Microscopic characterization of the bacterial cell envelope of Planococcus halocryophilus Or1 during subzero growth at −15 °C
- 540 Downloads
Microbial psychrophiles continue to expand our understanding of the adaptations required to thrive in cold environments. Planococcus halocryophilus strain Or1, a gram-positive, aerobic bacterial isolate from a Canadian high Arctic permafrost active layer, divides at temperatures as low as −15 °C and high salinity of 18 % NaCl. Initial studies of P. halocryophilus Or1 identified that under subzero conditions the cell envelope changed in appearance and composition. Our goal was to further analyze these features using scanning and transmission electron microscopy (SEM, TEM), confocal laser scanning microscopy (CLSM), and scanning transmission X-ray microscopy (STXM), which showed progressive changes in cell envelope composition during growth from optimal (25 °C) down to subzero (−15 °C) temperatures. S/TEM and CLSM illustrate that growth at −15 °C coincides with increasing hydrophobicity and distinct extracellular encrustations closely associated with the cell wall. STXM analyses resolved differences in cell composition with temperature, favoring higher amounts of protein and polysaccharide at higher temperatures compared to cells grown at −15 °C that were characterized by a cell envelope comprised of 20 % calcium carbonate, 50 % peptidoglycan, and 29 % choline. Analyses of the sequenced genome found the presence of several copies of carbonic anhydrase, a protein responsible for mineralization of calcium carbonate, and transcriptomic analyses revealed increased expression of a single copy at −15 °C along with the synthesis of peptidoglycan. The unique cell features of P. halocryophilus Or1 grown at −15 °C demonstrate unusual physiology that expands our understanding of psychrophilic adaptations and provides an example of microbially mediated calcium carbonate precipitation at subzero temperatures.
KeywordsPsychrophile Arctic Cellular adaptation Carbonate precipitation
Funding for this research was provided by the Natural Sciences and Engineering Research Council (NSERC), Canada Research Chair program (CRC), Canadian Foundation for Innovation (CFI), Polar Continental Shelf Program (PCSP), the Canadian Space Agency (CSA) Canadian Analogue Research Network (CARN) Program, and NSERC CREATE postdoctoral research/rotation support grants to NCSM and CRO. STXM data were acquired at beamline 10ID1 at the Canadian Light Source. CLS is supported by NSERC, the National Research Council Canada, the Canadian Institutes of Health Research, the Province of Saskatchewan, Western Economic Diversification Canada, and the University of Saskatchewan. We thank George D.W. Swerhone (Environment Canada) and the staff scientists at the CLS (Chithra Karunakaran, Jian Wang) for their work on the SM beamline.
Compliance with ethical standards
Conflict of interest
The authors state no conflict of interest. This article does not contain any studies with human or animal subjects.
- Bakermans C (2012) Psychrophiles: life in the cold. In: Anitori R (ed) Extremophiles: microbiology and biotechnology. Caister Academic Press, Beaverton, pp 53–76Google Scholar
- Carillo S, Casillo A, Pieretti E, Parrilli G, Sannino F, Bayer-Giraldi M, Cosconati S, Novellino E, Ewert M, Deming JW, Lanzetta R, Marino H, Parrilli M, Randazzo A, Tutino ML, Corsaro MM (2015) A unique capsular polysaccharide structure from the psychrophilic marine bacterium Colwellia psychrerythraea 34H that mimics antifreeze (glycol) proteins. J Am Chem Soc 137(1):179–189CrossRefPubMedGoogle Scholar
- Chahal N, Rajor A, Siddique R (2011) Calcium carbonate precipitation by different bacterial strains. Afr J Biotechnol 10:8359–8372Google Scholar
- Gilbert PUPA, Frazer BH, Abrecht H (2005) The organic-mineral interface in biominerals. In: Banfield JF, Nealson KH, Cervini-Silva J (eds) Reviews in mineralogy and geochemistry. Mineralogical Society of America, Washington, pp 157–185Google Scholar
- Hitchcock AP (2011) aXis2000 is written in interactive data language (IDL). It is available free for non-commercial use from http://unicorn.mcmaster.ca/aXis2000.html
- Hoover RB (2005) Microfossils, biominerals, and chemical biomarkers in meteorites. In: Hoover RB, Paepe RR, Yu A (eds) Perspectives in astrobiology, NATO science series: life and behavioural sciences. IOS Press, Amsterdam, pp 43–65Google Scholar
- Lawrence JR, Korber DR, Neu TR (2007) Analytical imaging techniques. In: Hurst CJ, Crawford RL, Garland JL, Lipson DA, Mills AL, Stetzenbach LD (eds) Manual of environmental microbiology, 3rd edn. American Society for Microbiology Press, Washington, pp 40–68Google Scholar
- Mykytczuk NCS, Wilhelm R, Whyte LG (2012) Planococcus halocryophilus sp. nov.; an extreme subzero species from high Arctic permafrost. Int J Syst Evol Microbiol 12:347–360Google Scholar
- Riding R (2011) Microbialites, stromatolites, and thrombolites. In: Reitner V, Thiel J (eds) Encyclopaedia of geobiology, (Encyclopaedia of earth sciences series). Springer, Heidelberg, pp 635–654Google Scholar