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R E S E A R C H Primordial proteins and the survival of nanobacteria Nanobacteria that range in size from 80 to 300 nm thrive in the humid, longer-lasting clouds caused by global warming. They become revitalized, are transported by winds, and eventually rain down on the earth, spreading disease across the planet. It may sound like something out of a science fiction movie, but increasing evidence is linking nanobacteria to a host of diseases, including atherosclerosis, kidney stones, ovarian cancer, peripheral neuropathy, HIV, and osteoporosis. The prevalence of these tiny pathogens can be attributed to the way they survive in hostile conditions. When their environment becomes unfavorable, they fortify a porous shell consisting of the mineral apatite and envelop themselves in a layer of slime. To better understand the survival mechanisms of nanobacteria, Andrei Sommer and colleagues at the University of Ulm (Germany), Cardiff University (U.K.), and the Inter-University Centre for Astronomy and Astrophysics (India) have begun to study the functions of primordial proteins. In a twopart series of letters in JPR (2004, 3, 1296 –1299; 2005, 4, 180 –184), the researchers investigate the proteins involved in slime production in nanobacteria. Knowledge of their functions and ways to inactivate them could be therapeutically important and may even shed light on the role of these primitive life-forms in the origin of life. “In the body, nanobacteria use slime to stick and form colonies. If they are not able to stick, they can be eliminated from the body,” says Sommer. The work is also important because these primordial proteins could be common to other bacteria. Finding ways to inactivate proteins involved in slime production could therefore be the first step in controlling the attachment of numerous kinds of bacteria to their host cells. “What experiments with nanobacteria suggest is that they produce this slime instantaneously. This is a strong indication for highly effective pores,
© 2005 American Chemical Society
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which allow them to press out liquids contained in their cavities,” says Sommer. This behavior led the researchers to wonder whether light would inhibit slime production by interfering with the pumping process. In previous work, they concluded that light can change the density and viscosity of aqueous liquids inside nanoscale cavities. Such density fluctuations change pumping behavior.
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In a series of experiments using polarized light, light emitting diodes, and laser light, the researchers discovered that light on the order of the intensity of the sun (∼1000 W/m2) does indeed inhibit slime production in nanobacteria. Light activates an ancient program, which nanobacteria probably use when they leave a cloud, says Sommer. “In a cloud, they have low light intensity and high humidity. It’s a highly favorable environment for biological processes,” he says. But when they leave a cloud, they face high light intensity, heat, and a dry environment. To protect themselves from desiccation, they seal off their pores. Once the pores are sealed, slime production stops, and the nanobacteria lose their ability to adhere to surfaces. Sommer initially got the idea that light could inhibit slime production in nanobacteria in the atmosphere from drug release studies he conducted with Attila Pavláth ( J. Proteome Res. 2003, 2,
558–560). That work, which was based on modeling the survival of nanobacteria in the atmosphere, and preliminary evidence for the prevalence of nanobacteria in people infected with HIV ( J. Proteome Res. 2003, 2, 665–666) led the researchers to speculate that nanobacteria must be present in the atmosphere. Recently, the researchers launched a balloon, which carried a battery of cryosampler tubes designed to capture atmospheric microorganisms, near the Himalaya Mountains in Hyderabad, India. They then used environmental scanning electron microscopy and energy dispersive spectroscopy to examine nanoparticles that were collected at an altitude of 41 km. On the basis of several parameters, including size, shape, size distribution, interconnection, chain arrangement, conglomeration, and the appearance of cracks, the researchers concluded that the captured structures were identical to those of nanobacteria. How did nanobacteria get into the stratosphere? Sommer believes there are multiple pathways, but one plausible route is via human excreta. High levels of nanobacteria have been found in HIV-infected patients. If only a small fraction of the 30 million people in subSaharan Africa who are infected with HIV excrete nanobacteria in their urine, nanobacteria will enter wastewater and water used for irrigation, he says. They will eventually attach to biomass particles or become aerosolized and find their way into the atmosphere. So far, nanobacteria have been identified in humans on four continents. Sommer believes this is an indication of their ability to spread globally. Once they reach the atmosphere, they can be transported by winds over large distances. Clouds alone would be sufficient for spreading, but longer-lasting clouds, which are predicted with global warming, will spread viable nanobacteria, says Sommer. Such nanobacteria could be pathogenic to humans and animals. “Suddenly, the story reaches a different dimension,” he warns. —Britt E. Erickson
Journal of Proteome Research • Vol. 4, No. 1, 2005
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