Organisms that utilize light for growth and energy require the light intensity to be high at the wavelengths that their specific pigments absorb. The PAR is the range of wavelengths in the electromagnetic spectrum that these organisms can absorb. 

Photosynthetically Active Radiation (PAR)

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

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

Light as a Physical Requirement for Growth

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

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

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