Formation and characterization of non-growth states in Clostridium thermocellum: spores and L-forms

BMC Microbiology

Research Article

Elizabeth B Mearls¹  Lee R Lynd¹  Javier A Izquierdo² 

[1] Thayer School of Engineering, Dartmouth College, 03755, Hanover, NH, USA;BioEnergy Science Center, Oak Ridge National Laboratory, 37831, Oak Ridge, TN, USA;Thayer School of Engineering, Dartmouth College, 03755, Hanover, NH, USA;BioEnergy Science Center, Oak Ridge National Laboratory, 37831, Oak Ridge, TN, USA;Center for Agricultural and Environmental Biotechnology, RTI, Research Triangle Park, 27709, USA;

关键词: Cellobiose;    Avicel;    Spore Formation;    Stationary Phase Cell;    Clostridium Thermocellum;   

DOI  :  10.1186/1471-2180-12-180

 received in 2012-04-17, accepted in 2012-07-03,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundClostridium thermocellum is an anaerobic thermophilic bacterium that exhibits high levels of cellulose solublization and produces ethanol as an end product of its metabolism. Using cellulosic biomass as a feedstock for fuel production is an attractive prospect, however, growth arrest can negatively impact ethanol production by fermentative microorganisms such as C. thermocellum. Understanding conditions that lead to non-growth states in C. thermocellum can positively influence process design and culturing conditions in order to optimize ethanol production in an industrial setting.ResultsWe report here that Clostridium thermocellum ATCC 27405 enters non-growth states in response to specific growth conditions. Non-growth states include the formation of spores and a L-form-like state in which the cells cease to grow or produce the normal end products of metabolism. Unlike other sporulating organisms, we did not observe sporulation of C. thermocellum in low carbon or nitrogen environments. However, sporulation did occur in response to transfers between soluble and insoluble substrates, resulting in approximately 7% mature spores. Exposure to oxygen caused a similar sporulation response. Starvation conditions during continuous culture did not result in spore formation, but caused the majority of cells to transition to a L-form state. Both spores and L-forms were determined to be viable. Spores exhibited enhanced survival in response to high temperature and prolonged storage compared to L-forms and vegetative cells. However, L-forms exhibited faster recovery compared to both spores and stationary phase cells when cultured in rich media.ConclusionsBoth spores and L-forms cease to produce ethanol, but provide other advantages for C. thermocellum including enhanced survival for spores and faster recovery for L-forms. Understanding the conditions that give rise to these two different non-growth states, and the implications that each has for enabling or enhancing C. thermocellum survival may promote the efficient cultivation of this organism and aid in its development as an industrial microorganism.

【 授权许可】

Unknown   
© Mearls et al.; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.