Featured Research

from universities, journals, and other organizations

Study Contradicts Assumption That Ulcer Bug Has Always Plagued Humans

Date:
May 16, 2000
Source:
Washington University School Of Medicine In St. Louis
Summary:
The bacterium that causes stomach ulcers might not have been with humans forever, a new study suggests, contradicting a long-held assumption. Comparing pieces of DNA from Helicobacter pylori, scientists discovered that strains from Peru resemble those from Spain and not those from eastern Asia.

St. Louis, May 12, 2000 – The bacterium that causes stomach ulcers might not have been with humans forever, a new study suggests, contradicting a long-held assumption. Comparing pieces of DNA from Helicobacter pylori, scientists discovered that strains from Peru resemble those from Spain and not those from eastern Asia.

Related Articles


"My favorite interpretation of this finding is that the Spanish brought H. pylori to Peru when they conquered the Incan empire nearly 500 years ago and that the bacterium was not present in the ancestors who crossed the Bering Strait from Asia more than 10,000 years ago," says Douglas E. Berg, Ph.D., the Alumni Professor of Molecular Microbiology and professor of genetics at Washington University School of Medicine in St. Louis.

Berg and collaborators in Britain, China, Guatemala, India, Japan, Peru, South Africa, Spain, Sweden and the United States report their findings in the June issue of the Journal of Bacteriology.

H. pylori is carried by more than half the world’s population, and it can thrive in the stomach for years. Whereas some people suffer no apparent consequences, others develop peptic ulcer disease. Gastric cancer, the leading cause of cancer deaths in some developing countries, also has been associated with H. pylori.

Analyzing DNA from more than 500 strains from five continents, Berg’s group focused mainly on a region called the cag pathogenicity island. One part of this region contains apparently vestigial genes, and it varies in size because some strains have lost pieces of DNA whereas others have inserts. Also, some base pairs, the building blocks of DNA, have been substituted for others.

As well as measuring the size of the vestigial segment, the researchers examined the DNA sequences of cagA, a gene that lies just next to it, and vacA, which lies elsewhere in the chromosome. The cagA gene codes for a protein that, when phosphorylated, alters the internal communication system of human cells, whereas vacA codes for a toxic protein.

The DNA analysis classified the H. pylori isolates into five types. Type I DNA motifs predominated in the strains from Spain, Peru, Guatemala and native Africans. Type II motifs were most common in the Chinese and Japanese strains, whereas type III motifs predominated in the Indian strains. Each of the three motifs was common in the strains from northern Europe. The rare type IV motif showed up in one English strain and two strains from West Virginia, and the type V motif was found in a few of the Indian strains. "So we can type H. pylori strains from different societies by differences in their DNA," Berg says. "One of the most striking differences was between strains from eastern Asia – China and Japan – and strains from Amerindians in Peru."

Berg speculates that H. pylori might have infected humans when agriculture brought animals and people into closer contact. "Many other diseases – tuberculosis, whooping cough, measles, mumps and chicken pox – are of animal origin and probably came into the human population when our ancestors started to practice agriculture and when their population densities increased," he says.

Until now, scientists have assumed that humans acquired H. pylori during their evolution from pre-human ancestors. "People haven’t paid any attention to the possibility that human H. pylori infection might have become widespread only in more recent history," Berg says.

His results are compatible with the idea that genetic differences between strains in different parts of the world reflect selection for different types of CagA protein in different animals hosts – either domesticated animals or rodent pests that came to live with early agriculturists. "For example, the ancestors of European strains of H. pylori might have come from mice or sheep, whereas the ancestors of various Asian strains might have come from cats, pigs or Mongolian gerbils," he says. "All of these animals can be infected with at least certain H. pylori strains recovered from human patients."

In another paper in the same issue of the Journal of Bacteriology, Berg and collaborators describe genetic differences between strains isolated from patients in Calcutta, India, and those from Europe and elsewhere in Asia. Their analysis of vacA was particularly instructive, revealing motifs that were present only in the Indian strains. "So the Indian motif is distinctive," Berg says, "reflecting either historic separations of people in India from people in Spain and in eastern Asia or selection for different traits in different ancestral animal hosts."


Story Source:

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


Cite This Page:

Washington University School Of Medicine In St. Louis. "Study Contradicts Assumption That Ulcer Bug Has Always Plagued Humans." ScienceDaily. ScienceDaily, 16 May 2000. <www.sciencedaily.com/releases/2000/05/000515085532.htm>.
Washington University School Of Medicine In St. Louis. (2000, May 16). Study Contradicts Assumption That Ulcer Bug Has Always Plagued Humans. ScienceDaily. Retrieved November 26, 2014 from www.sciencedaily.com/releases/2000/05/000515085532.htm
Washington University School Of Medicine In St. Louis. "Study Contradicts Assumption That Ulcer Bug Has Always Plagued Humans." ScienceDaily. www.sciencedaily.com/releases/2000/05/000515085532.htm (accessed November 26, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Wednesday, November 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Pet Dogs to Be Used in Anti-Ageing Trial

Pet Dogs to Be Used in Anti-Ageing Trial

Reuters - Innovations Video Online (Nov. 26, 2014) — Researchers in the United States are preparing to discover whether a drug commonly used in human organ transplants can extend the lifespan and health quality of pet dogs. Video provided by Reuters
Powered by NewsLook.com
Today's Prostheses Are More Capable Than Ever

Today's Prostheses Are More Capable Than Ever

Newsy (Nov. 26, 2014) — Advances in prosthetics are making replacement body parts stronger and more lifelike than they’ve ever been. Video provided by Newsy
Powered by NewsLook.com
From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) — The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Daily Serving Of Yogurt Could Reduce Risk Of Type 2 Diabetes

Newsy (Nov. 25, 2014) — Need another reason to eat yogurt every day? Researchers now say it could reduce a person's risk of developing type 2 diabetes. 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:

Strange & Offbeat Stories

 

Health & Medicine

Mind & Brain

Living & Well

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