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Non-spore-forming bacteria ofthe genera Micrococcus and Arthrobacter, including the isolates from permafrost sediments, were found to be able to form cystlike cells under special conditions. Cystlike cells maintained the viability during longterm storage (for up to several years), had undetectable respiratory activity and the elevated resistance to heating and other unfavorable conditions, possessed the specific fine structure and morphology, and were formed in the life cycles of the microorganism. These properties allow cystlike cells to be attributed to a new type ofresting microbial forms. Furthermore, the distinctive feature of resting cystlike cells was their low P/S ratios and high Ca/K ratios in comparison to vegetative cells as shown by X-ray microanalysis. The experimentally obtained bacterial cystlike cells with thickened and laminated cell walls and altered texture ofthe cytoplasm were similar to the cells abundant in native microbial populations isolated from permafrost sediments and ancient soils ofthe Kolyma lowland (Siberia, Russia). Due to the inherent elevated resistance to adverse conditions and maintenance of viability for prolonged periods, resting cystlike cells are likely to ensure long-term survival ofnon-spore-forming bacteria in cold environments. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 4939 209 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 4939 211 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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