インサイト - Cellular Microbiology - # Regulation of Polar Flagellum Formation

A Novel Protein FipA Interacts with FlhF to Regulate Polar Flagellum Formation in Motile Bacteria

Q: How does the interaction between FipA and FlhF affect the GTPase activity and oligomerization state of FlhF, and how does this impact the initiation of flagellum assembly?

The interaction between FipA and FlhF plays a crucial role in modulating the GTPase activity and oligomerization state of FlhF, which is essential for the initiation of flagellum assembly in polar flagellated bacteria. FlhF, when bound to GTP, exists in a dimeric form that is active and capable of localizing to the cell pole. The presence of FipA is believed to stabilize this GTP-bound dimeric state, thereby enhancing FlhF's ability to recruit the initial flagellar building blocks necessary for flagellum assembly. When FipA interacts with FlhF, it may facilitate the dimerization of FlhF or prevent its premature hydrolysis of GTP to GDP, which would lead to a loss of polar localization and activity. This stabilization is critical because once FlhF is localized at the cell pole, it can initiate the assembly of the MS-ring, a key structure in flagellum formation. Without the interaction with FipA, FlhF's GTPase activity may lead to a rapid transition to its inactive monomeric form, resulting in reduced recruitment of flagellar components and ultimately impairing flagellum assembly. Thus, the FipA-FlhF interaction is a pivotal regulatory mechanism that ensures the proper timing and localization of flagellar synthesis.

Q: What are the additional factors or mechanisms that recruit or guide FipA and the FipA-FlhF complex to the designated cell pole in the different bacterial species?

In addition to the direct interaction between FipA and FlhF, several other factors and mechanisms contribute to the recruitment and localization of FipA and the FipA-FlhF complex to the designated cell pole in various bacterial species. One significant factor is the polar landmark protein HubP (or its homolog FimV in Pseudomonas), which has been shown to interact with FlhF and facilitate its localization. HubP acts as an organizer at the cell pole, recruiting FlhF and potentially FipA to the site where flagellum assembly is initiated. In species like Shewanella putrefaciens, HubP appears to play a more dominant role in guiding FipA to the pole, as FipA can still localize in the absence of FlhF if HubP is present. This suggests that HubP may provide a scaffold or anchor for the FipA-FlhF complex, ensuring that it is positioned correctly for flagellum assembly. Additionally, the dynamic localization of FipA itself, which can form distinct foci at the cell pole, indicates that there may be other unidentified factors or cellular mechanisms that regulate its movement and stability at the pole. The interplay between these factors, including the cell cycle dynamics and the presence of other polar proteins, contributes to the precise spatial organization required for effective flagellum synthesis.

Q: Could the dynamic localization pattern of FipA be exploited to develop novel strategies for controlling bacterial motility and flagellum-dependent virulence in pathogenic species?

Yes, the dynamic localization pattern of FipA presents a promising avenue for developing novel strategies to control bacterial motility and flagellum-dependent virulence in pathogenic species. By understanding the mechanisms that regulate FipA localization and its interaction with FlhF, researchers could design targeted interventions that disrupt these processes. For instance, small molecules or peptides that inhibit the FipA-FlhF interaction could be developed, effectively reducing the recruitment of FlhF to the cell pole and subsequently impairing flagellum assembly. This would not only hinder bacterial motility but could also reduce the virulence of pathogenic bacteria that rely on flagella for infection and colonization. Moreover, manipulating the expression levels of FipA or its homologs could be another strategy to control flagellum formation. By using genetic engineering techniques, it may be possible to create strains with altered FipA localization patterns, leading to reduced motility and virulence. Additionally, the insights gained from studying FipA's localization dynamics could inform the development of novel antimicrobial agents that target the flagellar synthesis pathway, providing a new approach to combat bacterial infections, particularly those caused by motile pathogens. Overall, leveraging the knowledge of FipA's role in flagellum regulation could lead to innovative strategies for controlling bacterial behavior and pathogenicity.

核心概念

FipA, a conserved membrane protein, interacts with the flagellar regulator FlhF to facilitate its recruitment to the cell pole, thereby enabling proper polar flagellum formation in motile bacteria.

要約

The study identified a novel protein called FipA that is required for normal FlhF activity and function in polar flagellar synthesis. FipA is a conserved membrane-localized protein that interacts with FlhF and is essential for flagellum formation in three different polarly flagellated γ-proteobacteria: Vibrio parahaemolyticus, Pseudomonas putida, and Shewanella putrefaciens.

The key findings are:

FipA interacts directly with the flagellar regulator FlhF and is required for proper polar localization of FlhF. In the absence of FipA, FlhF fails to localize correctly to the cell pole.
The transmembrane domain and conserved residues in the cytoplasmic domain of FipA are essential for its function in regulating flagellum formation and FlhF localization.
FipA exhibits a dynamic localization pattern, being present at the designated pole before flagellar synthesis begins, suggesting its role in licensing flagellar formation.
FipA acts in concert with the polar landmark protein HubP/FimV to ensure proper polar localization of FlhF. Deleting both FipA and HubP/FimV completely abolishes FlhF localization to the cell pole.
The function of FipA in regulating FlhF and flagellum formation is conserved across the three distantly related γ-proteobacterial species, despite differences in the severity of the phenotypes.

This discovery provides insight into a new pathway for regulating flagellum synthesis and coordinating cellular organization in bacteria that rely on polar flagellation and FlhF-dependent localization.

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biorxiv.org

統計

"Absence of FipA in V. parahaemolyticus completely abolished swimming motility in soft-agar medium to the same degree as cells lacking FlhF."
"Planktonic cells lacking either FlhF or FipA, showed a complete absence of flagella on the bacterial surface, while a single polar flagellum was observed in ∼50 % of wild-type cells."
"In the double deletion strain ΔfipA ΔhubP, FlhF did not localize as foci at the cell pole at all but was instead localized diffusely in the cytoplasm in 100% of cells."

引用

"FipA constitutes a new family of FlhF interaction partners important for the γ-proteobacteria."
"FipA not only is required for proper polar recruitment of FlhF, but also for the stimulation of flagellum formation."
"The discovery of FipA provides a new point where spatiotemporal organization is coordinated."

抽出されたキーインサイト

A conserved cell-pole determinant organizes proper polar flagellum formation

by Arroyo-Perez... 場所 www.biorxiv.org 09-20-2023

https://www.biorxiv.org/content/10.1101/2023.09.20.558563v3

深掘り質問

How does the interaction between FipA and FlhF affect the GTPase activity and oligomerization state of FlhF, and how does this impact the initiation of flagellum assembly?

The interaction between FipA and FlhF plays a crucial role in modulating the GTPase activity and oligomerization state of FlhF, which is essential for the initiation of flagellum assembly in polar flagellated bacteria. FlhF, when bound to GTP, exists in a dimeric form that is active and capable of localizing to the cell pole. The presence of FipA is believed to stabilize this GTP-bound dimeric state, thereby enhancing FlhF's ability to recruit the initial flagellar building blocks necessary for flagellum assembly.
When FipA interacts with FlhF, it may facilitate the dimerization of FlhF or prevent its premature hydrolysis of GTP to GDP, which would lead to a loss of polar localization and activity. This stabilization is critical because once FlhF is localized at the cell pole, it can initiate the assembly of the MS-ring, a key structure in flagellum formation. Without the interaction with FipA, FlhF's GTPase activity may lead to a rapid transition to its inactive monomeric form, resulting in reduced recruitment of flagellar components and ultimately impairing flagellum assembly. Thus, the FipA-FlhF interaction is a pivotal regulatory mechanism that ensures the proper timing and localization of flagellar synthesis.

What are the additional factors or mechanisms that recruit or guide FipA and the FipA-FlhF complex to the designated cell pole in the different bacterial species?

In addition to the direct interaction between FipA and FlhF, several other factors and mechanisms contribute to the recruitment and localization of FipA and the FipA-FlhF complex to the designated cell pole in various bacterial species. One significant factor is the polar landmark protein HubP (or its homolog FimV in Pseudomonas), which has been shown to interact with FlhF and facilitate its localization. HubP acts as an organizer at the cell pole, recruiting FlhF and potentially FipA to the site where flagellum assembly is initiated.
In species like Shewanella putrefaciens, HubP appears to play a more dominant role in guiding FipA to the pole, as FipA can still localize in the absence of FlhF if HubP is present. This suggests that HubP may provide a scaffold or anchor for the FipA-FlhF complex, ensuring that it is positioned correctly for flagellum assembly.
Additionally, the dynamic localization of FipA itself, which can form distinct foci at the cell pole, indicates that there may be other unidentified factors or cellular mechanisms that regulate its movement and stability at the pole. The interplay between these factors, including the cell cycle dynamics and the presence of other polar proteins, contributes to the precise spatial organization required for effective flagellum synthesis.

Could the dynamic localization pattern of FipA be exploited to develop novel strategies for controlling bacterial motility and flagellum-dependent virulence in pathogenic species?

Yes, the dynamic localization pattern of FipA presents a promising avenue for developing novel strategies to control bacterial motility and flagellum-dependent virulence in pathogenic species. By understanding the mechanisms that regulate FipA localization and its interaction with FlhF, researchers could design targeted interventions that disrupt these processes.
For instance, small molecules or peptides that inhibit the FipA-FlhF interaction could be developed, effectively reducing the recruitment of FlhF to the cell pole and subsequently impairing flagellum assembly. This would not only hinder bacterial motility but could also reduce the virulence of pathogenic bacteria that rely on flagella for infection and colonization.
Moreover, manipulating the expression levels of FipA or its homologs could be another strategy to control flagellum formation. By using genetic engineering techniques, it may be possible to create strains with altered FipA localization patterns, leading to reduced motility and virulence.
Additionally, the insights gained from studying FipA's localization dynamics could inform the development of novel antimicrobial agents that target the flagellar synthesis pathway, providing a new approach to combat bacterial infections, particularly those caused by motile pathogens. Overall, leveraging the knowledge of FipA's role in flagellum regulation could lead to innovative strategies for controlling bacterial behavior and pathogenicity.