RESUMO
Contrary to multicellular organisms that display segmentation during development, communities of unicellular organisms are believed to be devoid of such sophisticated patterning. Unexpectedly, we find that the gene expression underlying the nitrogen stress response of a developing Bacillus subtilis biofilm becomes organized into a ring-like pattern. Mathematical modeling and genetic probing of the underlying circuit indicate that this patterning is generated by a clock and wavefront mechanism, similar to that driving vertebrate somitogenesis. We experimentally validated this hypothesis by showing that predicted nutrient conditions can even lead to multiple concentric rings, resembling segments. We additionally confirmed that this patterning mechanism is driven by cell-autonomous oscillations. Importantly, we show that the clock and wavefront process also spatially patterns sporulation within the biofilm. Together, these findings reveal a biofilm segmentation clock that organizes cellular differentiation in space and time, thereby challenging the paradigm that such patterning mechanisms are exclusive to plant and animal development.
Assuntos
Bacillus subtilis/crescimento & desenvolvimento , Bacillus subtilis/genética , Biofilmes/crescimento & desenvolvimento , Padronização Corporal/genética , Bacillus subtilis/metabolismo , Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Cinética , Modelos Biológicos , Nitrogênio/metabolismo , Transdução de Sinais/genética , Somitos/crescimento & desenvolvimento , Esporos Bacterianos/crescimento & desenvolvimento , Estresse Fisiológico/genética , Fatores de TempoRESUMO
The means by which the physicochemical properties of different cellular components together determine bacterial cell shape remain poorly understood. Here, we investigate a programmed cell-shape change during Bacillus subtilis sporulation, when a rod-shaped vegetative cell is transformed to an ovoid spore. Asymmetric cell division generates a bigger mother cell and a smaller, hemispherical forespore. The septum traps the forespore chromosome, which is translocated to the forespore by SpoIIIE. Simultaneously, forespore size increases as it is reshaped into an ovoid. Using genetics, timelapse microscopy, cryo-electron tomography, and mathematical modeling, we demonstrate that forespore growth relies on membrane synthesis and SpoIIIE-mediated chromosome translocation, but not on peptidoglycan or protein synthesis. Our data suggest that the hydrated nucleoid swells and inflates the forespore, displacing ribosomes to the cell periphery, stretching septal peptidoglycan, and reshaping the forespore. Our results illustrate how simple biophysical interactions between core cellular components contribute to cellular morphology.
Assuntos
Divisão Celular Assimétrica/fisiologia , Bacillus subtilis/fisiologia , Cromossomos Bacterianos/metabolismo , Esporos Bacterianos/metabolismo , Translocação Genética , Bacillus subtilis/ultraestrutura , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cromossomos Bacterianos/genética , Peptidoglicano/biossíntese , Peptidoglicano/genética , Biossíntese de Proteínas/fisiologia , Esporos Bacterianos/genética , Esporos Bacterianos/ultraestruturaRESUMO
Severe changes in the environmental redox potential, and resulting alterations in the oxidation states of intracellular metabolites and enzymes, have historically been considered negative stressors, requiring responses that are strictly defensive. However, recent work in diverse organisms has revealed that more subtle changes in the intracellular redox state can act as signals, eliciting responses with benefits beyond defense and detoxification. Changes in redox state have been shown to influence or trigger chromosome segregation, sporulation, aerotaxis, and social behaviors, including luminescence as well as biofilm establishment and dispersal. Connections between redox state and complex behavior allow bacteria to link developmental choices with metabolic state and coordinate appropriate responses. Promising future directions for this area of study include metabolomic analysis of species- and condition-dependent changes in metabolite oxidation states and elucidation of the mechanisms whereby the redox state influences circadian regulation.
Assuntos
Biofilmes/crescimento & desenvolvimento , Proteínas de Escherichia coli/metabolismo , Regulação Bacteriana da Expressão Gênica , Proteínas de Membrana/metabolismo , Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Esporos Bacterianos/metabolismo , Aliivibrio fischeri/genética , Aliivibrio fischeri/crescimento & desenvolvimento , Aliivibrio fischeri/metabolismo , Bacillus subtilis/genética , Bacillus subtilis/crescimento & desenvolvimento , Bacillus subtilis/metabolismo , Caulobacter crescentus/genética , Caulobacter crescentus/crescimento & desenvolvimento , Caulobacter crescentus/metabolismo , Escherichia coli/genética , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Glutationa/metabolismo , Proteínas de Membrana/genética , Oxirredução , Proteínas Quinases/genética , Proteínas Serina-Treonina Quinases/genética , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pseudomonas aeruginosa/metabolismo , Transdução de Sinais , Esporos Bacterianos/genética , Esporos Bacterianos/crescimento & desenvolvimento , Streptomyces/genética , Streptomyces/crescimento & desenvolvimento , Streptomyces/metabolismoRESUMO
Germination is the process by which spores emerge from dormancy. Although spores can remain dormant for decades, the study of germination is an active field of research. In this issue of Genes & Development, Gao and colleagues (pp. 31-45) address a perplexing question: How can a dormant spore initiate germination in response to environmental cues? Three distinct complexes are involved: GerA, a germinant-gated ion channel; 5AF/FigP, a second ion channel required for amplification; and SpoVA, a channel for dipicolinic acid (DPA). DPA release is followed by rehydration of the spore core, thus allowing the resumption of metabolic activity.
Assuntos
Proteínas de Bactérias , Esporos Bacterianos , Esporos Bacterianos/genética , Esporos Bacterianos/metabolismo , Proteínas de Bactérias/metabolismo , Esporos/metabolismo , Canais Iônicos/metabolismo , Bacillus subtilis/metabolismoRESUMO
Bacterial spores can remain dormant for decades yet rapidly germinate and resume growth in response to nutrients. GerA family receptors that sense and respond to these signals have recently been shown to oligomerize into nutrient-gated ion channels. Ion release initiates exit from dormancy. Here, we report that a distinct ion channel, composed of SpoVAF (5AF) and its newly discovered partner protein, YqhR (FigP), amplifies the response. At high germinant concentrations, 5AF/FigP accelerate germination; at low concentrations, this complex becomes critical for exit from dormancy. 5AF is homologous to the channel-forming subunit of GerA family receptors and is predicted to oligomerize around a central pore. 5AF mutations predicted to widen the channel cause constitutive germination during spore formation and membrane depolarization in vegetative cells. Narrow-channel mutants are impaired in germination. A screen for suppressors of a constitutively germinating 5AF mutant identified FigP as an essential cofactor of 5AF activity. We demonstrate that 5AF and FigP interact and colocalize with GerA family receptors in spores. Finally, we show that 5AF/FigP accelerate germination in B. subtilis spores that have nutrient receptors from another species. Our data support a model in which nutrient-triggered ion release by GerA family receptors activates 5AF/FigP ion release, amplifying the response to germinant signals.
Assuntos
Bacillus subtilis , Proteínas de Membrana , Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Proteínas de Membrana/genética , Esporos Bacterianos/genética , Esporos Bacterianos/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Canais Iônicos/genética , Canais Iônicos/metabolismoRESUMO
Sporulating bacteria can retreat into long-lasting dormant spores that preserve the capacity to germinate when propitious. However, how the revival transcriptional program is memorized for years remains elusive. We revealed that in dormant spores, core RNA polymerase (RNAP) resides in a central chromosomal domain, where it remains bound to a subset of intergenic promoter regions. These regions regulate genes encoding for most essential cellular functions, such as rRNAs and tRNAs. Upon awakening, RNAP recruits key transcriptional components, including sigma factor, and progresses to express the adjacent downstream genes. Mutants devoid of spore DNA-compacting proteins exhibit scattered RNAP localization and subsequently disordered firing of gene expression during germination. Accordingly, we propose that the spore chromosome is structured to preserve the transcriptional program by halting RNAP, prepared to execute transcription at the auspicious time. Such a mechanism may sustain long-term transcriptional programs in diverse organisms displaying a quiescent life form.
Assuntos
Bacillus subtilis , Esporos Bacterianos , Esporos Bacterianos/genética , Esporos Bacterianos/metabolismo , Bacillus subtilis/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Fator sigma/genética , Fator sigma/metabolismo , Regiões Promotoras Genéticas , RNA Polimerases Dirigidas por DNA/genética , RNA Polimerases Dirigidas por DNA/metabolismoRESUMO
Genes encoding proteins in a common regulatory network are frequently located close to one another on the chromosome to facilitate co-regulation or couple gene expression to growth rate. Contrasting with these observations, here, we demonstrate a functional role for the arrangement of Bacillus subtilis sporulation network genes on opposite sides of the chromosome. We show that the arrangement of two sporulation network genes, one located close to the origin and the other close to the terminus, leads to a transient gene dosage imbalance during chromosome replication. This imbalance is detected by the sporulation network to produce cell-cycle coordinated pulses of the sporulation master regulator Spo0Aâ¼P. This pulsed response allows cells to decide between sporulation and continued vegetative growth during each cell cycle spent in starvation. The simplicity of this coordination mechanism suggests that it may be widely applicable in a variety of gene regulatory and stress-response settings. VIDEO ABSTRACT.
Assuntos
Bacillus subtilis/fisiologia , Esporos Bacterianos/fisiologia , Bacillus subtilis/genética , Proteínas de Bactérias/metabolismo , Cromossomos Bacterianos , Replicação do DNA , Retroalimentação , Dosagem de Genes , Fosforilação , Fatores de Transcrição/metabolismoRESUMO
In response to starvation, endospore-forming bacteria differentiate into stress-resistant spores that can remain dormant for years yet rapidly germinate and resume growth in response to nutrients. The small molecule dipicolinic acid (DPA) plays a central role in both the stress resistance of the dormant spore and its exit from dormancy during germination. The spoVA locus is required for DPA import during sporulation and has been implicated in its export during germination, but the molecular bases are unclear. Here, we define the minimal set of proteins encoded in the Bacillus subtilis spoVA operon required for DPA import and demonstrate that these proteins form a membrane complex. Structural modeling of these components combined with mutagenesis and in vivo analysis reveal that the C and Eb subunits form a membrane channel, while the D subunit functions as a cytoplasmic plug. We show that point mutations that impair the interactions between D and the C-Eb membrane complex reduce the efficiency of DPA import during sporulation and reciprocally accelerate DPA release during germination. Our data support a model in which DPA transport into spores involves cycles of unplugging and then replugging the C-Eb membrane channel, while nutrient detection during germination triggers DPA release by unplugging it.
Assuntos
Proteínas de Bactérias , Esporos Bacterianos , Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Proteínas de Bactérias/metabolismo , Ácidos Picolínicos/metabolismo , Esporos Bacterianos/genéticaRESUMO
The cyclic dinucleotide c-di-GMP is a signaling molecule with diverse functions in cellular physiology. Here, we report that c-di-GMP can assemble into a tetramer that mediates the effective dimerization of a transcription factor, BldD, which controls the progression of multicellular differentiation in sporulating actinomycete bacteria. BldD represses expression of sporulation genes during vegetative growth in a manner that depends on c-di-GMP-mediated dimerization. Structural and biochemical analyses show that tetrameric c-di-GMP links two subunits of BldD through their C-terminal domains, which are otherwise separated by ~10 Å and thus cannot effect dimerization directly. Binding of the c-di-GMP tetramer by BldD is selective and requires a bipartite RXD-X8-RXXD signature. The findings indicate a unique mechanism of protein dimerization and the ability of nucleotide signaling molecules to assume alternative oligomeric states to effect different functions.
Assuntos
Proteínas de Bactérias/metabolismo , GMP Cíclico/análogos & derivados , Streptomyces/crescimento & desenvolvimento , Streptomyces/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Cristalografia por Raios X , GMP Cíclico/metabolismo , Dimerização , Modelos Moleculares , Dados de Sequência Molecular , Alinhamento de Sequência , Esporos Bacterianos/metabolismo , Streptomyces/citologia , Fatores de Transcrição/químicaRESUMO
Hygroscopic biological matter in plants, fungi and bacteria make up a large fraction of Earth's biomass1. Although metabolically inert, these water-responsive materials exchange water with the environment and actuate movement2-5 and have inspired technological uses6,7. Despite the variety in chemical composition, hygroscopic biological materials across multiple kingdoms of life exhibit similar mechanical behaviours including changes in size and stiffness with relative humidity8-13. Here we report atomic force microscopy measurements on the hygroscopic spores14,15 of a common soil bacterium and develop a theory that captures the observed equilibrium, non-equilibrium and water-responsive mechanical behaviours, finding that these are controlled by the hydration force16-18. Our theory based on the hydration force explains an extreme slowdown of water transport and successfully predicts a strong nonlinear elasticity and a transition in mechanical properties that differs from glassy and poroelastic behaviours. These results indicate that water not only endows biological matter with fluidity but also can-through the hydration force-control macroscopic properties and give rise to a 'hydration solid' with unusual properties. A large fraction of biological matter could belong to this distinct class of solid matter.
Assuntos
Esporos Bacterianos , Água , Molhabilidade , Transporte Biológico , Fungos/química , Fungos/metabolismo , Microscopia de Força Atômica , Água/metabolismo , Plantas/química , Plantas/metabolismo , Bactérias/química , Bactérias/citologia , Bactérias/metabolismo , Esporos Bacterianos/química , Esporos Bacterianos/metabolismo , Umidade , ElasticidadeRESUMO
Spore formation in Bacillus subtilis relies on a regulated intramembrane proteolysis (RIP) pathway that synchronizes mother-cell and forespore development. To address the molecular basis of this SpoIV transmembrane signaling, we carried out a structure-function analysis of the activating protease CtpB. Crystal structures reflecting distinct functional states show that CtpB constitutes a ring-like protein scaffold penetrated by two narrow tunnels. Access to the proteolytic sites sequestered within these tunnels is controlled by PDZ domains that rearrange upon substrate binding. Accordingly, CtpB resembles a minimal version of a self-compartmentalizing protease regulated by a unique allosteric mechanism. Moreover, biochemical analysis of the PDZ-gated channel combined with sporulation assays reveal that activation of the SpoIV RIP pathway is induced by the concerted activity of CtpB and a second signaling protease, SpoIVB. This proteolytic mechanism is of broad relevance for cell-cell communication, illustrating how distinct signaling pathways can be integrated into a single RIP module.
Assuntos
Bacillus subtilis/fisiologia , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Esporos Bacterianos , Sítio Alostérico , Sequência de Aminoácidos , Modelos Moleculares , Dados de Sequência Molecular , Domínios PDZ , Alinhamento de Sequência , Transdução de SinaisRESUMO
Streptomyces are our primary source of antibiotics, produced concomitantly with the transition from vegetative growth to sporulation in a complex developmental life cycle. We previously showed that the signaling molecule c-di-GMP binds BldD, a master repressor, to control initiation of development. Here we demonstrate that c-di-GMP also intervenes later in development to control differentiation of the reproductive hyphae into spores by arming a novel anti-σ (RsiG) to bind and sequester a sporulation-specific σ factor (σWhiG). We present the structure of the RsiG-(c-di-GMP)2-σWhiG complex, revealing an unusual, partially intercalated c-di-GMP dimer bound at the RsiG-σWhiG interface. RsiG binds c-di-GMP in the absence of σWhiG, employing a novel E(X)3S(X)2R(X)3Q(X)3D motif repeated on each helix of a coiled coil. Further studies demonstrate that c-di-GMP is essential for RsiG to inhibit σWhiG. These findings reveal a newly described control mechanism for σ-anti-σ complex formation and establish c-di-GMP as the central integrator of Streptomyces development.
Assuntos
GMP Cíclico/análogos & derivados , Fator sigma/metabolismo , Streptomyces/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/genética , GMP Cíclico/metabolismo , GMP Cíclico/fisiologia , Proteínas de Ligação a DNA/metabolismo , Regulação Bacteriana da Expressão Gênica/genética , Domínios Proteicos , RNA Bacteriano/metabolismo , Esporos Bacterianos/metabolismo , Streptomyces/genéticaRESUMO
The obligate anaerobic, enteric pathogen Clostridioides difficile persists in the intestinal tract by forming antibiotic-resistant endospores that contribute to relapsing and recurrent infections. Despite the importance of sporulation for C. difficile pathogenesis, environmental cues and molecular mechanisms that regulate sporulation initiation remain ill-defined. Here, by using RIL-seq to globally capture the Hfq-dependent RNA-RNA interactome, we discovered a network of small RNAs that bind to mRNAs encoding sporulation-related genes. We show that two of these small RNAs, SpoX and SpoY, regulate translation of the master regulator of sporulation, Spo0A, in an opposing manner, which ultimately leads to altered sporulation rates. Infection of antibiotic-treated mice with SpoX and SpoY deletion mutants revealed a global effect on gut colonization and intestinal sporulation. Our work uncovers an elaborate RNA-RNA interactome controlling the physiology and virulence of C. difficile and identifies a complex post-transcriptional layer in the regulation of spore formation in this important human pathogen.
Assuntos
Clostridioides difficile , Clostridioides , Animais , Humanos , Camundongos , Clostridioides/genética , Clostridioides/metabolismo , Clostridioides difficile/genética , Clostridioides difficile/metabolismo , Antibacterianos , RNA/metabolismo , Esporos Bacterianos/genética , Esporos Bacterianos/metabolismo , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão GênicaRESUMO
Clostridioides difficile is an important human pathogen, for which there are very limited treatment options, primarily the glycopeptide antibiotic vancomycin. In recent years, vancomycin resistance has emerged as a serious problem in several gram-positive pathogens, but high-level resistance has yet to be reported for C. difficile, although it is not known if this is due to constraints upon resistance evolution in this species. Here, we show that resistance to vancomycin can evolve rapidly under ramping selection but is accompanied by fitness costs and pleiotropic trade-offs, including sporulation defects that would be expected to severely impact transmission. We identified 2 distinct pathways to resistance, both of which are predicted to result in changes to the muropeptide terminal D-Ala-D-Ala that is the primary target of vancomycin. One of these pathways involves a previously uncharacterised D,D-carboxypeptidase, expression of which is controlled by a dedicated two-component signal transduction system. Our findings suggest that while C. difficile is capable of evolving high-level vancomycin resistance, this outcome may be limited clinically due to pleiotropic effects on key pathogenicity traits. Moreover, our data identify potential mutational routes to resistance that should be considered in genomic surveillance.
Assuntos
Antibacterianos , Clostridioides difficile , Resistência a Vancomicina , Vancomicina , Clostridioides difficile/efeitos dos fármacos , Clostridioides difficile/genética , Clostridioides difficile/patogenicidade , Resistência a Vancomicina/genética , Vancomicina/farmacologia , Antibacterianos/farmacologia , Aptidão Genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Humanos , Transdução de Sinais , Mutação , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Esporos Bacterianos/efeitos dos fármacos , Esporos Bacterianos/genéticaRESUMO
Upon starvation, the bacterium Bacillus subtilis enters the process of sporulation, lasting several hours and culminating in formation of a spore, the most resilient cell type known. We show that a few days following sporulation, the RNA profile of spores is highly dynamic. In aging spores incubated at high temperatures, RNA content is globally decreased by degradation over several days. This degradation might be a strategy utilized by the spore to facilitate its dormancy. However, spores kept at low temperature exhibit a different RNA profile with evidence supporting transcription. Further, we demonstrate that germination is affected by spore age, incubation temperature, and RNA state, implying that spores can acquire dissimilar characteristics at a time they are considered dormant. We propose that, in contrast to current thinking, entering dormancy lasts a few days, during which spores are affected by the environment and undergo corresponding molecular changes influencing their emergence from quiescence.
Assuntos
Bacillus subtilis/fisiologia , RNA Bacteriano/metabolismo , Esporos Bacterianos/genética , Bacillus subtilis/genética , Endorribonucleases/metabolismo , Estabilidade de RNA , RNA Bacteriano/classificação , RNA Mensageiro/metabolismo , RNA Ribossômico/metabolismo , Esporos Bacterianos/fisiologia , TemperaturaRESUMO
Bacterial spores have outstanding properties from the materials science perspective, which allow them to survive extreme environmental conditions. Recent work by [S. G. Harrellson et al., Nature 619, 500-505 (2023)] studied the mechanical properties of Bacillus subtilis spores and the evolution of these properties with the change of humidity. The experimental measurements were interpreted assuming that the spores behave as water-filled porous solids, subjected to hydration forces. Here, we revisit their experimental data using literature data on vapor sorption on spores and ideas from polymer physics. We demonstrate that upon the change of humidity, the spores behave like rubber with respect to their swelling, elasticity, and relaxation times. This picture is consistent with the knowledge of the materials comprising the bacterial cell walls-cross-linked peptidoglycan. Our results provide an interpretation of the mechanics of bacterial spores and can help in developing synthetic materials mimicking the mechanical properties of the spores.
Assuntos
Hidrogéis , Esporos Bacterianos , Umidade , Elasticidade , Fenômenos Químicos , Bacillus subtilisRESUMO
When faced with starvation, the bacterium Bacillus subtilis transforms itself into a dormant cell type called a "spore". Sporulation initiates with an asymmetric division event, which requires the relocation of the core divisome components FtsA and FtsZ, after which the sigma factor σF is exclusively activated in the smaller daughter cell. Compartment-specific activation of σF requires the SpoIIE phosphatase, which displays a biased localization on one side of the asymmetric division septum and associates with the structural protein DivIVA, but the mechanism by which this preferential localization is achieved is unclear. Here, we isolated a variant of DivIVA that indiscriminately activates σF in both daughter cells due to promiscuous localization of SpoIIE, which was corrected by overproduction of FtsA and FtsZ. We propose that the core components of the redeployed cell division machinery drive the asymmetric localization of DivIVA and SpoIIE to trigger the initiation of the sporulation program.
Assuntos
Bacillus subtilis , Proteínas de Bactérias , Bacillus subtilis/metabolismo , Ativação Transcricional , Proteínas de Bactérias/metabolismo , Esporos Bacterianos/genética , Esporos Bacterianos/metabolismo , Divisão Celular/genética , Fator sigma/genética , Fator sigma/metabolismoRESUMO
Spore formation is required for environmental survival and transmission of the human enteropathogenic Clostridioides difficile. In all bacterial spore formers, sporulation is regulated through activation of the master response regulator, Spo0A. However, the factors and mechanisms that directly regulate C. difficile Spo0A activity are not defined. In the well-studied Bacillus species, Spo0A is directly inactivated by Spo0E, a small phosphatase. To understand Spo0E function in C. difficile, we created a null mutation of the spo0E ortholog and assessed sporulation and physiology. The spo0E mutant produced significantly more spores, demonstrating Spo0E represses C. difficile sporulation. Unexpectedly, the spo0E mutant also exhibited increased motility and toxin production, and enhanced virulence in animal infections. We uncovered that Spo0E interacts with both Spo0A and the toxin and motility regulator, RstA. Direct interactions between Spo0A, Spo0E, and RstA constitute a previously unknown molecular switch that coordinates sporulation with motility and toxin production. Reinvestigation of Spo0E function in B. subtilis revealed that Spo0E induced motility, demonstrating Spo0E regulation of motility and sporulation among divergent species. Further, 3D structural analyses of Spo0E revealed specific and exclusive interactions between Spo0E and binding partners in C. difficile and B. subtilis that provide insight into the conservation of this regulatory mechanism among different species.
Assuntos
Proteínas de Bactérias , Clostridioides difficile , Regulação Bacteriana da Expressão Gênica , Esporos Bacterianos , Clostridioides difficile/patogenicidade , Clostridioides difficile/genética , Clostridioides difficile/metabolismo , Esporos Bacterianos/genética , Virulência , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/genética , Animais , Camundongos , Infecções por Clostridium/microbiologiaRESUMO
The biophysical properties of the cytoplasm are major determinants of key cellular processes and adaptation. Many yeasts produce dormant spores that can withstand extreme conditions. We show that spores of Saccharomyces cerevisiae exhibit extraordinary biophysical properties, including a highly viscous and acidic cytosol. These conditions alter the solubility of more than 100 proteins such as metabolic enzymes that become more soluble as spores transit to active cell proliferation upon nutrient repletion. A key regulator of this transition is the heat shock protein, Hsp42, which shows transient solubilization and phosphorylation, and is essential for the transformation of the cytoplasm during germination. Germinating spores therefore return to growth through the dissolution of protein assemblies, orchestrated in part by Hsp42 activity. The modulation of spores' molecular properties are likely key adaptive features of their exceptional survival capacities.
Assuntos
Proteínas de Saccharomyces cerevisiae , Saccharomycetales , Proteoma/metabolismo , Solubilidade , Saccharomycetales/metabolismo , Esporos Fúngicos , Citoplasma/metabolismo , Saccharomyces cerevisiae/metabolismo , Esporos Bacterianos/metabolismo , Bacillus subtilis/metabolismo , Proteínas de Choque Térmico/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Two hallmarks of the Firmicute phylum, which includes the Bacilli and Clostridia classes, are their ability to form endospores and their "Gram-positive" single-membraned, thick-cell-wall envelope structure. Acetonema longum is part of a lesser-known family (the Veillonellaceae) of Clostridia that form endospores but that are surprisingly "Gram negative," possessing both an inner and outer membrane and a thin cell wall. Here, we present macromolecular resolution, 3D electron cryotomographic images of vegetative, sporulating, and germinating A. longum cells showing that during the sporulation process, the inner membrane of the mother cell is inverted and transformed to become the outer membrane of the germinating cell. Peptidoglycan persists throughout, leading to a revised, "continuous" model of its role in the process. Coupled with genomic analyses, these results point to sporulation as a mechanism by which the bacterial outer membrane may have arisen and A. longum as a potential "missing link" between single- and double-membraned bacteria.