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J Bacteriol. 2019 Jan 22. pii: JB.00534-18. doi: 10.1128/JB.00534-18. [Epub ahead of print]

The GGDEF domain of the phosphodiesterase PdeB in Shewanella putrefaciens mediates recruitment by the polar landmark protein HubP.

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Justus-Liebig Universität, Department of Microbiology and Molecular Biology, 35392 Giessen, Germany.
LOEWE Center for Synthetic Microbiology (Synmikro) & Department of Chemistry, Philipps-Universität Marburg, 35043 Marburg, Germany.
Research Service Center Metabolomics, Hannover Medical School, 30625 Hannover, Germany.
Justus-Liebig Universität, Department of Microbiology and Molecular Biology, 35392 Giessen, Germany


Bacteria commonly exhibit a high degree of cellular organization and polarity, which affects many vital processes such as replication, cell division and motility. In Shewanella and other bacteria, HubP is a polar marker protein, which is involved in proper chromosome segregation, placement of the chemotaxis system and various aspects of pili- and flagella-mediated motility. Here we show that HubP also recruits a transmembrane multi-domain protein, PdeB, to the flagellated cell pole. PdeB is an active phosphodiesterase and degrades the second messenger c-di-GMP. In S. putrefaciens, PdeB affects both the polar and the lateral flagellar systems at the level of function and/or transcription in response to environmental medium conditions. Mutant analysis on fluorescently labeled PdeB indicated that a diguanylate cyclase (GGDEF) domain in PdeB is strictly required for HubP-dependent localization. Bacterial two-hybrid and in vitro interaction studies on purified proteins strongly indicate that this GGDEF domain of PdeB directly interacts with the C-terminal FimV domain of HubP. Polar localization of PdeB occurs late during the cell cycle after cell division and separation and is not dependent on media conditions. In vitro activity measurements did not reveal a difference in PdeB phosphodiesterase activity in the presence or absence of the HubP FimV domain. We hypothesize that recruitment of PdeB to the flagellated pole by HubP may create an asymmetry of c-di-GMP levels between mother and daughter cells and may assist in organization of c-di-GMP-dependent regulation within the cell.IMPORTANCE c-di-GMP-dependent signaling affects a range of processes in many bacterial species. Most bacteria harbor a plethora of proteins with domains, which are potentially involved in synthesis and breakdown of c-di-GMP. A potential mechanism to elicit an appropriate cd-GMP-dependent response is to organize the corresponding proteins in a spatiotemporal fashion. Here we show that a major contributor to c-di-GMP levels and flagella-mediated swimming in Shewanella, PdeB, is recruited to the flagellated cell pole by the polar marker protein HubP. Polar recruitment involves a direct interaction between HubP and a GGDEF-domain in PdeB, demonstrating a novel mechanism of polar targeting by the widely conserved HubP/FimV polar marker.


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