Hypothesis: nucleoid-associated proteins segregate with a parental DNA strand to generate coherent phenotypic diversity
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ORIGINAL ARTICLE
Hypothesis: nucleoid‑associated proteins segregate with a parental DNA strand to generate coherent phenotypic diversity Yoan Konto‑Ghiorghi1 · Vic Norris1 Received: 11 April 2020 / Accepted: 12 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The generation of a phenotypic diversity that is coherent across a bacterial population is a fundamental problem. We propose here that the DNA strand-specific segregation of certain nucleoid-associated proteins or NAPs results in these proteins being asymmetrically distributed to the daughter cells. We invoke a variety of mechanisms as responsible for this asymmetrical segregation including those based on differences between the leading and lagging strands, post-translational modifications, oligomerisation and association with membrane domains. Keywords Cell cycle · Hyperstructure · Heterogeneity · Assembly · DNA strand · Bacteria
Introduction Epigenetic inheritance and asymmetric division are two powerful ways of generating phenotypic diversity. The classic example of epigenesis in bacteria is based on the expression of the lac operon which, when induced by a high concentration of the inducer, can subsequently remain induced by a low concentration over many generations, whereas, without previous induction, this same low concentration is insufficient to induce expression (Laurent et al. 2005; Novick and Weiner 1957; Casadesus and Low 2013). Such epigenesis results in two alternative populations that are phenotypically different but is not generally associated with phenotypic diversity within a population. A classic example of asymmetric division in bacteria is evinced in the developmental cell cycle of the differentiating bacterium, Caulobacter crescentus, which leads to daughter cells with very different phenotypes. It has been argued that asymmetric division characterises the cell cycle of even non-differentiating bacteria such as Escherichia coli, essentially because at a fundamental level a dividing cell can be considered as a system of locally positive and globally negative feedback
* Vic Norris [email protected] 1
Laboratory of Microbiology Signals and Microenvironment, EA 4312, University of Rouen, 76821 Mont Saint Aignan, France
that naturally generates daughter cells with different phenotypes (Norris 1995; Norris and Madsen 1995). Epigenetic inheritance and asymmetric division are not mutually exclusive and can be combined, for example, to help solve the problem of how to both grow in favourable conditions and not grow (so as to survive) in unfavourable conditions. In the case of eukaryotic cells, it has been proposed that ‘the double-helix structure of DNA itself forms the physical basis of turning the developmental control gene ON in one chromatid and OFF in the sister chromatid during replication of the progenitor cell’s gene, and this binarycoded gene expression switching mechanism may be the underlying mechanism of development in general’ (Levin et al. 2016). This hypothesis is supported by rece
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