Bacteria transfer during sex could be the new secret weapon to uncovering perpetrators of sexual assault.

The so-called “sexome” bacteria, coined by Murdoch University forensic scientists Brendan Chapman and Ruby Dixon, will be a game-changer for sexual assault investigations.

The researchers say while everyone has the same “sexome” bacteria, an individual’s bacterial genetic code is unique and this could be used to help investigators find suspects.

Ms Dixon hopes sexome bacteria may be used one day in sexual assault cases where human DNA, such as sperm, is missing.

Because of the distinct genetic code of the bacteria, it can be linked back to a suspect, or at least eliminate other assault suspects, Ms Dixon says.

“Think of it like a packet of M&M’s,” Ms Dixon says describing how identification works.

“You know there’s six colours in each packet, so you’d think each bag is identical from the outside, but each packet has a different number of each colour, one might have five blue M&M’s, while another will have 3 blue M&M’s,” she says.

Murdoch University forensic scientists Brendan Chapman and Ruby Dixon. credit: Murdoch University

“In the case of a sexual assault, if the perpetrator doesn’t ejaculate… or uses a condom, there will be no male DNA to isolate”, Ms Dixon says.

The sexome bacteria can be found after any sexual contact between a man and woman, because ‘male bacteria’ stays on the vagina and ‘female bacteria’ will stay on the penis.

Ms Dixon says DNA swabs taken form the victim can be isolated and sequenced, then run through databases to help identify a perpetrator.

Ms Dixon also says that in some cases, the sexome bacteria can be found in female DNA even if a condom was used.

The scientists caution that the research project is still in its early stages.

The role of the sexome bacteria where there is other barrier contraceptives or in sexual assault of a homosexual nature is still being investigated.

“This research is a big step forward for forensic science and has the potential to lead to breakthroughs in cases that involve sexual assault,” Mr Chapman says.