Within the past few years there has been an explosion in human microbiome research - looking at the community of microorganisms that live in and on human beings. Within the body of a healthy adult, microbial cells are estimated to outnumber human cells ten to one! This community of microorganisms remains largely unstudied, and so their influence on human development, diseases, immunity, and health are almost entirely unknown. Some of the latest research looks at the microbiomes of healthy people and those with diseases, seeing how they differ, and from that looking at possible treatments using bacteria. This is a whole different mind-set from the one we've had for decades that viewed all bacteria as bad (pathogens) and needing to be eliminated.
An introduction to this emerging area of human microbiome research was written by Gina Kolata in the NY Times, June 13, 2013:
For years, bacteria have had a bad name. They are the cause of infections, of diseases. They are something to be scrubbed away, things to be avoided. But now researchers have taken a detailed look at another set of bacteria that may play even bigger roles in health and disease: the 100 trillion good bacteria that live in or on the human body.
No one really knew much about them. They are essential for human life, needed to digest food, to synthesize certain vitamins, to form a barricade against disease-causing bacteria. But what do they look like in healthy people, and how much do they vary from person to person?
In a new five-year federal endeavor, the Human Microbiome Project, which has been compared to the Human Genome Project, 200 scientists at 80 institutions sequenced the genetic material of bacteria taken from nearly 250 healthy people. They discovered more strains than they had ever imagined — as many as a thousand bacterial strains on each person. And each person’s collection of microbes, the microbiome, was different from the next person’s. To the scientists’ surprise, they also found genetic signatures of disease-causing bacteria lurking in everyone’s microbiome. But instead of making people ill, or even infectious, these disease-causing microbes simply live peacefully among their neighbors.
"Until recently, Dr. Bassler added, the bacteria in the microbiome were thought to be just “passive riders.” They were barely studied, microbiologists explained, because it was hard to know much about them.
The work also helps establish criteria for a healthy microbiome, which can help in studies of how antibiotics perturb a person’s microbiome and how long it takes the microbiome to recover.
In recent years, as investigators began to probe the microbiome in small studies, they began to appreciate its importance. Not only do the bacteria help keep people healthy, but they also are thought to help explain why individuals react differently to various drugs and why some are susceptible to certain infectious diseases while others are impervious. When they go awry they are thought to contribute to chronic diseases and conditions like irritable bowel syndrome, asthma, even, possibly, obesity.
"The microbiome starts to grow at birth, said Lita Proctor, program director for the Human Microbiome Project. As babies pass through the birth canal, they pick up bacteria from the mother’s vaginal microbiome.
Babies born by Caesarean section, Dr. Proctor added, start out with different microbiomes, but it is not yet known whether their microbiomes remain different after they mature.In adults, the body carries two to five pounds of bacteria, even though these cells are minuscule — one-tenth to one-hundredth the size of a human cell. The gut, in particular, is stuffed with them.
“The gut is not jam-packed with food; it is jam-packed with microbes,” Dr. Proctor said. “Half of your stool is not leftover food. It is microbial biomass.” But bacteria multiply so quickly that they replenish their numbers as fast as they are excreted.
Including the microbiome as part of an individual is, some researchers said, a new way to look at human beings. The next step, he said, is to better understand how the microbiome affects health and disease and to try to improve health by deliberately altering the microbiome. But, Dr. Relman said, “we are scratching at the surface now.”
FOR THOSE WHO WOULD LIKE TO SEE A VIDEO ON THIS TOPIC, this TED talk given by Dr. Jonathan Eisen is an excellent introduction to the human microbiome and how we should view ourselves as being covered in a microbial cloud. And that this microbial community within and on us should be viewed as an organ, and thus should be treated carefully and with respect.