It’s not as exciting as El Dorado’s source of eternal youth, but nitric oxide-producing bacteria are extending the lifespan of the humble roundworm Caenorhabditis elegans.
The worm lacks the enzyme needed to produce nitric oxide. In animals which are capable of manufacturing nitric oxide, it has been shown to increase blood flow, promote efficient nerve signal transmission and regulate the immune system, all factors that may contribute to a longer lifespan.
To see if nitric oxide alone could extend lifetime, researchers fed a group of C. elegans a soil-dwelling bacterium called Bacillus subtilis, which produces the gas. The worms, with colonies of B. subtilis established in their guts, had a lifespan of about two weeks—nearly 15 percent longer than a control group fed bacteria which didn’t produce nitric oxide.
Flukes that parasitize amphibians
The enemy of my enemy is my friend—especially if I’m a frog and my enemies are competing parasites. A recent study in PNAS found that frogs populations exposed to a more diverse set of flukes actually had lower rates of infection, with fewer frogs in the group afflicted with tiny hitchhikers.
Researchers at the University of Colorado-Boulder bred Pacific chorus frogs in a lab and put their tadpoles in different tanks with anywhere from one to six different types of flukes. On average, 40% of the frogs that came into contact with only a single fluke species developed infections, while 34% of frogs exposed to four flukes and 23% of frogs exposed to six flukes were infected (the numbers for two, three flukes followed a roughly similar trend). Additionally, some of the fluke species make frogs sicker than others, and oddly enough, the frogs exposed to a greater variety of flukes had a lower proportion of infections from these dangerous species.
Crawling my way to a healthier immune system.
Bacteria are practically everywhere around us, including on and inside you, but that is in many ways a good thing. For instance, having a diverse set of microbes living on your skin might help prevent allergies. A new study published in PNAS links two factors related to how microbes might affect our health: the observation that diversity of microbes on a person is related to the diversity of microbes in their environment, and the hygiene hypothesis, which suggests that the modern uptick in allergies and autoimmune diseases is caused by childhood under-exposure to bacteria.
For a while now, scientists have known that kids living on farms are less likely to have allergies or asthma. Being around livestock means the farm kids are also around a more diverse set of bacteria than city kids living in an apartment. In this new study, scientists swabbed the skin bacteria of 118 Finnish kids, some who lived in rural areas and some who lived in urban areas. They also tested the kids for levels of an antibody called IgE, high levels of which indicate hypersensitivity to allergens, or what is known as atopy. Lastly, they surveyed the parents about plant diversity around their homes.
It’s an exciting time for ecologists who study microbes. DNA sequencing has grown so cheap and fast that they can run around identifying bacteria living just about anywhere they can reach with a cotton swab. Turns out, bacteria are everywhere, even in the cleanest houses, and scientists are starting to wonder: do those bacteria in the home reflect the bacteria that live inside the inhabitants?
And if so, can they travel from person to person?
A small insight into this question came at one of the presentations at the International Human Microbiome Congress (covered by New Scientist in a short piece here). James Scott, who studies molecular genetics at the University of Toronto, reported that the gut microbes of babies, as found in their poop, were also in the dust in the babies’ homes. It’s not clear whether this means that bacteria in the dust are colonizing the babies or vice versa—or both—but it’s still something of a surprise. Gut microbes don’t seem like the sort to thrive outside the body, as they tend to require an oxygen-free environment. But maybe the gut bacteria in the dust are in a dormant form, waiting to be absorbed into a new gut before flowering into life again.
The corollary of this finding is that perhaps the other inhabitants of that home might pick up those microbes. Your gut microbiome, thus, would be closer to your roommates’ than to a stranger’s, something that would be easy to test with modern sequencing techniques. There’s also room to speculate that as we learn more about the microbiome’s relationship to disease, the swapping of microbes within a household could reveal an infectious component to illnesses that we don’t currently think of that way. It’s just a speculation now, but an interesting one.
What’s the News: The bacterial hordes that call your mouth home—and yes, even if you brush rigorously, you’ve got ‘em—are generally a pretty benign bunch. Mostly they just mooch around, snagging tastes of whatever you’re eating, but Streptococcus mutans, the bad boy that causes cavities, releases tooth-corroding acid whenever you eat sugar. Even mouthwash that kills everything it touches can’t save you from the ravages of S. mutans in the long term; it just grows back, along with the rest of your bacteria.
Scientists who study the mouth microbiome, however, think that a mouthwash that kills S. mutans and leaves the rest of the bacteria to take over S. mutans‘s real estate could spell the end of cavities. In a small clinical study last year, one team found that one application of the mouthwash knocked down S. mutans levels, and that harmless bacteria grew back in its place. If the mouthwash pans out, it could join the ranks of an emerging new type of treatment: better living through hacking the microbiome.
Statins are widely prescribed to reduce levels of LDL, the “bad cholesterol,” a vital goal in stemming and preventing cardiovascular disease. But they don’t work for everybody, often for inexplicable reasons. Researchers now think some of the blame rests with gut bacteria, that influential yet mysterious group that occupies our bowels and outnumbers our cells 10 to one. In a study published this month in PLoS One, researchers took blood samples from 944 study participants prior to and after six weeks of treatment with a statin called simvastatin. They measured the levels of various bile acids, many of which are produced by gut bacteria and help metabolize fat by acting like detergents, allowing cholesterol to be dissolved and transported in the blood. The researchers found that people whose LDL levels dropped the most had significant quantities of three bile acids produced by a particular type of gut bacteria. Those who responded least to the statins had significantly higher levels of five different bile acids from different gut flora. The researchers hypothesize that bile acids present in the non-responders compete with simvastatin for transporters that ferry both chemicals to the liver, where the drug has its effect.
If bacteria can’t grow in a Petri dish, sequencing them is difficult.
What’s the News: Want the genome of a bacterium you found in your belly button? Or, for that matter, of a bacterium producing a promising new antibiotic? Well, unless you can get it to thrive in a Petri dish and create a billion sister cells for analysis, you’re out of luck.
But sequencing the genomes of notoriously finicky bacteria, like those on skin, could be on the horizon with a new procedure that bypasses the Petri dish step. Pairing a new algorithm with an earlier technique, scientists from the Venter Institute and their collaborators can now get all that information from a single cell.
The health detriments of a Western diet—eating foods high in fat, sugar, and animal protein—are now well known. However, according to a group of studies out in this week’s Proceedings of the National Academy of Sciences, how you eat when you’re just a kid can have a great impact, influencing the gut microbes you’ll carry your entire life.
Researchers led by Carlotta de Filippo studied the gut microbes of African children raised in Burkina Faso versus those in European children from Italy. According to the team’s findings, the kids’ diet had a dramatic effect on what bacteria they harbored in their guts to help them with digestion. The Burkina Faso children, who grew up eating a lot of fiber, had gut bacteria that help to break down that tough material. Meanwhile the Italian children, who grew up on a Western diet, had guts dominated by a kind of bacteria that’s more common in obese people, and they had less bacterial diversity overall.
Two other PNAS papers this week took on the formation and evolution of a human’s gut microbiome. One showed how a nursing infant gets its first helpful gut microbes from mother’s milk, and the other followed the same baby for two and a half years—collecting “samples” from diapers—to show how its population of gut bacteria changed and developed.
For an in-depth take on these studies and insight on how they fit together, check out Ed Yong’s post at Not Exactly Rocket Science.
Not Exactly Rocket Science: You Are What You Eat—How Your Diet Defines You in Trillions of Ways
80beats: Scientists Sequence DNA from the Teeming Microbial Universe in Your Guts
80beats: My Excrement, Myself: The Unique Genetics of a Person’s Gut Viruses
Image: Wikimedia Commons
Here’s a new way to prove the maxim that we are what we eat: Take a peek into the teeming universe of bacteria that thrive in a Japanese person’s gut. Trillions of microbes in the gut help digest the foods we eat, and researchers have found that the “gut microbiomes” of Japanese people have adapted over the centuries to help digest seaweed–an integral part of sushi. Remarkably, they adapted by taking in genetic material found in that very sushi.
The new study, published in Nature, reveals that these gut bacteria engaged in a gene swap, grabbing algae-digesting genes from marine bacteria that live on red algae like nori, the seaweed used to wrap sushi. The marine bacteria traveled on the seaweed into human digestive systems, where the crucial genes were transferred to bacteria in the gut.
Scientists stumbled on this swap when they identified a new group of enzymes from the algae-chomping marine bacteria that help the microbes break down the unique carbohydrates in seaweed. When they searched for other organisms that had the same enzymes, they found one match that, oddly, came from a species of bacteria that lived in the gut of a Japanese volunteer. Further study revealed that this species of gut bacteria is seen only in Japanese individuals.
For an in-depth look at what the horizontal gene transfer means and how this could affect your sushi-chomping habits, turn to the new DISCOVER blog Not Exactly Rocket Science and Ed Yong’s illuminating post, “Gut bacteria in Japanese people borrowed sushi-digesting genes from ocean bacteria.”
Not Exactly Rocket Science: Gut bacteria in Japanese people borrowed sushi-digesting genes from ocean bacteria
Not Exactly Rocket Science: Gut bacteria reflect diet and evolutionary past
80beats: Scientists Sequence DNA From the Teeming Bacterial Universe in Your Guts
DISCOVER: I’m Not Fat—I’ve Just Got Fat Bacteria
DISCOVER: 70. How the Body Protects the Gut