Bacteria are into casual sex. Many species will gladly indulge in orgies with just about any other bugs they bump into, passing on genes for antibiotic resistance and who knows what else in the process.
Now scientists have discovered a kind of molecular condom that keeps disease-causing bacteria from spreading genes that defeat antibiotic drugs.
Blocking bacterial sex could stem the rise of antibiotic resistance in so-called superbugs, such as methicillin-resistant Staphylococcus aureus (MRSA), says , a molecular biologist at Northwestern University in Evanston, Illinois, who led the study.
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More than 18,000 Americans died from MRSA infection in 2005. Many strains of the pathogen and other deadly bacteria can acquire antibiotic resistance via bacterial sex, also known as conjugation.
Invasion blocker
In general, acquired genes prove beneficial to bacteria, says Northwestern microbiologist Luciano Marraffini, who was also involved in the study. But to exert some control over whom they have sex with, many species of bacteria have evolved a way to block the acquisition of new genes.
快猫短视频s initially thought that bacteria only used this trick 鈥� called CRISPR interference 鈥� to stymie viral infections, but Sontheimer and Marraffini discovered that it can stop MRSA from passing on antibiotic resistance to a bug that coats our skin, Staphylococcus epidermidis.
CRISPR interference works a little bit like RNA interference 鈥� a trick that complex eukaryotic cells use to block viruses and parasitic DNA stretches called transposons, Sontheimer says. Bacteria contain special CRISPR sequences that match the DNA of a potential sex partner.
The CRISPR sequences get transcribed into RNA then go after invading DNA sequences to destroy them, Sontheimer and Marraffini found. The defence also stops bacteria from sopping up DNA in the environment, another common route to antibiotic resistance.
鈥淭here鈥檚 still a lot that we don鈥檛 know about all this,鈥� Sontheimer admits.
Proteins probably help out in the defence, but those remain unidentified. And how do bacteria keep CRISPRs from going after their own DNA?
Hospital tool?
These questions might not stand for long, says John van der Oost, a molecular biologist at in the Netherlands, as numerous research groups are racing to explain precisely how CRISPR interference works.
鈥淭he cool thing about CRISPR is that it provides acquired immunity,鈥� says , a molecular biologist at Weizmann Institute of Science in Rehovot, Israel 鈥淏acteria learn how to defend themselves against phage and plasmid infections 鈥� in a way analogous to the way our immune system learns how to fight pathogens.鈥�
However, applying their immune system to combating infectious disease will be a challenge. 鈥淲e don鈥檛 have any specific way envisioned to put this into use yet,鈥� Sontheimer says.
One possibility would be to treat hospital surfaces with CRISPR RNAs to prevent bacteria such as MRSA from acquiring more resistance genes and from spreading them to non-resistant strains, Marraffini says.
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