All living cells contain DNA; the code for producing every protein needed by the cell. As DNA is important it needs to be kept safe. Plants and animals keep their DNA tightly twisted and organised inside a double-membrane bound nucleus while bacteria keep their DNA coiled up in a big circle, with the occasional loop floating around separately. With smaller cells, bacteria don’t have the space for large membrane-bound organelles, and they can also tolerate a bit of genetic damage slightly more than large multicellular structures.

To act as an intermediate between DNA and proteins cells also contain RNA – which is a more flexible and shorter lived molecule in the same family as DNA. If the DNA is a library with all cellular information neatly filed then RNA is a messy folder full of notes that can be scattered around the cell to wherever they are most needed. RNA has lots of jobs; it is a vital part of protein production and can also be used to regulate and control cellular processes.

Although bacterial DNA is not locked up in a nucleus, it is still useful for bacteria to be able to make and distribute copies of it. Small pieces of RNA, imaginatively called small-RNA (sRNA) can be used to control the production of proteins and other pieces of RNA. These little lines of code require little energy to produce and can regulate their targets in a coordinated manner, and because of this they are often used to help the bacteria respond quickly to changing circumstances.

A single strand of RNA. "ARNm-Rasmol" by Corentin Le Reun - Own work. Licensed under Public domain via Wikimedia Commons.

Recent studies have shown that when bacteria are exposed to antibiotics they produce more sRNA. Many of the cellular processes targeted by antibiotics (including damage to the cell wall and protein production) are normally controlled by sRNA so the sudden flurry of production may be the bacteria attempting to minimise damage or activate antibiotic resistance pathways. sRNA is also important for active antibacterial resistance such as the production of protein pumps that forcibly remove the antibiotic from the cell.

More interestingly, it was found that blocking the production of sRNA leaves the cell more vulnerable to antibiotic attack. While preventing sRNA production may not be a viable antibiotic therapy by itself the targeted blocking of specific small RNA pieces could be used as an adjuvant – a therapy added along with the antibiotic to make it more powerful. As antibiotic resistance starts to spread, the need for therapies to increase the power of the antibiotics currently in circulation will always be useful, and sRNA is a fascinating little molecule to study.

sRNA and antibiotics: a summary. Image from the reference.

Reference: Lalaouna D, Eyraud A, Chabelskaya S, Felden B, Mass? E (2014) Regulatory RNAs Involved in Bacterial Antibiotic Resistance. PLoS Pathog 10(8): e1004299. doi:10.1371/journal.ppat.1004299