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Chemoreceptors of the methyl-accepting chemotaxis protein family form clusters, typically at the cell pole(s), in both Bacteria and Archaea. To elucidate the architecture and signaling role of receptor clusters, we investigated interactions between the serine (Tsr) and aspartate (Tar) chemoreceptors in Escherichia coli by constructing Tsr mutations at the(More)
Motile bacteria seek optimal living habitats by following gradients of attractant and repellent chemicals in their environment. The signaling machinery for these chemotactic behaviors, although assembled from just a few protein components, has extraordinary information-processing capabilities. Escherichia coli, the best-studied model, employs a networked(More)
During chemotactic signalling by Escherichia coli, the small cytoplasmic CheW protein couples the histidine kinase CheA to chemoreceptor control. Although essential for assembly and operation of receptor signalling complexes, CheW in stoichiometric excess disrupts chemotactic behaviour. To explore the mechanism of the CheW excess effect, we measured the(More)
The team signaling model for bacterial chemoreceptors proposes that receptor dimers of different detection specificities form mixed trimers of dimers. These receptor "squads" then recruit the cytoplasmic signaling proteins CheA and CheW to form ternary signaling teams, which typically cluster at the poles of the cell. We devised cysteine-directed in vivo(More)
The team signaling model for bacterial chemoreceptors proposes that receptor dimers of different detection specificities form mixed trimers of dimers that bind the cytoplasmic proteins CheA and CheW to form ternary signaling complexes clustered at the cell poles. We used a trifunctional crosslinking reagent targeted to cysteine residues in the aspartate(More)
A serine protease secreted by the haloalkaliphilic archaeon Natrialba magadii at the end of the exponential growth phase was isolated. This enzyme was purified 83 fold with a total yield of 25% by ethanol precipitation, affinity chromatography, and gel filtration. The native molecular mass of the enzyme determined by gel filtration was 45 kDa. Na. magadii(More)
The chemoreceptor molecules that mediate chemotactic responses in bacteria and archaea are physically clustered and operate as highly cooperative arrays. Few experimental approaches are able to investigate the structure-function organization of these chemoreceptor networks in living cells. This chapter describes chemical crosslinking methods that can be(More)
In this report we describe the isolation of a strain from soil contaminated with gas oil by taking bacteria from a chemotactic ring on gas oil-containing soft agar plates. Partial 16 S rDNA sequencing of the isolated strain showed 99.1% identity with Flavimonas oryzihabitans. It was not only able to degrade different aliphatic hydrocarbons but it was also(More)
Chemotactic behavior in bacteria relies on the sensing ability of large chemoreceptor clusters that are usually located at the cell pole. In Escherichia coli, chemoreceptors exhibit higher-order interactions within those clusters based on a trimer-of-dimers organization. This architecture is conserved in a variety of other bacteria and archaea, implying(More)
A serine protease was purified from Natronococcus occultus stationary phase culture medium (328-fold, yield 19%) and characterized at the biochemical level. The enzyme has a native molecular mass of 130 kDa, has chymotrypsin-like activity, is stable and active in a broad pH range (5.5-12), is rather thermophilic (optimal activity at 60 degrees C in 1-2 M(More)