an induced-fit mechanism. Using RF2 that is methylated on the glutamine of its GGQ motif (RF2(m)), we show that methylation substantially increases the rate of ArfA/RF2-catalyzed peptide release on a nonstop mRNA that does not occupy the ribosomal A site, but has only a modest effect on k(cat) by the same proteins on longer nonstop mRNAs occupying the A site of the mRNA channel in the ribosome. Our data suggest that enhancement in the kcat of peptide release by ArfA and RF2 under the cognate decoding condition is the result of favorable conformational changes in the nonstop complex. We demonstrate a shared mechanism between canonical and nonstop termination, supported by similarities in the kinetic mechanisms in antibiotic inhibition and methylation-correlated enhancement in the rate of peptide release. Despite these similarities, our data suggest that nonstop termination differs from canonical pathway in the downstream event of recycling.
Topics: Biocatalysis; Escherichia coli; Escherichia coli Proteins; Methylation; Paromomycin; Peptide Chain Termination, Translational; Peptide Termination Factors; Peptides; Protein Biosynthesis; RNA-Binding Proteins; Ribosomes; Viomycin
PubMed: 26554029
DOI: 10.1261/rna.053082.115 -
The Journal of Biological Chemistry Sep 1988According to the allosteric three-site model for the ribosomal elongation cycle (Rheinberger, H.J. and Nierhaus, K.H. (1986) J. Biol. Chem. 261, 9133-9139), two types of...
According to the allosteric three-site model for the ribosomal elongation cycle (Rheinberger, H.J. and Nierhaus, K.H. (1986) J. Biol. Chem. 261, 9133-9139), two types of A site (aminoacyl-tRNA site) occupation exist. First is the A site occupation after initiation (i-type), with only one site, the P site (peptidyl-tRNA site), being prefilled with a tRNA (initiator tRNA). Second is the A site occupation after an elongation cycle (e-type), with two prefilled sites, namely the P and E sites containing peptidyl-tRNA and deacylated tRNA, respectively. The individual reactions of the elongation cycle were tested, including both types of A site occupation in the presence of various antibiotics. A test system was used allowing the functional studies to be made with quantitative tRNA binding at 6 mM Mg2+. The following results were obtained: 1) thiostrepton (5 x 10(-6) M) induced a complete block of both EF-(elongation factor) G dependent and EF-G independent translocation, in agreement with older observations. The A-site occupation of the e-type was severely inhibited in contrast to that of the i-type. Thus, thiostrepton blocks the allosteric transitions in both directions, i.e. the transition from pre- to post-translocational state (translocation) and that from the post- to the pre-translocational state (A site occupation of the e-type). In addition the ribosomal binding of EF-G.[3H] GMPPNP was inhibited by about 60%. 2) Similarly, viomycin (5 x 10(-5) M) appears to be an inhibitor of both allosteric transitions, since it strongly inhibited the e-type (but not the i-type) A site occupation in addition to translocation. 3) The aminoglycosides streptomycin, hygromycin B, neomycin, kanamycin, and gentamicin prevented A site occupation of the e-type (residual activity below 15%). Neomycin and hygromycin, in addition, blocked the translocation reaction. Only marginal effects were observed with A site occupation of the i-type. It appears that the inhibition of the A site binding of the e-type (allosteric transition from the post- to the pretranslocational state) is the predominant effect of the misreading-inducing aminoglycosides.
Topics: Aminoglycosides; Anti-Bacterial Agents; Escherichia coli; Galactosyltransferases; Guanylyl Imidodiphosphate; Lincomycin; Magnesium; Models, Genetic; Peptide Elongation Factor G; Peptide Elongation Factors; RNA, Transfer, Amino Acid-Specific; RNA, Transfer, Phe; Ribosomes; Thiostrepton; Viomycin
PubMed: 2843509
DOI: No ID Found