The role of FlhF and HubP as polar landmark proteins in Shewanella putrefaciensCN-32

• Published in: Molecular microbiology 2015-11, Vol.98 (4), p.727-742
• Main Authors: Rossmann, Florian, Brenzinger, Susanne, Knauer, Carina, Dorrich, Anja K, Bubendorfer, Sebastian, Ruppert, Ulrike, Bange, Gert, Thormann, Kai M
• Format: Article
• Language: English
• Subjects: Shewanella; Shewanella putrefaciens; Vibrio
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.13152

Spatiotemporal regulation of cell polarity plays a role in many fundamental processes in bacteria and often relies on 'landmark' proteins which recruit the corresponding clients to their designated position. Here, we explored the localization of two multi-protein complexes, the polar flagellar motor and the chemotaxis array, in Shewanella putrefaciensCN-32. We demonstrate that polar positioning of the flagellar system, but not of the chemotaxis system, depends on the GTPase FlhF. In contrast, the chemotaxis array is recruited by a transmembrane protein which we identified as the functional ortholog of Vibrio choleraeHubP. Mediated by its periplasmic N-terminal LysM domain, SpHubP exhibits an FlhF-independent localization pattern during cell cycle similar to its Vibrio counterpart and also has a role in proper chromosome segregation. In addition, while not affecting flagellar positioning, SpHubP is crucial for normal flagellar function and is involved in type IV pili-mediated twitching motility. We hypothesize that a group of HubP/FimV homologs, characterized by a rather conserved N-terminal periplasmic section required for polar targeting and a highly variable acidic cytoplasmic part, primarily mediating recruitment of client proteins, serves as polar markers in various bacterial species with respect to different cellular functions. Spatiotemporal regulation of cell polarity is crucial for numerous important or even essential cellular processes. Here we show how two landmark systems, FlhF/FlhG and HubP operate in Shewanella putrefaciens CN-32 to position cellular complexes such as the flagellum, the chemotaxis system, or the seggragation machinery. We suggest that HubP-like polar markers are likely present in a range of bacterial species and impact on various cellular processes.