Biomedical subjects

A Petris

Publications and source records attributed to A Petris.

26 records · Page 2Linked to original sources

PubMed1988

Triparental crosses in Streptomyces coelicolor A3(2) as a means of demonstrating the de-repression of SCP1 plasmid conjugative functions.

A conjugative plasmid free in the cytoplasm promotes recombination if it is transferred to two plasmid-less strain in triparental crosses of Streptomyces coelicolor. The recombination frequency is the same as that of biparental crosses between a plasmid-bearing and a plasmid-less strain. The "conjugative" functions of the plasmid are responsible for recombinant formation. Hyphal contact and subsequent heterokaryon formation are necessary but not sufficient steps for the recombinant process. This paper shows that the presence of a conjugative plasmid is necessary for chromosome mobilization and subsequent recombinant formation.

Conjugation, Genetic↗

PubMed1978

Chloramphenicol resistance in Streptomyces coelicolor A3(2): possible involvement of a transposable element.

The transfer of a Chl element, causing resistance to chloramphenicol in Streptomyces coelicolor A3(2), was studied in NF x SCP1- superfertile crosses. When the Chl element is on the donor side (NF) its transfer to the recombinant cells was virtually total as if the element acted as a second concomitant transfer origin. When the Chl element was on the recipient side (SCP1-) it was never displaced by the immigrant chromosome even when the region facing chl+ was selected for. A fraction of the original Chl- mutants presented a requirement for arginine (ArgB-). A Chl- mutant gave rise spontaneously to ArgB- derivatives at high frequency. The same ArgB- requirement come out at high frequency among Chl- derivatives from a cross NFChl- x SCP1-Chl+ in which neither parent required arginine or produced spontaneously arginine-less derivatives. It is suggested that the Chl element is a "transposable element" (Tn) presumably associated with "insertion sequences" (IS). The insertional inactivation of the Chl element may be accompanied or followed by a deletion in the adjacent ArgB gene.

Arginine↗

PubMed1977

A factor involved in chloramphenicol resistance in Streptomyces coelicolor A3(2): its transfer in the absence of the fertility factor.

An element controlling chloramphenicol resistance (chl) was detected in Streptomyces coelicolor A3(2). Strains sensitive to 1 microgram chloramphenicol ml-1 were obtained among dark scarlet variants. Transfer of the resistance factor was attempted in matings between chloramphenicol-resistant (Chl+) and chloramphenicol-sensitive (Chl-) strains, both of which lacked the SCP1 fertility factor. Transfer of chl was obtained at a much higher rate than that expected for chromosomal markers in SCP1- X SCP1- matings. However, in these particular crosses the latter was also several times higher than usual. All recombinants for chromosomal markers were Chl+. Attempts to locate the chl element failed to distinguish between a chromosomal and an extrachromosomal site. The observed increase in the recombination frequency for chromosomal markers suggests that the chl element may promote recombination.

Chloramphenicol↗

PubMed1975