GO:0010447 response to acidic pH: Cellular Stress Response, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0010447 response to acidic pH describes any cellular or organismal change triggered by a pH below 7, including altered gene expression, enzyme activity, movement, and secretion.
• Acidic pH is a universal stress signal encountered in tumors, macrophage phagosomes, fermented foods, and soil, making this process central to cancer biology, infection, and microbial ecology.
• Key adaptive mechanisms include two-component systems, phosphate starvation responses, succinoglycan production, and shifts in cytoplasmic pH homeostasis.
• Acidic pH directly modulates receptor function, as shown by reduced glycine receptor efficacy in zebrafish and rat neurons.
• Transcriptomic and fluorescence imaging studies reveal rapid, coordinated gene expression changes within minutes to hours of acid exposure.
• CRISPR knockout, point mutation, knock-in, and overexpression models are essential to dissect causal roles of genes in acidic pH response.
Description
Response to acidic pH (GO:0010447) is a fundamental biological process that enables cells and organisms to sense and adapt to environments where pH falls below 7. This process is critical for survival in diverse niches, from the acidic tumor microenvironment to the phagosomes of macrophages and the fermentation vats of probiotic bacteria. Understanding how cells reprogram their gene expression, metabolism, and physiology under acidic stress has broad implications for cancer therapy, infectious disease, and biotechnology.
response to acidic pH At A Glance
| GO ID | GO:0010447 |
|---|---|
| GO term | response to acidic pH |
| Ontology | biological_process |
| Synonym | response to acidity |
| Definition | Any process that results in a change in state or activity of a cell or an organism as a result of a pH stimulus with pH < 7. |
| Major function | Cellular and organismal adaptation to acidic environments, including gene expression changes, metabolic shifts, and stress tolerance. |
| Related processes | pH homeostasis, acid stress response, two-component signaling, phosphate starvation response. |
| Taxonomic range | Bacteria, archaea, eukaryotes, including human cells. |
| Key examples | RstAB two-component system in E. coli, succinoglycan production in Sinorhizobium meliloti, glycine receptor modulation in neurons. |
What Is GO:0010447?
According to the Gene Ontology, response to acidic pH (GO:0010447) is any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a pH stimulus with pH < 7. pH is a measure of the acidity or basicity of an aqueous solution. This term captures the full spectrum of adaptive and defensive reactions to acidic conditions, from immediate biophysical changes to long-term transcriptional reprogramming.
Why Is response to acidic pH Important in Cell Biology?
Acidic pH is a pervasive environmental and physiological stressor. In cancer, the acidic tumor microenvironment drives invasion, immune evasion, and metabolic reprogramming, making response to acidic pH a central node in oncology. In infectious diseases, pathogens such as adherent-invasive Escherichia coli and Mycobacterium tuberculosis rely on acidic pH response systems to survive within macrophages and establish chronic infection. In neuroscience, acidic pH modulates synaptic receptors, influencing neuronal excitability and signaling. Moreover, industrial and probiotic microorganisms require robust acid tolerance for fermentation and gut survival. Thus, dissecting the molecular players in GO:0010447 is essential for therapeutic development and biotechnological applications.
• Cancer progression: acidic tumor microenvironment selects for aggressive clones and promotes metastasis.
• Host-pathogen interactions: intracellular pathogens sense acidic phagosomal pH to activate virulence programs.
• Neuronal signaling: acidic pH alters ligand-gated ion channel function, affecting synaptic transmission.
• Probiotic and industrial microbiology: acid tolerance determines survival in fermented foods and the gut.
• Soil ecology: rhizobia adapt to acidic soils via exopolysaccharide production.
• Cellular homeostasis: cytoplasmic pH regulation is critical for enzyme activity and cell division.
• Transcriptional reprogramming: rapid and extensive gene expression changes underpin adaptation.
• Drug resistance: acidic pH can reduce drug efficacy, complicating treatment.
• Biomarker discovery: acid-response genes are potential diagnostic and prognostic markers.
• Synthetic biology: engineering acid-responsive circuits for biosensing and therapeutics.
What Happens During response to acidic pH?
Sensing acidic pH
In simple terms: Cells first detect that the environment has become acidic.
Cells sense acidic pH through membrane-bound sensors, two-component systems, and chemoreceptors. For example, the RstAB two-component system in adherent-invasive Escherichia coli is activated by acidic conditions within macrophages, leading to virulence gene expression. In Sinorhizobium meliloti, acidic pH triggers a rapid transcriptomic response, with genes involved in stress response and metabolism upregulated within minutes. Fluorescence ratio imaging has revealed that individual Escherichia coli and Bacillus subtilis cells maintain cytoplasmic pH homeostasis upon acid shock, indicating active sensing and regulation.
Signal transduction and gene expression changes
In simple terms: The sensor signals are relayed to the nucleus or nucleoid, turning genes on or off.
Upon sensing acidic pH, signal transduction cascades activate transcription factors that reprogram gene expression. In Mycobacterium tuberculosis, acidic pH exacerbates the phosphate starvation response, triggering glycerol utilization and metabolic remodeling. Similarly, Lactobacillus plantarum strains with probiotic potential exhibit acid resistance mechanisms that involve changes in gene expression and stress protein production. The time course of the transcriptomic response in Sinorhizobium meliloti 1021 following a shift to acidic pH shows coordinated upregulation of genes for exopolysaccharide synthesis, stress response, and metabolic pathways.
Metabolic and physiological adaptations
In simple terms: Cells change their metabolism and physiology to survive acid stress.
Adaptation to acidic pH often involves metabolic shifts. Sinorhizobium meliloti produces succinoglycan, an exopolysaccharide that contributes to acidic pH tolerance. In Mycobacterium tuberculosis, acidic pH triggers glycerol utilization as a carbon source, linked to the phosphate starvation response. Escherichia coli and Bacillus subtilis regulate cytoplasmic pH through proton pumps and antiporters to maintain internal homeostasis. These physiological changes allow survival and continued growth under acidic conditions.
Acidic pH effects on receptor function and signaling
In simple terms: Acidic pH can directly alter the behavior of receptors and ion channels.
Acidic pH modulates synaptic receptors. In zebrafish α1 and rat α1β recombinant glycine receptors, acidic pH reduces agonist efficacy and responses to synaptic-like glycine applications, indicating direct effects on receptor function. This suggests that acidic pH can fine-tune neuronal signaling independently of gene expression changes. Such direct modulation is an important component of the response to acidic pH in excitable cells.
Long-term tolerance and cross-protection
In simple terms: After initial stress, cells can become more resistant to future acid challenges.
Prolonged exposure to acidic pH can induce tolerance and cross-protection against other stresses. Lactobacillus plantarum strains with probiotic potential show acid resistance that may involve changes in membrane composition and stress protein expression. In Sinorhizobium meliloti, succinoglycan production not only aids in acid tolerance but may also protect against other environmental stresses. The transcriptomic response includes genes for general stress protection, suggesting a coordinated long-term survival strategy.
Key Genes Involved in GO:0010447 response to acidic pH
The following genes and proteins are experimentally validated players in response to acidic pH across model organisms.
| Gene | Major Role | Research Relevance |
|---|---|---|
| rstA | Response regulator of RstAB two-component system in adherent-invasive E. coli | Required for virulence and survival in macrophage phagosomes |
| rstB | Sensor kinase of RstAB two-component system | Senses acidic pH and activates RstA |
| phoB | Phosphate starvation response regulator in Mycobacterium tuberculosis | Links acidic pH to glycerol utilization and metabolic remodeling |
| phoR | Sensor kinase for phosphate starvation response | Activates PhoB under acidic pH |
| exoY | Succinoglycan biosynthesis in Sinorhizobium meliloti | Contributes to acidic pH tolerance |
| exoH | Succinoglycan succinylation | Modifies succinoglycan for acid tolerance |
| atpB | ATP synthase subunit in E. coli and B. subtilis | Involved in cytoplasmic pH homeostasis |
| nhaA | Na+/H+ antiporter in E. coli | Exports protons to maintain cytoplasmic pH |
| glpK | Glycerol kinase in Mycobacterium tuberculosis | Required for glycerol utilization at acidic pH |
| glpD | Glycerol-3-phosphate dehydrogenase | Metabolizes glycerol under acidic conditions |
| gadA | Glutamate decarboxylase in E. coli | Acid resistance via GABA production |
| gadB | Glutamate decarboxylase isozyme | Acid resistance in enteric bacteria |
| clcA | Chloride channel in E. coli | Helps maintain membrane potential under acid stress |
| kdpA | Potassium-transporting ATPase | Potassium uptake for pH homeostasis |
| phoP | Response regulator in M. tuberculosis | Regulates acid-responsive genes |
| phoQ | Sensor kinase in M. tuberculosis | Senses acidic pH and activates PhoP |
| gltB | Glutamate synthase in S. meliloti | Upregulated during acidic pH shift |
| nifH | Nitrogenase in S. meliloti | Expression changes under acidic pH |
How Is response to acidic pH Regulated?
The response to acidic pH is regulated at multiple levels. Two-component systems such as RstAB and PhoPQ sense acidic pH and activate downstream transcription factors. In Sinorhizobium meliloti, the transcriptomic response is temporally regulated, with early induction of stress genes followed by metabolic and exopolysaccharide genes. Cytoplasmic pH homeostasis is maintained by proton pumps and antiporters, which are themselves regulated by pH-sensitive promoters. Additionally, acidic pH can directly modulate receptor activity, as seen with glycine receptors, providing a rapid post-translational regulatory layer.
response to acidic pH and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| rstA | Adherent-invasive E. coli infection | Knockout in E. coli LF82, macrophage infection assay |
| phoB | Tuberculosis latency | Knockout in M. tuberculosis, macrophage and mouse infection |
| exoY | Rhizobial acid tolerance | Knockout in S. meliloti, acid stress growth assay |
| gadA | Enteric acid resistance | Knockout in E. coli, simulated gastric fluid survival |
| GLRA1 | Hyperekplexia and neuronal excitability | Point mutation in zebrafish or rat glycine receptor, electrophysiology |
Cancer and the acidic tumor microenvironment
The acidic tumor microenvironment is a hallmark of solid tumors and drives cancer progression, invasion, and immune evasion. Cancer cells respond to acidic pH by upregulating genes involved in glycolysis, angiogenesis, and metastasis. This response also contributes to resistance to chemotherapy and immunotherapy. Understanding GO:0010447 in cancer cells is therefore critical for developing novel therapeutic strategies that target acid-adaptive pathways.
Infectious diseases and intracellular pathogens
Many pathogens must survive within acidic phagosomes of macrophages. Adherent-invasive Escherichia coli uses the RstAB two-component system to sense acidic pH and promote pathogenicity within macrophages. Mycobacterium tuberculosis responds to acidic pH by exacerbating the phosphate starvation response, leading to glycerol utilization and metabolic adaptation that supports chronic infection. Targeting these acid-response pathways could yield new antimicrobials.
Neurological disorders and receptor modulation
Acidic pH can directly affect neuronal signaling by modulating ligand-gated ion channels. In zebrafish and rat glycine receptors, acidic pH reduces agonist efficacy, which may impact inhibitory neurotransmission. Dysregulation of pH in the brain is associated with epilepsy, ischemia, and neurodegenerative diseases, making acid-sensing mechanisms potential therapeutic targets.
From response to acidic pH-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X confer acid resistance? | Knockout cell line or bacterial strain, acid stress survival assay |
| Does a point mutation in gene X alter acid sensing? | Point mutation knock-in using CRISPR, pH imaging |
| Does overexpression of gene X enhance acid tolerance? | Overexpression cell line, growth and transcriptomics |
| Where is protein X localized under acidic pH? | Tagged knock-in with fluorescent protein, live-cell imaging |
| What is the transcriptional response to acidic pH? | RNA-seq of wild-type and knockout cells after acid shift |
| Does gene X regulate virulence in response to acidic pH? | Knockout in pathogen, macrophage infection model |
How to Study the response to acidic pH Process
| Method | What It Measures | Typical Application |
|---|---|---|
| RNA-seq | Global gene expression changes | Transcriptomic response to acidic pH |
| Fluorescence ratio imaging | Cytoplasmic pH in individual cells | pH homeostasis under acid stress |
| Patch-clamp electrophysiology | Ion channel activity | Receptor modulation by acidic pH |
| Acid stress survival assay | Cell viability at low pH | Gene knockout phenotyping |
| Macrophage infection model | Intracellular survival and virulence | Pathogen acid response |
| CRISPR knockout screening | Gene essentiality under acidic pH | Identify novel acid resistance genes |
| Proteomics | Protein abundance and modifications | Post-transcriptional acid response |
| Metabolomics | Metabolite changes | Metabolic adaptation to acidic pH |
Transcriptomic profiling by RNA-seq
RNA-seq is widely used to capture global gene expression changes during response to acidic pH. For example, the time course of the transcriptomic response of Sinorhizobium meliloti 1021 following a shift to acidic pH was elucidated using RNA-seq, revealing coordinated upregulation of stress and metabolic genes. In Mycobacterium tuberculosis, RNA-seq identified the phosphate starvation response and glycerol utilization genes induced at acidic pH. This method provides a comprehensive view of the regulatory networks activated by acid stress.
Fluorescence ratio imaging for cytoplasmic pH
Fluorescence ratio imaging microscopy allows real-time measurement of cytoplasmic pH in individual cells. Using pH-sensitive fluorescent dyes, researchers observed cytoplasmic pH responses to acid stress in individual Escherichia coli and Bacillus subtilis cells, revealing heterogeneity and homeostatic mechanisms. This technique is essential for linking gene function to physiological pH regulation.
Electrophysiology for receptor modulation
Electrophysiological recordings can directly measure the effect of acidic pH on ion channel function. In zebrafish α1 and rat α1β recombinant glycine receptors, acidic pH reduced agonist efficacy and responses to synaptic-like glycine applications, as demonstrated by patch-clamp recordings. This method is critical for understanding rapid, non-transcriptional effects of acidic pH on neuronal signaling.
Microbial survival and virulence assays
Acid stress survival assays and macrophage infection models are used to test the role of specific genes in response to acidic pH. For instance, knockout of the RstAB two-component system in adherent-invasive Escherichia coli reduced pathogenicity in macrophages, linking acid sensing to virulence. Similarly, succinoglycan production in Sinorhizobium meliloti was shown to contribute to acidic pH tolerance using growth assays. These functional assays validate gene function in relevant biological contexts.
How CRISPR Can Be Used to Study GO:0010447 response to acidic pH
Knockout
CRISPR knockout is used to delete candidate genes and assess their requirement for survival or growth under acidic pH. For example, knocking out the rstA gene in adherent-invasive Escherichia coli abolishes the acid-sensing response and reduces virulence in macrophages. Similarly, knockout of exoY in Sinorhizobium meliloti impairs succinoglycan production and acid tolerance. Knockout models are essential for establishing causality in response to acidic pH.
Point Mutation
CRISPR point mutation introduces specific amino acid substitutions to dissect protein function. For instance, point mutations in glycine receptor subunits can alter sensitivity to acidic pH, as shown in electrophysiological studies of zebrafish and rat receptors. Such models help identify residues critical for pH sensing and signal transduction.
Knock-in
Knock-in of reporter tags or disease-associated alleles allows visualization and functional analysis of proteins under acidic pH. Tagged knock-in of pH-sensitive proteins enables live-cell imaging of localization and dynamics. Knock-in of mutant alleles can model human diseases linked to acid-response genes.
Overexpression
CRISPR activation or cDNA overexpression is used to test whether increased levels of a gene enhance acid tolerance or alter signaling. Overexpression of phoB in Mycobacterium tuberculosis exacerbates the phosphate starvation response and glycerol utilization at acidic pH. Overexpression studies complement knockout approaches to reveal gain-of-function phenotypes.
How EDITGENE Supports response to acidic pH Research
Researchers studying response to acidic pH-related genes often need to determine whether a candidate gene is causally involved in acid sensing, adaptation, or pathology. This requires precise genetic models that can knockout, mutate, tag, or overexpress the gene of interest in relevant cell types. EDITGENE provides end-to-end CRISPR services to accelerate such discoveries.
Contact EDITGENE today to design your custom CRISPR model for response to acidic pH research.
Frequently Asked Questions About response to acidic pH
What is GO:0010447 response to acidic pH?
GO:0010447 is a Gene Ontology biological process term describing any change in a cell or organism as a result of a pH stimulus below 7, including gene expression, movement, and secretion changes.
What genes are involved in response to acidic pH?
Key genes include rstA and rstB in E. coli, phoB and phoR in M. tuberculosis, exoY in S. meliloti, and gadA in Lactobacillus, among others.
How do cells sense acidic pH?
Cells sense acidic pH via two-component systems, membrane receptors, and ion channels that detect proton concentration and trigger signaling cascades.
Why is acidic pH important in cancer?
The acidic tumor microenvironment promotes invasion, immune evasion, and drug resistance, making response to acidic pH a key area in oncology.
How does acidic pH affect neurons?
Acidic pH can reduce the efficacy of glycine receptors, altering inhibitory neurotransmission in the brain and spinal cord.
What methods study response to acidic pH?
Common methods include RNA-seq, fluorescence ratio imaging, patch-clamp electrophysiology, and acid stress survival assays.
Can CRISPR be used to study acid resistance genes?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect gene function in acidic pH response.
What is the role of succinoglycan in acidic pH tolerance?
Succinoglycan production in Sinorhizobium meliloti contributes to acidic pH tolerance, likely by protecting the cell envelope.
How does Mycobacterium tuberculosis respond to acidic pH?
It exacerbates the phosphate starvation response, leading to glycerol utilization and metabolic remodeling for survival in macrophages.
What are the research models for response to acidic pH?
Models include bacterial cultures, macrophage infection systems, neuronal cell lines, and CRISPR-engineered cell lines for gene function studies.
Conclusion
Response to acidic pH (GO:0010447) is a universal biological process with profound implications for cancer, infectious disease, neuroscience, and microbial ecology. The integration of CRISPR-based genetic models with transcriptomics, imaging, and electrophysiology is rapidly advancing our understanding of how cells sense and adapt to acidic environments. EDITGENE provides the tools and expertise to accelerate this research, from knockout and point mutation models to genome-wide screens and bioinformatics.
References
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- 2. Yao T et al.. 2024. Two-component system RstAB promotes the pathogenicity of adherent-invasive Escherichia coli in response to acidic conditions within macrophages.. Gut Microbes 16(1):2356642 PMID: 38769708
- 3. Ivica J et al.. 2022. Acidic pH reduces agonist efficacy and responses to synaptic-like glycine applications in zebrafish α1 and rat α1β recombinant glycine receptors.. J Physiol 600(2):333-347 PMID: 34802146
- 4. Hawkins JP et al.. 2017. Succinoglycan Production Contributes to Acidic pH Tolerance in Sinorhizobium meliloti Rm1021.. Mol Plant Microbe Interact 30(12):1009-1019 PMID: 28871850
- 5. Healy C et al.. 2025. An exacerbated phosphate starvation response triggers Mycobacterium tuberculosis glycerol utilization at acidic pH.. mBio 16(1):e0282524 PMID: 39611843
- 6. Šeme H et al.. 2015. Acid resistance and response to pH-induced stress in two Lactobacillus plantarum strains with probiotic potential.. Benef Microbes 6(3):369-79 PMID: 25380802
- 7. Martinez KA 2nd et al.. 2012. Cytoplasmic pH response to acid stress in individual cells of Escherichia coli and Bacillus subtilis observed by fluorescence ratio imaging microscopy.. Appl Environ Microbiol 78(10):3706-14 PMID: 22427503
- 8. Hellweg C et al.. 2009. The time course of the transcriptomic response of Sinorhizobium meliloti 1021 following a shift to acidic pH.. BMC Microbiol 9:37 PMID: 19216801
