Anreicherung auxotropher Mutanten von Serratia marcescens mittels Antibiotica

Summary

Enrichment methods — modified penicillin-techniques — were employed for Serratia marcescens HY and CV/rc ₃. This was done because Serratia is highly resistant to penicillin. the incubation of HY cells under growth conditions in the presence of 0.04 mg colistin/ml for 8 hrs was found to be effective in inactivating the population to more than 10^-2. Auxotrophic mutants under nongrowth conditions were not affected by the antibiotic. The mutant yield of a mutagenized HY culture (NG for 15 min; nearly 80% survival) was increased from 1% to 37–70% after 8 hrs of colistin treatment. Spheroplast formation was not caused by the enrichment procedure.

Nearly the same enrichment method was elaborated for CV/rc ₃ with flavomycin, a new antibiotic produced by some strains of Streptomyces, which interacts with cell wall biosynthesis: 9 hrs of incubation in minimal-medium with 0.2 mg flavomycin/ml and following dilution in dest. H₂O rose the mutant yield from 6% to 32% after NG treatment of CV/rc ₃. Dilution in buffer-saline after flavomycin treatment was less effective because the spheroplasts produced by flavomycin are osmotically fragile.

Four monoauxotrophic HY mutants were tested for selective enrichment after colistin treatment. Selection could not be recognized. Some experiments which are only preliminary show that selection may occur after flavomycin treatment.

Zusammenfassung

Es wurden Anreicherungsmethoden für die penicillinresistenten Serratia-Stämme HY und CV/rc ₃ entwickelt. 0,04 mg Colistin/ml Mi-Medium inaktiviert wachsende HY-Zellen auf ca. 10^-2 in 8 Std, auxotrophe Zellen werden nicht getötet. Der Anteil auxotropher Zellen in einer Mischung mit Prototrophen wurde durch 8stündige Colistinbehandlung von 1% auf 35–70% gesteigert. Ähnliche Resultate wurden mit Flavomycin an CV/rc ₃ gewonnen: 9stündige Behandlung mit 0,2 mg Flavomycin/ml Mi-Medium und anschließende Verdünnung in dest. H₂O steigerten den Auxotrophenanteil von 6 auf 32%. Flavomycin erzeugt osmotisch sensible Sphäroplasten, Colistin dagegen nicht.