Phase variation in Salmonella: analysis of Hin recombinase and hix recombination site interaction in vivo

Journal ArticleThe bacteriophage P22-based challenge phase selection was used to characterize the binding of Salmonella Hin recombinase to the wild-type hixL and hixR recombination sites, as well as to mutant and synthetic hix sequences in vivo. Hin recombinase binds to the hixL or hixR recombination sites and represses transcription from an upstream promoter in the challenge phage system

Electrical Characterization of Solar Cell using Arduino and Polarization Film

A solar cell laboratory course for high school and college undergraduate students is proposed. The electrical characterization of the solar cell is performed to confirm the functionality of the device as both a diode and a power source. The efficiency of the solar cell in the illuminated condition is found to be 13.1 %. We find the efficiency of the solar cell slightly decreases as the intensity of light decreases. However, there is no significant difference in efficiency except for in the opaque condition. A calibrated solar cell, multimeter, current sensor, Arduino, coding and polarization are used to perform the experiment.https://repository.upenn.edu/scn_educational/1002/thumbnail.jp

Physical map of the bacteriophage P22 genome

P22 mutations have been located relative to restriction endonuclease cleavage sites on the P22 chromosome by rescue of genetic markers from cloned DNA fragments. These data, in combination with prior genetic and physical mapping data, have allowed the construction of a detailed composite physical and genetic map.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24273/1/0000539.pd

Cloning, sequencing, and overexpression of gene 16 of salmonella bacteriophage P22

Umlauf B, Dreiseikelmann B. Cloning, sequencing, and overexpression of gene 16 of salmonella bacteriophage P22. Virology. 1992;188(2):495-501.It has been suggested that gene product 16 of bacteriophage P22 forms a pore for DNA transfer and/or that it functions as a pilot protein guiding the DNA across the membrane. We have cloned gene 16 and determined the nucleotide sequence. Within the sequenced region there is an open reading frame that could encode a protein of 609 amino acids having a molecular weight of 64,366. The hydropathic plot of this protein does not reveal putative membrane-spanning regions as expected for a protein forming a membrane pore. Overproduction of gene product 16 in Escherichia coli was successful only in a mutant in which the La protease was inactivated. Gene 16 mutants of phage P22 were not able to infect recBCD mutants of Salmonella typhimurium nor was protein 16, synthesized in E. colifrom a plasmid, able to substitute for the pilot protein of phage T4. It seems that gene product 16 is not a pilot protein in the meaning of binding to the ends of linear DNA, thus protecting it from degradation by nucleases

Genome Evolution and the Emergence of Fruiting Body Development in Myxococcus xanthus

BACKGROUND: Lateral gene transfer (LGT) is thought to promote speciation in bacteria, though well-defined examples have not been put forward. METHODOLOGY/PRINCIPLE FINDINGS: We examined the evolutionary history of the genes essential for a trait that defines a phylogenetic order, namely fruiting body development of the Myxococcales. Seventy-eight genes that are essential for Myxococcus xanthus development were examined for LGT. About 73% of the genes exhibit a phylogeny similar to that of the 16S rDNA gene and a codon bias consistent with other M. xanthus genes suggesting vertical transmission. About 22% have an altered codon bias and/or phylogeny suggestive of LGT. The remaining 5% are unique. Genes encoding signal production and sensory transduction were more likely to be transmitted vertically with clear examples of duplication and divergence into multigene families. Genes encoding metabolic enzymes were frequently acquired by LGT. Myxobacteria exhibit aerobic respiration unlike most of the delta Proteobacteria. M. xanthus contains a unique electron transport pathway shaped by LGT of genes for succinate dehydrogenase and three cytochrome oxidase complexes. CONCLUSIONS/SIGNIFICANCE: Fruiting body development depends on genes acquired by LGT, particularly those involved in polysaccharide production. We suggest that aerobic growth fostered innovation necessary for development by allowing myxobacteria access to a different gene pool from anaerobic members of the delta Proteobacteria. Habitat destruction and loss of species diversity could restrict the evolution of new bacterial groups by limiting the size of the prospective gene pool

FrzS Regulates Social Motility in Myxococcus xanthus by Controlling Exopolysaccharide Production

Myxococcus xanthus Social (S) motility occurs at high cell densities and is powered by the extension and retraction of Type IV pili which bind ligands normally found in matrix exopolysaccharides (EPS). Previous studies showed that FrzS, a protein required for S-motility, is organized in polar clusters that show pole-to-pole translocation as cells reverse their direction of movement. Since the leading cell pole is the site of both the major FrzS cluster and type IV pilus extension/retraction, it was suggested that FrzS might regulate S-motility by activating pili at the leading cell pole. Here, we show that FrzS regulates EPS production, rather than type IV pilus function. We found that the frzS phenotype is distinct from that of Type IV pilus mutants such as pilA and pilT, but indistinguishable from EPS mutants, such as epsZ. Indeed, frzS mutants can be rescued by the addition of purified EPS, 1% methylcellulose, or co-culturing with wildtype cells. Our data also indicate that the cell density requirement in S-motility is likely a function of the ability of cells to construct functional multicellular clusters surrounding an EPS core

Cyanobacteria in motion

This work was supported by a grant from the DFG (WI 2014/7-1) to A.W

Engineering transcription factors with novel DNA-binding specificity using comparative genomics

The transcriptional program for a gene consists of the promoter necessary for recruiting RNA polymerase along with neighboring operator sites that bind different activators and repressors. From a synthetic biology perspective, if the DNA-binding specificity of these proteins can be changed, then they can be used to reprogram gene expression in cells. While many experimental methods exist for generating such specificity-altering mutations, few computational approaches are available, particularly in the case of bacterial transcription factors. In a previously published computational study of nitrogen oxide metabolism in bacteria, a small number of amino-acid residues were found to determine the specificity within the CRP (cAMP receptor protein)/FNR (fumarate and nitrate reductase regulatory protein) family of transcription factors. By analyzing how these amino acids vary in different regulators, a simple relationship between the identity of these residues and their target DNA-binding sequence was constructed. In this article, we experimentally tested whether this relationship could be used to engineer novel DNA–protein interactions. Using Escherichia coli CRP as a template, we tested eight designs based on this relationship and found that four worked as predicted. Collectively, these results in this work demonstrate that comparative genomics can inform the design of bacterial transcription factors

Coupling of protein localization and cell movements by a dynamically localized response regulator in Myxococcus xanthus

Myxococcus xanthus cells harbor two motility machineries, type IV pili (Tfp) and the A-engine. During reversals, the two machineries switch polarity synchronously. We present a mechanism that synchronizes this polarity switching. We identify the required for motility response regulator (RomR) as essential for A-motility. RomR localizes in a bipolar, asymmetric pattern with a large cluster at the lagging cell pole. The large RomR cluster relocates to the new lagging pole in parallel with cell reversals. Dynamic RomR localization is essential for cell reversals, suggesting that RomR relocalization induces the polarity switching of the A-engine. The analysis of RomR mutants shows that the output domain targets RomR to the poles and the receiver domain is essential for dynamic localization. The small GTPase MglA establishes correct RomR polarity, and the Frz two-component system regulates dynamic RomR localization. FrzS localizes with Tfp at the leading pole and relocates in an Frz-dependent manner to the opposite pole during reversals; FrzS and RomR localize and oscillate independently. The Frz system synchronizes these oscillations and thus the synchronous polarity switching of the motility machineries