Nothing in Biology Makes Sense: Making sense of the relationship between gut microbes and obesity

Obese mouse, non-obese mouse. Photo via Nothing in Biology Makes Sense.

Over at Nothing in Biology Makes Sense, Sarah Hird discusses an attempt to suss out whether your gut microbes change when you’re overweight, or your gut microbes can make you overweight.

Historically, medical research has focused on pathogenic bacteria when trying to understand the relationship between human health and microorganisms. This makes intuitive sense – since pathogens make us sick – but our bodies host way more nonpathogenic bacteria than pathogens and they function in keeping us healthy. Our gastrointestinal tract has trillions of bacteria in it and much recent work has been trying to understand these complex communities. Mice are a common model for understanding human gut microbes and health. Enter Obie, the obese mouse (Figure 1, left) and Lenny, the lean mouse (right).

The new study demonstrates that bacteria cultured from the gut of an obese mouse cause normal-weight mice to gain weight when they’re fed a high-fat diet—and that the genetically similar mice without the bacteria can eat the same diet without becoming obese. You should definitely go read the whole thing.◼

Nothing in Biology Makes Sense: Making sense of “stinkbird” gut microbes

A hoatzin. Photo by Carine06.

I was off the grid last week, so I missed Sarah Hird’s latest post at the group blog Nothing in Biology Makes Sense!, discussing a cool new study of the microbes in the guts of hoatzins, a species of wonderfully weird birds.

The hoatzin has an enlarged crop for the purpose of fermentation (see figure below). A “crop” is an anatomical structure in throat of some animals (including most birds) that primarily stores food. In the hoatzin, however, it does much, much more. Foregut fermentation is a digestive strategy where microbes living in or before the stomach break down vegetation for their host. Microbes are required by foregut fermenters because only the microbes are capable of breaking down the cell wall of plants, a barrier that confines most of the nutrients found in plant cells. The hoatzin is the only bird to use foregut fermentation and is the smallest known foregut fermenter.

To learn what the new study reveals about the diversity of microbes in hoatzin foreguts, go read the whole thing, including the evolving plans for follow-up experiments in the comments. ◼

Nothing in biology makes sense: Gut microbes and mate preference

Will this male fruit fly pick a mate based on what she ate? Photo by Max xx.

This week at Nothing in Biology Makes Sense!, Sarah Hird tackles a series of studies suggesting that fruit flies may pick mates reared on similar diets because their gut microbes make them do it.

In 1989, Diane Dodd reared fruit flies (Drosophila pseudoobscura) from a common stock on two different food sources: starch and maltose. She found that after multiple generations of isolation on their separate substrates, starch-flies preferred to mate with starch-flies and maltose-flies preferred to mate with maltose-flies. The result was robust and repeatable, but the reason why and its mechanism were unknown.

To find out how the mechanism was discovered, go read the whole thing. ◼