Category Archives: Baby it’s cold outside!
I’m surprised that I missed this report when it first came out, but saw it recently on some science blogs and I wanted to share it here. First reported at NASA, and published in the Proceedings of the National Academy of Sciences, researchers have presented findings describing microbial life from permanently ice-covered lakes of liquid water in Antarctica. Organisms in this environment are thought to have been isolated from the surface for at least 2800 years, based on C-14 dating of organic sediments. The environment at the bottom of the lake is lightless, extremely cold (-13 °C), and very salty. Finding of microorganisms in an extreme environment supports the possibility of discovering life in other locations in the Solar System that have liquid water, such as Jupiter’s moon Europa.
The approach used by scientists at NASA, the University of Chicago, and other institutions was relatively straightforward. It has been known for decades that there are many permanently ice covered lakes of water in Antarctica, and so they drilled a hole through the 10 meters of ice in Lake Vida, which is in the McMurdo Dry Valley of eastern Antarctica. The main concern of these studies when proposed is to avoid introducing contaminants from the surface into the pristine environment, and so the sampling apparatus is designed to prevent this from occurring.
The water in Lake Vida is oxygen-free, and is high in soluble reduced metals, ammonia, molecular hydrogen, as well as some dissolved organic compounds. The dissolved compounds presumably are leached from the underlying rock surface, and are utilized by microorganisms to generate energy. The researchers did not report culturing microorganisms that they found, but instead described direct microscopic observations following filtration of cells approximately 1 micrometer in diameter. Isolation of genomic DNA from populations of bacteria was used to make template DNA for polymerase chain reaction (PCR) amplification of the 16S ribosomal gene, in order to identify genetic tags on the bacteria and facilitate identification. One hundred fifty-four DNA sequences were obtained, describing 32 unique prokaryotic species that spanned 8 previously described bacterial classification groups. Interestingly, only bacterial DNA signatures were detected, with no eukaryotic or archaeal sequences. Many similar cold, briny environments typically exhibit very diverse archaeal populations, suggesting that the Lake Vida biosphere is truly isolated.
Alright flu-fans! Here is a reprint of the my salute to flu 2012. You can get the latest updates by clicking the link over there on the right under “Welcome to Microbiology” and going to “The 2012 Seasonal Influenza Page.” Bookmark it for weekly updates!
It’s the start of the 2012-13 influenza season, and we’re tracking its spread here at BIO230. As always, I’ll bring weekly updates direct from the Centers for Disease Control and Prevention’s seasonal influenza page. The 2011-12 season was relatively mild. I got my flu shot early on, but probably would have gotten by just fine without it, as I didn’t know anyone who had flu last year. I’ll get a shot again this year, because you never know!
Monitoring for this season actually started with the week ending October 6, 2012, and currently we’ve had 4 weeks of reporting to date. Many suspect cases are sent to the CDC for analysis, but currently only about 6% of those cases actually turn out to be clinically confirmed by laboratory analysis. Sporadic influenza has been reported nationwide, with cases moving from “No activity” in the much of the United States, to some reports of “Localized” influenza or influenza-like illness in just a few states. As of the week ending October 27, 2012, the most consistent reportable influenza comes from Iowa, with 3 weeks running of this level of illness. Pennsylvania reports “Sporadic” influenza for 2 weeks straight.
Update for week ending November 3, 2012! Maine has moved from “localized” to “regional” status, and 8 states with “localized” reports of influenza, including our neighbor New York. Most of the rest of the United States report at least “sporadic” disease, and only 8 states (NV, UT, ND, NE, AR, IL, VA, and VT reporting “no activity.”
Turns out that I do greatly empathize with Indiana Jones. Via the New York Times, and reporting research published in the American Journal of Tropical Medicine and Hygiene from the University of South Florida and Auburn University, a study that describes the detection of Eastern Equine Encephalitis Virus in hibernating snakes. EEEV is one of a family of closely related viruses (West Nile Virus is a member of this family) that causes fatal disease in horses and about a dozen humans annually. Like West Nile, the disease is spread via a mosquito vector, and so it shows a seasonal variation that reflects the life of the insect. The normal host of these viruses are in birds, where they tend to not cause very significant levels of disease. When they jump to mammals, the disease is much more severe.
This brings up a conundrum as to where the virus resides during that portion of the year when the vector is essentially absent. West Nile Virus and Equine Encephalitis Virus were thought to be maintained in avian reservoirs over the winter, and that a further explanation for why the incidence of disease is essentially zero during the winter is because not only is the vector (mosquito) not present during the winter months, the reservoir (birds) fly south for the winter.
It was quite surprising then when the researchers in this study collected hibernating snakes and mosquitoes from swamps in Alabama. They identified snake blood in the digestive tracts of the mosquitoes and found molecular signs of Equine Encephalitis Virus in the snakes. This data clearly indicated that the virus can be propagated in a reptile reservoir as well as in birds. Viral titres peaked in the snakes in the spring and fall–in the summer the snakes innate immune response works better with the higher temperature, and are able to clear the viral infection. The presence of the virus in reptile reservoirs, which do not migrate for the winter, helps to explain how mammalian infections begin to rise so quickly in the spring before all of the birds return to the area. This research can likely be extended to other Encephalitis Viruses, and other potential viral reservoirs.
Scientists have held up Antarctica as an example of one of the few pristine environments left on Earth. This has likely been the case in the recent past, but as accessibility barriers to travel to Antarctica are removed, the potential exists for habitat degradation on both a macro- and microscopic level. A recent review article in Trends in Microbiology examines the relative risks of ecosystem damage, due to the introduction of exogenous microorganisms.
The authors define impact rather broadly; for large species, the numbers and distribution of individuals, as assessed by unit biomass, can give a relatively good idea of trends over time. For microorganisms, the distinctions are a bit more difficult to determine, in many cases because the microorganisms are exceedingly difficult to impossible to currently culture in the laboratory. Some of the environments that scientists are concerned about altering with non-indigenous microbes are ones such as Lake Vostok, a sub-glacial lake of liquid water found approximately 4 km below the ice surface, and is believed to contain water that was last exposed to the outside environment between 15 to 25 million years ago. The lake make contain a microbial ecosystem that would therefore be unique on Earth, and maintaining the integrity of that environment would be of paramount importance. Currently, scientists are exploring mechanisms to obtain a water sample from Lake Vostok that would prevent the introduction of surface microorganisms. Read the rest of this entry