Featured Research

from universities, journals, and other organizations

Scientists Dissect Bacterial Crosstalk

Date:
August 23, 1999
Source:
Washington University School Of Medicine
Summary:
Please pass the sugar, a hungry bacterium says. And the lining of the intestine complies. But how can microbes talk to mammals' With a dual-purpose protein, scientists find.

St. Louis, Aug. 20, 1999 -- Please pass the sugar, a hungry bacterium says. And the lining of the intestine complies. But how can microbes talk to mammals' With a dual-purpose protein, scientists find.

The microbes in our body -- more numerous than human cells -- fend off pathogens and do other essential chores. "But we know very little about how our relationships with them are forged," says Jeffrey I. Gordon, M.D. "We want to understand the conversations that occur between these microbial guests and their host."

The findings appear in the Aug. 17 Proceedings of the National Academy of Sciences. Gordon, the Alumni Professor and head of molecular biology and pharmacology and professor of medicine at Washington University School of Medicine in St. Louis, is senior author of the paper. Postdoctoral fellow Lora V. Hooper, Ph.D., is first author.

Four hundred species of microbes call our gut home, competing for space and food. To cut through the cacophony, the researchers studied just one species.

Bacteroides thetaiotaomicron lives in the lower part of the gut and feeds on a sugar called fucose. It arrives early in a mammal's life, paving the way for other friendly microbes.

Using germ-free mice, Gordon's group previously showed that cells lining the intestine make fucose, posting the sugar on the cell surface. At weaning, fucose production stops. But it starts up again if mice are exposed to B. thetaiotaomicron. So the bacterium somehow tells the intestine to give it food. And the researchers have found the molecular switch.

First, Hooper created mutants of B. thetaiotaomicron that were unable to utilize fucose. Analyzing these strains, she identified five genes in a row that shared a regulatory region.

Four were involved in fucose uptake or metabolism. But the first coded for a repressor protein, FucR. Hooper purified the repressor and studied FucR mutants. She deduced that the protein halts the transcription of the five genes by interacting with the common regulatory region. But when fucose is available, it no longer can bind to that spot on the DNA. So the bacterium can make the enzymes that metabolize fucose.

Bacteria frequently employ this type of regulation. But B. thetaiotaomicron uses the repressor to tie ordering to inventory.

To see how the bacterium communicates with intestinal cells, Hooper infected mice with various B. thetaiotaomicron mutants. Those that were unable to make fucose isomerase, the first enzyme in the fucose-metabolizing pathway, couldn't tell the mice to give them fucose. But mutants that were unable to make FucR had no trouble getting this message across, even though they didn't make fucose isomerase. So fuculose, the substance made by the isomerase, isn't the give-me-fucose signal.

The researchers proposed a different explanation. They suggest that FucR interacts with the regulator of at least one other gene, which they call csp (control of signal production). When the repressor silences csp, the bacterium stops talking to the intestine. When the repressor is absent, signaling proceeds. "So FucR is the key switch that determines whether the bacterium consumes fucose or asks for more fucose," Gordon says.

FucR's dual function depends on its ability to interact with fucose, the researchers suggest. Although the sugar allows the repressor to switch on the production of fucose-metabolizing enzymes, it enables it to switch off the signal to the intestinal cells.

If the bacterium contains plenty of fucose, most of its FucR will be attached to sugar. So the repressor will be powerless to prevent the production of fucose-metabolizing enzymes. But FucR will bind to the regulatory region of csp. So the pass-the-sugar message won't be sent.

If the bacterium runs short of fucose, most of the FucR will lack sugar. So it will switch off the production of fucose-metabolizing enzymes. But it no longer will silence csp, so the request for fucose will go forth.

Hooper obtained evidence for this model. The mutant that couldn't transport fucose into the cell cajoled mice into making fucose. And the mutant that lacked fucose isomerase signaled once more if the fucose transporter was removed. This type of communication might be too useful to be just an interesting fluke. The paradigm may apply to other nutrients and other forms of requests to hosts, Hooper and Gordon say.

Understanding microbe to mammal communication may help us cope when our friendly bacteria are slain by antibiotics and harmful microbes rush to fill the places at the table. "These messages undoubtedly contribute to the stability of intestinal ecosystems," Gordon says. "So the lessons we learn may help us keep the microbes we need and prevent the encroachment of those we would rather not have."

Grants from the National Institutes of Health supported this research, and fellowships from the Lucille P. Markey Foundation and the National Institutes of Health supported Hooper.

Hooper LV, Xu J, Falk PG, Midtvedt T, Gordon JI. A molecular sensor that allows a gut commensal to control its nutrient foundation in a competitive ecosystem. Proceedings of the National Academy of Sciences 96, 9833-9838, Aug. 17, 1999.


Story Source:

The above story is based on materials provided by Washington University School Of Medicine. Note: Materials may be edited for content and length.


Cite This Page:

Washington University School Of Medicine. "Scientists Dissect Bacterial Crosstalk." ScienceDaily. ScienceDaily, 23 August 1999. <www.sciencedaily.com/releases/1999/08/990823071819.htm>.
Washington University School Of Medicine. (1999, August 23). Scientists Dissect Bacterial Crosstalk. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/1999/08/990823071819.htm
Washington University School Of Medicine. "Scientists Dissect Bacterial Crosstalk." ScienceDaily. www.sciencedaily.com/releases/1999/08/990823071819.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Newsy (July 27, 2014) The satellite is back under ground control after a tense few days, but with a gecko sex experiment on board, the media just couldn't help themselves. Video provided by Newsy
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins