Spatiotemporal Organization of Chemotaxis Pathways in Magnetospirillum gryphiswaldense.

Magnetospirillum gryphiswaldense employs iron-rich nanoparticles for magnetic navigation within environmental redox gradients. This behavior termed magneto-aerotaxis was previously shown to rely on the sensory pathway CheOp1, but the precise localization of CheOp1-related chemoreceptor arrays during the cell cycle and its possible interconnection with three other chemotaxis pathways have remained unstudied. Here, we analyzed the localization of chemoreceptor-associated adaptor protein CheW ₁ and histidine kinase CheA ₁ by superresolution microscopy in a spatiotemporal manner. CheW ₁ localized in dynamic clusters that undergo occasional segregation and fusion events at lateral sites of both cell poles. Newly formed smaller clusters originating at midcell before completion of cytokinesis were found to grow in size during the cell cycle. Bipolar CheA ₁ localization and formation of aerotactic swim halos were affected depending on the fluorescent protein tag, indicating that CheA ₁ localization is important for aerotaxis. Furthermore, polar CheW ₁ localization was independent of cheOp2 to cheOp4 but lost in the absence of cheOp1 or cheA ₁ Results were corroborated by the detection of a direct protein interaction between CheA ₁ and CheW ₁ and by the observation that cheOp2 - and cheOp3 -encoded CheW paralogs localized in spatially distinct smaller clusters at the cell boundary. Although the findings of a minor aerotaxis-related CheOp4 phenotype and weak protein interactions between CheOp1 and CheOp4 by two-hybrid analysis implied that CheW ₁ and CheW ₄ might be part of the same chemoreceptor array, CheW ₄ was localized in spatially distinct polar-lateral arrays independent of CheOp1, suggesting that CheOp1 and CheOp4 are also not connected at the molecular level. IMPORTANCE Magnetotactic bacteria (MTB) use the geomagnetic field for navigation in aquatic redox gradients. However, the highly complex signal transduction networks in these environmental microbes are poorly understood. Here, we analyzed the localization of selected chemotaxis proteins to spatially and temporally resolve chemotaxis array localization in Magnetospirillum gryphiswaldense Our findings suggest that bipolar localization of chemotaxis arrays related to the key signaling pathway CheOp1 is important for aerotaxis and that CheOp1 signaling units assemble independent of the three other chemotaxis pathways present in M. gryphiswaldense Overall, our results provide deeper insights into the complex organization of signaling pathways in MTB and add to the general understanding of environmental bacteria possessing multiple chemotaxis pathways.
(Copyright © 2020 American Society for Microbiology.)