Abstract
SummaryHorizontal gene transfer (HGT) was observed by incubation of an amino acid-deficient strain of Escherichia coli (AB1157) with particles gained from an oligotrophic environment, when all deficiencies were restored with frequencies up to 1.94 × 10−5 and no preference for a single marker. Hence, the DNA transfer to the revertant cells was carried out by generalized transduction. Those particles display structural features of outer membrane vesicles (OMVs) but contain high amounts of DNA. Due to a process called serial transduction, the revertant’s particles were likewise transferring genetic information to deficient E. coli AB1157 cells. These results indicate a new way of HGT, in which mobilized DNA is transferred in particles from the donor to the recipient. Extracted OMV-associated DNA of known alpha-, and gamma-proteobacterials, Ahrensia kielensis and Pseudoalteromonas marina, respectively, was larger than 30 kbp with all sequences in single copy and identified as prokaryotic sequences. Inserted viral sequences were not found.
Highlights
Prokaryotes are unique in reacting to environmental alterations by a fast acquisition of essential and suitable genetic characteristics
The mechanisms and vectors responsible for the horizontal DNA transfer include: 1. the uptake of free DNA from the environment, i. e. transformation, 2. the transfer of DNA from a bacterial donor cell to a bacterial recipient cell termed conjugation, 3. the phage-mediated passage of bacterial genes referred to as transduction, 4. gene shuffling by gene transfer agents (GTA), which are unusual bacteriophage-like vehicles of genetic exchange, first discovered in the bacterium Rhodobacter capsulatus [33] containing a random 4.5 kb fragment of bacterial genomic DNA [46] that can be transferred between cells [3, 22, 23, 45, 47, 51] and
In follow-up studies [7, 49] and during preparatory investigations where we inspected over 1000 transmission electron microscope (TEM) slides and investigated whether OMVs within the mentioned size fraction (>100 nm in diameter) from natural seawater would trigger the above quoted features in recipient cells, the following traits were recorded for the produced outer membrane vesicles: 1. The observed vesicles appeared already in harvestable quantities before the end of the logarithmic phase of the recipient cell culture but reached their maximum in the stationary phase (Fig. 1)
Summary
Prokaryotes are unique in reacting to environmental alterations by a fast acquisition of essential and suitable genetic characteristics. Even populations of a single 16S rRNA species contain numerous genomic varieties [11]. This genetic flexibility of the prokaryotes is based in an advantage of the horizontal gene transfer among bacteria as well as between bacteria and other organisms [26, 30]. Gene shuffling by gene transfer agents (GTA), which are unusual bacteriophage-like vehicles of genetic exchange, first discovered in the bacterium Rhodobacter capsulatus [33] containing a random 4.5 kb fragment of bacterial genomic DNA [46] that can be transferred between cells [3, 22, 23, 45, 47, 51] and The mechanisms and vectors responsible for the horizontal DNA transfer include: 1. the uptake of free DNA from the environment, i. e. transformation, 2. the transfer of DNA from a bacterial donor cell to a bacterial recipient cell termed conjugation, 3. the phage-mediated passage of bacterial genes referred to as transduction, 4. gene shuffling by gene transfer agents (GTA), which are unusual bacteriophage-like vehicles of genetic exchange, first discovered in the bacterium Rhodobacter capsulatus [33] containing a random 4.5 kb fragment of bacterial genomic DNA [46] that can be transferred between cells [3, 22, 23, 45, 47, 51] and
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