[The increase of plasmid DNA copy number is a possible mechanism of the amplification of bacteria anti-lysozyme activity under the effect of chloramphenicol].
OBJECTIVE
Determination of copy number dynamics of plasmid DNA and anti-lysozyme activityunderthe influence of chloramphenicol in cells of Escherichia coli 252 and 242 strains (ICIS), that have identical biochemical profile and differ by antibiotic resistance, plasmid profile and level of anti-lysozyme activity.


METHODS
E.coli strains were isolated during screening of antibiotic resistant enteric bacteria of human intestinal biotope. The selected strains were cultivated in medium with 0.17; 0.5; 1 and 1.5 MIC of chloramphenicol by nonspecific amplification ofplasmid DNA in medium with chloramphenicol (technique by T. Maniatis et al.). Plasmid DNA was recovered by alkaline lysis method with subsequent electrophoresis in agarose gel. The quantity ofplasmid DNA was evaluated by comparison of luminescence intensity of marker and experimental DNA sample bands. Anti-lysozyme activity was measured photometrically (O.V.Bukharin et al.).


RESULTS
E. coli 252 strain had higher direct correlation of bacteria anti-lysozyme activity and increase of plasmid copy number per cell (r > or = 0.9) during increase of chloramphenicol concentration in sub-bacteriostatic range. Dynamics of these parameters in E. coli 242 control strain were not detected.


CONCLUSIONS
The data obtained give evidence in favor of the action of plasmid localized "gene dose" effect as a mechanism of anti-lysozyme activity increase of bacteria under the influence of chloramphenicol.
S V
SV
Andriushchenko
O V
OV
Bukharin
N B
NB
Perunova
E V
EV
Ivanova
D002701:Chloramphenicol / Q000494:pharmacology; D003470:Culture Media; D004269:DNA, Bacterial / Q000235:genetics*; D024881:Drug Resistance, Bacterial; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D018628:Gene Dosage; D006801:Humans; D008826:Microbial Sensitivity Tests; D009113:Muramidase / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*
D003470:Culture Media; D004269:DNA, Bacterial; D002701:Chloramphenicol; D009113:Muramidase