Protein binding sites involved in the assembly of the KplE1 prophage intasome

AbstractThe organization of the recombination regions of the KplE1 prophage in Escherichia coli K12 differs from that observed in the λ prophage. Indeed, the binding sites characterized for the IntS integrase, the TorI recombination directionality factor (RDF) and the integration host factor (IHF) vary in number, spacing and orientation on the attL and attR regions. In this paper, we performed site-directed mutagenesis of the recombination sites to decipher if all sites are essential for the site-specific recombination reaction and how the KplE1 intasome is assembled. We also show that TorI and IntS form oligomers that are stabilized in the presence of their target DNA. Moreover, we found that IHF is the only nucleoid associated protein (NAP) involved in KplE1 recombination, although it is dispensable. This is consistent with the presence of only one functional IHF site on attR and none on attL

A semi-automated high-throughput approach to the generation of transposon insertion mutants in the nematode Caenorhabditis elegans

The generation of a large collection of defined transposon insertion mutants is of general interest to the Caenorhabditis elegans research community and has been supported by the European Union. We describe here a semi-automated high-throughput method for mutant production and screening, using the heterologous transposon Mos1. The procedure allows routine culture of several thousand independent nematode strains in parallel for multiple generations before stereotyped molecular analyses. Using this method, we have already generated >17 500 individual strains carrying Mos1 insertions. It could be easily adapted to forward and reverse genetic screens and may influence researchers faced with making a choice of model organism

Pengaruh Kesadaran Politik terhadap Pasrtisipasi Politik Masyarakat Kecamatan Tenayan Raya dalam Pemilihan Umum Walikota Pekanbaru Tahun 2017

One manifestation of political consciousness is political participation in the election of the mayor. Political participation based on political consciousness will encourage people to exercise their right to vote rationally and in accordance with the aspirations of the people. But in reality, the level of voter participation in the election mayor of Pekanbaru in 2017 is still lacking. Percentage of voters\u27 participation in sub district Tenayan Raya only reached 43.72%, which means there are still many voters who did not participate that reached 56.28%. This study aims to explain the effect of political awareness on political participation. This study uses quantitative descriptive by spreading questionnaires to 100 respondents in four urban villages in Tenayan Raya sub district, then the data is analyzed by using logistic regression. Based on the result of research, it can be concluded that there is a significant influence between political awareness on political participation because the value of p value Chi-Square 13,105 > Chi-Square table 3,841. In the Pseudo R Square table of 16.4% political awareness contribution to political participation, in other words 83.6% other factors from outside the model that explain the dependent variable. Based on the analysis of political awareness data of Tenayan Raya sub-district is low down to 68%, while the political participation of Tenayan Raya community in the election of mayor of Pekanbaru is also categorized as low by 94%

A Genome-Wide Collection of Mos1 Transposon Insertion Mutants for the C. elegans Research Community

Methods that use homologous recombination to engineer the genome of C. elegans commonly use strains carrying specific insertions of the heterologous transposon Mos1. A large collection of known Mos1 insertion alleles would therefore be of general interest to the C. elegans research community. We describe here the optimization of a semi-automated methodology for the construction of a substantial collection of Mos1 insertion mutant strains. At peak production, more than 5,000 strains were generated per month. These strains were then subject to molecular analysis, and more than 13,300 Mos1 insertions characterized. In addition to targeting directly more than 4,700 genes, these alleles represent the potential starting point for the engineered deletion of essentially all C. elegans genes and the modification of more than 40% of them. This collection of mutants, generated under the auspices of the European NEMAGENETAG consortium, is publicly available and represents an important research resource

Tight Regulation of the intS Gene of the KplE1 Prophage: A New Paradigm for Integrase Gene Regulation

Temperate phages have the ability to maintain their genome in their host, a process called lysogeny. For most, passive replication of the phage genome relies on integration into the host's chromosome and becoming a prophage. Prophages remain silent in the absence of stress and replicate passively within their host genome. However, when stressful conditions occur, a prophage excises itself and resumes the viral cycle. Integration and excision of phage genomes are mediated by regulated site-specific recombination catalyzed by tyrosine and serine recombinases. In the KplE1 prophage, site-specific recombination is mediated by the IntS integrase and the TorI recombination directionality factor (RDF). We previously described a sub-family of temperate phages that is characterized by an unusual organization of the recombination module. Consequently, the attL recombination region overlaps with the integrase promoter, and the integrase and RDF genes do not share a common activated promoter upon lytic induction as in the lambda prophage. In this study, we show that the intS gene is tightly regulated by its own product as well as by the TorI RDF protein. In silico analysis revealed that overlap of the attL region with the integrase promoter is widely encountered in prophages present in prokaryotic genomes, suggesting a general occurrence of negatively autoregulated integrase genes. The prediction that these integrase genes are negatively autoregulated was biologically assessed by studying the regulation of several integrase genes from two different Escherichia coli strains. Our results suggest that the majority of tRNA-associated integrase genes in prokaryotic genomes could be autoregulated and that this might be correlated with the recombination efficiency as in KplE1. The consequences of this unprecedented regulation for excisive recombination are discussed

Molecular Biology and Genetic Tools to Investigate Functional Redundancy Among Fe-S Cluster Carriers in E. coli

International audienc

Silver potentiates aminoglycoside toxicity by enhancing their uptake

International audienceThe predicted shortage in new antibiotics has prompted research for chemicals that could act as adjuvant and enhance efficacy of available antibiotics. In this study, we tested the effects of combining metals with aminoglycosides on Escherichia coli survival. The best synergizing combination resulted from mixing aminoglycosides with silver. Using genetic and aminoglycoside uptake assays, we showed that silver potentiates aminoglycoside action in by-passing the PMF-dependent step, but depended upon protein translation. We showed that oxidative stress or Fe-S cluster destabilization were not mandatory factors for silver potentiating action. Last, we showed that silver allows aminoglycosides to kill an E. coli gentamicin resistant mutant as well as the highly recalcitrant anaerobic pathogen Clostridium difficile. Overall this study delineates the molecular basis of silver's potentiating action on aminoglycoside toxicity and shows that use of metals might offer solutions for battling against increased bacterial resistance to antibiotics

Oxidative stress antagonizes fluoroquinolone drug sensitivity via the SoxR-SUF Fe-S cluster homeostatic axis

International audienceThe level of antibiotic resistance exhibited by bacteria can vary as a function of environmental conditions. Here, we report that phenazine-methosulfate (PMS), a redox-cycling compound (RCC) enhances resistance to fluoroquinolone (FQ) norfloxacin. Genetic analysis showed that E. coli adapts to PMS stress by making Fe-S clusters with the SUF machinery instead of the ISC one. Based upon phenotypic analysis of soxR, acrA, and micF mutants, we showed that PMS antagonizes fluoroquinolone toxicity by SoxR-mediated up-regulation of the AcrAB drug efflux pump. Subsequently, we showed that despite the fact that SoxR could receive its cluster from either ISC or SUF, only SUF is able to sustain efficient SoxR maturation under exposure to prolonged PMS period or high PMS concentrations. This study furthers the idea that Fe-S cluster homeostasis acts as a sensor of environmental conditions, and because its broad influence on cell metabolism, modifies the antibiotic resistance profile of E. coli