scholarly journals Peptide signaling without feedback in signal production operates as a true quorum sensing communication system in Bacillus subtilis

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Iztok Dogsa ◽  
Mihael Spacapan ◽  
Anna Dragoš ◽  
Tjaša Danevčič ◽  
Žiga Pandur ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bacillus Subtilis ◽  
Quorum Sensing ◽  
Cell Density ◽  
Communication System ◽  
Communication Systems ◽  
Feedback Loop ◽  
Signal Molecules ◽  
Specific Cell ◽  
Sharp Transition

AbstractBacterial quorum sensing (QS) is based on signal molecules (SM), which increase in concentration with cell density. At critical SM concentration, a variety of adaptive genes sharply change their expression from basic level to maximum level. In general, this sharp transition, a hallmark of true QS, requires an SM dependent positive feedback loop, where SM enhances its own production. Some communication systems, like the peptide SM-based ComQXPA communication system of Bacillus subtilis, do not have this feedback loop and we do not understand how and if the sharp transition in gene expression is achieved. Based on experiments and mathematical modeling, we observed that the SM peptide ComX encodes the information about cell density, specific cell growth rate, and even oxygen concentration, which ensure power-law increase in SM production. This enables together with the cooperative response to SM (ComX) a sharp transition in gene expression level and this without the SM dependent feedback loop. Due to its ultra-sensitive nature, the ComQXPA can operate at SM concentrations that are 100–1000 times lower than typically found in other QS systems, thereby substantially reducing the total metabolic cost of otherwise expensive ComX peptide.

scholarly journals Quorum Sensing of Acidophiles: A Communication System in Microorganisms

2021 ◽  
Author(s):  
Xueyan Gao ◽  
Jianqiang Lin ◽  
Linxu Chen ◽  
Jianqun Lin ◽  
Xin Pang
Keyword(s):  
Quorum Sensing ◽  
Population Density ◽  
Intercellular Communication ◽  
Communication System ◽  
Communication Systems ◽  
Biological Function ◽  
Regulatory Mechanism ◽  
Signal Molecules ◽  
Acidic Environment ◽  
Cell Cooperation

Communication is important for organisms living in nature. Quorum sensing system (QS) are intercellular communication systems that promote the sociality of microbes. Microorganisms could promote cell-to-cell cooperation and population density to adapt to the changing environment through QS-mediated regulation that is dependent on the secretion and the detection of signal molecules (or called autoinducers). QS system is also discovered in acidophiles, a microorganism that is widely used in the bioleaching industry and can live in an acidic environment. An example is the LuxI/R-like QS system (AfeI/R) that has been reported in the chemoautotrophic species of the genus Acidithiobacillus. In this chapter, we will introduce the types and distribution of the QS system, and the biological function and regulatory mechanism of QS in acidophiles. We will also discuss the potential ecological function of QS system and the application value of the QS system in the control and regulation of the bioleaching process in the related industries and acid mine damage.

scholarly journals Stringent Response Activates Quorum Sensing and Modulates Cell Density-Dependent Gene Expression inPseudomonas aeruginosa

2001 ◽  
Vol 183 (18) ◽  
pp. 5376-5384 ◽  
Author(s):  
Christian van Delden ◽  
Rachel Comte ◽  
And Marc Bally
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Cell Density ◽  
Stringent Response ◽  
Transcriptional Regulators ◽  
Homoserine Lactone ◽  
Density Dependent ◽  
Sensing Systems ◽  
Acid Analogue ◽  
Enhanced Expression

ABSTRACT During nutrient starvation, Escherichia coli elicits a stringent response involving the ribosome-associated protein RelA. Activation of RelA results in a global change in the cellular metabolism including enhanced expression of the stationary-phase sigma factor RpoS. In the human pathogen Pseudomonas aeruginosa, a complex quorum-sensing circuitry, linked to RpoS expression, is required for cell density-dependent production of many secreted virulence factors, including LasB elastase. Quorum sensing relies on the activation of specific transcriptional regulators (LasR and RhlR) by their corresponding autoinducers (3-oxo-C12-homoserine lactone [HSL] and C4-HSL), which function as intercellular signals. We found that overexpression of relA activated the expression of rpoS in P. aeruginosa and led to premature, cell density-independent LasB elastase production. We therefore investigated the effects of the stringent response on quorum sensing. Both lasR and rhlR gene expression and autoinducer synthesis were prematurely activated during the stringent response induced by overexpression of relA. Premature expression of lasR and rhlR was also observed when relA was overexpressed in a PAO1 rpoSmutant. The stringent response induced by the amino acid analogue serine hydroxamate (SHX) also led to premature production of the 3-oxo-C12-HSL autoinducer. This response to SHX was absent in a PAO1 relA mutant. These findings suggest that the stringent response can activate the two quorum-sensing systems of P. aeruginosa independently of cell density.

scholarly journals Hierarchical Transcriptional Control of the LuxR Quorum-Sensing Regulon of Vibrio harveyi

2020 ◽  
Vol 202 (14) ◽  
Author(s):  
Ryan R. Chaparian ◽  
Alyssa S. Ball ◽  
Julia C. van Kessel
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Quorum Sensing ◽  
Cell Density ◽  
Regulatory Networks ◽  
Vibrio Harveyi ◽  
Sugar Transport ◽  
Content Type ◽  
Second Tier

ABSTRACT In vibrios, quorum sensing controls hundreds of genes that are required for cell density-specific behaviors including bioluminescence, biofilm formation, competence, secretion, and swarming motility. The central transcription factor in the quorum-sensing pathway is LuxR/HapR, which directly regulates ∼100 genes in the >400-gene regulon of Vibrio harveyi. Among these directly controlled genes are 15 transcription factors, which we predicted would comprise the second tier in the hierarchy of the LuxR regulon. We confirmed that LuxR binds to the promoters of these genes in vitro and quantified the extent of LuxR activation or repression of transcript levels. Transcriptome sequencing (RNA-seq) indicates that most of these transcriptional regulators control only a few genes, with the exception of MetJ, which is a global regulator. The genes regulated by these transcription factors are predicted to be involved in methionine and thiamine biosynthesis, membrane stability, RNA processing, c-di-GMP degradation, sugar transport, and other cellular processes. These data support a hierarchical model in which LuxR directly regulates 15 transcription factors that drive the second level of the gene expression cascade to influence cell density-dependent metabolic states and behaviors in V. harveyi. IMPORTANCE Quorum sensing is important for survival of bacteria in nature and influences the actions of bacterial groups. In the relatively few studied examples of quorum-sensing-controlled genes, these genes are associated with competition or cooperation in complex microbial communities and/or virulence in a host. However, quorum sensing in vibrios controls the expression of hundreds of genes, and their functions are mostly unknown or uncharacterized. In this study, we identify the regulators of the second tier of gene expression in the quorum-sensing system of the aquaculture pathogen Vibrio harveyi. Our identification of regulatory networks and metabolic pathways controlled by quorum sensing can be extended and compared to other Vibrio species to understand the physiology, ecology, and pathogenesis of these organisms.

scholarly journals In VivoProgrammed Gene Expression Based on Artificial Quorum Networks

2015 ◽  
Vol 81 (15) ◽  
pp. 4984-4992 ◽  
Author(s):  
Teng Chu ◽  
Yajun Huang ◽  
Mingyu Hou ◽  
Qiyao Wang ◽  
Jingfan Xiao ◽  
...  
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Cell Density ◽  
Protective Antigen ◽  
Expression System ◽  
Edwardsiella Tarda ◽  
Content Type ◽  
Genetic Components ◽  
Wide Range

ABSTRACTThe quorum sensing (QS) system, as a well-functioning population-dependent gene switch, has been widely applied in many gene circuits in synthetic biology. In our work, an efficient cell density-controlled expression system (QS) was established via engineering of theVibrio fischeri luxI-luxRquorum sensing system. In order to achievein vivoprogrammed gene expression, a synthetic binary regulation circuit (araQS) was constructed by assembling multiple genetic components, including the quorum quenching protein AiiA and the arabinose promoter ParaBAD, into the QS system.In vitroexpression assays verified that the araQS system was initiated only in the absence of arabinose in the medium at a high cell density.In vivoexpression assays confirmed that the araQS system presented anin vivo-triggered and cell density-dependent expression pattern. Furthermore, the araQS system was demonstrated to function well in different bacteria, indicating a wide range of bacterial hosts for use. To explore its potential applicationsin vivo, the araQS system was used to control the production of a heterologous protective antigen in an attenuatedEdwardsiella tardastrain, which successfully evoked efficient immune protection in a fish model. This work suggested that the araQS system could program bacterial expressionin vivoand might have potential uses, including, but not limited to, bacterial vector vaccines.

scholarly journals The Vibrio cholerae Quorum-Sensing Protein VqmA Integrates Cell Density, Environmental, and Host-Derived Cues into the Control of Virulence

mBio ◽  
2020 ◽  
Vol 11 (4) ◽  
Author(s):  
Ameya A. Mashruwala ◽  
Bonnie L. Bassler
Keyword(s):  
Small Intestine ◽  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Chemical Communication ◽  
Bile Salts ◽  
Anaerobic Growth ◽  
Signal Molecules ◽  
Content Type ◽  
Collective Behaviors

ABSTRACT Quorum sensing is a chemical communication process in which bacteria use the production, release, and detection of signal molecules called autoinducers to orchestrate collective behaviors. The human pathogen Vibrio cholerae requires quorum sensing to infect the small intestine. There, V. cholerae encounters the absence of oxygen and the presence of bile salts. We show that these two stimuli differentially affect quorum-sensing function and, in turn, V. cholerae pathogenicity. First, during anaerobic growth, V. cholerae does not produce the CAI-1 autoinducer, while it continues to produce the DPO autoinducer, suggesting that CAI-1 may encode information specific to the aerobic lifestyle of V. cholerae. Second, the quorum-sensing receptor-transcription factor called VqmA, which detects the DPO autoinducer, also detects the lack of oxygen and the presence of bile salts. Detection occurs via oxygen-, bile salt-, and redox-responsive disulfide bonds that alter VqmA DNA binding activity. We propose that VqmA serves as an information processing hub that integrates quorum-sensing information, redox status, the presence or absence of oxygen, and host cues. In response to the information acquired through this mechanism, V. cholerae appropriately modulates its virulence output. IMPORTANCE Quorum sensing (QS) is a process of chemical communication that bacteria use to orchestrate collective behaviors. QS communication relies on chemical signal molecules called autoinducers. QS regulates virulence in Vibrio cholerae, the causative agent of the disease cholera. Transit into the human small intestine, the site of cholera infection, exposes V. cholerae to the host environment. In this study, we show that the combination of two stimuli encountered in the small intestine, the absence of oxygen and the presence of host-produced bile salts, impinge on V. cholerae QS function and, in turn, pathogenicity. We suggest that possessing a QS system that is responsive to multiple environmental, host, and cell density cues enables V. cholerae to fine-tune its virulence capacity in the human intestine.

scholarly journals One Perturbation of the Mother Cell Gene Regulatory Network Suppresses the Effects of Another during Sporulation of Bacillus subtilis

2007 ◽  
Vol 189 (23) ◽  
pp. 8467-8473 ◽  
Author(s):  
Lijuan Wang ◽  
John Perpich ◽  
Adam Driks ◽  
Lee Kroos
Keyword(s):  
Gene Expression ◽  
Bacillus Subtilis ◽  
Rna Polymerase ◽  
Regulatory Network ◽  
Mother Cell ◽  
Feedback Loop ◽  
Network Functions ◽  
Regulatory Loop ◽  
Cell Gene ◽  
Spore Coat Protein

ABSTRACT In the mother cell of sporulating Bacillus subtilis, a regulatory network functions to control gene expression. Four transcription factors act sequentially in the order σE, SpoIIID, σK, GerE. σE and σK direct RNA polymerase to transcribe different regulons. SpoIIID and GerE are DNA-binding proteins that activate or repress transcription of many genes. Several negative regulatory loops add complexity to the network. First, transcriptionally active σK RNA polymerase inhibits early sporulation gene expression, resulting in reduced accumulation of σE and SpoIIID late during sporulation. Second, GerE represses sigK transcription, reducing σK accumulation about twofold. Third, SpoIIID represses cotC, which encodes a spore coat protein, delaying its transcription by σK RNA polymerase. Partially circumventing the first feedback loop, by engineering cells to maintain the SpoIIID level late during sporulation, causes spore defects. Here, the effects of circumventing the second feedback loop, by mutating the GerE binding sites in the sigK promoter region, are reported. Accumulation of pro-σK and σK was increased, but no spore defects were detected. Expression of σK-dependent reporter fusions was altered, increasing the expression of gerE-lacZ and cotC-lacZ and decreasing the expression of cotD-lacZ. Because these effects on gene expression were opposite those observed when the SpoIIID level was maintained late during sporulation, cells were engineered to both maintain the SpoIIID level and have elevated sigK expression late during sporulation. This restored the expression of σK-dependent reporters to wild-type levels, and no spore defects were observed. Hence, circumventing the second feedback loop suppressed the effects of perturbing the first feedback loop. By feeding information back into the network, these two loops appear to optimize target gene expression and increase network robustness. Circumventing the third regulatory loop, by engineering cells to express cotC about 2 h earlier than normal, did not cause a detectable spore defect.

scholarly journals LuxS Is Required for Persistent Pneumococcal Carriage and Expression of Virulence and Biosynthesis Genes

2004 ◽  
Vol 72 (5) ◽  
pp. 2964-2975 ◽  
Author(s):  
Elizabeth A. Joyce ◽  
Amita Kawale ◽  
Stefano Censini ◽  
Charles C. Kim ◽  
Antonello Covacci ◽  
...  
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Cell Density ◽  
High Cell Density ◽  
Signaling System ◽  
Cellular Processes ◽  
Disease States ◽  
Pneumococcal Carriage ◽  
A Cell ◽  
Dependent Mechanism

ABSTRACT Streptococcus pneumoniae causes several diseases, including otitis media, pneumonia, and meningitis. Although little is known about the regulation of or how individual pneumococcal factors contribute to these disease states, there is evidence suggesting that some factors are regulated by a cell-density-dependent mechanism (quorum sensing). Quorum sensing allows bacteria to couple transcription with changes in cell density; bacteria achieve this by sensing and responding to small diffusible signaling molecules. We investigated how the LuxS signaling system impacts the biology of S. pneumoniae. An analysis of the transcriptional profiles of a serotype 2 strain and an isogenic luxS deletion strain utilizing an S. pneumoniae-specific microarray indicated that LuxS regulates gene expression involved in discrete cellular processes, including pneumolysin expression. Contrary to the paradigm for quorum sensing, we observed pronounced effects on transcription in early log phase, where gene expression was repressed in the mutant. Assessing the mutant for its ability to infect and cause disease in animals revealed a profound defect in ability to persist in the nasopharyngeal tissues. Our analysis of an S. pneumoniae transcriptome revealed a function for LuxS in gene regulation that is not dependent upon high cell density and is likely involved in the maintenance of pneumococcal load in susceptible hosts.

scholarly journals Three Parallel Quorum-Sensing Systems Regulate Gene Expression in Vibrio harveyi

2004 ◽  
Vol 186 (20) ◽  
pp. 6902-6914 ◽  
Author(s):  
Jennifer M. Henke ◽  
Bonnie L. Bassler
Keyword(s):  
Quorum Sensing ◽  
Communication Systems ◽  
Vibrio Harveyi ◽  
Signal Molecules ◽  
Phenotypic Analysis ◽  
Regulate Gene Expression ◽  
Sensing Systems ◽  
Extracellular Signal ◽  
System 2 ◽  
System 1

ABSTRACT In a process called quorum sensing, bacteria communicate using extracellular signal molecules termed autoinducers. Two parallel quorum-sensing systems have been identified in the marine bacterium Vibrio harveyi. System 1 consists of the LuxM-dependent autoinducer HAI-1 and the HAI-1 sensor, LuxN. System 2 consists of the LuxS-dependent autoinducer AI-2 and the AI-2 detector, LuxPQ. The related bacterium, Vibrio cholerae, a human pathogen, possesses System 2 (LuxS, AI-2, and LuxPQ) but does not have obvious homologues of V. harveyi System 1. Rather, System 1 of V. cholerae is made up of the CqsA-dependent autoinducer CAI-1 and a sensor called CqsS. Using a V. cholerae CAI-1 reporter strain we show that many other marine bacteria, including V. harveyi, produce CAI-1 activity. Genetic analysis of V. harveyi reveals cqsA and cqsS, and phenotypic analysis of V. harveyi cqsA and cqsS mutants shows that these functions comprise a third V. harveyi quorum-sensing system that acts in parallel to Systems 1 and 2. Together these communication systems act as a three-way coincidence detector in the regulation of a variety of genes, including those responsible for bioluminescence, type III secretion, and metalloprotease production.

scholarly journals Regulation of rpoS Gene Expression in Pseudomonas: Involvement of a TetR Family Regulator

2001 ◽  
Vol 183 (12) ◽  
pp. 3712-3720 ◽  
Author(s):  
Milan Kojic ◽  
Vittorio Venturi
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Quorum Sensing ◽  
Stationary Phase ◽  
Cell Density ◽  
Promoter Activity ◽  
Regulatory Protein ◽  
Insertion Mutant ◽  
Regulatory Cascade ◽  
A Cell

ABSTRACT The rpoS gene encodes the sigma factor which was identified in several gram-negative bacteria as a central regulator during stationary phase. rpoS gene regulation is known to respond to cell density, showing higher expression in stationary phase. For Pseudomonas aeruginosa, it has been demonstrated that the cell-density-dependent regulation response known as quorum sensing interacts with this regulatory response. Using therpoS promoter of P. putida, we identified a genomic Tn5 insertion mutant of P. putida which showed a 90% decrease in rpoSpromoter activity, resulting in less RpoS being present in a cell at stationary phase. Molecular analysis revealed that this mutant carried a Tn5 insertion in a gene, designatedpsrA (Pseudomonas sigma regulator), which codes for a protein (PsrA) of 26.3 kDa. PsrA contains a helix-turn-helix motif typical of DNA binding proteins and belongs to the TetR family of bacterial regulators. The homolog of thepsrA gene was identified in P. aeruginosa; the protein showed 90% identity to PsrA ofP. putida. ApsrA::Tn5 insertion mutant ofP. aeruginosa was constructed. In bothPseudomonas species, psrA was genetically linked to the SOS lexA repressor gene. Similar to what was observed for P. putida, a psrA null mutant of P. aeruginosa also showed a 90% reduction inrpoS promoter activity; both mutants could be complemented for rpoS promoter activity when thepsrA gene was provided in trans.psrA mutants of both Pseudomonas species lost the ability to induce rpoS expression at stationary phase, but they retained the ability to produce quorum-sensing autoinducer molecules. PsrA was demonstrated to negatively regulatepsrA gene expression in Pseudomonas and in Escherichia coli as well as to be capable of activating the rpoS promoter in E. coli. Our data suggest that PsrA is an important regulatory protein ofPseudomonas spp. involved in the regulatory cascade controlling rpoS gene regulation in response to cell density.

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