The integrative element pSAM2 from Streptomyces: kinetics and mode of conjugal transfer

Possoz, C Ribard, C Gagnat, J Pernodet, JL Guerineau, M

C. Possoz et al., The integrative element pSAM2 from Streptomyces: kinetics and mode of conjugal transfer, MOL MICROB, 42(1), 2001, pp. 159-166

38

INGLESE

Article

Microbiology

MOLECULAR MICROBIOLOGY

0950-382X → ACNP

42

1

2001

159 - 166

ISI

0950-382X(200110)42:1<159:TIEPFS>2.0.ZU;2-U

pSAM2 is an 11 kb integrative element from Streptomyces ambofaciens that is capable of conjugal transfer. A system based on differential DNA modificat ion by SalI methyltransferase was used to localize pSAM2 in the donor or re cipient strain, and thus to determine the various steps associated with tra nsfer. Initiation (i.e. excision and replication of pSAM2 in the donor) occ urs a few hours after mating with a recipient strain. pSAM2 replicates in t he recipient strain, spreads within the mycelium and then integrates into t he chromosome. Transfer generally involves single-stranded DNA. In Streptom yces, only a few genes, such as traSA for pSAM2, are required for conjugal transfer. Using the differential sensitivity to the SalI restriction-modifi cation system of transfers involving single- and double-stranded DNA, we fo und that pSAM2 was probably transferred to the recipient as double-stranded DNA. This provides the first experimental evidence for the transfer of dou ble-stranded DNA during bacterial conjugation. Thus, TraSA, involved in pSA M2 transfer, and SpoIIIE, which is involved in chromosome partitioning in B acillus subtilis, display similarities in both sequence and function: both seem to transport double-stranded DNA actively, either from donor to recipi ent or from mother cell to prespore.