To see if horizontal gene transfer was occurring, they tested the bacteria in the stools of the seven using colostomy bags before and six hours after the GM meal for the presence of the transgene. The wet bowel samples contained c.1 million bacteria per gram.
They could not detect any transgenes in the gut bacteria using normal PCR methods. However, after multiplying the bacteria in a broth to make detection more sensitive, they found that, in three of the seven volunteers, they had taken up a fragment of the transgenic epsps gene (conventional culture techniques cannot recover more than a tiny minority of the microbes in the gastrointestinal tract).
The frequency of the transfer was low: 1-3 copies of the transgene fragment per million bacteria. None contained the entire transgene. The researchers say that the levels of transgene in the bacteria were similar in the samples before and after the GM meal (though no data for the latter is given). Sequence analysis confirmed that the transgenic material was identical to the GM plant transgene, rather than the bacterial one, confirming that the source was GM. Interestingly, they could not detect any transfer of one of the native genes in soya, that for lectin. None of the bacteria sampled from the stools of subjects with complete intestinal tracts contained the transgene.