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Tag: microbial communities

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Excerpts from an interesting article about microbes and some findings from 2014. From Wired:

9 Amazing and Gross Things Scientists Discovered About Microbes This Year

We can’t see them, but they are all around us. On us. In us. Our personal microbes—not to mention those in the environment around us—have us outnumbered by orders of magnitude, but scientists are only beginning to understand how they influence our health and other aspects of our lives. It’s an increasingly hot area of science, though, and this past year saw lots of interesting developments. Here are some of the highlights.

When you move, your microbes move with you

In a study published in Science in August, scientists cataloged the microbes of seven families, swabbing the hands, feet, and noses of each family member—including pets—for six weeks. They also collected samples from doorknobs, light switches, and other household surfaces. Each home had a distinct microbial community that came mostly from its human inhabitants, and the scientists could tell which home a person lived in just by matching microbial profiles. Three of the families moved during the study period, and it only took about a day for their microbes to settle in to the new place. As the journal’s editors put it: “When families moved, their microbiological ‘aura’ followed.”

Microbes could help solve crimes

Scientists made several findings this year that could potentially show up in court one day. One study found that the microbiome of human cadavers evolves in a predictable way, hinting at a new way to determine time of death. And earlier this month, researchers suggested that bacteria on pubic hair could be used to identify the perpetrators of sex crimes—especially useful when a rapist uses a condom to avoid leaving behind DNA evidence.

Your gut bacteria may be inherited

Exactly which bacteria choose to take up residence in your gut is determined, in part, by your genes, scientists reported this year after examining more than 1,000 fecal samples from 416 pairs of twins... One of the most heritable types was a family of bacteria called Christensenellaceae, which are more abundant in lean people than in obese people. 

Forget fecal transplants, poo pills may be just as effective

Clostridium difficile (pictured) is a nasty bacteria that wreaks havoc on the guts and kills 14,000 people a year in the US alone. Normally, other intestinal bacteria keep C. diff in check, but in the worst infections it starts to dominate. One effective but off putting treatment is a fecal transplant: taking a stool sample from a healthy person and transplanting it into the patient (in through the out door, so to speak). This year researchers developed a less cringe-inducing alternative. They created odorless frozen capsules that contained bacteria isolated from healthy stool samples. The poo pills successfully treated 18 of 20 patients with antibiotic-resistant C. diff infections, the team reported in JAMA in October.

Yeast evolved to lure fruit flies (not to make delicious beer)

There is crazy microbial diversity in cheese rinds

A tiny crumb of cheese rind contains about 10 billion microbial cells: bacteria and fungi that turn boring milk into something funky and delicious. Although cheesemakers have been manipulating them for centuries, not much is known about these microbes. This year scientists conducted the largest study yet on the microbial diversity of cheese, examining 137 cheeses from 10 countries.They found that microbial communities vary according to the style of cheese, but not so much according to where the cheese is made.

The microbiome could be a source of novel drugs

The bacteria that live on and in our bodies make countless molecules. Some of those molecules might make good drugs. 

We may need new branches on the tree of life for all the microbes

Life on Earth has traditionally been divided into three domains: Eukaryotes (plants, animals, and all other organisms that stash their DNA in a special compartment—the nucleus—inside their cells), Bacteria (our familiar one-celled friends and foes), and Archaea (single-celled organisms that are biochemically and genetically distinct from the other two groups). But do we really know that’s all there is? We do not, two scientists argued last month in Science. There may be entire domains of life that have eluded our methods of detection.

Without microbes, life as we know it would end

In December, two scientists posed a thought question in the journal PLOS Biology: What would happen in a world without microbes? ...Without nitrogen-fixing soil bacteria, crops would begin to fail. Decomposition would stop, waste would pile up, and the nutrient recycling that supports life as we know it would grind to a halt. “We predict complete societal collapse only within a year or so, linked to catastrophic failure of the food supply chain,” the researchers write. “Annihilation of most humans and nonmicroscopic life on the planet would follow a prolonged period of starvation, disease, unrest, civil war, anarchy, and global biogeochemical asphyxiation.”

 Clostridium difficile. Credit: CDC

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A recently released report from the American Academy of Microbiology explains the basics of the human microbiome (the collection of trillions of microbes living in and on the human body) and its role in human health in easy to understand language and illustrations. It's a primer for the general public that addresses questions about this growing area of research. There is also a section on the role of the microbiome in human conditions such as obesity and inflammatory bowel disease, and there are general tips on what can be done to maintain a healthy microbiome. It is well worth reading. Below is part of the answer to the question "How big is the microbiome?" The answer shows that it is amazingly big by all measures.

FAQ: HUMAN MICROBIOME

3) How big is the microbiome?

The microbiome is big by almost any measure — number of organisms, total volume, species diversity, and genetic diversity.

NUMBER OF ORGANISMS:
The microbiome includes approximately 100 trillion bacterial cells.                                                   That’s 100,000,000,000,000! You may have heard that there are 10 times more microbial cells than human cells in the human body, but that commonly cited ratio was based on an estimate of 10 trillion cells in the human body. More recent estimates suggest that the human body actually is made up of about 37 trillion human cells. Thus at any given time, the average human body is carrying around 3 times more bacterial cells than human ones. But the microbiome includes more than just bacteria. Remember that it also includes plenty of viruses, fungi, archaea, and single-celled eukaryotes. There is general agreement that viruses outnumber bacterial cells, maybe by as much as 5 to 1. There are thought to be about 10-fold fewer fungal cells than bacteria. All of these numbers are estimates and because the microbiome is a dynamic community, the numbers may change under different circumstances. 
TOTAL VOLUME:
The microbiome is also pretty big in terms of the space it occupies and its total weight. Even though each individual member is microscopic, those large numbers do add up. Most estimates put the weight of an average human microbiome at about 2.5 pounds. In volume, if consolidated, the microbiome would occupy about 3 pints. Keep in mind though, that the microbiome is not all consolidated in one place, and the density of the various microbial communities varies greatly from body site to body site. Blood and lymphatic fluids are practically sterile, while the intestines and colon contain one of the densest known microbial communities on Earth. What is the secret to that high density in the intestinal tract?
Surface area. The inner surfaces of the human intestine and colon are highly convoluted. If you were to flatten out the entire inner surface of the intestine, it would be the size of a tennis court! Dense microbial communities coat that entire surface and also fill the interior spaces of the intestines, resulting in a very dense community.

SPECIES DIVERSITY:
The microbiome is also diverse — a normal microbiome includes around a thousand different species. Thinking back again to your high school biology class, you might recall learning about three basic kinds of bacteria: rods, spheres, and spirals. Certainly bacteriologists developed and used a much more detailed classification system that took into account bacterial physiology and metabolism, but until quite recently, known bacterial diversity was confined to the approximately 5,000 bacterial species that could be grown in the laboratory. Technological advances, especially the capacity to sequence genetic material from environmental samples, have allowed scientists to explore the bacterial world at much greater depth and resolution. 

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If you missed these recent articles about weight and gut bacteria, please go read them now. Amazing stuff. From the December 9, 2013 Washington Post:

The microbes in your gut may be making you fat or keeping you thin

 ...a growing body of evidence suggesting that naturally occurring bacteria and other microbes in the body, and possibly even viruses, can influence weight in ways that scientists are only just beginning to understand. Numerous studies are underway looking at the role of intestinal organisms in obesity, with a focus on how they extract energy from food and how this affects weight gain or loss.

From September 5, 2013 Science News: Gut infections keep mice lean

Skinniness could be contagious. Gut bacteria from thin people can invade the intestines of mice carrying microbes from obese people. And these invaders can keep mice from getting tubby, researchers report in the Sept. 6 Science.

But the benefits come with a catch. The invading microbes drop in and get to work only when mice eat healthy food. Even fat-blocking bacteria can’t fight a bad diet, suggests study leader Jeffrey Gordon, a microbiologist at Washington University in St. Louis. 

Fat and thin people have different microbes teeming in their intestines, for example. And normal-weight mice given microbes from obese mice pack on extra fat, says coauthor Vanessa Ridaura, also of Washington University.