MicrobiologyLesson 3 of 6 in the course Microbial Growth

Microbial pH Growth Ranges, Adaptations, and H. pylori Survival

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Acidity depends on the concentration of hydrogen ions, written as [H+][H^+], and is measured using the pH scale. A pH below 7 is acidic, pH 7 is neutral, and pH above 7 is basic (alkaline). Foods such as yogurt, pickles, and sauerkraut taste tangy partly because they contain acids.

Microbes encounter different pH conditions in soil, water, food, and host tissues. Their ability to grow in a particular environment depends partly on whether they can keep their cellular structures and processes functioning at that pH.

All flashcards

What does pH indicate?
A measure related to hydrogen-ion concentration; below 7 is acidic, 7 is neutral, and above 7 is basic.
How can extreme pH affect proteins?
It can alter amino-acid ionization and disrupt interactions, changing protein folding and potentially impairing activity.
What is an acidophile?
A microorganism that grows optimally at acidic pH, defined here as below pH 5.55.
How does H. pylori improve its local conditions in the stomach?
It produces urease, which breaks down urea and raises the pH near the bacterium.
What does the urea breath test detect?
Labeled carbon dioxide produced when H. pylori urease breaks down labeled urea.

Quiz questions

  1. How can some acidophiles help maintain cellular function at low pH?Answer: They can pump hydrogen ions out of the cell.
  2. How can Bacillus firmus use a sodium-ion gradient?Answer: To power transport and motility.
  3. Why can Helicobacter pylori persist in the acidic stomach despite being a neutrophile?Answer: Urease raises the pH in the bacterium’s immediate surroundings.
  4. What does a positive urea breath test detect in exhaled breath?Answer: Labeled carbon dioxide formed from labeled urea.
  5. Which set of cellular features can be disrupted by extreme pH?Answer: DNA interactions, membrane lipids, and the proton motive force.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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