Share this article

print logo

SCIENCE NOTES

Huge population of bacteria resides in the human gut

Scientists have discovered a trove of life forms lurking in the human gut - 395 different bacteria, 60 percent of which had never before been described, according to a report in the journal Science.

The study analyzed samples of stool and mucous from six different parts of people's colons. The results were "surprising" and "a bit sobering," said the paper's first author, Stanford University researcher Dr. Paul Eckburg.

Eckburg and his coauthors used DNA analysis to identify the bacteria in the samples harvested from three middle-aged Canadians during colonoscopy examinations. About 80 percent of the bacteria had never been cultured in a laboratory, probably because they need the oxygen-free conditions of the gut in order to grow.

The scientists also found that the species of bacteria varied enormously from one gut to the next, perhaps because of dietary differences or because people are exposed to different microbes when their guts - sterile at birth - are first colonized.

Most of the bacteria belong to two groups known as Firmicutes and Bacteroidetes, some of which are thought to feed the gut wall, stimulate the growth of nutrient-supplying blood vessels and prevent disease-causing germs from taking up residence in the colon.

The findings are part of a much larger study seeking links between microbes in the gut and bowel disorders such as Crohn's disease and ulcerative colitis.

- Los Angeles Times

A scientific analysis of "old maids'

Why is it that whenever you make popcorn, there are always unpopped kernels left at the bottom of the bowl or the bag at the movies - the ones that stick in your throat, plug up your teeth and pop your fillings?

"It's a matter of scientific curiosity, and we are in the food business, " said Purdue University's Rengaswami Chandrasekaran. "So we decided to find out."

In research scheduled to appear in the journal BioMacromolecules, scientists led by food chemist Bruce Hamaker of Purdue analyzed 14 varieties of microwaveable popcorn to determine what causes the BB-hard leftovers known as "old maids." The number of unpopped kernels ranged from 4 to 47 percent.

The key popability factor, it turned out, is the kernel's cellulose hull, known as the pericarp. Chandrasekaran, a crystallographer, found that the pericarp in the better poppers had a stronger crystalline structure than the pericarp in the old maids.

"With a better organized crystal structure, the kernel retains moisture better," Chandrasekaran said. The kernel swells as it heats up, until it finally explodes, creating popcorn. If the moisture leaks out prematurely, or the pericarp collapses, the pressure will not build, and the frustrated consumer is left with old maids.

- Washington Post