FlhF regulates the number and configuration of periplasmic flagella in Borrelia burgdorferi

• Published in: Molecular microbiology 2020-06, Vol.113 (6), p.1122-1139
• Main Authors: Zhang, Kai, He, Jun, Cantalano, Claudio, Guo, Youzhong, Liu, Jun, Li, Chunhao
• Format: Article
• Language: English
• Subjects: Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Basal Bodies - physiology; Borrelia burgdorferi; Borrelia burgdorferi - genetics; Borrelia burgdorferi - metabolism; Configurations; Electron Microscope Tomography; Enzymatic activity; Flagella; Flagella - genetics; Flagella - metabolism; Flagella - physiology; Gene Deletion; Genetics; Guanosine triphosphatases; Homology; Localization; Locomotion - genetics; Lyme disease; Monomeric GTP-Binding Proteins - genetics; Monomeric GTP-Binding Proteins - metabolism; Morphology; motility; periplasmic flagella; Polarity; Poles; Proteins; Signal recognition particle; signal recognition particle (SRP)‐GTPase; Spirochetes; Vector-borne diseases
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.14482

The Lyme disease bacterium Borrelia burgdorferi has 7–11 periplasmic flagella (PF) that arise from the cell poles and extend toward the midcell as a flat‐ribbon, which is distinct from other bacteria. FlhF, a signal recognition particle (SRP)‐like GTPase, has been found to regulate the flagellar number and polarity; however, its role in B. burgdorferi remains unknown. B. burgdorferi has an FlhF homolog (BB0270). Structural and biochemical analyses show that BB0270 has a similar structure and enzymatic activity as its counterparts from other bacteria. Genetics and cryo‐electron tomography studies reveal that deletion of BB0270 leads to mutant cells that have less PF (4 ± 2 PF per cell tip) and fail to form a flat‐ribbon, indicative of a role of BB0270 in the control of PF number and configuration. Mechanistically, we demonstrate that BB0270 localizes at the cell poles and controls the number and position of PF via regulating the flagellar protein stability and the polar localization of the MS‐ring protein FliF. Our study not only provides the detailed characterizations of BB0270 and its profound impacts on flagellar assembly, morphology and motility in B. burgdorferi, but also unveils mechanistic insights into how spirochetes control their unique flagellar patterns. FlhF, a signal‐recognition‐particle (SRP)‐like GTPase, regulates the number and configuration of periplasmic flagella in Borrelia burgdorferi mechanistically via controlling other flagellar protein stability and polar localization.