Microbial Communities in Atacama Desert

Study Notes

Dessicated and UV Stressed Environments

Atacama Desert, Chile: one of the driest deserts on Earth, with lithobiontic microbial communities that interact between cyanobacteria and green algae with heterotrophic bacteria, colonizing minerals like dolomite, granite, and gypsum.
Chroococcidiopsis spp.: a cyanobacterium that is desiccation and radiation tolerant, with survival strategies including the ability to protect and repair DNA damaged by UV, and maintaining proteins and membrane integrity via EPS sheath.
May help understand life on other planets like Mars.

Hot Environments

Endolithic community: contains only procaryotes, with photosynthetic primary producers being cyanobacteria, accompanied by small colorless or orange-pigmented non-photosynthetic bacteria.
Example: limestone rock from Negev desert, Israel.

Aphotice Environments Based on Chemolithoautotrophy

Deep Sea Hydrothermal Vents: magma-derived hydrothermal convection causes hot water laced with minerals to flow up through cracks and fissures, resulting in anoxic, acidic conditions enriched in CO2, H2S, CH4, H2, Fe2+, Zn2+, and Cu2+.
Microbial communities develop based on chemoautotrophy, e.g. methanotrophic microbes.
Black smoker vent: chemolithotrophic sulfur-oxidizing bacteria associated with the trophosome tissue of tube worms.
Entire food web in a hydrothermal vent community is based on chemoautotrophy, not photoautotrophy.

Extreme Environments

"Extreme" based on temperature, moisture, pH, salinity, contaminants, etc.

Low Temperature Environments

McMurdo Dry Valleys, Antarctica: driest and coldest ecosystem on Earth, with sulfide gradients in Lake Fryxell resulting in microbial sulfur cycling.
Cold adapted microbes synthesize cold adapted enzymes, which have higher activity at low temperatures, used in biotechnology.

Endolithic Microorganisms

Colonization is dependent on physical properties of the rock, such as color, opacity, and porosity or presence of fissures.
Rock with low specific gravity does not support endolithic growth.
Morphology of endolithic colonization in cold and hot deserts is remarkably similar, with an uppermost 1 to 3 mm of the rock being free from microorganisms.

Aphotice Environments Based on Chemolithoautotrophy

Acid Mine Drainage: mining of pyrite (FeS2) deposits results in S2- oxidized to SO42+ + H+, lowering pH and mobilizing metals.
Specialized microbial communities develop based on chemoautotrophy.
Metagenomic analysis: sequences were reconstructed to give nearly complete genomes for two iron-oxidizing bacteria, Leptospirillum group II and Ferroplasma type II.
Fluorescent in situ hybridization analysis: Leptospirillum group II is dominant (75%) with Ferroplasma type II representing approximately 10% of the community.

Aphotice Environments Based on Chemolithoautotrophy

Desert Carbonate Cave: devoid of phototrophic primary production, receiving fixed organic carbon from drip water that forms speleotherms.
Kartchner Caverns: unexpectedly high bacterial diversity, with ≃ 2000 operational taxonomic units, dominated by heterotrophic growth, and 10% of metagenome comprised of archael sequences.
One gene category that was significantly overrepresented in the cave metagenomes was DNA repair enzyme genes belonging to the RAMP (Repair Associated Mysterious Proteins) superfamily.

Description

Explore the unique interactions between microorganisms in the Atacama Desert, one of the driest places on Earth. Learn about the survival strategies of cyanobacteria and their relationships with other microorganisms.