Plasmids - from single cell dynamics to overall marine population

Plasmids are among the most numerous self-replicators in the biosphere, with most bacteria containing several types of plasmid and each type being present in several copies. In nature, plasmids promote themselves virulently by conjugating into neighboring cells and symbiotically by promoting host survival in adverse environments. These activities are largely responsible for their evolutionary and ecological roles - plasmids are a major contributor for horizontal gene transfer between species and serve as a reservoir of genes for quick adaptation of the host to unknown types of stress and conditions. Plasmids are also used as a basic tool in molecular biology and biotechnology, serving as cloning vectors and/or expression vectors. Here we present two different studies of plasmids at two different levels – a study of plasmids’ maintenance systems at the single cell level and a population study at the environmental level.

For studying plasmids at the single cell level, we developed assays for measuring plasmids copy number distributions and partitioning statistics and found that plasmids are doing surprisingly better than expected to avoid plasmid lose.

For studying plasmids at the environmental level, we reanalyzed available metagenomics data of marine samples from the Red Sea. This data was collected with microbial genomes in mind and no purification and/or plasmid DNA amplification was done before sequencing. Nevertheless, with our analysis we were able to identify plasmids within the samples. Most of the plasmids found in the samples are novel plasmids which were not identified before.