The Maintenance of Sex in Bacteria Is Ensured by Its Potential to Reload Genes

Szöllősi, Gergely J; Derényi, Imre; Vellai, Tibor

doi:10.1534/genetics.106.063412

Cited by 20 publications

(13 citation statements)

References 32 publications

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“…In accord with this hypothesis selection operates at the level of the collective, the group, rather than individuals; populations capable of transformation evolve more rapidly than those without this capacity. While group-or population-level selection may not have the parsimonious appeal of individual selection, in theory at least there are conditions where they can occur (Levin and Kilmer 1975;Szollosi et al 2006). In theory there are also conditions where at least for sexually reproducing eukaryotes recombination could be favored within a population, by individual selection (Felsenstein and Yokoyama 1976).…”

Section: Discussionmentioning

confidence: 99%

Episodic Selection and the Maintenance of Competence and Natural Transformation inBacillus subtilis

Johnsen

Dubnau²,

Levin

2009

Genetics

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We present a new hypothesis for the selective pressures responsible for maintaining natural competence and transformation. Our hypothesis is based in part on the observation that in Bacillus subtilis, where transformation is widespread, competence is associated with periods of nongrowth in otherwise growing populations. As postulated for the phenomenon of persistence, the short-term fitness cost associated with the production of transiently nongrowing bacteria can be compensated for and the capacity to produce these competent cells can be favored due to episodes where the population encounters conditions that kill dividing bacteria. With the aid of a mathematical model, we demonstrate that under realistic conditions this ''episodic selection'' for transiently nongrowing (persisting) bacteria can maintain competence for the uptake and expression of exogenous DNA transformation. We also show that these conditions for maintaining competence are dramatically augmented even by rare episodes where selection favors transformants. Using experimental populations of B. subtilis and antibiotic-mediated episodic selection, we test and provide support for the validity of the assumptions behind this model and the predictions generated from our analysis of its properties. We discuss the potential generality of episodic selection for the maintenance of competence in other naturally transforming species of bacteria and critically evaluate other hypotheses for the maintenance (and evolution) of competence and their relationship to this hypothesis.

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Section: Discussionmentioning

confidence: 99%

Episodic Selection and the Maintenance of Competence and Natural Transformation inBacillus subtilis

Johnsen

Dubnau²,

Levin

2009

Genetics

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“…However, environments and bacteria are not stationary in time and space either. Therefore, bacteria having transformation competence can be stably maintained due to the advantage of HGT, resulting in gene reloading (64). It also seems that, on the whole, bacteria could not avoid Muller's ratchet either without some form of recombination (65) because, despite occasionally very high population numbers, starvation and bottlenecks are also common.…”

Section: Origins Of Life: Three Early Phases Of Transitions To Cellsmentioning

confidence: 99%

Toward major evolutionary transitions theory 2.0

Szathmáry

2015

Proc. Natl. Acad. Sci. U.S.A.

324

343

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The impressive body of work on the major evolutionary transitions in the last 20 y calls for a reconstruction of the theory although a 2D account (evolution of informational systems and transitions in individuality) remains. Significant advances include the concept of fraternal and egalitarian transitions (lower-level units like and unlike, respectively). Multilevel selection, first without, then with, the collectives in focus is an important explanatory mechanism. Transitions are decomposed into phases of origin, maintenance, and transformation (i.e., further evolution) of the higher level units, which helps reduce the number of transitions in the revised list by two so that it is less top-heavy. After the transition, units show strong cooperation and very limited realized conflict. The origins of cells, the emergence of the genetic code and translation, the evolution of the eukaryotic cell, multicellularity, and the origin of human groups with language are reconsidered in some detail in the light of new data and considerations. Arguments are given why sex is not in the revised list as a separate transition. Some of the transitions can be recursive (e.g., plastids, multicellularity) or limited (transitions that share the usual features of major transitions without a massive phylogenetic impact, such as the microand macronuclei in ciliates). During transitions, new units of reproduction emerge, and establishment of such units requires high fidelity of reproduction (as opposed to mere replication).egalitarian transitions | fraternal transitions | multilevel selection | aggregative unit formation | recursive transitions T he book The Major Transitions in Evolution was published 20 y ago (1) and popularized 16 y ago (2). The impressive work accomplished by the interested community has made time ripe for a resynthesis of the field. In this paper, I outline the revised theory for transitions research while noting that the full account can be taken only in a new book. First, I present the key points of the theory, followed by an impressionist overview of some of the transitions, highlighting (without being all-inclusive) some of the most exciting findings pertinent to the major transitions in a revised list. In doing so, I rebuild some of the foundations of the theory. A scholarly account of all relevant contributions is beyond the scope of the present paper. For lack of space, I deliberately omit discussion on the origin of animal societies (3), except humans.

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“…Szöllősi et al (2006), described a computer model based on natural populations with weak migration and environmental fluctuations. In this case, the eDNA pool acted as a collective reservoir of lost functions that could be quickly recovered by DNA uptake when the physical conditions demand its reloading.…”

Section: Biological Functions Of Ednamentioning

confidence: 99%

Mechanisms and Regulation of Extracellular DNA Release and Its Biological Roles in Microbial Communities

2017

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The capacity to release genetic material into the extracellular medium has been reported in cultures of numerous species of bacteria, archaea, and fungi, and also in the context of multicellular microbial communities such as biofilms. Moreover, extracellular DNA (eDNA) of microbial origin is widespread in natural aquatic and terrestrial environments. Different specific mechanisms are involved in eDNA release, such as autolysis and active secretion, as well as through its association with membrane vesicles. It is noteworthy that in microorganisms, in which DNA release has been studied in detail, the production of eDNA is coordinated by the population when it reaches a certain cell density, and is induced in a subpopulation in response to the accumulation of quorum sensing signals. Interestingly, in several bacteria there is also a relationship between eDNA release and the development of natural competence (the ability to take up DNA from the environment), which is also controlled by quorum sensing. Then, what is the biological function of eDNA? A common biological role has not been proposed, since different functions have been reported depending on the microorganism. However, it seems to be important in biofilm formation, can be used as a nutrient source, and could be involved in DNA damage repair and gene transfer. This review covers several aspects of eDNA research: (i) its occurrence and distribution in natural environments, (ii) the mechanisms and regulation of its release in cultured microorganisms, and (iii) its biological roles. In addition, we propose that eDNA release could be considered a social behavior, based on its quorum sensing-dependent regulation and on the described functions of eDNA in the context of microbial communities.

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The Maintenance of Sex in Bacteria Is Ensured by Its Potential to Reload Genes

Cited by 20 publications

References 32 publications

Episodic Selection and the Maintenance of Competence and Natural Transformation inBacillus subtilis

Episodic Selection and the Maintenance of Competence and Natural Transformation inBacillus subtilis

Toward major evolutionary transitions theory 2.0

Mechanisms and Regulation of Extracellular DNA Release and Its Biological Roles in Microbial Communities

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