The Chamberland filter, designed by Charles Chamberland and Louis Pasteur in 1884, is a porcelain filtration device with a pore size of $${}0.1\text{ }\mu\text{m}$$. This pore size is small enough to remove all bacteria greater than or equal to $${}0.2\text{ }\mu\text{m}$$ from any liquids passed through the device. In early virology, its small pore size allowed viruses to pass through, leading to the discovery of the tobacco mosaic virus (TMV). Today, these porcelain filters have been replaced by membrane filters and other devices for virus isolation and identification.

Chamberland Filter

Membrane filters and other modern devices are used to isolate and identify viruses by separating them from host cells. While a larger pore size, such as $${}5\text{ }\mu\text{m}$$, blocks only the largest particles, a filter pore size of $${}200\text{ nm}$$ ($${}0.2\text{ }\mu\text{m}$$) physically removes larger microbes like bacteria, allowing the smaller virions to pass through and be collected in the filtrate.

Membrane Filter

Filtration involves physically separating microbes from samples. Air is commonly filtered through high-efficiency particulate air (HEPA) filters that can be found in vacuum cleaners, air-conditioning systems, and air purifiers.

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We can use physical methods of microbial control to preserve our food by manipulating the physical environment to inhibit or prevent microbial growth.
Common control methods include:
- moisture control
- radiation
- filtration
- temperature control

Many of these methods kill cells by disrupting membranes, changing their permeability, or denaturing proteins.

Physical Ways to Control 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.

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.

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Dehydration is used to preserve foods like jerky or seaweed. It works by stripping the cell of water, preventing it from carrying out its metobolic processes. Drying controls microbial growth, however it does not kill all organisms or endospores, which can start to regrow when the water content is restored.

Desiccation

Ionizing radiation and nonionizing radiation can be used to control microbial growth.

Radiation

Exposing microbes to either extreme heat or extreme cold is a very effective method of microbial control. Temperature control methods include 
- Sterilization
- Pasteurization
- Refrigeration
- Freezing

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