scholarly journals MglC, a Paralog of Myxococcus xanthus GTPase-Activating Protein MglB, Plays a Divergent Role in Motility Regulation

2015 ◽  
Vol 198 (3) ◽  
pp. 510-520 ◽  
Author(s):  
Anna L. McLoon ◽  
Kristin Wuichet ◽  
Michael Häsler ◽  
Daniela Keilberg ◽  
Dobromir Szadkowski ◽  
...  
Keyword(s):  
Gene Duplication ◽  
Cell Polarity ◽  
Response Regulator ◽  
Myxococcus Xanthus ◽  
Social Behaviors ◽  
Gliding Motility ◽  
Cellular Polarity ◽  
Gtpase Activating Protein ◽  
Content Type ◽  
Motility Regulation

ABSTRACTIn order to optimize interactions with their environment and one another, bacteria regulate their motility. In the case of the rod-shaped cells ofMyxococcus xanthus, regulated motility is essential for social behaviors.M. xanthusmoves over surfaces using type IV pilus-dependent motility and gliding motility. These two motility systems are coordinated by a protein module that controls cell polarity and consists of three polarly localized proteins, the small G protein MglA, the cognate MglA GTPase-activating protein MglB, and the response regulator RomR. Cellular reversals are induced by the Frz chemosensory system, and the output response regulator of this system, FrzZ, interfaces with the MglA/MglB/RomR module to invert cell polarity. Using a computational approach, we identify a paralog of MglB, MXAN_5770 (MglC). Genetic epistasis experiments demonstrate that MglC functions in the same pathway as MglA, MglB, RomR, and FrzZ and is important for regulating cellular reversals. Like MglB, MglC localizes to the cell poles asymmetrically and with a large cluster at the lagging pole. Correct polar localization of MglC depends on RomR and MglB. Consistently, MglC interacts directly with MglB and the C-terminal output domain of RomR, and we identified a surface of MglC that is necessary for the interaction with MglB and for MglC function. Together, our findings identify an additional member of theM. xanthuspolarity module involved in regulating motility and demonstrate how gene duplication followed by functional divergence can add a layer of control to the complex cellular processes of motility and motility regulation.IMPORTANCEGene duplication and the subsequent divergence of the duplicated genes are important evolutionary mechanisms for increasing both biological complexity and regulation of biological processes. The bacteriumMyxococcus xanthusis a soil bacterium with an unusually large genome that carries out several social processes, including predation of other bacterial species and formation of multicellular, spore-filled fruiting bodies. One feature of the largeM. xanthusgenome is that it contains many gene duplications. Here, we compare the products of one example of gene duplication and divergence, in which a paralog of the cognate MglA GTPase-activating protein MglB has acquired a different and opposing role in the regulation of cellular polarity and motility, processes critical to the bacterium's social behaviors.

scholarly journals The polarity of myxobacterial gliding is regulated by direct interactions between the gliding motors and the Ras homolog MglA

2014 ◽  
Vol 112 (2) ◽  
pp. E186-E193 ◽  
Author(s):  
Beiyan Nan ◽  
Jigar N. Bandaria ◽  
Kathy Y. Guo ◽  
Xue Fan ◽  
Amirpasha Moghtaderi ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Cell Polarity ◽  
Myxococcus Xanthus ◽  
Proton Motive Force ◽  
Gliding Motility ◽  
Cellular Polarity ◽  
Gtpase Activating Protein ◽  
Chemosensory Pathway ◽  
Ras Family ◽  
Ras Family Proteins

Gliding motility in Myxococcus xanthus is powered by flagella stator homologs that move in helical trajectories using proton motive force. The Frz chemosensory pathway regulates the cell polarity axis through MglA, a Ras family GTPase; however, little is known about how MglA establishes the polarity of gliding, because the gliding motors move simultaneously in opposite directions. Here we examined the localization and dynamics of MglA and gliding motors in high spatial and time resolution. We determined that MglA localizes not only at the cell poles, but also along the cell bodies, forming a decreasing concentration gradient toward the lagging cell pole. MglA directly interacts with the motor protein AglR, and the spatial distribution of AglR reversals is positively correlated with the MglA gradient. Thus, the motors moving toward lagging cell poles are less likely to reverse, generating stronger forward propulsion. MglB, the GTPase-activating protein of MglA, regulates motor reversal by maintaining the MglA gradient. Our results suggest a mechanism whereby bacteria use Ras family proteins to modulate cellular polarity.

scholarly journals Three-Dimensional Observations of an Aperiodic Oscillatory Gliding Behavior in Myxococcus xanthus Using Confocal Interference Reflection Microscopy

mSphere ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Liam M. Rooney ◽  
Lisa S. Kölln ◽  
Ross Scrimgeour ◽  
William B. Amos ◽  
Paul A. Hoskisson ◽  
...  
Keyword(s):  
Myxococcus Xanthus ◽  
Three Dimensional ◽  
Oscillatory Behavior ◽  
Gliding Motility ◽  
Bacterial Cells ◽  
Force Transmission ◽  
Content Type ◽  
Gliding Bacteria ◽  
Microscopy Techniques

ABSTRACT The deltaproteobacterium Myxococcus xanthus is a model for bacterial motility and has provided unprecedented insights into bacterial swarming behaviors. Fluorescence microscopy techniques have been invaluable in defining the mechanisms that are involved in gliding motility, but these have almost entirely been limited to two-dimensional (2D) studies, and there is currently no understanding of gliding motility in a three-dimensional (3D) context. We present here the first use of confocal interference reflection microscopy (IRM) to study gliding bacteria, revealing aperiodic oscillatory behavior with changes in the position of the basal membrane relative to the substrate on the order of 90 nm in vitro. First, we use a model planoconvex lens specimen to show how topological information can be obtained from the wavelength-dependent interference pattern in IRM. We then use IRM to observe gliding M. xanthus bacteria and show that cells undergo previously unobserved changes in their adhesion profile as they glide. We compare the wild type with mutants that have reduced motility, which also exhibit the same changes in the adhesion profile during gliding. We find that the general gliding behavior is independent of the proton motive force-generating complex AglRQS and suggest that the novel behavior that we present here may be a result of recoil and force transmission along the length of the cell body following firing of the type IV pili. IMPORTANCE 3D imaging of live bacteria with optical microscopy techniques is a challenge due to the small size of bacterial cells, meaning that previous studies have been limited to observing motility behavior in 2D. We introduce the application of confocal multiwavelength interference reflection microscopy to bacteria, which enables visualization of 3D motility behaviors in a single 2D image. Using the model organism Myxococcus xanthus, we identified novel motility behaviors that are not explained by current motility models, where gliding bacteria exhibit aperiodic changes in their adhesion to an underlying solid surface. We concluded that the 3D behavior was not linked to canonical motility mechanisms and that IRM could be applied to study a range of microbiological specimens with minimal adaptation to a commercial microscope.

scholarly journals A gated relaxation oscillator controls morphogenetic movements in bacteria

2017 ◽  
Author(s):  
Mathilde Guzzo ◽  
Seán M. Murray ◽  
Eugénie Martineau ◽  
Sébastien Lhospice ◽  
Grégory Baronian ◽  
...  
Keyword(s):  
Cell Polarity ◽  
Myxococcus Xanthus ◽  
Dynamic Control ◽  
Relaxation Oscillator ◽  
Critical Importance ◽  
Gtpase Activating Protein ◽  
Wide Range ◽  
Direction Of Movement ◽  
Polarity Reversals ◽  
Cellular Development

SummaryDynamic control of cell polarity is of critical importance for many aspects of cellular development and motility. In Myxococcus xanthus, a G-protein and its cognate GTPase-activating protein establish a polarity axis that defines the direction of movement of the cell and which can be rapidly inverted by the Frz chemosensory system. Although vital for collective cell behaviours, how Frz triggers this switch has remained unknown. Here, we use genetics, imaging and mathematical modelling to show that Frz controls polarity reversals via a gated relaxation oscillator. FrzX, which we newly identify as the primary Frz output, provides the gating and thus acts as the trigger for reversals. Slow relocalisation of the polarity protein RomR then creates a refractory period during which another switch cannot be triggered. A secondary Frz output, FrzZ, decreases this delay allowing rapid reversals when required. This architecture thus results in a highly tunable switch that allows a wide range of motility responses.

scholarly journals The Orphan Response Regulator DigR Is Required for Synthesis of Extracellular Matrix Fibrils in Myxococcus xanthus

2006 ◽  
Vol 188 (12) ◽  
pp. 4384-4394 ◽  
Author(s):  
Martin Overgaard ◽  
Sigrun Wegener-Feldbrügge ◽  
Lotte Søgaard-Andersen
Keyword(s):  
Extracellular Matrix ◽  
Response Regulator ◽  
Cell Envelope ◽  
Transcriptional Profiling ◽  
Myxococcus Xanthus ◽  
Gliding Motility ◽  
Differentially Expressed ◽  
Type Iv Pilus ◽  
Receiver Domain ◽  
Type Iv

ABSTRACT In Myxococcus xanthus, two-component systems have crucial roles in regulating motility behavior and development. Here we describe an orphan response regulator, consisting of an N-terminal receiver domain and a C-terminal DNA binding domain, which is required for A and type IV pilus-dependent gliding motility. Genetic evidence suggests that phosphorylation of the conserved, phosphorylatable aspartate residue in the receiver domain is required for DigR activity. Consistent with the defect in type IV pilus-dependent motility, a digR mutant is slightly reduced in type IV pilus biosynthesis, and the composition of the extracellular matrix fibrils is abnormal, with an increased content of polysaccharides and decreased accumulation of the FibA metalloprotease. By using genome-wide transcriptional profiling, 118 genes were identified that are directly or indirectly regulated by DigR. These 118 genes include only 2, agmQ and cheY4, previously implicated in A and type IV pilus-dependent motility, respectively. In silico analyses showed that 36% of the differentially expressed genes are likely to encode exported proteins. Moreover, four genes encoding homologs of extracytoplasmic function (ECF) sigma factors, which typically control aspects of cell envelope homeostasis, are differentially expressed in a digR mutant. We suggest that the DigR response regulator has an important function in cell envelope homeostasis and that the motility defects in a digR mutant are instigated by the abnormal cell envelope and abnormal expression of agmQ and cheY4.

scholarly journals Cyclic Di-GMP Regulates Type IV Pilus-Dependent Motility in Myxococcus xanthus

2015 ◽  
Vol 198 (1) ◽  
pp. 77-90 ◽  
Author(s):  
Dorota Skotnicka ◽  
Tobias Petters ◽  
Jan Heering ◽  
Michael Hoppert ◽  
Volkhard Kaever ◽  
...  
Keyword(s):  
Myxococcus Xanthus ◽  
Lifestyle Changes ◽  
Gliding Motility ◽  
Cyclase Activity ◽  
Diguanylate Cyclase ◽  
Type Iv Pilus ◽  
Cell Agglutination ◽  
Content Type ◽  
Type Iv ◽  
Altered Cell

ABSTRACTThe nucleotide-based second messenger bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) is involved in regulating a plethora of processes in bacteria that are typically associated with lifestyle changes.Myxococcus xanthusundergoes major lifestyle changes in response to nutrient availability, with the formation of spreading colonies in the presence of nutrients and spore-filled fruiting bodies in the absence of nutrients. Here, we investigated the function of c-di-GMP inM. xanthusand show that this bacterium synthesizes c-di-GMP during growth. Manipulation of the c-di-GMP level by expression of either an active, heterologous diguanylate cyclase or an active, heterologous phosphodiesterase correlated with defects in type IV pilus (T4P)-dependent motility, whereas gliding motility was unaffected. An increased level of c-di-GMP correlated with reduced transcription of thepilAgene (which encodes the major pilin of T4P), reduced the assembly of T4P, and altered cell agglutination, whereas a decreased c-di-GMP level correlated with altered cell agglutination. The systematic inactivation of the 24 genes inM. xanthusencoding proteins containing GGDEF, EAL, or HD-GYP domains, which are associated with c-di-GMP synthesis, degradation, or binding, identified three genes encoding proteins important for T4P-dependent motility, whereas all mutants had normal gliding motility. Purified DmxA had diguanylate cyclase activity, whereas the hybrid histidine protein kinases TmoK and SgmT, each of which contains a GGDEF domain, did not have diguanylate cyclase activity. These results demonstrate that c-di-GMP is important for T4P-dependent motility inM. xanthus.IMPORTANCEWe provide the first direct evidence thatM. xanthussynthesizes c-di-GMP and demonstrate that c-di-GMP is important for T4P-dependent motility, whereas we did not obtain evidence that c-di-GMP regulates gliding motility. The data presented uncovered a novel mechanism for regulation of T4P-dependent motility, in which increased levels of c-di-GMP inhibit transcription of thepilAgene (which encodes the major pilin of T4P), ultimately resulting in the reduced assembly of T4P. Moreover, we identified an enzymatically active diguanylate cyclase that is important for T4P-dependent motility.

scholarly journals Comprehensive Set of Integrative Plasmid Vectors for Copper-Inducible Gene Expression in Myxococcus xanthus

2012 ◽  
Vol 78 (8) ◽  
pp. 2515-2521 ◽  
Author(s):  
Nuria Gómez-Santos ◽  
Anke Treuner-Lange ◽  
Aurelio Moraleda-Muñoz ◽  
Elena García-Bravo ◽  
Raquel García-Hernández ◽  
...  
Keyword(s):  
Gene Expression ◽  
Myxococcus Xanthus ◽  
Gliding Motility ◽  
Expression Vectors ◽  
Plasmid Vectors ◽  
Inducible Gene Expression ◽  
Content Type ◽  
Marker Selection ◽  
Effect Of Copper ◽  
Inducible Gene

ABSTRACTMyxococcus xanthusis widely used as a model system for studying gliding motility, multicellular development, and cellular differentiation. Moreover,M. xanthusis a rich source of novel secondary metabolites. The analysis of these processes has been hampered by the limited set of tools for inducible gene expression. Here we report the construction of a set of plasmid vectors to allow copper-inducible gene expression inM. xanthus. Analysis of the effect of copper on strain DK1622 revealed that copper concentrations of up to 500 μM during growth and 60 μM during development do not affect physiological processes such as cell viability, motility, or aggregation into fruiting bodies. Of the copper-responsive promoters inM. xanthusreported so far, the multicopper oxidasecuoApromoter was used to construct expression vectors, because no basal expression is observed in the absence of copper and induction linearly depends on the copper concentration in the culture medium. Four different plasmid vectors have been constructed, with different marker selection genes and sites of integration in theM. xanthuschromosome. The vectors have been tested and gene expression quantified using thelacZgene. Moreover, we demonstrate the functional complementation of the motility defect caused by lack of PilB by the copper-induced expression of thepilBgene. These versatile vectors are likely to deepen our understanding of the biology ofM. xanthusand may also have biotechnological applications.

scholarly journals Orphan Hybrid Histidine Protein Kinase SinK Acts as a Signal Integrator To Fine-Tune Multicellular Behavior inMyxococcus xanthus

2019 ◽  
Vol 201 (6) ◽  
Author(s):  
Maike M. Glaser ◽  
Penelope I. Higgs
Keyword(s):  
Environmental Conditions ◽  
Histidine Kinase ◽  
Response Regulator ◽  
Myxococcus Xanthus ◽  
Histidine Kinases ◽  
Content Type ◽  
Environmental Bacterium ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Fine Tune

ABSTRACTHis-Asp phosphorelay (also known as two-component signal transduction) proteins are the predominant mechanism used in most bacteria to control behavior in response to changing environmental conditions. In addition to systems consisting of a simple two-component system utilizing an isolated histidine kinase/response regulator pair, some bacteria are enriched in histidine kinases that serve as signal integration proteins; these kinases are usually characterized by noncanonical domain architecture, and the responses that they regulate may be difficult to identify. The environmental bacteriumMyxococcus xanthusis highly enriched in these noncanonical histidine kinases.M. xanthusis renowned for a starvation-induced multicellular developmental program in which some cells are induced to aggregate into fruiting bodies and then differentiate into environmentally resistant spores. Here, we characterize theM. xanthusorphan hybrid histidine kinase SinK (Mxan_4465), which consists of a histidine kinase transmitter followed by two receiver domains (REC1and REC2). NonphosphorylatablesinKmutants were analyzed under two distinct developmental conditions and using a new high-resolution developmental assay. These assays revealed that SinK autophosphorylation and REC1impact the onset of aggregation and/or the mobility of aggregates, while REC2impacts sporulation efficiency. SinK activity is controlled by a genus-specific hypothetical protein (SinM; Mxan_4466). We propose that SinK serves to fine-tune fruiting body morphology in response to environmental conditions.IMPORTANCEBiofilms are multicellular communities of microorganisms that play important roles in host disease or environmental biofouling. Design of preventative strategies to block biofilms depends on understanding the molecular mechanisms used by microorganisms to build them. The production of biofilms in bacteria often involves two-component signal transduction systems in which one protein component (a kinase) detects an environmental signal and, through phosphotransfer, activates a second protein component (a response regulator) to change the transcription of genes necessary to produce a biofilm. We show that an atypical kinase, SinK, modulates several distinct stages of specialized biofilm produced by the environmental bacteriumMyxococcus xanthus. SinK likely integrates multiple signals to fine-tune biofilm formation in response to distinct environmental conditions.

scholarly journals Spontaneous Reversions of an Evolutionary Trait Loss Reveal Regulators of a Small RNA That Controls Multicellular Development in Myxobacteria

2016 ◽  
Vol 198 (23) ◽  
pp. 3142-3151 ◽  
Author(s):  
Yuen-Tsu N. Yu ◽  
Manuel Kleiner ◽  
Gregory J. Velicer
Keyword(s):  
Gene Regulation ◽  
Small Rna ◽  
Histidine Kinase ◽  
Response Regulator ◽  
Myxococcus Xanthus ◽  
Content Type ◽  
Body Development ◽  
Two Component ◽  
Fruiting Body Development ◽  
Spontaneous Mutants

ABSTRACTLost traits can reevolve, but the probability of trait reversion depends partly on a trait's genetic complexity. Myxobacterial fruiting body development is a complex trait controlled by the small RNA (sRNA) Pxr, which blocks development under conditions of nutrient abundance. In developmentally proficient strains ofMyxococcus xanthus, starvation relaxes the inhibition by Pxr, thereby allowing development to proceed. In contrast, the lab-evolved strain OC does not develop because it fails to relay an early starvation signal that alleviates inhibition by Pxr. A descendant of OC, strain PX, previously reevolved developmental proficiency via a mutation inpxrthat inactivates its function. A single-colony screen was used to test whether reversion of OC to developmental proficiency occurs only by mutation ofpxror might also occur through alternative regulatory loci. Five spontaneous mutants of OC that exhibited restored development were isolated, and all five showed defects in Pxr synthesis, structure, or processing, including one that incurred an eight-nucleotide deletion inpxr. Two mutations occurred in the σ54response regulator (RR) geneMXAN_1078(namedpxrRhere), immediately upstream ofpxr. PxrR was found to positively regulatepxrtranscription, presumably via the σ54promoter ofpxr. Two other mutations were identified in a histidine kinase (HK) gene (MXAN_1077; namedpxrKhere) immediately upstream ofpxrR. Evolutionarily, the rate of trait restoration documented in this study suggests that reversion of social defects in natural microbial populations may be common. Molecularly, these results suggest a mechanism by which the regulatory functions of an HK-RR two-component signaling system and an sRNA are integrated to control initiation of myxobacterial development.IMPORTANCEMany myxobacteria initiate a process of multicellular fruiting body development upon starvation, but key features of the regulatory network controlling the transition from growth to development remain obscure. Previous work withMyxococcus xanthusidentified the first small RNA (sRNA) regulator (Pxr) known to serve as a gatekeeper in this life history transition, as it blocks development when nutrients are abundant. In the present study, a screen for spontaneous mutants ofM. xanthuswas developed that revealed a two-component system operon (encoding a histidine kinase and a σ54response regulator) associated with the production and processing of Pxr sRNA. This discovery broadens our knowledge of early developmental gene regulation and also represents an evolutionary integration of two-component signaling and sRNA gene regulation to control a bacterial social trait.

scholarly journals AglZ Is a Filament-Forming Coiled-Coil Protein Required for Adventurous Gliding Motility of Myxococcus xanthus

2004 ◽  
Vol 186 (18) ◽  
pp. 6168-6178 ◽  
Author(s):  
Ruifeng Yang ◽  
Sarah Bartle ◽  
Rebecca Otto ◽  
Angela Stassinopoulos ◽  
Matthew Rogers ◽  
...  
Keyword(s):  
Response Regulator ◽  
Myxococcus Xanthus ◽  
Coiled Coil ◽  
Gliding Motility ◽  
Isolated Cells ◽  
Genetic Studies ◽  
C Terminus ◽  
Heptad Repeats ◽  
Two Hybrid

ABSTRACT The aglZ gene of Myxococcus xanthus was identified from a yeast two-hybrid assay in which MglA was used as bait. MglA is a 22-kDa cytoplasmic GTPase required for both adventurous and social gliding motility and sporulation. Genetic studies showed that aglZ is part of the A motility system, because disruption or deletion of aglZ abolished movement of isolated cells and aglZ sglK double mutants were nonmotile. The aglZ gene encodes a 153-kDa protein that interacts with purified MglA in vitro. The N terminus of AglZ shows similarity to the receiver domain of two-component response regulator proteins, while the C terminus contains heptad repeats characteristic of coiled-coil proteins, such as myosin. Consistent with this motif, expression of AglZ in Escherichia coli resulted in production of striated lattice structures. Similar to the myosin heavy chain, the purified C-terminal coiled-coil domain of AglZ forms filament structures in vitro.

scholarly journals Three PilZ domain proteins, PlpA, PixA and PixB, have distinct functions in regulation of motility and development in Myxococcus xanthus

2021 ◽  
Author(s):  
Sofya Kuzmich ◽  
Dorota Skotnicka ◽  
Dobromir Szadkowski ◽  
Philipp Klos ◽  
Maria Perez-Burgos ◽  
...  
Keyword(s):  
Response Regulator ◽  
Myxococcus Xanthus ◽  
Type Iv Pili ◽  
Gliding Motility ◽  
Chemosensory System ◽  
Developmental Program ◽  
Type Iv ◽  
Genes Encoding ◽  
Acetyltransferase Domain

In bacteria, the nucleotide-based second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP) binds to effectors to generate outputs in response to changes in the environment. In Myxococcus xanthus, c-di-GMP regulates type IV pili-dependent motility and the starvation-induced developmental program that results in the formation of spore-filled fruiting bodies; however, little is known about the effectors that bind c-di-GMP. Here, we systematically inactivated all 24 genes encoding PilZ domain-containing proteins, which are among the most common c-di-GMP receptors. We confirm that PlpA, a stand-alone PilZ-domain protein, is specifically important for motility and that Pkn1, which is composed of a Ser/Thr domain and a PilZ domain, is specifically important for development. Moreover, we identify two PilZ-domain proteins that have distinct functions in regulating motility and development. PixB, which is composed of two PilZ domains and an acetyltransferase domain, binds c-di-GMP in vitro and regulates type IV pili-dependent and gliding motility upstream of the Frz chemosensory system as well as development. The acetyltransferase domain is required and sufficient for function during growth while all three domains and c-di-GMP binding are essential for PixB function during development. PixA is a response regulator composed of a PilZ domain and a receiver domain, binds c-di-GMP in vitro, and regulates motility downstream of the Frz chemosensory system by setting up the polarity of the two motility systems. Our results support a model whereby the three proteins PlpA, PixA and PixB act in parallel pathways and have distinct functions to regulation of motility.

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