The U.S. National Institutes of Health says its Human Microbiome Project has analyzed 178 genomes from microbes living in or on the human body.

The researchers said they discovered novel genes and proteins that serve functions in human health and disease, adding a new level of understanding to what is known about the complexity and diversity of these organisms.

The NIH said the human microbiome consists of all the microorganisms that reside in or on the human body.

"Outnumbering cells in the human body by 10 to 1, some of the microorganisms cause illnesses, but many are necessary for good health," NIH scientists said. "Currently, researchers can grow only some of the bacteria, fungi and viruses in a laboratory setting. However, new genomic techniques can identify minute amounts of microbial DNA in an individual and determine its identity by comparing the genetic signature to known sequences in the project's data base."

NIH Director Dr. Francis Collins said the work is critical for understanding the role the microbiome plays in human health and disease.

"We are only at the very beginning of a fascinating voyage that will transform how we diagnose, treat and ultimately, prevent many health conditions," Collins said.

The NIH said the Human Microbiome Project, started in 2008, is a $157 million, five-year effort designed to reveal the interactive role of the microbiome in human health.

The research appears in the journal Science.