Researchers discover 'acquired' DNA key to certain bacterial infection

Researchers announced this week the discovery of a mechanism by which Mycobacterium avium – a bacterium which can result in serious lung infections and is prevalent in emphysema and AIDS patients among others – infects tissue cells or “macrophages” and thus compromises the body’s immunity.

Results of the study, led by researchers at Oregon State University, will be published online this week in the Proceedings of the National Academy of Sciences. Other co-authors were from the University of Nebraska.

The key to the bacterium’s ability to enter environmental amoebas – and ultimately humans – is an “island” of genetic material acquired through evolution from another bacterium, according to Luiz E. Bermudez, a professor of biomedical sciences in OSU’s College of Veterinary Medicine and an author of the study.

“Without these acquired genes, the bacterium is very inefficient in infecting environmental amoeba, which is the environmental host,” Bermudez said. “In fact, its efficiency is close to zero. But with this ‘island’ of acquired genetic material, the bacterium finds a way to get inside the cells and it takes control, not the phagocyte.”

Phagocytes are cells that engulf and digest pathogens and cellular debris, and in humans serve as the body’s initial immune response.

The researchers did not find a similar island of acquired genetic material in two similar bacteria, Mycobacterium tuberculosis and Mycobacterium paratuberculosis, which causes Johne’s disease.

M. avium exists in the environment and is thought to infect humans when the infected environmental hosts – amoebas – are inhaled or swallowed.

Incidence of M. avium as a cause of syndromes may be decreasing because of changes in treatment for HIV-infected patients, according to the Centers for Disease Control and Prevention, which estimates that 1 out of 100,000 persons may be affected. However, CDC also notes that the bacterium’s resistance to antibiotics – already a problem – may be increasing. In contrast, the incidence of lung infection in patients with chronic lung diseases and cystic fibrosis is increasing.

Understanding the mechanism by how M. avium penetrates the macrophage and infects humans may eventually lead to interventions that can prevent, or at least, reduce the chance of infections, though Bermudez cautioned that it is early in the process.

“We still don’t know what most of the individual genes do,” he said, “and none of the DNA sequences match those in known databases.”

The researchers did discover that one of the genes provides coding for a protein that targets action in the host cell, which may help the bacterium survive in the macrophage.

Bermudez said the researchers learned the genetic “island” was acquired from another bacterium because of its unique nucleotide structure, which differs from its Mycobacterium cousins. Such evolution likely took place over thousands of years, he pointed out, and may have come from a pathogen which also has the ability to infect environmental amoeba.

Source: Oregon State University

Related stories:

Researchers identify biofilms that cause infections
Understanding the way bacterial cells "talk" to each other could lead to more effective methods for fighting the often persistent and serious infections caused by the biofilms they form, says a Texas A&M University professor of chemical engineering who not only has deciphered their language but also discovered how to quell their conversation.
How bacteria evolve into superbugs
Researchers at McGill and Oxford Universities have applied ecological and evolutionary theory to demonstrate how bacteria become resistant to antibiotics in hospitals.
Groundbreaking, lifesaving TB vaccine a step closer
Researchers at Aberystwyth University, following a number of years of investment by the Biotechnology and Biological Sciences Research Council (BBSRC), have licensed ground-breaking research to a non-profit product development partnership working to develop new, more effective vaccines against Tuberculosis (TB). This development will give hope that significantly better prevention and treatment of TB will be available within the next few years.
'Deadly dozen' reports diseases worsened by climate change
Health experts from the Wildlife Conservation Society today released a report that lists 12 pathogens that could spread into new regions as a result of climate change, with potential impacts to both human and wildlife health and global economies. Called The Deadly Dozen: Wildlife Diseases in the Age of Climate Change, the new report provides examples of diseases that could spread as a result of changes in temperatures and precipitation levels. The best defense, according to the report's authors, is a good offense in the form of wildlife monitoring to detect how these diseases are moving so health professionals can learn and prepare to mitigate their impact.
TB Bacterium Uses Its Sugar Coat To Sweeten Its Chances Of Living In Lungs
(PhysOrg.com) -- Common strains of tuberculosis-causing bacteria have hijacked the human body’s immune response to play tricks on cells in the lungs, scientists say.
Benchmark cyanobacterium sequenced could be cheap renewable energy source
(PhysOrg.com) -- A team of researchers headed by biologists at Washington University in St. Louis has sequenced the genome of a unique bacterium that manages two disparate operations — photosynthesis and nitrogen fixation — in one little cell during two distinct cycles daily.
Is re-emerging superbug the next MRSA?
Dr. Ed Corboy had no idea what was afflicting his 80-year-old mother, Joan Corboy. All he knew for certain was that since being treated for what was a routine diarrheal infection, she seemed to be wasting away and none of her doctors or other health specialists could explain why.
Researchers advance cellulosic ethanol production
A team of researchers from Dartmouth's Thayer School of Engineering and Mascoma Corporation in Lebanon, N.H., have made a discovery that is important for producing large quantities of cellulosic ethanol, a leading candidate for a sustainable and secure alternative to petroleum-derived transportation fuel. For the first time, the group has genetically engineered a thermophilic bacterium, meaning it's able to grow at high temperatures, and this new microorganism makes ethanol as the only product of its fermentation.

News discussion:

Medicine & Health news