![]() ![]() Distinct stages of sporulation are denoted with a Roman numeral, according to the numbering scheme proposed by Ryter ( Ryter, 1965). Schematic representation of morphological changes that occur during sporulation in Bacillus subtilis. The forespore eventually matures into a partially dehydrated, dormant cell that is released into the environment when the mother cell undergoes programmed cell lysis. The initially flat polar septum then begins to curve as the mother cell swallows the forespore (a process called “engulfment”), producing a forespore that resides as a double membrane-bound, roughly spherical, organelle inside the mother cell cytosol. Both compartments briefly remain side-by-side, held together by the external cell wall. subtilis divides asymmetrically, elaborating a “polar septum” that results in two genetically identical but morphologically distinct compartments: a larger “mother cell” and a smaller “forespore”, each of which will ultimately experience different cell fates ( Fig. Sporulation initiates when the rod-shaped B. When the spore senses environmental conditions are conducive to growth, it is able to germinate and resume its vegetative cell cycle. Bacterial spores are one of nature’s most resilient cell types and are able to survive under controlled laboratory conditions for several decades, and perhaps even longer in the environment ( Jacotot and Virat, 1954 Cano and Borucki, 1995 Setlow, 2007 Vreeland et al., 2000). The purpose of sporulation is to produce a largely metabolically inactive dormant cell type called an “endospore” (hereafter, referred to simply as a “spore”) that is able to survive harsh environmental conditions until favorable growth conditions are restored ( Paredes-Sabja et al., 2011). subtilis is able to initiate many survival mechanisms such as motility, uptake of exogenous DNA, biofilm formation and sporulation ( Vlamakis et al., 2013 Rao et al., 2008 Burton and Dubnau, 2010). subtilis is ubiquitous in nature and can successfully adapt to various changes in the environment. As a result, sporulation studies have provided significant insights into basic biological processes such as differential gene expression, membrane remodeling, intercellular communication, subcellular protein localization, and morphogenesis.ī. ![]() subtilis is naturally competent and genes necessary for sporulation are often non-essential for normal growth, both of which facilitate the identification of novel factors that participate in this developmental process. subtilis is a particularly attractive system to look at cell differentiation and morphogenesis not only because of the relative simplicity of the sporulation developmental program, but also because of the genetic tractability of the system. During sporulation a single rod-shaped cell divides asymmetrically, resulting in two genetically identical daughter cells that undergo different cell fates ( Stragier and Losick, 1996 Errington, 2003 Piggot and Hilbert, 2004). One approach to this problem has been to study the relatively simple developmental program of endospore formation (“sporulation”) in the bacterium Bacillus subtilis. However, elucidating these mechanisms can be difficult due to the complex and intertwined processes that occur during development ( Sasai, 2013 Hartwell and Weinert, 1989). The timestamp is only as accurate as the clock in the camera, and it may be completely wrong.Understanding the mechanisms that drive cell differentiation and morphogenesis are essential in answering the question of how organisms develop. If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. This file contains additional information such as Exif metadata which may have been added by the digital camera, scanner, or software program used to create or digitize it. ![]()
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