Chapter 50, Problem 3Q

Summary Introduction

To review:

The difference between the outcomes from summer versus winter microbiota and a hypothesis to explain it.

Given:

Researchers, for their study, took the brown bears (Ursus arctos) for the role of gut microbiota in the digestion of food and in many other aspects of nutrition. Brown bears have the ability of hibernating when the environment is drastically cold. Researchers studied if the gut microbiome of the bear has some difference before and after fasting. For this, the scientists studied the fecal and the blood samples of about 16 brown bears during hibernation, which starts from February and continued their study till June of following hibernation year. They found the presence of the different microbe communities in different amounts during different seasons and same was with the triglycerides and other nutrients.

The following graphs were plotted after observing the conditions in winters and summers. Figure 1 shows the presence of different composition of the microbiome during different seasons. Also, the differences in the blood levels of triglycerides, lactate, and succinate are depicted.

The effects of the microbiota were also examined after introducing them into germ-free mice. Germ-free mice, unlike normal mice, are devoid of gut microbiota and are unable to gain mass when they are kept on a high-fat diet. Fecal transplants from summer and the winter bears were given to the germ-free mice. Figure 2 shows the changes in body mass, fat content, and blood triglyceride levels of the mice after 2 weeks.

Introduction:

Germ-free mice are those mice that do not have any microbes in their gut. These mice are different from the normal mice as they are unable to gain weight when kept on a high-fat diet. These mice are used for the experiment and introduced with the microbiota of summer bears and winter nears. The difference in the microbiota leads to the difference in the body mass of the mice