Photoautotrophs can convert light energy, carbon dioxide, and water, into their metabolic energy. Some examples are cyanobacteria and green sulfur bacteria. 

Photoautotroph

Photoheterotrophs utilize both light and other elements to carry out their metabolic processes and create energy. An example is purple nonsulfur bacteria.

Photoheterotroph

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

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

Physical Factors Influencing Microbial Growth

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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.

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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

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. 

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