Rubrobacter

​We are pleased to share that our paper about our fertilization experiments on Volcán Llullaillaco have been published in the journal Microorganisms (https://doi.org/10.3390/microorganisms8071061) and is openly accessible for everyone. In line with the theme from last month and the theme of microbes that can tolerate extreme environmental conditions, I will write about another radiation resistant bacterial genus – Rubrobacter. This genus was not abundant in soils at our site on Volcán Llullaillaco, but has been found in other dry environments.

Photo of Rubrobacter xylanophilus. Photo by Margaret C. Henk, from https://genome.jgi.doe.gov/portal/rubxy/rubxy.home.html.

The Rubrobacter genus was first described in 1988 (Suzuki et al. 1988) and now contains several described species. In contrast to our high elevation field site which experiences freezing temperatures, Rubrobacter has been described as a thermophilic, or heat loving, genus. The genus is also known to be radiation resistant, even to powerful gamma radiation (Ferreira et al. 1999; Chen et al. 2004)! This is notable because gamma radiation is a commonly used sterilization method. Rubrobacter species have been isolated from diverse environments including hot springs (Ferreira et al. 1999; Chen et al. 2004), biofilms on buildings and monuments (Laiz et al. 2009), arid Australian soils (Holmes et al. 2000), and industrial runoff (Carreto et al. 1996). As an example of just how thermophilic some Rubrobacter species are, consider that the optimal growth temperature for Rubrobacter taiwanensis is approximately 60˚C (Chen et al. 2004)! One adaptation that radiation-resistant organisms have is colored pigments. Rubrobacter tolerans (aptly named as it tolerates gamma radiation) contains red pigments identified as the carotenoids bacterioruberin and monoanhydrobacterioruberin (Saito et al. 1994). The interesting thing about these two pigments is that they are common in halophilic, or salt-loving, bacteria.
 
References:
Carreto L, Moore E, Nobre MF, et al. 1996. Rubrobacter xylanophilus sp. nov., a new thermophilic species isolated from a thermally polluted effluent. Int J Syst Bacteriol 46:460–465. https://doi.org/10.1099/00207713-46-2-460

Chen MY, Wu SH, Lin GH, et al. 2004. Rubrobacter taiwanensis sp. nov., a novel thermophilic, radiation-resistant species isolated from hot springs. Int J Syst Evol Microbiol 54:1849–1855. https://doi.org/10.1099/ijs.0.63109-0

Ferreira AC, Fernanda · M, Moore NE, et al. 1999. Characterization and radiation resistance of new isolates of Rubrobacter radiotolerans and Rubrobacter xylanophilus

Holmes AJ, Bowyer J, Holley MP, et al. 2000. Diverse, yet-to-be-cultured members of the Rubrobacter subdivision of the Actinobacteria are widespread in Australian arid soils. FEMS Microbiol Ecol 33:111–120. https://doi.org/10.1111/j.1574-6941.2000.tb00733.x

Laiz L, Miller AZ, Jurado V, et al. 2009. Isolation of five Rubrobacter strains from biodeteriorated monuments. Naturwissenschaften 96:71–79. https://doi.org/10.1007/s00114-008-0452-2

Saito T, Terato H, Yamamoto O. 1994. Pigments of Rubrobacter radiotolerans. Arch Microbiol 162:414–421. https://doi.org/10.1007/BF00282106

Suzuki K, Collins MD, Iijima E, Komagata K. 1988. Chemotaxonomic characterization of a radiotolerant bacterium, Arthrobacter radiotolerans : Description of Rubrobacter radiotolerans gen. nov., comb. nov. FEMS Microbiol Lett 52:33–39. https://doi.org/10.1111/j.1574-6968.1988.tb02568.x