Thursday 24 July 2014

Lung Microbiome Research

The the lung microbiome play a key role in respiratory health.

If the human digestive tract were a river from the mouth extending through the stomach and intestines, ending at the anus, the lungs would be pools alongside that river that are often swept by eddying currents, according to Gary Huffnagle from the University of Michigan, who began studying the bacterial communities that inhabit these pool-like organs nearly a decade ago. “There’s a constant flow into [the] lungs of aspirated bacteria from the mouth,” he said. But through the action of cilia and the cough reflex, among other things, there’s also an outward flow of microbes, making the lung microbiome a dynamic community.

The surface area of the healthy lung is a dynamic environment. The respiratory organ is constantly bombarded by debris and microbes that make their way from the mouth and nose through the trachea. Ciliated cells on branching bronchioles within the lungs beat rhythmically to move debris and invading microbes, while alveolar macrophages constantly patrol for and destroy unwelcome bugs.

The lung microbiome is about 1,000 times less dense than the oral microbiome and about 1 million to 1 billion times sparser than the microbial community of the gut, said Huffnagle. That is in part because the lung lacks the microbe-friendly mucosal lining found in the mouth and gastrointestinal tract, instead harboring a thin layer of much-less-inviting surfactant to keep the respiratory organs from drying out. In a review article published in The Lancet Respiratory Medicine this March, Huffnagle and his colleagues argued that the lungs are like the South Pacific, with small islands of clustered bacteria and wide stretches of unpopulated regions between them. It appears that the lung microbiome is populated from the oral microbiome, and among this population exists a small subset of bacteria that can survive the unique environment of the lung. The most common bacteria found in healthy lungs are Streptococcus, Prevotella, and Veillonella species.

Source: The Scientist

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