Due to its resistance to harsh environmental conditions, especially low temperature, low moisture, and radiation tolerance, Chroococcidiopsis has been thought of as an organism capable of living on Mars.
As other commenters have said, the lack of water on Mars would probably prevent these guys from growing on their own. But with a little human intervention, they may be able to grow in Martian soil and help with the terraforming process (assuming we ever terraform Mars).
Edit: for anyone interested in a great vision of colonizing and terraforming Mars, I highly recommend the Mars trilogy (Red Mars, Green Mars, Blue Mars) by Kim Stanley Robinson!
I second the recommendation of reading the Mars trilogy.
https://old.reddit.com/r/askscience/comments/4vff6z/what_earth_microorganisms_if_any_would_thrive_on/
I second the recommendation of reading the Mars trilogy.