Researchers at the Indian Institute of Science (IISc) and Kiel University have shown in a study that antimicrobial resistance (AMR) can be found in soil bacterial communities due to microbial interactions driven by a species of predatory bacteria.
Published in Current Biology, the study looked at how the presence of the bacterium Myxococcus xanthus affects the number of antimicrobial-resistant bacteria in soil samples.
Predatory species
According to IISc, M. xanthus is a predatory species that is known to release antimicrobials and other molecules to kill its prey.
“Human-driven (antibiotic) resistance is a major problem, but the question is: Are there other aspects that we completely ignore? This was very exciting to explore,” said Samay Pande, Assistant Professor at the Department of Microbiology and Cell Biology (MCB), IISc, and corresponding author of the study.
Pande and others found that the death of M. xanthus in soil bacterial communities increased the frequency of resistant isolates – bacterial cells resistant to antibiotics – in many different species of soil bacteria. These cells also showed resistance to certain antibiotics even without exposure to these drugs.
When faced with starvation, populations of M. xanthus die en masse. In famine-like conditions, which are very common in soil environments, these bacterial cells form stress-resistant structures called fruiting bodies that are filled with spores.
During the development of fruiting bodies, only a minority of cells succeed in becoming spores, whereas the majority of the bacterial cells undergo lysis (rupture) and release growth-inhibitory substances into the environment.
Biosynthetic clusters
The researchers believe that exposure to these growth inhibitory molecules is the reason behind the increased frequency of resistant isolates in the soil bacterial community. Interestingly, not all strains of M. xanthus triggered enrichment of resistance; it was the ones with higher diversity of biosynthetic clusters that seem to drive it.
“We identified multiple different molecules and did a very crude classification. Individually, these molecules might not do anything, but when you put them together, they suddenly do this strange thing where they can enrich other resistant isolates,”said Saheli Saha, PhD student at MCB and co-first author of the study.
The researchers found that resistance was enriched against several antibiotics, which include commonly used drugs such as tetracycline and rifampicin.
Published – March 05, 2025 08:25 pm IST
