Protocol measuring horizontal gene transfer from algae to non-photosynthetic organisms.

Horizontal gene transfer (HGT) is a natural process for an organism to transfer genetic material to another organism that is a completely different species, for example, from a blue-green alga to a non-photosynthetic bacterium. The phenomenon of HGT is not only of an interest to the science of molecular genetics and biology, but also to the biosafety issue of genetic engineering. The novel protocol reported here for the first time teaches how to measure HGT from a genetically engineered (GE) blue-green alga (gene donor) to wild-type (recipient). This novel protocol can be used to measure HGT frequency for both plasmid transgenes and/or genomic transgenes from a donor to recipient organism. •According to this novel protocol, the HGT frequency may be calculated from the number of HGT recipient colonies observed, the number of recipient cells plated, and the donor-recipient co-incubation time.•This approach can also help test the possible HGT routes to assess whether a HGT is through a direct cell-to-cell interaction or by an indirect cell-to-liquid environment-to-cell process.•The protocol may be applied in full and/or in part with adjustments to measure HGT for a wide range of donor and recipient organisms of interest.