Hypoxia-induced localization of chemotaxis-related signaling proteins in Vibrio cholerae.

Vibrio cholerae has three sets of chemotaxis-related signaling proteins, of which only System II has been shown to be involved in chemotaxis. Here, we examined localization of green fluorescent protein (GFP)-fused components of System I. The histidine kinase (CheA1) and the adaptor (CheW0) of System I localized to polar and lateral membrane regions with standing incubation (microaerobic conditions), but their localization was lost after shaking (aerobic conditions). A transmembrane receptor of System I also showed polar and lateral localization with standing incubation. By contrast, GFP-fused components of System II localized constitutively to the flagellated pole. Nitrogen gas, sodium azide or carbonylcyanide m-chlorophenylhydrazone induced localization of CheA1-GFP even with shaking incubation, suggesting that the localization is controlled in response to changes in energy metabolism. Fluorescently labeled tetracysteine-tagged CheA1 also showed azide-induced localization, arguing against artifactual effects of GFP fusions. These results suggest that System I components are assembled into the supramolecular signaling complex in response to reduced cellular energy states, raising the possibility that the System I complex plays a role in sensing and signaling under microaerobic environments, such as in the host intestine.