Self-resistance Mechanism Research Articles

Isolation of 3′- O-Acetylchloramphenicol: A possible intermediate in chloramphenicol biosynthesis

3′- O-Acetylchloramphenicol, commonly formed from chloramphenicol by resistant bacteria, has been isolated from the antibiotic-producing organism. Biosynthetic experiments suggest that it is a protected intermediate in chloramphenicol biosynthesis, implicating acetylation as a self-resistance mechanism in the producing organism.

5 クロイソカイメンの自己防御機構に関わるオカダ酸結合タンパク質(口頭発表の部)

5 クロイソカイメンの自己防御機構に関わるオカダ酸結合タンパク質(口頭発表の部)

Characterization of the fomA and fomB gene products from Streptomyces wedmorensis, which confer fosfomycin resistance on Escherichia coli.

Together, the fomA and fomB genes in the fosfomycin biosynthetic gene cluster of Streptomyces wedmorensis confer high-level fosfomycin resistance on Escherichia coli. To elucidate their functions, the fomA and fomB genes were overexpressed in E. coli and the gene products were characterized. The recombinant FomA protein converted fosfomycin to fosfomycin monophosphate, which was inactive on E. coli, in the presence of a magnesium ion and ATP. On the other hand, the recombinant FomB protein did not inactivate fosfomycin. However, a reaction mixture containing FomA and FomB proteins converted fosfomycin to fosfomycin monophosphate and fosfomycin diphosphate in the presence of ATP and a magnesium ion, indicating that FomA and FomB catalyzed phosphorylations of fosfomycin and fosfomycin monophosphate, respectively. These results suggest that the self-resistance mechanism of the fosfomycin-producing organism S. wedmorensis is mono- and diphosphorylation of the phosphonate function of fosfomycin catalyzed by FomA and FomB.

Reevaluation of the Final Steps in the Biosynthesis of Blasticidin S by Streptomyces griseochromogenes and Identification of a Novel Self-Resistance Mechanism

The final steps in the biosynthesis of the antifungal peptidyl-nucleoside blasticidin S ( 3) have been revised to include a novel self-resistance mechanism wherein the previously proposed final precursor, demethylblasticidin S ( 7), is modified with a leucine residue yielding leucyldemethylblasticidin S ( 10) which exhibits reduced antibiotic activity. Methylation of 10 yields leucylblasticidin S ( 9) which can be exported from the bacterium and hydrolyzed to 3. Also disclosed is the finding of a blasticidin S N-acetyltransferase activity that may function to detoxify 3 and 7 inadvertently produced prior to export or which gain reentry to the cell.

Biosynthesis of Desosamine: Molecular Evidence Suggesting β-Glucosylation as a Self-Resistance Mechanism in Methymycin/Neomethymycin Producing Strain, Streptomyces venezuelae

Biosynthesis of Desosamine: Molecular Evidence Suggesting β-Glucosylation as a Self-Resistance Mechanism in Methymycin/Neomethymycin Producing Strain, <i>Streptomyces venezuelae</i>

Streptomycin biosynthesis and self-resistance mechanism in streptomycin-producing Streptomyces griseus.

Streptomycin biosynthesis and self-resistance mechanism in streptomycin-producing Streptomyces griseus.

Streptogramins-inactivating activity in three producer streptomycetes

The mechanism of self-resistance in three streptogramins-producing streptomycetes was analysed. The three organisms had ribosomes which were sensitive both to A- and B-components of the streptogramin complex. However, cell-free extracts of these producers showed streptogramins-inactivating activity which was independent on the addition of exogenous cofactors (S-adenosylmethionine, ATP or acetyl coenzyme A). The activity was retained by the extracts after dialysis and inactivated by boiling, indicating the presence of enzymatic activity. The inactivating activity was found throughout the growth cycle of the organisms indicating a constitutive nature.

Streptogramins-inactivating activity in three producer streptomycetes

The mechanism of self-resistance in three streptogramins-producing streptomycetes was analysed. The three organisms had ribosomes which were sensitive both to A- and B-components of the streptogramin complex. However, cell-free extracts of these producers showed streptogramins-inactivating activity which was independent on the addition of exogenous cofactors (S-adenosylmethionine, ATP or acetyl coenzyme A). The activity was retained by the extracts after dialysis and inactivated by boiling, indicating the presence of enzymatic activity. The inactivating activity was found throughout the growth cycle of the organisms indicating a constitutive nature.

Self-resistance of a Streptomyces which produces istamycins.

Streptomyces tenjimariensis SS-939, a producer of istamycins, is highly resistant to its own antibiotics and grows in Tryptic Soy Broth containing istamycin A or B at 3,000 microgram/ml. No istamycin-inactivating enzyme was detected in extracts of strain SS-939. Polyphenylalanine synthesis in an in vitro system, consisting of the S-150 fraction and ribosomes prepared from strain SS-939, was not inhibited by 200 microgram/ml of istamycins. Using reciprocally reconstituted systems consisting of S-150 fractions and ribosomes from strain SS-939 and those from Streptomyces griseus ISP5236 (istamycin-sensitive strain), ribosomes of strain SS-939 were found to be resistant to istamycins. Thus, ribosomes have the main role in the self-resistance mechanism of S. tenjimariensis SS-939.