Filtration can also be used to remove microbes from liquid samples using
membrane filtration . Membrane filters for liquids function similarly to HEPA filters for air. Typically, membrane filters that are used to remove bacteria have an effective pore size of 0.2 µm, smaller than the average size of a bacterium (1 µm), but filters with smaller pore sizes are available for more specific needs. Membrane filtration is useful for removing bacteria from various types of heat-sensitive solutions used in the laboratory, such as antibiotic solutions and vitamin solutions. Large volumes of culture media may also be filter sterilized rather than autoclaved to protect heat-sensitive components. Often when filtering small volumes,
syringe filter s are used, but
vacuum filter s are typically used for filtering larger volumes (
[link] ).
Membrane filters come in a variety of sizes, depending on the volume of solution being filtered. (a) Larger volumes are filtered in units like these. The solution is drawn through the filter by connecting the unit to a vacuum. (b) Smaller volumes are often filtered using syringe filters, which are units that fit on the end of a syringe. In this case, the solution is pushed through by depressing the syringe’s plunger. (credit a, b: modification of work by Brian Forster)
Would membrane filtration with a 0.2-µm filter likely remove viruses from a solution? Explain.
Name at least two common uses of HEPA filtration in clinical or laboratory settings.
[link] and
[link] summarize the physical methods of control discussed in this section.
Key concepts and summary
Heat is a widely used and highly effective method for controlling microbial growth.
Dry-heat sterilization protocols are used commonly in aseptic techniques in the laboratory. However,
moist-heat sterilization is typically the more effective protocol because it penetrates cells better than dry heat does.
Pasteurization is used to kill pathogens and reduce the number of microbes that cause food spoilage.
High-temperature, short-time pasteurization is commonly used to pasteurize milk that will be refrigerated;
ultra-high temperature pasteurization can be used to pasteurize milk for long-term storage without refrigeration.
Refrigeration slows microbial growth; freezing stops growth, killing some organisms. Laboratory and medical specimens may be frozen on dry ice or at ultra-low temperatures for storage and transport.
High-pressure processing can be used to kill microbes in food. Hyperbaric oxygen therapy to increase oxygen saturation has also been used to treat certain infections.
Desiccation has long been used to preserve foods and is accelerated through the addition of salt or sugar, which decrease water activity in foods.
Lyophilization combines cold exposure and desiccation for the long-term storage of foods and laboratory materials, but microbes remain and can be rehydrated.
Ionizing radiation , including gamma irradiation, is an effective way to sterilize heat-sensitive and packaged materials.
Nonionizing radiation , like ultraviolet light, is unable to penetrate surfaces but is useful for surface sterilization.
HEPA filtration is commonly used in hospital ventilation systems and biological safety cabinets in laboratories to prevent transmission of airborne microbes.
Membrane filtration is commonly used to remove bacteria from heat-sensitive solutions.
Fill in the blank
In an autoclave, the application of pressure to ________ is increased to allow the steam to achieve temperatures above the boiling point of water.
The lymphatic system plays several crucial roles in the human body, functioning as a key component of the immune system and contributing to the maintenance of fluid balance. Its main functions include:
1. Immune Response: The lymphatic system produces and transports lymphocytes, which are a type of
asegid
to transport fluids fats proteins and lymphocytes to the blood stream as lymph
Anatomy is the study of the structure of the body, while physiology is the study of the function of the body. Anatomy looks at the body's organs and systems, while physiology looks at how those organs and systems work together to keep the body functioning.
Enzymes are proteins that help speed up chemical reactions in our bodies. Enzymes are essential for digestion, liver function and much more. Too much or too little of a certain enzyme can cause health problems
Kamara
yes
Prince
how does the stomach protect itself from the damaging effects of HCl
the normal temperature is 37°c or 98.6 °Fahrenheit is important for maintaining the homeostasis in the body
the body regular this temperature through the process called thermoregulation which involves brain skin muscle and other organ working together to maintain stable internal temperature
