Microbial communities vary greatly between different households but are similar among members of the same household – including pets – according to research published in Science today.
Microbes are everywhere. They live on and inside us, and cover most things we come into contact with, including our personal belongings. We also know that microbes play a role in human health, and the destruction of our personal microbial community (known as our microbiome) is thought to be contributing to the rapid rise of certain diseases.
The research shows humans affect the microbial populations of their surroundings rather than the other way around.
The dynamics of microbial transmission was studied, revealing that, more often than not, humans are the microbial vectors (transporters). When we move into a new house, rather than acquiring microbes from the new location, we bring our unique microbial profile with us.
Andrew Holmes, a microbial ecologist from the University of Sydney, said the results indicate microbial communities on household surfaces are “ecologically inert”. He said that, rather than harbouring actively growing microbes, surfaces “are continually reloaded with what you had already growing in and on you”.
“To put it another way – we inoculate the house, rather than the house inoculating us,” he said.
The results of the study highlight the complex exchanges between humans and the microbes residing with us, and contribute to an understanding of how these microscopic communities may play a role in human health, disease treatment and transmission.
Your unique blend of housemates
Researchers from Argonne National Laboratory studied seven families and their homes over six weeks, sequencing the genomes of bacteria found daily on their skin, household surfaces and pets.
Four million different microbial DNA sequences were identified.
Within households, the most microbial similarity was found on the hands of individuals. Intriguingly, the most microbial variation between individuals was found in the nose.
Frequent physical contact between members of a household was also a factor, with those in close relationships sharing the most microbes.
The researchers suggest that samples of household microbial communities could potentially serve as a forensic tool to predict which family the sample came from.
Silvana Gaudieri, associate professor in the Centre for Forensic Science at the University of Western Australia, said that in the context of forensic microbiology, there is potential “predictive value” in the relationship between home surfaces microbiomes and those of occupants.
The research also showed that when individuals (and their microbes) leave a house, the microbial community changes markedly in the days following. This suggests the decay of a microbial signature could be used to assess not only if, but when, the person was in the house.
Don’t evict microbial tenants
While the study suggests that humans may routinely encounter potentially harmful microbes, there is no need to worry as they only cause problems for those with otherwise compromised immune systems.
“[The results] most certainly do not mean that the microbes occupying the household surfaces are biologically significant to the health of the household,” Associate Professor Holmes said.
“What it does emphasise is that we are continually surrounded by bacteria. In our domestic residences our bacterial environment strongly reflects our personal microbiota – which are essentially beneficial.”
“One reason for household members sharing similar microbial communities is that we have a high likelihood of exchanging microbes within a household,” he said. “This is relevant for control of the spread of antibiotic resistant bacteria within household members or in hospital wards.”
Cheryl Power, an Honorary Fellow in microbiology and immunology at the University of Melbourne, said other studies have shown excessive use of antibacterial compounds selects for more resilient bacteria.
“We should relax about the need to forensically clean our home spaces and not feel the need to use products that contain antibacterial chemicals claimed to make our home safe from ‘house germs’, as we are so often encouraged to do,” she said.
“This research shows that the microbiota of different home spaces are basically our normal microbiota with whom we live peacefully, even productively, most of the time.”