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one operon-one messenger RNA hypothesis translation in English-French dictionary

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N2 - The ribosomal RNA (rrn) operon is a key suite of genes related to the production of protein synthesis machinery and thus to bacterial growth physiology. Experimental evidence has suggested an intrinsic relationship between the number of copies of this operon and environmental resource availability, especially the availability of phosphorus (P), because bacteria that live in oligotrophic ecosystems usually have few rrn operons and a slow growth rate. The Cuatro Ciénegas Basin (CCB) is a complex aquatic ecosystem that contains an unusually high microbial diversity that is able to persist under highly oligotrophic conditions. These environmental conditions impose a variety of strong selective pressures that shape the genome dynamics of their inhabitants. The genus Bacillus is one of the most abundant cultivable bacterial groups in the CCB and usually possesses a relatively large number of rrn operon copies (6-15 copies). The main goal of this study was to analyze the variation in the number of rrn operon copies of Bacillus in the CCB and to assess their growth-related properties as well as their stoichiometric balance (N and P content). We defined 18 phylogenetic groups within the Bacilli clade and documented a range of from six to 14 copies of the rrn operon. The growth dynamic of these Bacilli was heterogeneous and did not show a direct relation to the number of operon copies. Physiologically, our results were not consistent with the Growth Rate Hypothesis, since the copies of the rrn operon were decoupled from growth rate. However, we speculate that the diversity of the growth properties of these Bacilli as well as the low P content of their cells in an ample range of rrn copy number is an adaptive response to oligotrophy of the CCB and could represent an ecological mechanism that allows these taxa to coexist. These findings increase the knowledge of the variability in the number of copies of the rrn operon in the genus Bacillus and give insights about the physiology of this bacterial group under extreme oligotrophic conditions.

1/28/2011 · What is the 'operon hypothesis' of bacterial gene regulation

Although highly efficient, the clear disadvantage of the prokaryotic operon is the constraint placed upon gene expression by physically coupling the production of multiple proteins in a fixed group. For example, the presence of a nonsense mutation in an operon can result in polarity effects that disrupt downstream functions. Also, the ability to independently regulate the production of proteins with multiple functions is limited when genes are confined to a polycistronic architecture. In eukaryotes, many proteins have become multifunctional (Hentze, 1994; Jeffery, 1999). Thus, producing a protein contained within an operon for a new function would be inefficient because the other proteins in the operon would have to be expressed concurrently (Figure 1A). Genomic array analysis of endogenous mammalian ribonucleoproteins has recently revealed three novel findings: (1) mRNA binding proteins are associated with unique subpopulations of messages, (2) the compositions of these mRNA subsets can vary with growth conditions, and (3) the same mRNA species can be found in multiple mRNP complexes. Based on these How Do Mammalian Cells Efficiently Coordinate and other findings, we propose a model of posttran- Gene Expression without Operons? scriptional gene expression in which mRNA binding The coordinated regulation of multiple genes is needed proteins regulate mRNAs as subpopulations during in higher eukaryotes to accomplish complex phenotypic cell growth and development. This model predicts that functions such as cell growth and differentiation (Niehrs functionally related genes are regulated posttran- and Pollet, 1999; Qian et al., 2001). This includes the scriptionally as groups by specific mRNA binding pro- production of proteins for generalized housekeeping teins that recognize sequence elements in common functions and proteins for specialized functions that can among the mRNAs. be tissue or developmental specific (Ideker et al., 2001;

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The ribosomal RNA (rrn) operon is a key suite of genes related to the production of protein synthesis machinery and thus to bacterial growth physiology. Experimental evidence has suggested an intrinsic relationship between the number of copies of this operon and environmental resource availability, especially the availability of phosphorus (P), because bacteria that live in oligotrophic ecosystems usually have few rrn operons and a slow growth rate. The Cuatro Ciénegas Basin (CCB) is a complex aquatic ecosystem that contains an unusually high microbial diversity that is able to persist under highly oligotrophic conditions. These environmental conditions impose a variety of strong selective pressures that shape the genome dynamics of their inhabitants. The genus Bacillus is one of the most abundant cultivable bacterial groups in the CCB and usually possesses a relatively large number of rrn operon copies (6-15 copies). The main goal of this study was to analyze the variation in the number of rrn operon copies of Bacillus in the CCB and to assess their growth-related properties as well as their stoichiometric balance (N and P content). We defined 18 phylogenetic groups within the Bacilli clade and documented a range of from six to 14 copies of the rrn operon. The growth dynamic of these Bacilli was heterogeneous and did not show a direct relation to the number of operon copies. Physiologically, our results were not consistent with the Growth Rate Hypothesis, since the copies of the rrn operon were decoupled from growth rate. However, we speculate that the diversity of the growth properties of these Bacilli as well as the low P content of their cells in an ample range of rrn copy number is an adaptive response to oligotrophy of the CCB and could represent an ecological mechanism that allows these taxa to coexist. These findings increase the knowledge of the variability in the number of copies of the rrn operon in the genus Bacillus and give insights about the physiology of this bacterial group under extreme oligotrophic conditions.

The expression of the srf operon of Bacillus subtilis, encoding surfactin synthetase and the competence regulatory protein ComS, was observed to be reduced when cells were grown in a rich glucose- and glutamine containing medium in which late-growth culture pH was 5.0 or lower. The production of the surfactin synthetase subunits and of surfactin itself was also reduced. Raising the pH to near neutrality resulted in dramatic increases in srf expression and surfactin production. This apparent pH- dependent induction of srf expression required spoOK, which encodes the oligopeptide permease that functions in cell-density-dependent control of sporulation and competence, but not CSF, the competence-inducing pheromone that regulates srf expression in a SpoOK-dependent manner. Both ComP and ComA, the two-component regulatory pair that stimulates cell-density- dependent srf transcription, were required for optimal expression of srf at low and high pHS, but ComP was not required for pH-dependent srf induction. The known negative regulators of srf, RapC and CodY, were found not to function significantly in pH-dependent srf expression. Late-growth culture supernatants at low pH were not active in inducing srf expression in cells of low-density cultures but were rendered active when their pH was raised to near neutrality. ComQ (and very likely the srf-inducing pheromone ComX) and SpoOK were found to be required for the extracellular induction of srf-lacZ at neutral pH. The results suggest that srf expression, in response to changes in culture pH, requires SpoOK and another, as yet unidentified, extracellular factor. The study also provides evidence consistent with the hypothesis that ComP acts both positively and negatively in the regulation of Coma and that both activities are controlled by the ComX pheromone.

SBI4U – Grade 12 Biology – Molecular Genetics— …

N2 - The expression of the srf operon of Bacillus subtilis, encoding surfactin synthetase and the competence regulatory protein ComS, was observed to be reduced when cells were grown in a rich glucose- and glutamine containing medium in which late-growth culture pH was 5.0 or lower. The production of the surfactin synthetase subunits and of surfactin itself was also reduced. Raising the pH to near neutrality resulted in dramatic increases in srf expression and surfactin production. This apparent pH- dependent induction of srf expression required spoOK, which encodes the oligopeptide permease that functions in cell-density-dependent control of sporulation and competence, but not CSF, the competence-inducing pheromone that regulates srf expression in a SpoOK-dependent manner. Both ComP and ComA, the two-component regulatory pair that stimulates cell-density- dependent srf transcription, were required for optimal expression of srf at low and high pHS, but ComP was not required for pH-dependent srf induction. The known negative regulators of srf, RapC and CodY, were found not to function significantly in pH-dependent srf expression. Late-growth culture supernatants at low pH were not active in inducing srf expression in cells of low-density cultures but were rendered active when their pH was raised to near neutrality. ComQ (and very likely the srf-inducing pheromone ComX) and SpoOK were found to be required for the extracellular induction of srf-lacZ at neutral pH. The results suggest that srf expression, in response to changes in culture pH, requires SpoOK and another, as yet unidentified, extracellular factor. The study also provides evidence consistent with the hypothesis that ComP acts both positively and negatively in the regulation of Coma and that both activities are controlled by the ComX pheromone.

AB - The ribosomal RNA (rrn) operon is a key suite of genes related to the production of protein synthesis machinery and thus to bacterial growth physiology. Experimental evidence has suggested an intrinsic relationship between the number of copies of this operon and environmental resource availability, especially the availability of phosphorus (P), because bacteria that live in oligotrophic ecosystems usually have few rrn operons and a slow growth rate. The Cuatro Ciénegas Basin (CCB) is a complex aquatic ecosystem that contains an unusually high microbial diversity that is able to persist under highly oligotrophic conditions. These environmental conditions impose a variety of strong selective pressures that shape the genome dynamics of their inhabitants. The genus Bacillus is one of the most abundant cultivable bacterial groups in the CCB and usually possesses a relatively large number of rrn operon copies (6-15 copies). The main goal of this study was to analyze the variation in the number of rrn operon copies of Bacillus in the CCB and to assess their growth-related properties as well as their stoichiometric balance (N and P content). We defined 18 phylogenetic groups within the Bacilli clade and documented a range of from six to 14 copies of the rrn operon. The growth dynamic of these Bacilli was heterogeneous and did not show a direct relation to the number of operon copies. Physiologically, our results were not consistent with the Growth Rate Hypothesis, since the copies of the rrn operon were decoupled from growth rate. However, we speculate that the diversity of the growth properties of these Bacilli as well as the low P content of their cells in an ample range of rrn copy number is an adaptive response to oligotrophy of the CCB and could represent an ecological mechanism that allows these taxa to coexist. These findings increase the knowledge of the variability in the number of copies of the rrn operon in the genus Bacillus and give insights about the physiology of this bacterial group under extreme oligotrophic conditions.

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Genetics of Organisms Virtual Lab - Prentice Hall Bridge …

AB - The expression of the srf operon of Bacillus subtilis, encoding surfactin synthetase and the competence regulatory protein ComS, was observed to be reduced when cells were grown in a rich glucose- and glutamine containing medium in which late-growth culture pH was 5.0 or lower. The production of the surfactin synthetase subunits and of surfactin itself was also reduced. Raising the pH to near neutrality resulted in dramatic increases in srf expression and surfactin production. This apparent pH- dependent induction of srf expression required spoOK, which encodes the oligopeptide permease that functions in cell-density-dependent control of sporulation and competence, but not CSF, the competence-inducing pheromone that regulates srf expression in a SpoOK-dependent manner. Both ComP and ComA, the two-component regulatory pair that stimulates cell-density- dependent srf transcription, were required for optimal expression of srf at low and high pHS, but ComP was not required for pH-dependent srf induction. The known negative regulators of srf, RapC and CodY, were found not to function significantly in pH-dependent srf expression. Late-growth culture supernatants at low pH were not active in inducing srf expression in cells of low-density cultures but were rendered active when their pH was raised to near neutrality. ComQ (and very likely the srf-inducing pheromone ComX) and SpoOK were found to be required for the extracellular induction of srf-lacZ at neutral pH. The results suggest that srf expression, in response to changes in culture pH, requires SpoOK and another, as yet unidentified, extracellular factor. The study also provides evidence consistent with the hypothesis that ComP acts both positively and negatively in the regulation of Coma and that both activities are controlled by the ComX pheromone.

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