England [UK], September 30 : Scientists have discovered that some antibiotics have an unexpected effect on particular germs: the drugs occasionally aid microorganisms by extending their lives.
Antibiotics are commonly used as a general treatment for bacterial diseases since it has long been recognised that they either kill germs or prevent them from growing. Because some treatments are no longer effective due to antibiotic resistance, untreatable diseases may be the main cause of mortality worldwide by 2050.
For the first time, researchers at the University of Exeter have demonstrated that antibiotics can really benefit bacteria and protect them from death.
In an EPSRC-funded study published today in PNAS, the researchers discovered that particular antibiotics can ease stress and help prevent bacterial decline.
The researchers discovered that specific antibiotics can ease stress and assist in preventing the fall of bacterial populations when they are dying out in research sponsored by the EPSRC and published today in PNAS. This suggests that more bacteria live longer in treated populations than in untreated populations.
Professor Robert Beardmore, lead author from the University of Exeter, said “The study began when we realised that surprisingly, some bacterial strains didn’t grow in the lab until we treated them with antibiotics. As a result, this is the first evidence that antibiotics can promote bacterial survival. To tackle antibiotic resistance worldwide, we need to understand far more about the impact of these drugs on the balance of bacterial ecosystems, like those in the gut microflora, or in rivers that are exposed to antibiotics. Our research is evidence of unseen side effects – we just don’t know how drugs are changing the balance of bacterial populations in those contexts.”
In real-world environments, bacteria undergo periods of rapid growth, punctuated by periods where growth stops because nutrients are scarce, so the bacteria die off. So far, little has been understood about how antibiotics mediate populations during those periods.
The researchers examined E.coli in lab experiments. They found that antibiotics targeting ribosomes – factories that help cells make protein from DNA – slowed bacteria down when they were growing but also stopped them from dying, meaning the bacteria survived for longer overall.
Dr Emily Wood said, “Many antibiotics slow the growth of bacteria, but we show that can help bacteria overcome stresses caused by a lack of nutrients that might otherwise kill them off, ultimately helping them to survive. In our experiments, this comes about because antibiotics are antioxidants, meaning they help cells deal with some of the waste products they make as they grow. Importantly, the antibiotic-resistant bacteria we tested didn’t get the same benefits so in our study, treatment does not promote resistance, which is unusual. Our next step will be to measure how these findings alter the dynamics of multi-species bacterial communities.”
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