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 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.
Interfakultaeres Institut für Mikrobiologie und Infektionsmedizin Tuebingen IMIT, Mikrobiologie/Biotechnologie, Eberhard Karls Universitaet Tuebingen, Auf der Morgenstelle 28, 72076 Tuebingen, Germany.
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Interfakultaeres Institut für Mikrobiologie und Infektionsmedizin Tuebingen IMIT, Mikrobiologie/Biotechnologie, Eberhard Karls Universitaet Tuebingen, Auf der Morgenstelle 28, 72076 Tuebingen, Germany. Electronic address: gmuth@biotech.uni-tuebingen.de.
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D001426:Bacterial Proteins / Q000378:metabolism; D002876:Chromosomes, Bacterial; D003227:Conjugation, Genetic; D004269:DNA, Bacterial; D005819:Genetic Markers; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology*; D006801:Humans; D025282:Mycelium; D010957:Plasmids / Q000235:genetics; D013302:Streptomyces / Q000502:physiology*; D000069319:Type IV Secretion Systems / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005819:Genetic Markers; D000069319:Type IV Secretion Systems; C082576:traB protein, Bacteria
Conjugation; FtsK; Plasmid transfer; Streptomyces; T4SS