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Investigation of the Directionality and Kinetics of DNA Transfer by a Bacterial Type IV Secretion System
Author(s) -
Akinleye Olukemi P.,
Gemechu Betelhem B.,
Ali Sabrina,
Berkmen Melanie B.
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.00625
Subject(s) - bacterial conjugation , plasmid , bacillus subtilis , mobilization , dna , secretion , bacteria , mating type , exogenous dna , chemistry , biology , gene , microbiology and biotechnology , biophysics , genetics , biochemistry , history , archaeology
Conjugation is the transfer of DNA from a donor cell to a recipient cell through a Type IV Secretion System (T4SS). The T4SS is encoded by the DNA conjugative element and is assembled in the donor cell membrane. T4SSs can also mediate the mobilization of resident plasmids that do not encode their own conjugation machinery from the donor to a recipient. In addition, in some cases, T4SSs have been shown to mediate retro‐transfer, or reverse mobilization, in which a donor cell containing the conjugative element receives DNA from a recipient cell. Conjugation, mobilization, and reverse mobilization are all important mechanisms of horizontal gene transfer that contribute to bacterial evolution and the spread of antibiotic resistance genes. Previously, it has been shown that the integrative and conjugative element ICE Bs1 of Bacillus subtilis exhibits very high frequencies of conjugation and plasmid mobilization. Here, we compare the timing and frequency of ICE Bs1 ‐dependent conjugation, plasmid mobilization, and reverse mobilization. Donor and recipient cells having different antibiotic markers were mixed and placed on solid filters for different periods of time to allow for DNA transfer. After incubation, the cell mixtures were plated on selective media to measure the frequency of DNA transfer. We found that both mating and plasmid mobilization can be detected within 2 minutes and peak after about 1–2 hours. Mating was generally more frequent than mobilization at most time points. Reverse mobilization was not detected until 1–2 hours, and was more than 100‐fold less frequent than mating. Reverse mobilization also required the transfer of T4SS genes to the recipient. Our data are consistent with the T4SS acting unidirectionally; in other words, reverse mobilization requires that a conjugative DNA element be transferred from donor to recipient prior to the recipient making its own T4SS that transfers DNA back into the donor. Support or Funding Information This research was supported by Suffolk University and an NSF‐RUI grant to M. Berkmen.