pH is a scale of acidity based on the concentration of hydrogen ions. pH of 7 is considered neutral, below 7 is acidic, and above 7 is basic or alkaline. pH influences the structure of DNA via hydrogen bonds, lipid structure, and production of ATP due to hydrogen ion gradient.

Osmotic pressure is the pressure created across a membrane due to differences in solute concentrations.

Osmotic Pressure

Barometric pressure is also known as the Earth's atmospheric pressure. 

Barometric Pressure

Different organisms require various levels of oxygen for their metabolic processes, including some who are found in completely anaerobic ecosystems where no molecular oxygen is present. 

Environmental Oxygen Requirements for Microbial Growth

Some microbes require light for their metabolic processes and therefore to survive and grow.

Light as a Physical Requirement for Growth

The optimum growth temperature is where a population experiences its highest growth rates. The minimum growth temperature is the lowest temperature at which a population can grow and the maximum growth temperature is the highest. 

Temperature as a Physical Requirement for Growth

- Temperature 
- pH
- Osmotic Pressure
- Barometric Pressure
- Light 
- Oxygen (environmental)

The maximum growth of a microbial population is dependent upon its specific ideal physical and chemical conditions.

Growth Conditions

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Physical Factors Influencing Microbial Growth

Nutritional media is utilized in laboratory settings to facilitate the growth or restraint of certain microbes. Media is essential to support the diverse highly specific nutritional and environmental requirements of various species. 

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