Ancient resistance - ice age bacteria that could fight off antibiotics by S.E. Gould
Antibiotic resistance is often seen as a modern phenomenon - an
ability generated by bacteria in order to defend against the challenges
of modern medicine. This is supported by the fact that bacteria from
before the era of antibiotics are often more susceptible to their use.
Which is why I found it intriguing that recent studies (ref below) have
unearthed bacteria from 30 000-year old permafrost sediment and have
found evidence of genes that provide resistance against three of the
most common types of antibiotics used in hospitals: β-lactam, tetracycline and glycopeptide antibiotics.
As every microbiologist knows, a good way to get bacteria to stay in an
unchanged state is to freeze them. Digging down beneath the surface in
areas such as Dawson City in Yukon, Canada reveals layers that have
remained frozen since the ice-age and contain, among all the mammoths
and toothy-tigers, frozen and uncontamined samples of bacteria.
The researchers focused on Actinobacteria; a soil bacteria with many strains still around in modern times. As a soil bacteria, modern Actinobacteria
carries a whole arsenal of antibiotic and antifungal agents in order to
protect itself in the cut-throat world of soil microbiotica. The
researchers were looking to see what kind of antibiotic substances this
ancient bacteria would have.
To do this they carried out a set of PCR reactions.
These worked by amplifying any sequences of tetracyclin, vancomycin and
B-lactam resistance. To the researchers' surprise, all of these genes
were present in the ancient bacteria. What's more the vancomycin
resistance genes (which were first discovered in bacteria in the late
1980s!) were remarkably similar to the modern ones.
Why is the resistance there? Around thirty thousand years before the NHS the gene that would go on to make Staphylococcus aureus even
more unbeatable was hanging around in the permafrost. The paper doesn't
really go into that but I think a good contender for the answer is that
while people might not be using antibiotics, other bacteria certainly
are. A lot of antibiotics are extracted from soil bacteria in the first
place, which use them to defend their living spaces and protect
themselves against predatory bacteria or fungi.
I suspect that back in the permafrost days, antibiotics would be exist
almost exclusively in soil bacteria. For any bacteria not in this
environment antibiotics aren't much more than an unnecessary load on the
genome. Nowadays, however, by strongly selecting for any bacteria that
carry resistance, humans have helped those genes to spread out of soil
bacteria and into more pathogenic strains.
Bacteria have been fighting each other with antibiotics for millions of
years. It's only recently we've begun to steal their weapons.
D'Costa VM, King CE, Kalan L, Morar M, Sung WW, Schwarz C, Froese D,
Zazula G, Calmels F, Debruyne R, Golding GB, Poinar HN, & Wright GD
(2011). Antibiotic resistance is ancient. Nature PMID: 21881561
About the Author: A biochemist with a love of
microbiology, the Lab Rat enjoys exploring, reading about and writing
about bacteria. Having finally managed to tear herself away from
university, she now works for a small company in Cambridge where she
turns data into manageable words and awesome graphs. Follow on Twitter @labratting.