Conjugative DNA-transfer in Streptomyces, a mycelial organism

Conjugative DNA-transfer in the Gram-positive mycelial soil bacterium Streptomyces, well known for the production of numerous antibiotics, is a unique process involving the transfer of a double-stranded DNA molecule. Apparently it does not depend on a type IV secretion system but resembles the segre...

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Bibliographic Details
Published in:Plasmid 2016-09, Vol.87-88, p.1-9
Main Authors: Thoma, L., Muth, G.
Format: Article
Language:English
Subjects:
Bacterial Proteins - metabolism
Chromosomes, Bacterial
Conjugation
Conjugation, Genetic
DNA, Bacterial
FtsK
Genetic Markers
Gram-Positive Bacterial Infections - microbiology
Humans
Mycelium
Plasmid transfer
Plasmids - genetics
Streptomyces
Streptomyces - physiology
T4SS
Type IV Secretion Systems - genetics
Type IV Secretion Systems - metabolism
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Summary:Conjugative DNA-transfer in the Gram-positive mycelial soil bacterium Streptomyces, well known for the production of numerous antibiotics, is a unique process involving the transfer of a double-stranded DNA molecule. Apparently it does not depend on a type IV secretion system but resembles the segregation of chromosomes during bacterial cell division. A single plasmid-encoded protein, TraB, directs the transfer from the plasmid-carrying donor to the recipient. TraB is a FtsK-like DNA-translocase, which recognizes a specific plasmid sequence, clt, via interaction with specific 8-bp repeats. Chromosomal markers are mobilized by the recognition of clt-like sequences randomly distributed all over the Streptomyces chromosomes. Fluorescence microcopy with conjugative reporter plasmids and differentially labelled recipient strains revealed conjugative plasmid transfer at the lateral walls of the hyphae, when getting in contact. Subsequently, the newly transferred plasmids cross septal cross walls, which occur at irregular distances in the mycelium and invade the neighboring compartments, thus efficiently colonizing the recipient mycelium. This intramycelial plasmid spreading requires the DNA-translocase TraB and a complex of several Spd proteins. Inactivation of a single spd gene interferes with intramycelial plasmid spreading. The molecular function of the Spd proteins is widely unknown. Spd proteins of different plasmids are highly diverse, none showing sequence similarity to a functionally characterized protein. The integral membrane protein SpdB2 binds DNA, peptidoglycan and forms membrane pores in vivo and in vitro. Intramycelial plasmid spreading is an adaptation to the mycelial growth characteristics of Streptomyces and ensures the rapid dissemination of the plasmid within the recipient colony before the onset of sporulation. •The FtsK-like DNA translocase TraB transfers a double-stranded plasmid molecule.•TraB binds to a specific plasmid sequence clt and to clt-like sequences distributed in the Streptomyces chromosome.•Conjugative plasmid transfer takes place at the lateral walls of the hyphae.•Copies of the newly transferred plasmid spread within the recipient mycelium across septal cross walls.•Intramycelial plasmid spreading depends on a protein complex of TraB and Spd proteins.
ISSN:0147-619X
1095-9890
DOI:10.1016/j.plasmid.2016.09.004