Designed potent multivalent chemoattractants for Escherichia coli

Abstract

Abstract-Bacterial chemotactic responses are initiated when certain small molecules (i.e., carbohydrates, amino acids) interact with bacterial chemoreceptors. Although bacterial chemotaxis has been the subject of intense investigations, few have explored the influence of attractant structure on signal generation and chemotaxis. Previously, we found that polymers bearing multiple copies of galactose interact with the chemoreceptor Trg via the periplasmic binding protein glucose/galactose binding protein (GGBP). These synthetic multivalent ligands were potent agonists of Escherichia coli chemotaxis. Here, we report on the development of a second generation of multivalent attractants that possess increased chemotactic activities. Strikingly, the new ligands can alter bacterial behavior at concentrations 10-fold lower than those required with the original displays; thus, they are some of the most potent synthetic chemoattractants known. The potency depends on the number of galactose moieties attached to the oligomer backbone and the length of the linker tethering these carbohydrates. Our investigations reveal the plasticity of GGBP; it can bind and mediate responses to several carbohydrates and carbohydrate derivatives. These attributes of GGBP may underlie the ability of bacteria to sense a variety of ligands with relatively few receptors. Our results provide insight into the design and development of compounds that can modulate bacterial chemotaxis and pathogenicity. #

Conserved Amplification of Chemotactic Responses through Chemoreceptor Interactions

“…Monomers 1, 5, and 8 were also tested as attractants for comparison. Such experiments were critical to verify that the modification of the attractant for incorporation into the polymer did not abolish its activity (25). In addition, fluorescent derivatives 12 to 14 were generated for colocalization studies with the MCPs (27,61).…”

“…Multivalent ligands often have higher avidity for their target than monovalent derivatives (37,38,43,49). Although a multivalent chemoattractant can exhibit an increase in binding through avidity (25), this mechanism does not account for all of the data. If the enhanced chemotactic response were due to avidity alone, saccharide-bearing ligands should not influence B. subtilis responses to serine (Fig.…”

Diversity in Chemotaxis Mechanisms among the Bacteria and Archaea

“…However, the significance of clustering for signal amplification is uncertain, since it was unaltered in E. coli strains lacking CheR or CheB (138), but strains lacking CheB are very impaired in sensitivity to attractants, although strains lacking CheR are still very sensitive (108,210). Moreover, addition of a multivalent ligand that can bind two receptors simultaneously greatly increases the sensitivity of heterologous receptors to their ligands, and this sensitivity is diminished when other heterologous receptors are deleted (71,72). Thus, it would appear that clustering of receptors may facilitate taxis since receptors are close to each other but active signaling must require a particular arrangement of the receptors, a goal that is hard to achieve when they are fully methylated.…”

Multivalency in Ligand Design

“…Generalizing this single result to the potential in vivo efficacy of other polymers is, of course, not possible. Kiessling and co-workers also investigated the clustering of cell-surface receptors by multivalent polymers displaying galactose and the influence of this clustering on such downstream effects as bacterial chemotaxis [11][12][13]162].…”