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Cliff Kapono has walked many beaches of the world, searching.

Often, the long-time surfer has looked for a great swell. He’s scanned waves off Morocco and Ireland; off Hawaii and Southern California.

But Kapono, 30, a doctoral candidate in chemistry at UC San Diego, has searched in some of those same places for something other than waves. He’s hunted for something so small he couldn’t possibly see it with the naked eye, yet so powerful it could turn a grain of sand into a mini-metropolis.

What Kapono sought — and still seeks — is bacteria. Specifically, he’s looking for bacteria that’s inside the guts and on the skin of surfers. He wants to look at as much surfer-held bacteria, from as many surfers as possible, to test his theory that long-term exposure to the ocean can change surfers at a molecular level.

All Kapono needs for his effort, known as the Surfer Biome Project, are some swabs off surfer’s boards and skin — and a tiny bit of their poop.

Say hello to our little friends

Kapono is part of a growing world of scientists studying human-based bacteria, much as geneticists from around the world have collectively studied the human genome for much of this century. The goal, with DNA and with gut bugs, is to learn more about the building blocks of humanity.

But the subject of the current wave of research — bacteria — has an image problem.

Salmonella, E. coli and listeria are household name bacteria that are widely (and rightfully) feared. Some of the diseases caused by bacteria — botulism, anthrax, tetanus — are notorious killers. Fear of bacteria, in fact, is part of why the developed world has created a range of products, including antibacterial soaps and cleansers, to ward off and, if possible, eradicate pathogenic bacteria.

But that part of the effort — to wipe out bacteria — might be misguided.

A growing body of research suggests bacteria are crucial to human health. Not only do bacterial microorganisms break down complex fibers and help humans turn food into nutrition, but our microbial gut bugs also are starting to be seen as windows offering new views of pervasive and mystifying illnesses and conditions, including Parkinson’s Disease, diabetes and autism. Bacteria even can show us more about mood disorders, such as anxiety and depression.

“All over your body you have microbes. (And) you’re interfacing and interacting, whether you like it or not, with your microbes,” said Daniel McDonald, manager of the non-profit American Gut, a citizen-science project at UC San Diego that is studying human microbes using volunteer donors. Kapono’s surfer project is a subset of the larger American Gut project, the largest known crowd-sourced science experiment.

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Though microbes live on or in humans, they are independent, living organisms with their own genetic makeup. “These organisms,” McDonald said, of microbes, “are not you.”

Sometimes, microbes work against their human host, McDonald added, and sometimes they work to assist it.

Microbes are so important that many scientists consider the human gut — where most bacteria reside — akin to a second brain.

In fact, all of the microscopic bugs that live in and on the human body weigh as much as a typical brain. It’s estimated that a human body has roughly an equal number of bacteria as he or she has cells. And the variety of bacterial organisms is such that the bacteria that live between your canine teeth often are distinct from the bacteria that live between your molars.

Bacterial research is a burgeoning area of both scientific inquiry and consumer marketing.

Since 2008, the number of scientific papers released annually that are focused on the human microbiome — the name for the bacteria, yeast, fungi, protozoa and virsuses that live on and in the human body — have grown by 35 percent, said Richard Lin, chief executive of Bay Area startup Thryve. Lin’s company sells supplements — probiotics — purported to be custom-tailored to a customer’s bacterial ecosystem.

“I think the general consumer, and the market, is starting to see an upward trend,” Lin said. “But I would say the mass consumer still doesn’t understand the human microbiome.”

There are several reasons why science is looking harder at the human microbiome. One is money: it’s getting cheaper to track the genetics of microbes. The DNA testing that cost $100 million in 2001 now costs about $1,000. And McDonald says the American Gut project is able to process samples nearly at cost, for $99.

Also, other advances in molecular technologies and computational techniques, make it easier for scientists to process genetic information once they get it.

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“The combination of being able to take a look at organisms without having to grow them, combined with being able to do really cheap DNA sequencing, is why this field has been able to take off,” McDonald said.

An extra special gift

The body part that hosts the most bacterial data is the colon. It’s estimated that a single teaspoon of fecal matter carries enough genetic information to be stored on a metric ton of DVDs.

It’s why Kapono and McDonald and others involved in various elements of the American Gut project regularly ask donors to give the gift of poop. Since launching in 2012, American Gut researchers have processed more than 10,000 stool samples.

It’s not an easy sell. While some American Gut participants have physical conditions that mean they regularly let doctors draw blood or test their stools, many others don’t, and the topic can turn them squeamish.

“Some people are not excited,” McDonald said. “There’s no good way around that.”

Despite the ick factor, researchers with the American Gut project have received samples from as far away as Australia and Vietnam as well as from Los Angeles, Riverside and Orange counties.

One major caveat is that the group of people who contribute their stools (and less invasive microbe swabs) are volunteers, so the data is not yet representative of all humanity. Donors pay to donate and when the testing is over, they receive a map of their internal microbiome. Bottom line: The gut bugs studied so far come from the part of the world that has at least some disposable income.

Individual bug maps are not (yet) medically critical information. The science that might someday tell an individual what microbes to take, and which ones to avoid, is in its infancy.

Still, American Gut researchers aren’t the only people thinking about microbes. In fact, many people increasingly are interested in what’s inside them, and some are venturing into risky, do-it-yourself techniques to get answers. Online tutorials offer step-by-step instructions for potentially dangerous procedures such as at-home fecal transplants in the hopes of cultivating a more diverse microbiome, even though researchers are unsure of exactly how certain strains of bacteria benefit health.

“As much as I’m excited about this field, and I love it when others are excited too, I find it important to continue to urge caution,” McDonald said. “I encourage people to be careful. This is a new area of research (and) there are a lot of questions we’re working on answering. … I don’t want to see people get harmed.”

Scientists are reaching out to more diverse populations, people living with a variety of conditions, extreme athletes and populations outside the U.S., in their quest to understand how (and why) gut bugs differ from place to place.

Ocean creatures

For all the study of bacteria that occupy the human gut, there is still much that is unknown. Scientists can’t explain the mechanics of how certain bacterial strains can affect mood, or why they notice an imbalance in the bacterial makeup of people with certain ailments.

“We don’t really understand, at a basic level, how or why consuming these organisms may be beneficial or may not do anything at all,” McDonald said.

After months of traveling the world and processing microbeal data he collected from surfers, Kapono has made one advance in the overall understanding of microbes: Early indications show that at a basic, molecular level, the ocean is changing surfers. Specifically, the tiny microbes that live on the skin of many surfers is also shared by sharks, otters and sea urchins — all animals with which we share the ocean.

For Kapono, a native Hawaiian, that link is both a revelation and an affirmation of what his culture has long believed — that humans and nature are intertwined, and that both can change each other.

Microbes “give us really empirical evidence” that people nature are connected, Kapono said.

“You don’t have to talk about myths and legends.”