Digging in the dirt

My new research article is out as early view! Almost two years ago I went to the Atacama Desert and what caught my eye were these quartz boulders and stones. As I took them off the soil, I saw a greenish band at their ventral side and I directly knew, that's it! I've read a lot about hypolithic biofilms and cyanobacteria that dominate those, but I never saw it in nature. These cyanobacteria colonize the back side of the stones because that's their strategy to escape from UV radiation and to have access to liquid whater. How that works? Pretty simple! The stones are whitish because they are made of quartz which means that they remain cooler than the surrounding which enables dew and fog water to condensate more easily on the surface of the stones. At the same time the stones allow photosynthesis because of their translucent character. Isn't that amazing?

Two quartz stones taken off the ground in the Atacama Desert. The greenish biofilm contains cyanobacteria and green algae besides bacteria.

In that very moment I told my supervisor that I wanted to conduct a study on these hypolithic biofilms. I wanted to compare the community of hypolithic cyanobacteria to those found in the soil in close vicinity. Are they the same and are they just more abundant at the stone because there is more water or are only specialists growing at the stones? We collected any samples from various environments in order to follow a precipitation gradient from the coast towards the inland of the Atacama Desert. Several days later we also drove 800 km to the South of the desert we we again found colonized quartz stones. Here we collected the stones and soil in the same way.

Back in the lab I started with the enrichment cultures to get the cyanobacteria growing, I sequenced them, prepared the phylogenetics and combined everything to soil and precipitation data from my colleagues and here we are!

Cyanobacterial biofilm on quartz stone from the Atacama Desert, visualized with light microscopy, scanning electron microscopy and confocal laser scanning microscopy.

It was a study during which I earned a lot and I also prepared most of my cyanobacterial isolates from this sampling set up and we got the real special species including endemic species that are assumed to exist only in the Atacama Desert.

Enjoy reading my research article and don't hesitate to ask if you want to have more information on a specific topic.