Even the infamous bacteria Helicobacter pylori , which can cause chronic gastritis and peptic ulcers, may have qualities redemption. The inhabitant of the ubiquitous stomach produces an antibacterial peptide that can offer protection against other enteric pathogens, according to a study in tomorrow's issue of Nature .
H. pylori plagues one in two human stomachs in the Western world, often for life, but most infections go unnoticed. The microbe is even more widespread in the developing world, leading some scientists to speculate that H. pylori can be part of our natural gastrointestinal flora - some say it might even offer some benefits his host, like many other enteric bacteria. Last year, a study suggested that H. pylori could boost immunity to other intestinal pathogens such as cholera causing Vibrio cholerae . It is also known that many bacteria produce antibiotics compounds that ward off competitors.
So molecular microbiologist Staffan Normark of the Karolinska Institute in Stockholm, Sweden, wondered if H. pylori did something similar. Preparation of H. pylori "shake" in a high-tech version of a blender, Normark and his team found that it effectively killed other bacteria, such as Escherichia coli and Bacillus megaterium . They then searched the genome of H. pylori for sequences that match those of two dozen antibacterial peptides called cecropins, first isolated from insects in the 70 They found that the first 20 amino acids of a protein called RpL1 match a sequence of the cecropin. When the researchers synthesized this peptide, they found that he killed 99.5% of E. coli culture in just 20 minutes. H. pylori , on the other hand, was resistant to cecropin.
"Unlike conventional antibiotics, these peptides kill very quickly," said Normark, "and they are also active against bacteria that do not divide," which would make them attractive cecropins for drug developers. But it remains to see if the H. pylori in your stomach protects against notorious bugs such as E. coli strain that causes food poisoning or V. cholerae .
For Martin Blaser, an infectious disease specialist at Vanderbilt University in Nashville, Tennessee, "it is very refreshing to see evidence that there are potential benefits" of H. pylori to compensate for the damage it causes. "In a world in black and white," he said, " H. pylori is gray."
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