by Henry Bortman
The weather has taken a turn toward the dramatic. For the first few days we were here, the sky was practically cloudless all day long. Then for a couple of days, puffy white clouds would build up in the afternoon. But in the past couple of days, the afternoon sky has gone dark, we’ve heard thunder in the distance, and the peaks of the mountains that surround the lake have been obscured in mist.
And it snowed. Not down here in base camp. Here we got a half an hour or so of light rain. But up on Cerro Echaurren to the north and even more so on Meson Alto to the east, there are new dustings of white powder. That may not seem odd to those of you reading this in the northern hemisphere, where winter is approaching. But here below the Equator, we are only two weeks from the first day of summer.
Although some of us would prefer to sit on a rock overlooking the lake, listening to the wind and watching cloud formations roll through, the threat of thunderstorms has sent us scurrying to zip up the rain flies on our tents and has forced most of our activity indoors. It has also put a temporary halt to biological sampling on the lake.
But biologists are dedicated lot, and some members of the PLL team have plenty of samples, collected when the weather was better, that need to be filtered and prepared for laboratory analysis. This process involves sucking up water, liters and liters of water collected from Laguna Negra and Laguna Lo Encañado, into a syringe, some 50 milliliters at a time, and then forcing the water through a small circular filter laced with pores tiny enough to trap microbial cells.
The water gets discarded, except a small volume that will be use for measuring dissolved cations and anions. Also of interest is the yellowish-brown stain left behind on the filter paper, comprised largely of microorganisms from the lake.
Some of these filters are preserved in ethanol, for later DNA extraction. Other filters are kept on dry ice until they can be transported down to Santiago de Chile University, where they will be freeze-dried for the trip back to Madrid, Spain.
Madrid is where microbial ecologists Yolanda Blanco and Luis A. Rivas work, at the Centro de Astrobiología. They are part of a team that for the past several years has been developing a life-detection device, a device they hope will be sent one day to Mars, or perhaps to other worlds in our solar system, in search of evidence for extra-terrestrial life.
The device goes by the name SOLID (Signs Of LIfe Detector), which includes an antibody microarray in its sample analysis unit. This microarray crams hundreds of microscopic dots, each a distinct biological probe, onto a small glass slide. The dots, printed onto the slide, contain antibodies. Some of these antibodies react to specific types of organisms. Others react to common biological molecules, such as amino acids, the building blocks of proteins; or the lipids found in cell walls. Unlike past life-detection methods that look for biosignatures by heating a sample to high temperatures and sniffing at the released gases, the antibody-microarray approach is less destructive, more precise and capable of searching for hundreds of different biosignatures simultaneously.
The array is exposed to a sample, such as the material trapped by filtering water from Laguna Negra. If the organism or biomolecule that a particular antibody is designed to detect is present in the sample, the antibody binds to the sample material. This captured material is revealed by using a fluorescent probe. Examined under the right type of light, these fluorescent tags appear as glowing dots. The position of the dot on the glass slide tells researchers which organism or molecule has been detected.
Blanco, Rivas and their colleagues previously tested detectors at Rio Tinto, in Spain, and in Chile’s Atacama Desert, each time with a slightly different emphasis tuned to the environmental conditions of those field sites. One focus of the work at Laguna Negra will be looking for psychrophilic, or cold-loving, organisms.