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Related Concept Videos

Microbiota of the Stomach and Small Intestine01:27

Microbiota of the Stomach and Small Intestine

The human gastrointestinal (GI) tract is characterized by distinct physicochemical conditions that shape its microbial communities. Among these, the stomach presents a particularly challenging environment for microbial colonization due to its highly acidic pH, ranging from 1 to 3. This extreme acidity effectively limits microbial density. However, certain acid-tolerant microorganisms are capable of surviving in this niche. Notably, Helicobacter pylori can colonize the gastric mucosa,...
Factors Influencing Microbial Growth: pH01:29

Factors Influencing Microbial Growth: pH

Microorganisms are classified as acidophiles, neutrophiles, or alkaliphiles based on their pH growth preferences, reflecting their adaptations to specific environments. Maintaining a stable intracellular pH is critical for macromolecular stability and enzymatic activity, which can be challenged by external pH variations.Neutrophiles, such as Escherichia coli, grow optimally between pH 5.5 and 8.0. These microorganisms inhabit neutral or slightly acidic environments and employ mechanisms like...
Stomach pH Regulation01:21

Stomach pH Regulation

The human body carefully regulates the internal pH of different organs to maintain homeostasis. For example, while the blood plasma maintains a neutral pH of 7, the stomach lumen has an acidic pH of 1.5 - 3.5. The low pH of stomach lumen helps kill pathogens in the food and break down complex food molecules.
The acid-secreting gastric mucosal epithelial cells (parietal cells) lining the stomach lumen maintain the low pH in the lumen. Numerous ion transporters and channels on these parietal...
Acids, Bases and Neutralization Reactions01:27

Acids, Bases and Neutralization Reactions

Acids and bases play several important roles in biology. The pH of a biological system can significantly impact the function of biological molecules, including enzymes, proteins, and nucleic acids. For example, enzymes have optimal pH ranges for their activity, and changes in pH can denature or alter their structure, affecting their function. Acids and bases also play a crucial role in cellular signaling and communication. The pH of the extracellular fluid around cells can influence the...
Acids, Bases and Neutralization Reactions03:26

Acids, Bases and Neutralization Reactions

An acid-base reaction is one in which a hydrogen ion, H+, is transferred from one chemical species to another. Such reactions are of central importance to numerous natural and technological processes, ranging from the chemical transformations within cells or lakes and oceans to the industrial-scale production of fertilizers, pharmaceuticals, and other substances essential to the society.
pH Homeostasis01:31

pH Homeostasis

Acid-base homeostasis is essential for maintaining normal physiological activities in humans. The pH of various body fluids is strictly regulated because it is critical for the optimal activity of enzymes involved in metabolic reactions. Enzymes are basically proteins, so, any significant change in pH can affect their structure and activity. In humans, pH is regulated using three primary mechanisms— chemical buffer systems, respiratory regulation, and renal regulation.
Respiratory Regulation of...

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Updated: May 23, 2026

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo
08:32

Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo

Published on: October 23, 2016

Acidic pH: enemy or ally for enteric bacteria?

Francisco Ramos-Morales1

  • 1Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain. framos@us.es

Virulence
|March 31, 2012
PubMed
Summary
This summary is machine-generated.

Salmonella enterica serovar Typhimurium uses STM1485, an acid shock protein, not for acid survival, but for intracellular replication and virulence. This protein is crucial for pathogen survival within host cells.

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Measuring Phagosome pH by Ratiometric Fluorescence Microscopy
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Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo
08:32

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Published on: October 23, 2016

Measuring Phagosome pH by Ratiometric Fluorescence Microscopy
14:39

Measuring Phagosome pH by Ratiometric Fluorescence Microscopy

Published on: December 7, 2015

Area of Science:

  • Microbiology
  • Pathogen Biology
  • Molecular Biology

Background:

  • Foodborne pathogens like Salmonella face acidic environments in the host stomach and within host cells.
  • Acid survival systems, including acid resistance and tolerance responses, involve acid shock proteins.
  • Low pH acts as a signal, triggering virulence gene expression in bacteria.

Purpose of the Study:

  • To investigate the role of STM1485, a homolog of the acid shock protein Asr, in Salmonella enterica serovar Typhimurium.
  • To determine the function of STM1485 in acid survival and virulence of Salmonella.

Main Methods:

  • Investigated the role of STM1485 in Salmonella enterica serovar Typhimurium.
  • Assessed acid survival and intracellular replication in human epithelial cells and murine macrophages.
  • Evaluated virulence in a mouse model.

Main Results:

  • STM1485 is not essential for Salmonella's acid survival.
  • STM1485 is required for intracellular replication in host cells.
  • STM1485 prevents the degradation of the Salmonella-containing vacuole.
  • STM1485 deficiency leads to reduced virulence in a mouse model.

Conclusions:

  • STM1485 plays a critical role in Salmonella virulence, particularly in intracellular survival and vacuole maintenance.
  • While not involved in direct acid resistance, STM1485 is essential for Salmonella pathogenesis within the host.