Legionella bacteria can contaminate many water sources, even windshield wiper fluid, and if inhaled as aerosols in contaminated water mists, these microbes can cause a type of pneumonia known as Legionnaires' disease or Legionellosis. Symptoms include fever, headache, cough, acing muscles, and breathing difficulties. The disease can vary in severity, and can be treated with certain antibiotics, but it has to be diagnosed in time. Legionnaires' is estimated to be fatal in about one of every ten cases, due to lung failure. There is no vaccine for the disease.
A recent outbreak of Legionnaires' disease in New York City was traced to water cooling towers on the roof of Harlem Hospital and a construction site nearby. Seven people died during this outbreak and dozens of people were sickened. Previous outbreaks in NYC have been traced to showers, spas, fountains, and even water misters in supermarkets. The bacteria is thought to pose a problem worldwide, but infections can be prevented by maintaining water systems to minimize the growth of these microbes.
Scientists have also recently used cryo-electron microscopy (cryo-EM) to reveal more about how Legionella takes over cells. This work, which was reported in the Proceedings of the National Academy of Sciences (PNAS), could help researchers develop better treatments for Legionnaires’.
Legionella bacteroa use what’s known as a type IV secretion system (T4SS), which moves proteins across the bacterial cell membrane, from the microbe into a target cell. In this study, the structure of the Legionella T4SS was deciphered. This microbial nanomachine was captured as it morphed from a closed to an open structure, allowing it to send bacterial proteins into a target cell. This T4SS is notable because it can move as many as 330 microbial proteins into its target.
"We needed the power of the cryo-EM to be able to manipulate the bacterial cells so we could finally reveal the action," said study co-author Samira Heydari, a postdoctoral researcher in the lab of senior study author Professor Jun Liu of Yale University.
Sources: Yale Univerity, NYC Health, Proceedings of the National Academy of Sciences (PNAS)
