Showerheads and toothbrushes filled with unexpected bacteriophages

BY MARIA BURKE

US researchers have found a surprising diversity of viruses living in household biofilms, specifically in showerheads and on toothbrushes, many of which they have never seen before. They suggest that this previously untapped biodiversity, which includes viruses that infect bacteria, could become a source of materials for exploring antibiotic resistance.

While much is known about the microbial composition of domestic biofilms, the role of viruses is not well understood. A team from Northwestern University collected bacteriophages, a type of virus that infects and replicates inside bacteria, from samples taken from 34 toothbrushes and 92 showerheads. Recently, bacteriophages have shown promise in treating antibiotic-resistant bacterial infections.

After characterising bacteria in the samples, the researchers used DNA sequencing to examine the viruses living on them. Altogether they found more than 600 different viruses, and no two samples were alike (Frontiers in Microbiomes, DOI: 10.3389/frmbi.2024.1396560.)

‘The number of viruses that we found is absolutely wild,’ says study leader Erica Hartmann. ‘We found many viruses that we know very little about and many others that we have never seen before. It’s amazing how much untapped biodiversity is all around us.’

There was no overlap in virus types between showerheads and toothbrushes and very little overlap between any two samples at all, she adds.

The team found more mycobacteriophage than other types of phage. Mycobacteriophage infect mycobacteria, a pathogenic species that causes diseases like leprosy, tuberculosis and chronic lung infections; such phages could potentially be harnessed to treat these infections.

‘We could envisage taking these mycobacteriophage and using them as a way to clean pathogens out of your plumbing system,’ she says. ‘We want to look at all the functions these viruses might have and figure out how we can use them.’

The study is of particular interest because it provides new insights on viruses in domestic bacterial biofilms, says Dirk Bockmühl, a microbiologist at Rhine-Waal University of Applied Sciences in Germany. ‘The bacteriophages that coexist with bacteria in these biofilms might be an interesting future source when it comes to controlling biofilms and their bacterial communities, for instance, in terms of new antimicrobials. Moreover, the findings suggest there’s very limited exchange between the microbial communities in the domestic environment, which could have been a problem, for example, regarding the spread of antimicrobial resistance.’ However, he would have liked the study to have taken a broader view rather than focusing so much on biofilms harbouring Mycobacteria.