Draft:Optimum pH levels of Microorganisms Growth

• Comment: There is a list of references, but footnotes are needed to show what reference supports which statement. For books we also need page numbers. Graeme Bartlett (talk) 22:44, 17 December 2023 (UTC)

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Type of microorganisms based on pH

Acidophiles: These microorganisms thrive in acidic environments where the pH is below 6. They are often found in environments like sulfuric hot springs, acidic mines, or areas where volcanic activity is present. Examples include certain types of bacteria, like Acidithiobacillus ferrooxidans, and some archaea, like Sulfolobus.

Neutrophiles: These are the most common type of microorganisms. Neutrophiles prefer a neutral pH environment, typically around pH 6 to 8. This category includes a wide range of bacteria and fungi that are commonly found in soil, water, and living organisms. Examples include Escherichia coli and Staphylococcus.

Alkaliphiles: These microorganisms thrive in basic or alkaline conditions where the pH is above 9. Alkaliphiles are often found in soda lakes, high-carbonate soils, and other alkaline environments. Examples include certain species of the Bacillus genus and some archaea like Natronomonas.

Halophiles: While not classified based on pH, halophiles are worth mentioning as they thrive in high salt concentrations, which can affect pH. They are often found in salt pans, brine pools, and salted foods. Halophiles can be acidophilic, neutrophilic, or alkaliphilic.

Pharmacopoeia guidelines often mention the optimal pH levels for the growth of various bacterial and fungal organisms, especially in the context of pharmaceutical manufacturing and quality control. These pH levels are crucial for ensuring the correct growth conditions for microbial cultures used in testing and for preventing the growth of contaminating organisms. Here's a detailed look at the optimum pH levels for some common organisms mentioned in pharmacopoeia guidelines:

Escherichia coli:

Optimum pH: Typically around 6.0 to 7.5. Context: E. coli is often used in the pharmacopoeia for sterility testing and as an indicator organism for testing antibiotics.

Lactobacillus species:

Optimum pH: Generally between 5.5 and 6.2. Context: Lactobacillus species are used in probiotic preparations and are also important for testing certain types of antibiotics.

Bacillus alcalophilus:

Optimum pH: Around 9.0 to 10.5. Context: Alkaliphilic Bacillus species are less commonly mentioned in pharmacopoeia but may be relevant in environmental monitoring and in the manufacturing of certain pharmaceuticals.

Aspergillus niger:

Optimum pH: About 5.5 to 6.5. Context: A. niger is used in pharmacopoeia for fungal contamination testing and in the production of certain enzymes and antibiotics.

Rhodotorula glutinis:

Optimum pH: Approximately 5.0 to 6.5. Context: This yeast-like fungus may be mentioned in pharmacopoeial guidelines concerning the production of certain pharmaceuticals and quality control processes.

Sodiomyces alkalinus (or similar alkaliphilic fungi):

Optimum pH: Typically above 9.0. Context: While not commonly mentioned in pharmacopoeia, alkaliphilic fungi can be important in specific industrial pharmaceutical processes.

Helicobacter pylori: Known for causing stomach ulcers, it can survive in the highly acidic environment of the stomach, with an optimal pH of around 4.0 to 6.0.

Bacillus subtilis: Common in soil, this bacterium prefers a pH range of 6.0 to 7.5.

Pseudomonas aeruginosa: This opportunistic pathogen is adaptable but generally prefers a neutral to slightly alkaline pH, around 7.0 to 7.5.

Saccharomyces cerevisiae (Baker's yeast): Widely used in baking and brewing, it prefers a slightly acidic environment, with an optimum pH of around 4.0 to 6.0.

Aspergillus niger: Used in industrial enzyme production, it thrives best at a slightly acidic pH, typically around 5.5 to 6.5.

Candida albicans (Fungus): Used for fungal contamination and antimicrobial testing. Optimum pH: Slightly acidic to neutral, approximately 5.5 to 7.0. Widely mentioned in pharmacopoeias for fungal growth media.

Penicillium chrysogenum: Known for producing the antibiotic penicillin, it prefers a slightly acidic to neutral pH, around 5.0 to 7.0.

Trichophyton rubrum: A fungus causing athlete's foot, it grows well at slightly alkaline pH levels, usually between 7.0 and 8.0.

Staphylococcus aureus: Typically grows best at a pH range of 7.0 to 7.5. It's a common Gram-positive bacterium referenced in pharmacopoeia for sterility testing.

Clostridium sporogenes (Bacteria): Used in anaerobic testing and as a biological indicator. Optimum pH: Neutral to slightly alkaline, around 6.8 to 7.5. Referenced in pharmacopoeias for culture under anaerobic conditions.

Penicillium notatum (Fungus): Known for its role in antibiotic production; used in contamination testing. Optimum pH: Slightly acidic, typically around 5.0 to 6.0. Included in pharmacopoeial methods for testing environmental fungal contamination.

Salmonella Species: Salmonella is a genus of bacteria that includes many pathogens responsible for foodborne illnesses. The optimum pH for the growth of most Salmonella species is generally between pH 6.5 and 7.5.

Shigella Species: Shigella species are known for causing dysentery and have similar environmental requirements as E. coli, as they are closely related. The optimum pH for Shigella species is usually between pH 7.0 and 7.5.

Burkholderia Species: Burkholderia encompasses a variety of species, some of which are pathogenic, while others are environmentally important. The optimum pH range for Burkholderia species varies but generally falls between pH 6.0 and 7.5.

For all these microbial species, their sensitivity or resistance to extreme pH conditions like those created by strong acids and bases varies depending on the strain, the environmental context, and their ability to adapt or form protective structures (such as spores) that enable survival in harsh conditions. In the context of pharmaceutical testing following USP guidelines, extreme pH levels are used to inhibit the growth of potential contaminants as part of quality control measures.

In laboratory and clinical settings, maintaining the optimal pH is crucial for the accurate cultivation and identification of these bacteria. The pH not only influences their growth rate but also affects the expression of certain genes and metabolic pathways, which can be important for studies related to pathogenicity, antibiotic resistance, and environmental adaptations. For pharmaceutical testing, particularly in the context of sterility testing and antimicrobial effectiveness testing, the right pH ensures the reliability of the results.

References

Clinical Microbiology Procedures Handbook: Authors: Amy L. Leber

Manual of Clinical Microbiology: Editors: James H. Jorgensen, Michael A. Pfaller, Karen C. Carroll, Guido Funke, Marie Louise Landry, Sandra S. Richter, David W. Warnock

Prescott's Microbiology: Authors: Joanne Willey, Linda Sherwood, Christopher J. Woolverton

Microbiology: An Introduction: Authors: Gerard J. Tortora, Berdell R. Funke, Christine L. Case

The Prokaryotes: A Handbook on the Biology of Bacteria: Editors: Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer, Erko Stackebrandt

Atlas of Clinical Fungi: Authors: G.S. de Hoog, J. Guarro, J. Gené, M.J. Figueras

Practical Handbook of Microbiology: Editors: Emanuel Goldman, Lorrence H. Green

"Microbiology and Sterility Assurance in Pharmaceuticals and Medical Devices": Authors: Madhu Raju Saghee, Tim Sandle, and Edward C. Tidswell. This book is a comprehensive guide on various aspects of microbiology and sterility in the pharmaceutical industry.

"Pharmaceutical Microbiology: Essentials for Quality Assurance and Quality Control": Author: Tim Sandle. A well-known figure in the field, Tim Sandle provides extensive insights into pharmaceutical microbiology, covering quality assurance and quality control.

"Clinical Microbiology Procedures Handbook": Editor: Amy L. Leber. This handbook is a collection of procedures and techniques used in clinical microbiology, compiled under the editorship of Amy L. Leber.

"Handbook of Media for Clinical and Public Health Microbiology": Authors: Ronald M. Atlas and James W. Snyder. This handbook is a valuable resource for information on media used for cultivating bacteria and fungi in both clinical and public health microbiology.

"Brock Biology of Microorganisms" by Madigan, Martinko, Bender, Buckley, Stahl, and Brock. This textbook provides comprehensive information on the biology of microorganisms, including their environmental preferences.

"Microbiology: An Introduction" by Tortora, Funke, and Case.

"Fungi: Biology and Applications" by Kevin Kavanagh.

"The Physiology and Biochemistry of Prokaryotes" by David White, James Drummond, and Clay Fuqua.