성범죄 용의자, 머리카락 세균으로 검거 Could a bacterial ‘fingerprint’ solve a sexual assault case?
호주 연구진 “두피에 사는 세균 사람마다 달라”
(Photo by Alexandra Garcia/The Washington Post)
사람의 장내세균 중 하나인 '락토바실러스 불가리쿠스'의
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범죄 현장에 떨어진 머리카락은 범인을 잡는데 중요한 단서다. 하지만 머리카락에 들어있는 DNA의 양이 부족하거나 머리카락에 모근이 붙어있지 않다면 머리카락에서 범인의 정보를 얻기는 어렵다.
하지만 최근 이런 머리카락에서도 범인의 흔적을 발견할 수 있다는 연구 결과가 나왔다. 바로 머리카락에 남아있는 세균을 분석하는 방법이다.
호주 머독대 연구팀은 사람 몸에 사는 세균이 마치 지문처럼 사람마다 고유하다는 점에 주목했다.
연구팀은 실제로 남자 3명과 여자 4명의 두피와 음모에 사는 세균을 분석한 결과 세균의 종류와 차지하는 비율이 달라진다는 사실을 발견했다. 심지어 같은 사람이라 하더라도 부위별로 큰 차이가 났다.
남자의 두피에서는 세균이 총 50종, 여자의 경우는 55종이 나왔지만 음모에는 이보다 많은 73종(남자)과 76종(여자)이 발견됐다.
또한 연구팀은 성행위를 한 뒤 음모에 사는 세균이 옮는다는 것도 밝혔다. 이번 연구에 참여한 7명 중 2명은 동거를 하는 커플인데, 둘의 음모 세균 군집은 매우 유사했다. 또 이들이 성행위를 한 뒤 18시간 뒤에 음모에 사는 세균을 분석한 결과 연구팀은 실제로 세균이 옮아 갔다는 사실도 확인했다.
연구를 진행한 실바나 트리디코 교수는 “사람의 DNA는 옮지 않지만 세균은 전염된다”며 “몸 속에 사는 세균을 이용한 프로파일링 기법을 개발한다면 특히 성범죄에 유용할 것”이라고 밝혔다.
연구 결과는 ‘실험유전학(Investigative Genetics)’ 저널 16일자에 실렸다. |
Could a bacterial ‘fingerprint’ solve a
sexual assault case?
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By Rachel Feltma A new study suggests that the microbes present on pubic hair -- which vary from person to person -- could be used as evidence in sexual assault cases. This particular research is in its early stages, so you probably won't hear about genital microbes in a courtroom anytime soon. But the study is just one example of the effort to turn the incredible diversity of the bacteria that live on human beings into a high-tech forensic toolkit. Research on the human microbiome -- the bacteria that colonize our bodies and surroundings -- has exploded in recent years. In fact, the microbiome has such a mysterious air, with so many new kinds of bacteria being found in such surprising places, that sometimes the health implications of having one kind of microbiome or another can get pretty overblown. The truth is that we don't know what a human's bacterial population should look like, or even if there's any way all humans should look, bacterially, at all. But what we do know is that our bacteria are very much a part of ourselves. A recent study found that humans colonize new living spaces with their own personal bacterial stamp within just a few hours. So if bacteria can be used as a fingerprint, it follows that they can be used to finger perpetrators of crime. In the new study, published Monday in the journal Investigative Genetics, researchers did some preliminary work to show that these microbial prints might be useful in sexual assault investigations. The researchers, led by Silvana Tridico from Murdoch University, took scalp and pubic hair samples from seven individuals (three male and four female, with one co-habitating couple in the mix). While hair from the head had around 50 kinds of bacteria a pop, and seemed to be influenced by the environment, pubic hairs had over 70 kinds of bacteria each, which were highly individualized. That's in line with previous studies on the vaginal microbiome, which has shown an unexpected diversity distinguishing one individual from another. "The advent of DNA profiling has resulted in an increase of sexual offenders using condoms, which they take away, post-assault," Tridico said in a statement. "The implication of this present study is that the transfer of bacteria between victim and offender, in rape cases, may provide a new way of linking the offender to the victim, in instances in which no human DNA is transferred." But the scientists were most excited about a tiny, very speculative nugget of the study. At one point in the study, the two people who lived together suddenly had more similarity in their pubic hair bacteria than they had before. It turned out that they'd had sex 18 hours before the sample collection. Ergo, the study authors suggest, a forensic investigator could use microbial shifts to help prove that two people had had intimate contact. "It's an interesting paper, but of course it's a small study and a very cursory analysis," said Jack Gilbert, an environmental microbiologist at Argonne National Laboratory who wasn't involved in the new study. "It's essentially saying that if two people interact, you can see that exchange." At such a small scale, Gilbert doesn't think it's safe to tout this as the future of assault investigation -- especially when it would compete with traditional DNA and physical evidence. But maybe one day it could contribute to a case. But Gilbert is glad to see others working on the forensic applications of bacterial signatures. Gilbert himself is collaborating with police in Hawaii to test the microbial prints left on victims of homicide. Unlike a traditional fingerprint, he said, bacterial signatures slowly decay with time -- so they could help determine who was last with the deceased, but also when their interaction occurred. It would be interesting to explore the use of this bacterial time-stamp for assault victims as well, he said. "I fully support the idea, but a lot more data is needed to prove its efficacy," Gilbert said of bacterial forensics. "We're probably 5 or 10 years out from using this in even rudimentary investigations." washingtonpost |
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