Some observations on the nature of reactive groups involved in reversal of mycobacillin inhibition by sterols and lipids

Antifungal action of di- and triacetyl derivatives of mycobacillin is not antagonised by cholesterol or lecithin which antagonise the action of its heptamethyl derivative. Considering the reactive groups of mycobacillin, the antagonism may involve the tyrosine hydroxyl groups of the antibiotic and the 3-hydroxyl group of cholesterol of the oleic acid component of lecithin having unsaturation at the 9:10 position with cis-configuration.

Evaluation of mycobacillin and versicolin as agricultural fungicides. III. Growth pattern and antibiotic production in soil by Aspergillus versicolor

Soil supports the growth of a jute pathogen Colletotrichum gloeosporioides but only to a limited extent that of its antagonist Aspergillus versicolor. The growth of the sensitive pathogen is considerably checked by the antagonist in mixed soil culture although versicolin production could not be demonstrated within the limits of assay. Both the sensitive and the antagonistic organisms grow well in soil-compost medium and versicolin production by the latter is also enhanced. The antagonistic effect of Aspergillus versicolor on Colletotrichum gloeosporioides is expectedly more marked in soil-compost medium than in soil medium.

Evaluation of mycobacillin and versicolin as agricultural fungicides. II. Stability in soil

The effect of paddy soils on mycobacillin and versicolin was investigated. Soil inactivated mycobacillin as determined by spectral analysis and microbiological assay. Soil can inactive mycobacillin only at or above the threshold concentration (125 approximately 130 mug per 10 mg of soil), the excess being unreacted. No new peak appears in the ultraviolet spectrum (240 approximately 300 nm) while mycobacillin is inactivated. Soil is without any effect on versicolin.

In vitro and in vivo evaluation of versicolin, an antifungal antibiotic

Versicolin is mainly active against Trichophyton rubrum. It is inactivated by serum. However, attainable blood level can be fifteen to twenty times higher than the fungicidal concentration for as long as 4 hours after a single intravenous administration of the maximum tolerable dose of 25 mg/kg body weight of mouse. It has no haemolytic activity like other polypeptide antibiotics. Skin does not show the presence of any measurable amount of the antibiotic. It is excreted through urine to the extent of 65% of the maximum tolerable dose of the antibiotic administered intravenously. Versicolin is effective against experimental infection by T. rubrum in guinea pigs at dose as low as 2.5 mg/kg body weight. The antibiotic shows no sign of subacute toxicity at these curative doses.

Evaluation of mycobacillin and versicolin as agricultural fungicides. I. Antifungal spectrum and phytotoxicity

Two antifungal antibiotics, mycobacillin and versicolin, were studied as agricultural fungicides in the control of fungal infection of rice and jute. Mycobacillin is especially active against Piricularia oryzae at a concentration of 10 mug/ml, and versicolin against Colletotrichum gloeosporioides at a concentration of 2.5 mug/ml. Mycobacillin has no adverse effect on germination of seeds and growth of seedlings of rice and jute plants as a concentration of 500ppm, even for prolonged exposure. (24 or 48 hours); in fact, it is stimulatory. On the other hand, versicolin has showed detectable phytotoxicity at 500ppm for prolonged exposure

Requirement for cellular protein synthesis in reversal of ethidium-bormide-induced inhibition of cell transformation by murine sarcoma virus

Cultures of mouse Balb 3T3 fibroblasts exposed to a noncytotoxic dose of ethidium bromide for 16-18 hr are unable to produce foci after infection with murine sarcoma virus. Such cultures regain susceptibility to infection when incubated for 6-8 hr in drug-free growth medium. Pretreated but not untreated cultures exhibit sensitivity toward brief (6 hr) exposure to cycloheximide, chloramphenicol, and actinomycin D before infection. Pretreatment with cordy-cepin inhibits the ability of cultures to produce foci after infection. The recovery of ethidium-bromide-treated cultures requires the synthesis of cellular proteins which may have some important role in the establishment of RNA tumor virus infection.

Growth-and density-dependent inhibition of deoxyglucose transport in Balb 3T3 cells and its absence in cells transformed by murine sarcoma virus

The earliest measurable parameter that shows density-dependent inhibition is the uptake of [(3)H]deoxyglucose by Balb 3T3 cells. The rate decreases even during the exponential phase of growth and reaches a minimum, about 8- to 10-times lower than maximum, as the culture approaches the saturation density. Cells transformed by murine sarcoma virus fail to show either growth-dependent or density-dependent inhibition of deoxyglucose uptake. Treatment with dibutyryl cyclic AMP in the presence of theophylline results in premature cessation of growth and in an arrest in the decline of deoxyglucose transport. Culture in serum-deficient medium also produces rapid inhibition of growth at low cell density, but these cultures exhibit a markedly decreased rate of deoxyglucose uptake.

Stereoconfiguration of amino acids in peptides from a mycobacillin-synthesizing cell-free system

The stereoconfiguration of amino acids, as determined by treatment with L-amino acid oxidase, d-amino acid oxidase and l-glutamate decarboxylase (containing l-aspartate decarboxylase activity), in the peptides from a mycobacillin-synthesizing cell-free system is identical with that of the growing mycobacillin peptide chaid if its synthesis starts from l-proline and is interrupted at various points by amino acid deprivation.

Peptides from a mycobacillin-synthesizing cell-free system

In a cell-free system from Bacillus subtilis B(3), ATP-P(i) exchange was catalysed by l-proline at a pH optimum of 7.2. Further stimulation by component amino acids of mycobacillin was inhibited by deprivation from the synthesizing system of even a single amino acid occurring at any point of the cyclic peptide. This inhibition, however, decreased with the distance in the molecule of the given amino acid from l-proline. Peptides containing respectively two, three, four, five and six amino acids were isolated from the mycobacillin-synthesizing system by an amino acid-deprivation technique. The amino acid composition of these peptides and also their N- and C-terminal amino acid residues were the same as those of peptides that would be obtained if mycobacillin synthesis occurred starting from l-proline and was interrupted at various points along the polypeptide chain.

Gamma-glutamyl and D- or L-peptide linkages in mycobacillin, a cyclic peptide antibiotic

Mycobacillin lacks amino groups but contains two free alpha-carboxyl groups, indicating the presence of two side-chain peptide linkages. The five aspartic acid residues of mycobacillin are all in alpha-peptide linkage whereas the two glutamic acid residues are in gamma-linkage. Mycobacillin does not react with hydroxylamine to give hydroxamate, indicating the absence of anhydride, lactone and ester linkages. This is also confirmed by i.r. spectroscopy and titration of the molecule. Of the 15 peptides obtained from partial hydrolysates of mycobacillin, 12 contain aspartic acid. Results obtained by treatment of hydrolysates of aspartic acid-containing peptides with d-amino acid oxidase and l-glutamate decarboxylase (containing l-aspartate decarboxylase activity) indicate that residue 5 is l-aspartic acid and residues 2, 8, 11 and 13 are d-aspartic acid. The d- or l-peptide sequence and nature of peptide linkages in mycobacillin are proposed on the basis of these findings and the amino acid sequence reported earlier.

Bacteriophage-induced inhibition of host functions. II. Evidence for multiple, sequential bacteriophage-induced deoxyribonucleases responsible for degradation of cellular deoxyribonucleic acid

Degradation of bacterial deoxyribonucleic acid (DNA) after infection with T4 bacteriophage was studied in an endonuclease I-deficient host. The kinetics of degradation were similar to those seen in other hosts with a normal level of this enzyme. Irradiation of extracellular phage with ultraviolet (UV) destroyed the capacity of the infecting virus to induce extensive breakdown of host DNA, which was, however, converted to high-molecular-weight material. Addition of chloramphenicol to T4-infected cells provided data which can be interpreted to indicate the involvement of at least two endodeoxyribonucleases and one exodeoxyribonuclease having a high degree of specificity. A model is proposed showing the sequential action of two endodeoxyribonucleases followed by an exodeoxyribonuclease in the degradation of host DNA. The appearance of these hydrolytic enzymes requires protein synthesis. Infections leading to partial degradation only (UV-irradiated phages, gene 46 mutants) effectively inhibited the synthesis of bacterial messenger ribonucleic acid and of beta-galactosidase.

Studies on versicolin, a new antifungal antibiotic from Aspergillus versicolor. II. Isolation and purification

Versicolin is a new antifungal agent isolated from the culture broth of a new strain of Aspergillus versicolor. The antibiotic is specifically active against pathogenic fungi, particularly Trichophyton rubrum which causes 90% of the skin infections occurring in Calcutta and eastern India.

Bacteriophage-induced inhibition of host functions. I. Degradation of Escherichia coli deoxyribonucleic acid after T4 infection

The kinetics of degradation of bacterial deoxyribonucleic acid (DNA) after infection of Escherichia coli with T4D, ultraviolet-irradiated T4D, and two amber mutants, N122 and N94, was studied by zone sedimentation through linear glycerol gradients. Within 5 min after infection with any of the bacteriophages, breakdown of host genome was evident. The first product was a high-molecular-weight material (50S to 70S) and further degradation appeared to occur in discrete steps. Rapid and extensive breakdown of bacterial DNA was seen after infection with am N122 and T4D. Infection with ultraviolet-irradiated phage or with am N94 resulted in an accumulation of high-molecular-weight material. These results suggest that the observed degradation of host DNA begins early and requires sequential action of several phage-induced endo- as well as exodeoxyribonucleases.

Mutagens for regeneration of an antibiotic-producing strain of Aspergillus versicolor

The individual colonies of a partially degenerated culture of Aspergillus versicolor vary widely in their ability to produce an antibiotic active against Trichophyton rubrum. Mutagenic treatment with nitrous acid or ultraviolet light gave potent colonies. Nitrous acid gave better results in terms of stability and yield. This treatment may therefore prove useful in the regeneration of partially degenerated cultures.