Faculty Opinions recommendation of FrzZ, a dual CheY-like response regulator, functions as an output for the Frz chemosensory pathway of Myxococcus xanthus.

ABSTRACT Starvation and cell density regulate the developmental expression of Myxococcus xanthus gene 4521. Three classes of mutants allow expression of this developmental gene during growth on nutrient agar, such that colonies of strains containing a Tn5 lac Ω4521 fusion are Lac+. One class of these mutants inactivates SasN, a negative regulator of 4521expression; another class activates SasS, a sensor kinase-positive regulator of 4521 expression; and a third class blocks lipopolysaccharide (LPS) O-antigen biosynthesis. To identify additional positive regulators of 4521 expression, 11 Lac− TnV.AS transposon insertion mutants were isolated from a screen of 18,000 Lac+ LPS O-antigen mutants containing Tn5 lac Ω4521 (Tcr). Ten mutations identified genes that could encode positive regulators of4521 developmental expression based on their ability to abolish 4521 expression during development in the absence of LPS O antigen and in an otherwise wild-type background. Eight of these mutations mapped to the sasB locus, which encodes the known 4521 regulators SasS and SasN. One mapped tosasS, whereas seven identified new genes. Three mutations mapped to a gene encoding an NtrC-like response regulator homologue, designated sasR, and four others mapped to a gene designated sasP. One mutation, designatedssp10, specifically suppressed the LPS O-antigen defect; the ssp10 mutation had no effect on 4521expression in an otherwise wild-type background but reduced4521 developmental expression in the absence of LPS O antigen to a level close to that of the parent strain. All of the mutations except those in sasP conferred defects during growth and development. These data indicate that a number of elements are required for 4521 developmental expression and that most of these are necessary for normal growth and fruiting body development.

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Coupling of protein localization and cell movements by a dynamically localized response regulator in Myxococcus xanthus

The EMBO Journal ◽

10.1038/emboj.2009.95 ◽

2009 ◽

Vol 28 (8) ◽

pp. 1192-1192

Author(s):

Simone Leonardy ◽

Gerald Freymark ◽

Sabrina Hebener ◽

Eva Ellehauge ◽

Lotte Søgaard-Andersen

Keyword(s):

Response Regulator ◽

Protein Localization ◽

Myxococcus Xanthus ◽

Cell Movements

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Coupling of protein localization and cell movements by a dynamically localized response regulator in Myxococcus xanthus

The EMBO Journal ◽

10.1038/sj.emboj.7601877 ◽

2007 ◽

Vol 26 (21) ◽

pp. 4433-4444 ◽

Cited By ~ 70

Author(s):

Simone Leonardy ◽

Gerald Freymark ◽

Sabrina Hebener ◽

Eva Ellehauge ◽

Lotte Søgaard-Andersen

Keyword(s):

Response Regulator ◽

Protein Localization ◽

Myxococcus Xanthus ◽

Cell Movements

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Regulation of the Myxococcus xanthus C-Signal-Dependent Ω4400 Promoter by the Essential Developmental Protein FruA

Journal of Bacteriology ◽

10.1128/jb.00318-06 ◽

2006 ◽

Vol 188 (14) ◽

pp. 5167-5176 ◽

Cited By ~ 18

Author(s):

Deborah R. Yoder-Himes ◽

Lee Kroos

Keyword(s):

Dna Binding ◽

Response Regulator ◽

Myxococcus Xanthus ◽

Cell Movement ◽

Binding Domain ◽

Dna Binding Domain ◽

Consensus Binding Site ◽

Multicellular Development

ABSTRACT The bacterium Myxococcus xanthus employs extracellular signals to coordinate aggregation and sporulation during multicellular development. Extracellular, contact-dependent signaling that involves the CsgA protein (called C-signaling) activates FruA, a putative response regulator that governs a branched signaling pathway inside cells. One branch regulates cell movement, leading to aggregation. The other branch regulates gene expression, leading to sporulation. C-signaling is required for full expression of most genes induced after 6 h into development, including the gene identified by Tn5 lac insertion Ω4400. To determine if FruA is a direct regulator of Ω4400 transcription, a combination of in vivo and in vitro experiments was performed. Ω4400 expression was abolished in a fruA mutant. The DNA-binding domain of FruA bound specifically to DNA upstream of the promoter −35 region in vitro. Mutations between bp −86 and −77 greatly reduced binding. One of these mutations had been shown previously to reduce Ω4400 expression in vivo and make it independent of C-signaling. For the first time, chromatin immunoprecipitation (ChIP) experiments were performed on M. xanthus. The ChIP experiments demonstrated that FruA is associated with the Ω4400 promoter region late in development, even in the absence of C-signaling. Based on these results, we propose that FruA directly activates Ω4400 transcription to a moderate level prior to C-signaling and, in response to C-signaling, binds near bp −80 and activates transcription to a higher level. Also, the highly localized effects of mutations between bp −86 and −77 on DNA binding in vitro, together with recently published footprints, allow us to predict a consensus binding site of GTCG/CGA/G for the FruA DNA-binding domain.

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

Journal of Bacteriology ◽

10.1128/jb.00548-15 ◽

2015 ◽

Vol 198 (3) ◽

pp. 510-520 ◽

Cited By ~ 8

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.

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Myxococcus xanthus mokA Encodes a Histidine Kinase-Response Regulator Hybrid Sensor Required for Development and Osmotic Tolerance

Journal of Bacteriology ◽

10.1128/jb.183.4.1140-1146.2001 ◽

2001 ◽

Vol 183 (4) ◽

pp. 1140-1146 ◽

Cited By ~ 15

Author(s):

Yoshio Kimura ◽

Hiromi Nakano ◽

Hideaki Terasaka ◽

Kaoru Takegawa

Keyword(s):

Histidine Kinase ◽

Genomic Library ◽

Response Regulator ◽

Myxococcus Xanthus ◽

Amino Terminal ◽

Receiver Domain ◽

Osmotic Tolerance ◽

Input Domain ◽

Carboxy Terminal ◽

Hybrid Histidine Kinase

ABSTRACT A gene, mokA, encoding a protein with similarities to histidine kinase-response regulator hybrid sensor, was cloned from aMyxococcus xanthus genomic library. The predictedmokA gene product was found to contain three domains: an amino-terminal input domain, a central transmitter domain, and a carboxy-terminal receiver domain. mokA mutants placed under starvation conditions exhibited reduced sporulation. Mutation ofmokA also caused marked growth retardation at high osmolarity. These results indicated that M. xanthus MokA is likely a transmembrane sensor that is required for development and osmotic tolerance. The putative function of MokA is similar to that of the hybrid histidine kinase, DokA, of the eukaryotic slime moldDictyostelium discoideum.

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

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1421073112 ◽

2014 ◽

Vol 112 (2) ◽

pp. E186-E193 ◽

Cited By ~ 14

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.

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Combinatorial Regulation by a Novel Arrangement of FruA and MrpC2 Transcription Factors during Myxococcus xanthus Development

Journal of Bacteriology ◽

10.1128/jb.01818-08 ◽

2009 ◽

Vol 191 (8) ◽

pp. 2753-2763 ◽

Cited By ~ 25

Author(s):

Sheenu Mittal ◽

Lee Kroos

Keyword(s):

Binding Site ◽

Binding Sites ◽

Promoter Region ◽

Developmental Process ◽

Response Regulator ◽

Myxococcus Xanthus ◽

Control Cell ◽

Cooperative Binding ◽

Regulatory Sequence

ABSTRACT Myxococcus xanthus is a gram-negative soil bacterium that undergoes multicellular development upon nutrient limitation. Intercellular signals control cell movements and regulate gene expression during the developmental process. C-signal is a short-range signal essential for aggregation and sporulation. C-signaling regulates the fmgA gene by a novel mechanism involving cooperative binding of the response regulator FruA and the transcription factor/antitoxin MrpC2. Here, we demonstrate that regulation of the C-signal-dependent fmgBC operon is under similar combinatorial control by FruA and MrpC2, but the arrangement of binding sites is different than in the fmgA promoter region. MrpC2 was shown to bind to a crucial cis-regulatory sequence in the fmgBC promoter region. FruA was required for MrpC and/or MrpC2 to associate with the fmgBC promoter region in vivo, and expression of an fmgB-lacZ fusion was abolished in a fruA mutant. Recombinant FruA was shown to bind to an essential regulatory sequence located slightly downstream of the MrpC2-binding site in the fmgBC promoter region. Full-length FruA, but not its C-terminal DNA-binding domain, enhanced the formation of complexes with fmgBC promoter region DNA, when combined with MrpC2. This effect was nearly abolished with fmgBC DNA fragments having a mutation in either the MrpC2- or FruA-binding site, indicating that binding of both proteins to DNA is important for enhancement of complex formation. These results are similar to those observed for fmgA, where FruA and MrpC2 bind cooperatively upstream of the promoter, except that in the fmgA promoter region the FruA-binding site is located slightly upstream of the MrpC2-binding site. Cooperative binding of FruA and MrpC2 appears to be a conserved mechanism of gene regulation that allows a flexible arrangement of binding sites and coordinates multiple signaling pathways.

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