Deinococcus

by Cliff Bueno de Mesquita

We (Lara, Cliff, Steve) recently received positive reviews on our manuscript about our project analyzing soil microbial community response to water and nutrient additions on Volcán Llullaillaco, in the Atacama Desert in Chile. One interesting comment from a reviewer was about the bacterial genus Deinococcus. They claimed that it was a typical desert microbe known to be resistant to desiccation and asked if it was present in our dataset. We replied that it was absent to not very abundant in our dataset, perhaps due to the high elevation of our sampling (5,100 meters above sea level) differentiating our site from previous desert samples where it had been found. Our site freezes daily and experiences diurnal freeze-thaw cycles. On the other hand, Deinococcus has been described as a heat tolerant and even heat preferring genus - indeed, in addition to the Atacama, it has been found in other hot deserts, including the Sahara and Sonoran deserts (1).
            There have been a number of previous studies on this genus or mentioning this genus, and species within the genus appear to be quite fascinating microorganisms! Research in the Atacama Desert, the driest and oldest desert on Earth, has been funded by NASA’s astrobiology program over the past several decades, as it has been described as a Mars analogue (2). Annual average rainfall many parts of the Atacama is less than 2 mm, making it a “hyperarid” desert, even drier than other deserts such as the Gobi and Sahara deserts. Deinococcus is described as being extremely desiccation resistant, having been found in the extremely dry core of the Atacama, living on quartz stones (3). Its presence on rocks also makes these organisms “hypoliths”, literally meaning “under stone”. One cool study found that the species Deinococcus geothermalis was able to withstand temperatures from -25˚C to 60˚C, vacuum, and Mars atmosphere conditions (4)! They are also described as being radiation resistant, and have received some interest for biotechnology applications(5).

Transmission election micrograph of Deinococcus radiodurans. Photo by Michael Daly, Uniformed Services University, Bethesda, MD, USA.

            The genus contains quite a few species (47 have been described). Two of the most well-studied for astrobiology, found in the Atacama Desert, are Deinococcus radiodurans and D. geothermalis. Deinococcus deserti was described in the Sahara Desert. Other species include D. planocerae (6). One study in the Sonoran Desert found nine species and 60 strains of Deinococcus in one soil sample (1)!

​References:
 
1.        Rainey, F. A. et al. Extensive diversity of ionizing-radiation-resistant bacteria recovered from Sonoran Desert soil and description of nine new species of the genus Deinococcus obtained from a single soil sample. Appl. Environ. Microbiol. 71, 5225–5235 (2005).
2.        Azua-Bustos, A., Urrejola, C. & Vicuña, R. Life at the dry edge: Microorganisms of the Atacama Desert. in FEBS Letters vol. 586 2939–2945 (2012).
3.        Lacap, D. C., Warren-Rhodes, K. A., Mckay, C. P. & Pointing, S. B. Cyanobacteria and chloroflexi-dominated hypolithic colonization of quartz at the hyper-arid core of the Atacama Desert, Chile. ExtremophilesExtremophiles 15, 31–38 (2011).
4.        Frösler, J., Panitz, C., Wingender, J., Flemming, H.-C. & Rettberg, P. Survival of Deinococcus geothermalis in Biofilms under Desiccation and Simulated Space and Martian Conditions. Astrobiology 17, 431–447 (2017).
5.        Sajjad, W. Production and Characterization of Extremolytes from Indigenous Radio-resistant Microorganisms and their Evaluation for Potential Biotechnological Applications. (2017).
6.        Lin, H., Wang, Y., Huang, J., Lai, Q. & Xu, Y. Deinococcus planocerae sp. nov., isolated from a marine flatworm. Antonie van Leeuwenhoek, Int. J. Gen. Mol. Microbiol. 110, 811–817 (2017).