The following is an excerpt.
A team of scientists from the University of Maryland School of Medicine has found the strongest evidence yet that bacteria occasionally transfer their genes into human genomes, finding bacterial DNA sequences in about a third of healthy human genomes and in a far greater percentage of cancer cells. The results, published today (20 June) in PLOS Computational Biology, suggest that gene transfer from bacteria to humans is not only possible, but also somehow linked to over-proliferation: either cancer cells are prone to these intrusions or the incoming bacterial genes help to kick-start the transformation from healthy cells into cancerous ones.
Read the full story here: Bacterial DNA in Human Genomes