More Information on Horizontal Gene Transfer and Biotech Crops

The most likely mode of HGT from biotech crops to other organisms is transformation. Only certain microbes are naturally competent and, therefore, “transformable” under natural conditions. Therefore, the physiological state (competent or non-competent) of the recipient microbe affects the rate of transformation, in general, but should not have an impact on “preferences” for transgenes or non-transgenes. In laboratory experiments, the success of bacterial transformation with transgenic DNA drops quickly when non-transgenic DNA molecules are added to the solution; so there is no greater tendency for transgenes or non-transgenes to be taken up by microbes. The probability of uptake of a given DNA sequence depends on the concentration of the sequence in the immediate environment of the recipient cell, whether the environment is the soil around biotech crops or the intestines of organisms that have ingested transgenic material. Therefore, an important variable in determining whether a cell is more likely to be transformed with transgenic or naturally occurring DNA is their relative amounts in the cell’s immediate environment.

A transgene represents only a miniscule portion of the total DNA in the plant cell. Considering the genome size of most plants, the amount of natural DNA in a biotech plant is one million times greater than the amount of transgenic DNA. So, if one focuses only on the biotech plant, the probability of one of the natural plant genes being taken up is one million times greater than the transgene. When one adds to that the amount of DNA organisms are exposed to, whether from other soil organisms or other ingested food, the amount of transgenic DNA available for uptake becomes even more miniscule in comparison to the amount of other naturally occurring DNA. Therefore, because DNA uptake is concentration dependent, the probability of transformation via a transgene is many orders of magnitude less than that of non-transgenes.