The technology was introduced by a team of researchers including Charles Peter Romaine and Xi Chen at Penn State.

As part of the study, scientists developed a technique to genetically modify Agaricus bisporus, which is the predominant edible species worldwide by attaching a gene that confers resistance to hygromycin, an antibiotic, to circular pieces of bacterial DNA called plasmids, which have the ability to multiply within a bacterium known as Agrobacterium.

The hygromycin resistance gene was a marker gene to help sort out the transgenic mushroom cells from the non-transgenic cells.

Scientists then cut small pieces off the mushroom's gill tissue and added it to a flask containing the altered bacterium. Over the course of several days, as the bacterium went through its lifecycle, it transferred a portion of its plasmid into the mushroom cell, and integrated the introduced gene into the chromosome of the mushroom.

The researchers then exposed the mushroom cells to hygromycin. The antibiotic killed all the normal cells, separating out those that had been genetically altered for resistance.

The study demonstrated that if a second gene, insulin for example, were to be patched in the plasmid, that gene would be expressed as well.

"There is a high probability that if the mushroom cell has the hygromycin resistance gene, it will also have the partner gene," Romaine said.