CSUN microbial ecologist Gilberto E. Flores.

It has been known for some time that each of us hosts distinct bacterial communities, with no two individuals hosting the same combinations of bacteria. A new study, led by California State University, Northridge microbial ecologist Gilberto E. Flores, now shows that the amount these communities change through time is also unique to each individual.

These findings are important as scientists work toward linking changes in the human microbiome to human diseases.

“If we are to ever establish cause and effect between changes in the human microbiome and certain diseases, we need a better understanding of the ecology of these communities, including how and why they change through time,” Flores said.

The study, “Temporal variability is a personalized feature of the human microbiome,” was published in the Dec. 15, 2014, edition of the open-access journal Genome Biology. In addition to Flores, the research team included 11 other scientists from Northern Arizona University, the University of Colorado at Boulder and North Carolina State University.

The scientists profiled the bacterial communities found in and on the human body to understand how these communities vary over time within individuals. They specifically looked at the communities found in the gut and on the forehead, palm and tongue of 85 adults once a week over the course of three months. They found that within each body habitat, there was a wide range of variability in the individual microbiome, with some people hosting communities that changed dramatically over time.

That bacterial variability is unique to each person and needs to be taken into consideration by scientists and doctors as they work toward personalized medicine, a medical model in which doctors customize the care of a patient based on that patient’s genetic content and other molecular makeup.

The study’s findings are a significant advancement for this burgeoning field, as scientists have largely assumed that the adult microbiome is stable through time.

“One of the strongest predictors of which individuals are more variable than others was the number of different bacterial species found in that individual,” Flores said. “For example, individuals who had more bacterial species within their gut were more stable through time. From an ecological perspective, diverse communities are generally more resistant to invasions and are more productive.”

Flores said research like this wasn’t possible even 10 years ago. But with the advances in DNA sequencing technology, the cost of studying microbial communities has plummeted. Thus, scientists are able to use the technology to explore such minute specimens as the bacteria in the human body and are able to differentiate the samples from a variety of individuals.

“I know this all sounds sort of esoteric, but as medicine becomes more and more personalized, doctors may need to use information like this to help treat their patients better,” Flores said. “The more a doctor knows what is going on in your body, the better he or she is able to prescribe the best course to keep you healthy.”

Biology, College of Science and Mathematics