Researcher Scavenges Ancient Human Bones for Answers on DNA : Bacteria: Other remains, including guts and feces, are examined by paleomicrobiologists seeking insights into epidemics and ailments.
After 25 years of surgery, Dr. Mark Spigelman left his patients in Australia to look after a much older clientele here. About 1,500 years older, in fact.
The surgeon-turned-sleuth scours remains of human bones, guts and feces searching for bits of bacterial DNA. These remnants from long-dead bacteria, he believes, will provide one of the most accurate pictures of medical history and may also offer clues to understand current epidemics.
Scientists still do not understand the ebb and flow of germs--why the same bug can wipe out a community one year and barely cause illness the next. The answer may lurk in the genes and how they slowly mutate over time.
“We are giving a handle to a lot of historical diseases, but there is also the practical application. I’ve always felt that a lot of problems of modern diseases lay in ancient times,” said Spigelman. He was surrounded by boxes of human bones and glass cases of skulls in an office at the Institute of Archaeology.
Some of the research has important implications outside medicine. A team at the University of Minnesota retrieved TB from a 1,000-year-old Peruvian mummy, a finding that suggests Columbus has been wrongly accused of bringing the disease to the Americas.
Spigelman is one of a small but growing group of scientists worldwide studying genes from ancient germs. The fledgling field, called paleomicrobiology, involves an eclectic group of researchers, including archeologists, pathologists, microbiologists and, in Spigelman’s case, a surgeon with a penchant for the past.
“I wanted to learn archeology, not medical history, because I’m a surgeon, a hands-on man,” said Spigelman.
He displayed a vial of ancient feces--now looking more like sand--that he collected recently at a dig in Israel.
“This stuff to me is even more important than bones,” he said. “Bone is from an individual, but when you go into the toilet it’s like a community roll call for disease.”
DNA scavengers have no intention of reincarnating microbes from yesteryear, building a microscopic “Jurassic Park.”
Their goal is threefold: to verify historical theories about how infections have spread, to provide insight into current diseases and perhaps to shed light on the origin of some species, such as tuberculosis or leprosy.
The scraps of DNA lurking in human remains are far from enough raw material to create a bug. They are more like fingerprints that scientists examine to identify a particular microbe.
“Up until now you were only able to look at ancient diseases by the impact on the growth of bone. A lot of illnesses kill too soon, before it impacts bone, or they don’t have an impact on bones at all,” said Dr. Martin Jones, a professor of archeological science at Cambridge University. Jones also heads Britain’s Ancient Biomolecules Initiative.
So far, most of Spigelman’s research has been on bones, which seems to be the best for preserving DNA.
Typically, Spigelman fetches the bones from digs in England and Israel and brings them to his collaborators in the department of microbiology at the University of London.
“What we’ve really done is apply modern diagnostic clinical techniques to the ancient bone,” said Dr. Helen Donahue, one of the microbiologists.
Within the last 10 years, scientists realized that bacterial DNA can survive centuries, escaping enzymes that degrade the rest of the human body. At the same time, researchers devised a technique, called polymerase chain reaction, or PCR, that amplifies DNA so it can be studied more easily.
Donahue and her colleagues X-ray bones to zero in on where the germ seemed to do its damage, the most likely spot for hunting its DNA. Then they jab the bone with a sharp needle and retrieve a sample, perhaps half a gram.
Using chemicals that clean off excess proteins, they isolate the DNA and then amplify using PCR, comparing the pattern of genes to the known pattern of the incriminated germ. The pattern looks like lines of ink blots.
So far, Spigelman said he’s retrieved genes of E. coli, a gut bacteria, from a bog man dating to AD 500, tuberculosis DNA from ancient bones and leprosy DNA from a bone dating to 600 BC.
The TB findings were published last year in the International Journal of Osteoarchaeology and the leprosy study in a letter in a recent issue of the Lancet, a medical journal.
Other experts said the research may be an important step forward but the findings need to be confirmed, particularly because the group did not do any gene sequencing--identifying the precise order of the DNA--to validate their preliminary findings.
Dr. Svante Paabo, a pioneering DNA hunter and professor of biology at University of Munich, said gene sequencing--identifying the precise order of DNA--is crucial because PCR can sometimes gives false results.
If confirmed, the findings would provide yet another step forward in a lengthy trail of chasing the bacterial culprits, Paabo said.
‘It’s extremely interesting if one can go back and look at the evolution of pathogens and see how rapidly they change over time,” Paabo said.
If it turns out that some genes don’t change over time, they could be targeted by new drugs or vaccines, he said.
