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Joshua W Shaevitz - One of the best experts on this subject based on the ideXlab platform.
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Topological defects promote layer formation in Myxococcus xanthus colonies
Nature Physics, 2020Co-Authors: Katherine Copenhagen, Ricard Alert, Ned S. Wingreen, Joshua W ShaevitzAbstract:The soil bacterium Myxococcus xanthus lives in densely packed groups that form dynamic three-dimensional patterns in response to environmental changes, such as droplet-like fruiting bodies during starvation^ 1 . The development of these multicellular structures begins with the sequential formation of cell layers in a process that is poorly understood^ 2 . Here, using confocal three-dimensional imaging, we find that motile, rod-shaped M. xanthus cells are densely packed and aligned in each layer, forming an active nematic liquid crystal. Cell alignment is nearly perfect throughout the population except at point defects that carry half-integer topological charge. We observe that new cell layers preferentially form at the position of +1/2 defects, whereas holes preferentially open at −1/2 defects. To explain these findings, we model the bacterial colony as an extensile active nematic fluid with anisotropic friction. In agreement with our experimental measurements, this model predicts an influx of cells towards the +1/2 defects and an outflux of cells from the −1/2 defects. Our results suggest that cell motility and mechanical cell–cell interactions are sufficient to promote the formation of cell layers at topological defects, thereby seeding fruiting bodies in colonies of M. xanthus . Topological defects in active nematic systems such as epithelial tissues and neural progenitor cells can be associated with biological functions. Here, the authors show that defects can play a role in the layer formation of the soil bacterium Myxococcus xanthus .
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topological defects induce layer formation in Myxococcus xanthus colonies
arXiv: Biological Physics, 2020Co-Authors: Katherine Copenhagen, Ricard Alert, Ned S. Wingreen, Joshua W ShaevitzAbstract:The soil bacterium Myxococcus xanthus lives in densely packed groups that form dynamic three-dimensional patterns in response to environmental changes, such as droplet-like fruiting bodies during starvation. The development of these multicellular structures begins with the sequential formation of cell layers in a process that is poorly understood. Using confocal three-dimensional imaging, we find that motile rod-shaped M. xanthus cells are densely packed and aligned in each layer, forming an active nematic liquid crystal. Cell alignment is nearly perfect throughout the population except at point defects that carry half-integer topological charge. We observe that new cell layers preferentially form at the position of +1/2 defects, whereas holes open at -1/2 defects. To explain these findings, we model the bacterial colony as an extensile active nematic fluid with anisotropic friction. In agreement with our experimental measurements, this model predicts an influx of cells toward +1/2 defects, and an outflux of cells from -1/2 defects. Our results suggest that cell motility and mechanical cell-cell interactions are sufficient to induce the formation of cell layers at topological defects, thereby seeding fruiting bodies in colonies of M. xanthus.
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self driven phase transitions drive Myxococcus xanthus fruiting body formation
Physical Review Letters, 2019Co-Authors: Adam Patch, Fatmagul Bahar, Roy D Welch, Cristina M Marchetti, Shashi Thutupalli, David Yllanes, Joshua W ShaevitzAbstract:: Combining high-resolution single cell tracking experiments with numerical simulations, we show that starvation-induced fruiting body formation in Myxococcus xanthus is a phase separation driven by cells that tune their motility over time. The phase separation can be understood in terms of cell density and a dimensionless Peclet number that captures cell motility through speed and reversal frequency. Our work suggests that M. xanthus takes advantage of a self-driven nonequilibrium phase transition that can be controlled at the single cell level.
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directional reversals enable Myxococcus xanthus cells to produce collective one dimensional streams during fruiting body formation
Journal of the Royal Society Interface, 2015Co-Authors: Shashi Thutupalli, Kannappan Palaniappan, Filiz Bunyak, Joshua W ShaevitzAbstract:The formation of a collectively moving group benefits individuals within a population in a variety of ways. The surface-dwelling bacterium Myxococcus xanthus forms dynamic collective groups both to feed on prey and to aggregate during times of starvation. The latter behaviour, termed fruiting-body formation, involves a complex, coordinated series of density changes that ultimately lead to three-dimensional aggregates comprising hundreds of thousands of cells and spores. How a loose, two-dimensional sheet of motile cells produces a fixed aggregate has remained a mystery as current models of aggregation are either inconsistent with experimental data or ultimately predict unstable structures that do not remain fixed in space. Here, we use high-resolution microscopy and computer vision software to spatio-temporally track the motion of thousands of individuals during the initial stages of fruiting-body formation. We find that cells undergo a phase transition from exploratory flocking, in which unstable cell groups move rapidly and coherently over long distances, to a reversal-mediated localization into one-dimensional growing streams that are inherently stable in space. These observations identify a new phase of active collective behaviour and answer a long-standing open question in Myxococcus development by describing how motile cell groups can remain statistically fixed in a spatial location.
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from individual cell motility to collective behaviors insights from a prokaryote Myxococcus xanthus
Fems Microbiology Reviews, 2012Co-Authors: Joshua W Shaevitz, Yong Zhang, Adrien Ducret, Tâm MignotAbstract:In bird flocks, fish schools, and many other living organisms, regrouping among individuals of the same kin is frequently an advantageous strategy to survive, forage, and face predators. However, these behaviors are costly because the community must develop regulatory mechanisms to coordinate and adapt its response to rapid environmental changes. In principle, these regulatory mechanisms, involving communication between individuals, may also apply to cellular systems which must respond collectively during multicellular development. Dissecting the mechanisms at work requires amenable experimental systems, for example, developing bacteria. Myxococcus xanthus , a Gram-negative delatproteobacterium , is able to coordinate its motility in space and time to swarm, predate, and grow millimeter-size spore-filled fruiting bodies. A thorough understanding of the regulatory mechanisms first requires studying how individual cells move across solid surfaces and control their direction of movement, which was recently boosted by new cell biology techniques. In this review, we describe current molecular knowledge of the motility mechanism and its regulation as a lead-in to discuss how multicellular cooperation may have emerged from several layers of regulation: chemotaxis, cell–cell signaling, and the extracellular matrix. We suggest that Myxococcus is a powerful system to investigate collective principles that may also be relevant to other cellular systems. Myxococcus motility is regulated at multiple levels leading to coherent multicellular behaviours.
John R. Kirby - One of the best experts on this subject based on the ideXlab platform.
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identification of functions affecting predator prey interactions between Myxococcus xanthus and bacillus subtilis
Journal of Bacteriology, 2016Co-Authors: Susanne Müller, Sarah N Strack, Sarah E Ryan, Mary E Shawgo, Abigail Walling, Susanna L Harris, Chris Chambers, Jennifer D Boddicker, John R. KirbyAbstract:ABSTRACT Soil bacteria engage each other in competitive and cooperative ways to determine their microenvironments. In this study, we report the identification of a large number of genes required for Myxococcus xanthus to engage Bacillus subtilis in a predator-prey relationship. We generated and tested over 6,000 individual transposon insertion mutants of M. xanthus and found many new factors required to promote efficient predation, including the specialized metabolite myxoprincomide, an ATP-binding cassette (ABC) transporter permease, and a clustered regularly interspaced short palindromic repeat (CRISPR) locus encoding bacterial immunity. We also identified genes known to be involved in predation, including those required for the production of exopolysaccharides and type IV pilus (T4P)-dependent motility, as well as chemosensory and two-component systems. Furthermore, deletion of these genes confirmed their role during predation. Overall, M. xanthus predation appears to be a multifactorial process, with multiple determinants enhancing predation capacity. IMPORTANCE Soil bacteria engage each other in complex environments and utilize multiple traits to ensure survival. Here, we report the identification of multiple traits that enable a common soil organism, Myxococcus xanthus, to prey upon and utilize nutrients from another common soil organism, Bacillus subtilis. We mutagenized the predator and carried out a screen to identify genes that were required to either enhance or diminish capacity to consume prey. We identified dozens of genes encoding factors that contribute to the overall repertoire for the predator to successfully engage its prey in the natural environment.
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molecular mechanisms of signaling in Myxococcus xanthus development
Journal of Molecular Biology, 2016Co-Authors: Daniel J Bretl, John R. KirbyAbstract:Myxococcus xanthus is an environmental bacterium that displays a complex life cycle that includes motility, predation, multicellular fruiting body development, and sporulation. Given the elaborate fruiting body development of this bacterial species, M. xanthus has served as a model organism for the study of multicellular development of bacteria, and a remarkable number of genes have been identified that contribute to the regulation of this highly dynamic process. Included among these developmental factors is a robust repertoire of signaling proteins, which have arisen from extensive gene duplication in M. xanthus and related species. In this review, we explore several aspects of the molecular mechanisms of signaling in M. xanthus development. This includes mechanisms of kin selection, single-cell sensing of nutrient depletion and the stringent response, the production of and response to extracellular population cues, and the contribution of several two-component signaling systems regulating developmental transcriptional programs. Collectively, these signaling mechanisms function to tightly regulate the sensing of nutrient depletion, the aggregation of populations of cells, and the temporal and spatial formation of complex fruiting bodies and sporulation of M. xanthus.
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draft genome of a type 4 pilus defective Myxococcus xanthus strain dzf1
Genome Announcements, 2013Co-Authors: Susanne Müller, Jonathan W. Willett, Sarah M. Bahr, Cynthia L. Darnell, Hera Vlamakis, Jodie Scott, Janet M Wilson, John R. KirbyAbstract:ABSTRACT Myxococcus xanthus is a member of the Myxococcales order within the deltaproteobacterial subdivision. Here, we report the whole-genome shotgun sequence of the type IV pilus (T4P) defective strain DZF1, which includes many genes found in strain DZ2 but absent from strain DK1622.
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Draft Genome Sequence of Myxococcus xanthus Wild-Type Strain DZ2, a Model Organism for Predation and Development.
Genome announcements, 2013Co-Authors: Susanne Müller, Jonathan W. Willett, Sarah M. Bahr, Cynthia L. Darnell, Katherine R. Hummels, Carolyn K. Dong, Hera Vlamakis, John R. KirbyAbstract:Myxococcus xanthus is a member of the Myxococcales order within the Deltaproteobacteria subdivision. The myxobacteria reside in soil, have relatively large genomes, and display complex life cycles. Here, we report the whole-genome shotgun sequence of strain DZ2, which includes unique genes not found previously in strain DK1622.
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predataxis behavior in Myxococcus xanthus
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: James E Berleman, Jodie Scott, Tatiana Chumley, John R. KirbyAbstract:Spatial organization of cells is important for both multicellular development and tactic responses to a changing environment. We find that the social bacterium, Myxococcus xanthus utilizes a chemotaxis (Che)-like pathway to regulate multicellular rippling during predation of other microbial species. Tracking of GFP-labeled cells indicates directed movement of M. xanthus cells during the formation of rippling wave structures. Quantitative analysis of rippling indicates that ripple wavelength is adaptable and dependent on prey cell availability. Methylation of the receptor, FrzCD is required for this adaptation: a frzF methyltransferase mutant is unable to construct ripples, whereas a frzG methylesterase mutant forms numerous, tightly packed ripples. Both the frzF and frzG mutant strains are defective in directing cell movement through prey colonies. These data indicate that the transition to an organized multicellular state during predation in M. xanthus relies on the tactic behavior of individual cells, mediated by a Che-like signal transduction pathway.
David R. Zusman - One of the best experts on this subject based on the ideXlab platform.
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chemosensory signaling controls motility and subcellular polarity in Myxococcus xanthus
Current Opinion in Microbiology, 2012Co-Authors: Christine Kaimer, James E Berleman, David R. ZusmanAbstract:Myxococcus xanthus is a model system for the study of dynamic protein localization and cell polarity in bacteria. M. xanthus cells are motile on solid surfaces enabled by two forms of motility. Motility is controlled by the Che-like Frz pathway, which is essential for fruiting body formation and differentiation. The Frz signal is mediated by a GTPase/GAP protein pair that establishes cell polarity and directs the motility systems. Pilus driven motility at the leading pole of the cell requires dynamic localization of two ATPases and the coordinated production of EPS synthesis. Gliding motility requires dynamic movement of large protein complexes, but the mechanism by which this system generates propulsive force is still an active area of investigation.
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chemosensory pathways motility and development in Myxococcus xanthus
Nature Reviews Microbiology, 2007Co-Authors: David R. Zusman, Zhaomin Yang, Ansley E Scott, John R. KirbyAbstract:The complex life cycle of Myxococcus xanthus includes predation, swarming, fruiting-body formation and sporulation. The genome of M. xanthus is large and comprises an estimated 7,400 open reading frames, of which approximately 605 code for regulatory genes. These include eight clusters of chemotaxis-like genes that define eight chemosensory pathways, most of which have dedicated functions. Although many of these chemosensory pathways have a role in controlling motility, at least two of these pathways control gene expression during development.
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evidence that focal adhesion complexes power bacterial gliding motility
Science, 2007Co-Authors: Tâm Mignot, Joshua W Shaevitz, Patricia L Hartzell, David R. ZusmanAbstract:The bacterium Myxococcus xanthus has two motility systems: S motility, which is powered by type IV pilus retraction, and A motility, which is powered by unknown mechanism(s). We found that A motility involved transient adhesion complexes that remained at fixed positions relative to the substratum as cells moved forward. Complexes assembled at leading cell poles and dispersed at the rear of the cells. When cells reversed direction, the A-motility clusters relocalized to the new leading poles together with S-motility proteins. The Frz chemosensory system coordinated the two motility systems. The dynamics of protein cluster localization suggest that intracellular motors and force transmission by dynamic focal adhesions can power bacterial motility.
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accordion waves in Myxococcus xanthus
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Oleksii Sliusarenko, David R. Zusman, John C Neu, George OsterAbstract:Myxococcus xanthus are Gram-negative bacteria that glide on solid surfaces, periodically reversing their direction of movement. When starved, M. xanthus cells organize their movements into waves of cell density that sweep over the colony surface. These waves are unique: Although they appear to interpenetrate, they actually reflect off one another when they collide, so that each wave crest oscillates back and forth with no net displacement. Because the waves reflect the coordinated back and forth oscillations of the individual bacteria, we call them “accordion” waves. The spatial oscillations of individuals are a manifestation of an internal biochemical oscillator, probably involving the Frz chemosensory system. These internal “clocks,” each of which is quite variable, are synchronized by collisions between individual cells using a contact-mediated signal-transduction system. The result of collision signaling is that the collective spatial behavior is much less variable than the individual oscillators. In this work, we present experimental observations in which individual cells marked with GFP can be followed in groups of unlabeled cells in monolayer cultures. These data, together with an agent-based computational model demonstrate that the only properties required to explain the ripple patterns are an asymmetric biochemical limit cycle that controls direction reversals and asymmetric contact-induced signaling between cells: Head-to-head signaling is stronger than head-to-tail signaling. Together, the experimental and computational data provide new insights into how populations of interacting oscillators can synchronize and organize spatially to produce morphogenetic patterns that may have parallels in higher organisms.
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Aggregation during Fruiting Body Formation in Myxococcus xanthus Is Driven by Reducing Cell Movement � †
2006Co-Authors: Oleksii Sliusarenko, David R. Zusman, George OsterAbstract:When starved, Myxococcus xanthus cells assemble themselves into aggregates of about 10 5 cells that grow into complex structures called fruiting bodies, where they later sporulate. Here we present new observations on the velocities of the cells, their orientations, and reversal rates during the early stages of fruiting body formation. Most strikingly, we find that during aggregation, cell velocities slow dramatically and cells orient themselves in parallel inside the aggregates, while later cell orientations are circumferential to the periphery. The slowing of cell velocity, rather than changes in reversal frequency, can account for the accumulation of cells into aggregates. These observations are mimicked by a continuous agent-based computational model that reproduces the early stages of fruiting body formation. We also show, both experimentally and computationally, how changes in reversal frequency controlled by the Frz system mutants affect the shape of these early fruiting bodies. Myxococcus xanthus is a rod-shaped gram-negative bacterium that grows in soil, animal dung, or other natural environments rich in organic matter (2). The bacteria move by gliding over solid surfaces, periodically reversing their direction of movement. Gliding motility in this bacterium is driven by tw
Lotte Søgaard-andersen - One of the best experts on this subject based on the ideXlab platform.
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Transcriptomic analysis of the Myxococcus xanthus FruA regulon, and comparative developmental transcriptomic analysis of two fruiting body forming species, Myxococcus xanthus and Myxococcus stipitatus
'Springer Science and Business Media LLC', 2021Co-Authors: Anna L. Mcloon, Max E. Boeck, Marc Bruckskotten, Alexander C. Keyel, Lotte Søgaard-andersenAbstract:Abstract Background The Myxococcales are well known for their predatory and developmental social processes, and for the molecular complexity of regulation of these processes. Many species within this order have unusually large genomes compared to other bacteria, and their genomes have many genes that are unique to one specific sequenced species or strain. Here, we describe RNAseq based transcriptome analysis of the FruA regulon of Myxococcus xanthus and a comparative RNAseq analysis of two Myxococcus species, M. xanthus and Myxococcus stipitatus, as they respond to starvation and begin forming fruiting bodies. Results We show that both species have large numbers of genes that are developmentally regulated, with over half the genome showing statistically significant changes in expression during development in each species. We also included a non-fruiting mutant of M. xanthus that is missing the transcriptional regulator FruA to identify the direct and indirect FruA regulon and to identify transcriptional changes that are specific to fruiting and not just the starvation response. We then identified Interpro gene ontologies and COG annotations that are significantly up- or down-regulated during development in each species. Our analyses support previous data for M. xanthus showing developmental upregulation of signal transduction genes, and downregulation of genes related to cell-cycle, translation, metabolism, and in some cases, DNA replication. Gene expression in M. stipitatus follows similar trends. Although not all specific genes show similar regulation patterns in both species, many critical developmental genes in M. xanthus have conserved expression patterns in M. stipitatus, and some groups of otherwise unstudied orthologous genes share expression patterns. Conclusions By identifying the FruA regulon and identifying genes that are similarly and uniquely regulated in two different species, this work provides a more complete picture of transcription during Myxococcus development. We also provide an R script to allow other scientists to mine our data for genes whose expression patterns match a user-selected gene of interest
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Regulation by Cyclic di-GMP in Myxococcus xanthus
Microbial Cyclic Di-Nucleotide Signaling, 2020Co-Authors: María Pérez-burgos, Lotte Søgaard-andersenAbstract:Myxococcus xanthus has a complex lifecycle that is regulated by nutrient availability. In the presence of nutrients, M. xanthus cells grow, divide, and move to assemble into colonies that feed cooperatively either saprophytically or on prey. In response to starvation, a developmental program is initiated that culminates in formation of multicellular spore-filled fruiting bodies. The nucleotide-based second messenger cyclic di-GMP accumulates in M. xanthus and has critical functions in both stages of the lifecycle. Here, we describe the roles of cyclic di-GMP, its metabolizing proteins, and receptor proteins. During growth, the correct level of cyclic di-GMP is important for type IV pili-dependent motility. During development, the cyclic di-GMP level increases and a threshold concentration of cyclic di-GMP is essential for completion of the developmental program. By individually inactivating the genes involved in cyclic di-GMP synthesis or degradation, two diguanylate cyclases, DmxA and DmxB, were identified to function at specific stages of the lifecycle with DmxA involved in type IV pili-dependent motility and DmxB in development. Similarly, the phosphodiesterase PmxA is specifically important for development but functions independently of DmxB. Bioinformatics analyses suggest the existence of various cyclic di-GMP receptor proteins, a few of which have been confirmed experimentally while the remainder are still uncharacterized. We are only just beginning to understand regulation by cyclic di-GMP in M. xanthus and it will be exciting to identify all the processes regulated by cyclic di-GMP and the underlying mechanisms.
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A TonB-dependent transporter is required for secretion of protease PopC across the bacterial outer membrane
Nature Publishing Group, 2019Co-Authors: Nuria Gómez-santos, Ralf Koebnik, Timo Glatter, Magdalena Anna Świątek-połatyńska, Lotte Søgaard-andersenAbstract:TonB-dependent transporters (TBDTs) are outer membrane proteins that import nutrients and bacteriocins in bacteria. Here, Gómez-Santos et al. show that a TBDT is required for secretion of a protease in Myxococcus xanthus, suggesting that some TBDTs may be involved in protein secretion
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Regulation by cyclic di-GMP in Myxococcus xanthus
Philipps-Universität Marburg Biologie, 2016Co-Authors: Skotnicka Dorota, Lotte Søgaard-andersenAbstract:The 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 xanthus undergoes 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 in M. xanthus. We show that this bacterium synthesizes c-di-GMP. Manipulation of the cellular c-di-GMP level by expression of either an active, heterologous diguanylate cyclase or an active, heterologous phosphodiesterase in vegetative cells caused defects in type IV pili (T4P)-dependent motility whereas gliding motility was unaffected. An increased level of c-di-GMP caused reduced transcription of the pilA gene that encodes the major pilin of T4P, reduced assembly of T4P and altered cell agglutination whereas a decreased level of c-di-GMP caused altered cell agglutination. The systematic inactivation of the 24 genes in M. xanthus encoding 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. These three proteins named DmxA, TmoK and SgmT all contain a GGDEF domain. Purified DmxA had diguanylate cyclase activity whereas the TmoK and SgmT (both hybrid histidine protein kinases) did not have diguanylate cyclase activity. During starvation, the c-di-GMP level in M. xanthus increases significantly. Manipulation of this level revealed that a low c-di-GMP level negatively affects the developmental program while an increased level does not interfere with development. Moreover, among the 24 genes encoding proteins containing GGDEF, EAL or HD-GYP domains, we identified two which are specifically involved in development: pmxA and dmxB. pmxA codes for an enzymatically active phosphodiesterase with an HD-GYP domain. dmxB codes for a developmentally induced, enzymatically active diguanylate cyclase. DmxB is essential for the increased c-di-GMP level and regulates exopolysaccharide accumulation during starvation. Our results show that c-di-GMP acts as an important signaling molecule during M. xanthus development, and suggest a model in which a minimal threshold level of c-di-GMP is essential for the successful progression and completion of the developmental program. Additionally, candidates for c-di-GMP effectors in M. xanthus were identified using a capture compound mass spectrometry approach. Some of the candidates were confirmed to bind c-di-GMP in vitro and deletion mutants for genes encoding those proteins were characterized in terms of T4P-dependent motility and development
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Correlated cryogenic photoactivated localization microscopy and cryo-electron tomography.
Nature Methods, 2014Co-Authors: Yi-wei Chang, Songye Chen, Elitza I. Tocheva, Anke Treuner-lange, Stephanie Löbach, Lotte Søgaard-andersen, Grant J. JensenAbstract:Cryo-electron tomography (CET) produces three-dimensional images of cells in a near-native state at macromolecular resolution, but identifying structures of interest can be challenging. Here we describe a correlated cryo-PALM (photoactivated localization microscopy)-CET method for localizing objects within cryo-tomograms to beyond the diffraction limit of the light microscope. Using cryo-PALM-CET, we identified multiple and new conformations of the dynamic type VI secretion system in the crowded interior of Myxococcus xanthus.
Roy D Welch - One of the best experts on this subject based on the ideXlab platform.
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self driven phase transitions drive Myxococcus xanthus fruiting body formation
Physical Review Letters, 2019Co-Authors: Adam Patch, Fatmagul Bahar, Roy D Welch, Cristina M Marchetti, Shashi Thutupalli, David Yllanes, Joshua W ShaevitzAbstract:: Combining high-resolution single cell tracking experiments with numerical simulations, we show that starvation-induced fruiting body formation in Myxococcus xanthus is a phase separation driven by cells that tune their motility over time. The phase separation can be understood in terms of cell density and a dimensionless Peclet number that captures cell motility through speed and reversal frequency. Our work suggests that M. xanthus takes advantage of a self-driven nonequilibrium phase transition that can be controlled at the single cell level.
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spatial organization of Myxococcus xanthus during fruiting body formation
Journal of Bacteriology, 2007Co-Authors: Patrick D Curtis, Rion G Taylor, Roy D WelchAbstract:Microcinematography was used to examine fruiting body development of Myxococcus xanthus. Wild-type cells progress through three distinct phases: a quiescent phase with some motility but little aggregation (0 to 8 h), a period of vigorous motility leading to raised fruiting bodies (8 to 16 h), and a period of maturation during which sporulation is initiated (16 to 48 h). Fruiting bodies are extended vertically in a series of tiers, each involving the addition of a cell monolayer on top of the uppermost layer. A pilA (MXAN_5783) mutant produced less extracellular matrix material and thus allowed closer examination of tiered aggregate formation. A csgA (MXAN_1294) mutant exhibited no quiescent phase, aberrant aggregation in phase 2, and disintegration of the fruiting bodies in the third phase.
