Learn More
We have developed a microfluidic assay for bacterial chemotaxis in which a gradient of chemoeffectors is established inside a microchannel via diffusion between parallel streams of liquid in laminar flow. The random motility and chemotactic responses to L-aspartate, L-serine, L-leucine, and Ni(2+) of WT and chemotactic-mutant strains of Escherichia coli(More)
Streptococcus strain V4051 is motile in the presence of glucose. The cells move steadily along smooth paths (run), jump about briefly with little net displacement (twiddle), and then run in new directions. They stop swimming when deprived of glucose. These cells become motile when an electrical potential or a pH gradient is imposed across the membrane.(More)
We have investigated the conditions required for polar localization of the CheZ phosphatase by using a CheZ-green fluorescent protein fusion protein that, when expressed from a single gene in the chromosome, restored chemotaxis to a DeltacheZ strain. Localization was observed in wild-type, DeltacheZ, DeltacheYZ, and DeltacheRB cells but not in cells with(More)
The Tap (taxis toward peptides) receptor and the periplasmic dipeptide-binding protein (DBP) of Escherichia coli together mediate chemotactic responses to dipeptides. Tap is a low-abundance receptor. It is present in 5- to 10-fold-fewer copies than high-abundance receptors like Tar and Tsr. Cells expressing Tap as the sole receptor, even from a multicopy(More)
Suppression analysis is well suited to study the interactions of gene products. It offers the advantage of simplicity for any organism for which a convenient genetic system has been developed, which holds for a wide spectrum of bacteria and an ever-increasing number of unicellular as well as complex eukaryotes. No other method provides as much information(More)
The Tar protein of Escherichia coli is a chemotactic signal transducer that spans the cytoplasmic membrane and mediates responses to the attractants aspartate and maltose. Aspartate binds directly to Tar, whereas maltose binds to the periplasmic maltose-binding protein, which then interacts with Tar. The Arg-64, Arg-69, and Arg-73 residues of Tar have(More)
The chemoreceptors of Escherichia coli localize to the cell poles and form a highly ordered array in concert with the CheA kinase and the CheW coupling factor. However, a high-resolution structure of the array has been lacking, and the molecular basis of array assembly has thus remained elusive. Here, we use cryoelectron tomography of flagellated E. coli(More)
The dipeptide permease (Dpp) of Escherichia coli transports peptides consisting of two or three L-amino acids. The periplasmic dipeptide-binding protein (DBP), encoded by the dppA gene, also serves as a chemoreceptor. We sequenced the dpp locus, which comprises an operon of five genes, dppABCDE. Its organization is the same as the oligopeptide permease(More)
Transmembrane helix 2 (TM2) of the Tar chemoreceptor undergoes an inward piston-like displacement of 1 to 3 Å upon binding aspartate. This signal is transmitted to the kinase-control module via the HAMP domain. Within Tar, the HAMP domain forms a parallel four-helix bundle consisting of a dimer of two amphipathic helices connected by a flexible linker. In(More)