Desert Soil Biology

...or where our intrepid hero attempts to learn and explain graduate-level microbiology.

The first of four "Science Themes" we will be exploring while in the Mojave is an examination of the microbiology of the soil there. Obviously, we're expecting something vastly different from what you would find in your backyard. The Mojave is considered an extreme environment, with multiple conditions combining to make it nearly impossible for "normal" life. The Zzyzyx research station is located in the driest area of the Mojave, where they receive less than 2.5 inches of rain annually. Combining with the lack of water, high temperatures (100°F+), high radiation (that would be UV radiation, not nuclear), and in some areas, high salt or alkaline concentrations all mean that we will be searching for a class of bacteria know as extremophiles.

The extremophile most people know about is the bacteria living around the "Black Smoker" hydrothermal vents in the Pacific. These bacteria thrive in water that is up to 350°C (600°F+) and at pressures above 250 atmospheres. Conditions in the Mojave are mild in comparison! Well, except for the fact that there's no water.

The previous Spaceward Bound! expedition was to the Atacama Desert in Chile. Conditions there are even drier than in the Mojave, yet they were able to find and culture several bacteria colonies from air samples taken in the driest part.

I expect that we will find all sorts of lil' critters in the driest, hottest part of the Mojave. It's really just a question of what we will find and, more importantly, how they have adapted to live in these extreme conditions.

Dr. Kress' Astrobiology class is lucky to have one of the principal researchers for the extremophile portion of the expedition, as a regular attendee of our class. She, and one of the other researchers have given us a real crash course in what we can expect to find, how we're going to be detecting the critters, and what kind of things would be "cool" to find.

Our method will be to collect soil samples from various locations near our research base, and attempt to find the things growing within them. We'll probably start with the classic method of attempting to grow the sample in a petri dish. We should get a pretty good sample this way, since it worked even in the Atacama.

We will also have more technically advanced methods available. We'll be using "microplates" to determine which organic compounds are present in the soil. We'll even have a "DGGE" gene sequencer on site to do DNA analysis. Since bacteria are relatively simple organisms, their genomes are well known, and we can tell which bacteria are present in a sample by seeing which genes come up. We don't actually have to have a live bacteria to know it is present in a sample.

Personally, I'm hoping that we find some chemolithoautotrophs. :D

Yeah, yeah, I'm using a scary biology word! Breaking it down, it's just describing a type of bacteria that uses oxydation of chemical compounds as an energy source (chemo-), as opposed to light (photo-), reduced inorganic molecules (-litho-), instead of organics (-organo-), and CO2 as a carbon source (-autotroph) instead of other organic compounds (-heterotroph).

I'm not a biologist (but I will be playing one in a couple of weeks!), but I suspect that finding such a beastie would be nigh impossible in the Mojave. With such an abundance of sunlight, pretty much everything there would use the "easy" energy source.

Honestly, I'm going to have fun finding pretty much anything. If its unusual, I'll be ecstatic.

I'll also be curious to see if we take samples from below the surface. If we do, we'll potentially find some anaerobic and/or some non-light-dependant cultures.

The long term goal of our investigation of what we find in the Mojave is to increase the efficiency and accuracy of our planetary probes, and future manned expeditions. Using samples and data gathered in the Atacama, the previous expedition determined that if the Viking landers had touched down in a place like the Atacama, they would have failed to find the life there. Considering that Mars is even drier than the Atacama, its not all that surprising that the Viking landers came up empty. The question is: did they come up empty because there wasn't life to find, or that they were using flawed techniques?

Our expedition is providing a critical data point on the path to determine the "right" techniques.


Photo Deinococcus Radiodurans - A radiation tolerant extremophile. Photo Credit: Public Domain