Yale University researchers have shed new light how bacteria like the ones that cause Legionnaires' disease and Q-fever raise such havoc in human patients.
In order to survive, the gram-negative bacteria use genes that have evolved in tandem with ones in their hosts to essentially disarm immune system cells trying to kill them, the scientists report Friday in the journal
Science.
"Because of their life style, trying to identify how these organisms cause disease has been really difficult,'' said
Craig Roy, professor at the Yale School of Medicine in the section of microbial pathogenesis.
Roy and his group described one innovative way the organisms inflict their damage with impunity.
Some gram-negative pathogens such as Legionella pneumophila, and Coxiella burnetii, the cause of Q fever, actually secrete proteins into eukaryotic cells, or cells with a nucleus. But exactly what those proteins did was not known.
Legionnaires' disease is a dangerous form of pneumonia often contracted by inhaling water droplets containing the organism. Q-fever in humans can cause high fevers, chills and can also develop into pneumonia. Both often go undiagnosed.
Previous genome scans of the gram-negative bacteria that cause these diseases had identified a high prevalence of genes called Anks, for ankyrin repeat homology domains. These genes fascinated scientists because they appear very similar to numerous genes in eukaryotic cells that regulate a multitude of processes. These bacteria have "borrowed'' or co-evolved genes from their hosts to survive in the cell. In fact, some species of these bacteria cannot exist outside of a eukaryotic cell.
Roy's lab showed that Ank proteins are secreted into immune system cells called macrophages, and once inside, turn off mechanisms within the cell designed to destroy the bacteria.
Roy believes that more such survival tricks of gram-negative pathogens will be found but adds, "this study at least gives us a foothold" for further study.
Because these bacteria tend to behave like viruses and actually invade cells, they might be susceptible to a vaccine that targets specific elements of the Ank protein and allow macrophages to complete the job, he said.
Source: Yale University
Related stories:
Scientists uncover molecule that keeps pathogens like salmonella in check
Scientists at UT Southwestern Medical Center have found a potential new way to stop the bacteria that cause gastroenteritis, tularemia and severe diarrhea from making people sick.
Accumulated bits of a cell's own DNA can trigger autoimmune disease
A security system wired within every cell to detect the presence of rogue viral DNA can sometimes go awry, triggering an autoimmune response to single-stranded bits of the cell's own DNA, according to a report in the August 22nd issue of the journal
Cell, a Cell Press publication. The source of that single-stranded DNA is so-called endogenous retroelements—genetic elements accounting for a substantial portion of the genome that can move to new locations using a "copy and paste" mechanism, according to the researchers.
Chemical liberated by leaky gut may allow HIV to infect the brain
In up to 20 percent of people infected with HIV, the virus manages to escape from the bloodstream and cross into the brain, resulting in HIV-associated dementia and other cognitive disorders. Now, scientists at the Albert Einstein College of Medicine of Yeshiva University have found strong evidence that a component of the cell walls of intestinal bacteria—a chemical present in high levels in the blood of HIV-infected people—helps HIV to penetrate the usually-impregnable blood brain barrier (BBB). The findings, published in the August issue of the
Journal of Virology, could lead to strategies for preventing HIV from entering the brain and causing serious complications.
Key site in iron metabolism aids in diagnosing anemia of chronic disease
University of Utah School of Medicine researchers have developed a new tool that facilitates diagnosis of anemia related to chronic illness, as well as diseases of iron overload. The results of a study detailing the new tool are published in the August 2008 issue of the journal
Cell Metabolism, a publication of Cell Press.
New study of gene evolution could lead to better understanding of neurodegenerative disease
Genetic evolution is strongly shaped by genes' efforts to prevent or tolerate errors in the production of proteins, scientists at The University of Texas at Austin and Harvard University have found.
Various species' genes evolve to minimize protein production errors
Scientists at Harvard University and the University of Texas at Austin have found that genetic evolution is strongly shaped by genes' efforts to prevent or tolerate errors in protein production.
Researchers Discover Remnant of an Ancient 'RNA World'
(PhysOrg.com) -- Some bacterial cells can swim, morph into new forms and even become dangerously virulent - all without initial involvement of DNA. Yale University researchers describe Friday in the journal
Science how bacteria accomplish this amazing feat - and in doing so provide a glimpse of what the earliest forms of life on Earth may have looked like.
Tumor-inhibiting protein could be effective in treating leukemia
(PhysOrg.com) -- Angiocidin, a tumor-inhibiting novel protein discovered by Temple University researchers, may also have a role as a new therapeutic application in treating leukemia, according to a study by the researchers.