Biology subjects

Jacq, M.

Publications and source records attributed to Jacq, M..

3 recordsLinked to original sources

bioRxiv2024

Functional specialization of the subdomains of a bactofilin driving stalk morphogenesis in Asticcacaulis biprosthecum

Bactofilins are a recently discovered class of cytoskeletal protein, widely implicated in subcellular organization and morphogenesis in bacteria and archaea. Several lines of evidence suggest that bactofilins polymerize into filaments using a central {beta}-helical core domain, flanked by variable N- and C-terminal domains that may be important for scaffolding and other functions. However, a systematic exploration of the characteristics of these domains has yet to be performed. In Asticcacaulis biprosthecum, the bactofilin BacA serves as a topological organizer of stalk synthesis, localizing to the stalk base and coordinating the synthesis of these long, thin extensions of the cell envelope. The easily distinguishable phenotypes of wild-type A. biprosthecum stalks and{Delta} bacA "pseudostalks" make this an ideal system for investigating how mutations in BacA affect its functions in morphogenesis. Here, we redefine the core domain of A. biprosthecum BacA using various bioinformatics and biochemical approaches to precisely delimit the N- and C-terminal domains. We then show that loss of these terminal domains leads to cells with severe morphological abnormalities, typically presenting a pseudostalk phenotype. BacA mutants lacking the N- and C-terminal domains also exhibit localization defects, implying that the terminal domains of BacA may be involved in its subcellular positioning, whether through membrane interactions through the N-terminal domain or through interactions with the stalk-specific morphological regulator SpmX through the C-terminal domain. We further show that point mutations that render BacA defective for polymerization lead to stalk synthesis defects. Overall, our study suggests that BacAs polymerization, membrane association, and interactions with other morphological factors all play a crucial role in the proteins function as a morphogenic regulator. The specialization and modularity of the terminal domains may underlie the remarkable functional versatility of the bactofilins in different species. Author summaryBacteria exhibit a wide variety of shapes and structures, many of which are crucial for their cellular functions. Among these structures is the stalk--a thin, tubular extension of the cell envelope formed by bacteria such as Asticcacaulis biprosthecum. Stalk synthesis in Asticcacaulis biprosthecum relies on the bactofilin BacA, a self-polymerizing cytoskeletal protein, whose deletion results in the dysregulation of stalk synthesis, and the formation of short, stubby "pseudostalks". We use this unique phenotype to characterize the subdomains of BacA, and find that BacAs ability to coordinate stalk synthesis depends on its conserved polymerization domain as well as its flanking N- and C-terminal domains, which are essential for proper localization and interactions. Our findings highlight how bactofilins combine conserved and variable regions to generate complex structures that serve as a platform for evolving new functions.

microbiology↗

bioRxiv2024

Phenotypic plasticity in bacterial elongation among closely related species

Cell elongation is a fundamental component of the bacterial cell cycle and has been studied over many decades, in part owing to its mechanisms being a target of numerous antibiotic classes. While several distinct modes of cell elongation have been described, these studies have largely relied on a handful of model bacterial species. Therefore, we have a limited view of the diversity of cell elongation approaches that are employed by bacteria, and how these vary in response to evolutionary and environmental influences. Here, by employing fluorescent D-amino acids (FDAAs) to track the spatiotemporal dynamics of elongation, we reveal previously unsuspected diversity of elongation modes among closely related species of the Caulobacteraceae, with species-specific combinations of dispersed, midcell and polar elongation that can be either unidirectional or bidirectional. Using genetic, cell biology, and phylogenetic approaches, we demonstrate that evolution of unidirectional-midcell elongation is accompanied by changes in the localization pattern of the peptidoglycan synthase PBP2 and infer that elongation complexes display a high degree of phenotypic plasticity, both among the Caulobacteraceae and more widely among the Alphaproteobacteria. Demonstration that even closely related bacterial species employ highly distinct mechanisms of cell elongation reshapes our understanding of the evolution and regulation of bacterial cell growth, with broad implications for bacterial morphology, adaptation, and antibiotic resistance.

microbiology↗

bioRxiv2019

A Division of Labor in the Recruitment and TopologicalOrganization of a Bacterial Morphogenic Complex

Bacteria come in an array of shapes and sizes, but the mechanisms underlying diverse morphologies are poorly understood. The peptidoglycan (PG) cell wall is the primary determinant of cell shape. At the molecular level, morphological variation often results from the regulation of enzymes involved in cell elongation and division. These enzymes are spatially controlled by cytoskeletal scaffolding proteins, that both recruit and organize the PG synthesis complex. How then do cells define alternative morphogenic processes that are distinct from cell elongation and division? To address this, we have turned to the specific morphotype of Alphaproteobacterial stalks. Stalk synthesis is a specialized form of zonal growth, which requires PG synthesis in a spatially constrained zone to extend a thin cylindrical projection of the cell envelope. The morphogen SpmX defines the site of stalk PG synthesis, but SpmX is a PG hydrolase. How then does a non-cytoskeletal protein, SpmX, define and constrain PG synthesis to form stalks? Here we report that SpmX and the bactofilin BacA act in concert to regulate stalk synthesis in Asticcacaulis biprosthecum. We show that SpmX recruits BacA to the site of stalk synthesis. BacA then serves as a stalk-specific topological organizer for PG synthesis activity, including its recruiter SpmX, at the base of the stalk. In the absence of BacA, cells produce "pseudostalks" that are the result of unconstrained PG synthesis. Therefore, the protein responsible for recruitment of a morphogenic PG remodeling complex, SpmX, is distinct from the protein that topologically organizes the complex, BacA.

microbiology↗