Control of Microbial Growth

minna baraili
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I Turner
Created by I Turner over 5 years ago
minna baraili
Copied by minna baraili 2 months ago


Part of AQA GCSE Science on Enzymes and Respration

Resource summary

Control of Microbial Growth
1 Mechanical Methods
1.1 Filtration
1.1.1 HEPA High - efficiency particulate air use for air in ventilation system Lower the microbes Burn units Laminar flow hood in the laboratory
1.1.2 Millipore filter Pass fluid through filter with the small pore. physical separation of bacterial from liquid Sterilize hear sensitives substance such as antibiotics, serum, hormones
1.2 Scrubbing
1.2.1 Washing hands with soap and water
1.2.2 physically washing microbes in skin
1.2.3 Sanitizing
2 Physical Methods
2.1 Radiation
2.1.1 Ionizing Radiation water becomes ionized & form reactive hydroxyl radicals Damage DNA X-rays, gamma rays Very penetrating pass via plastic, glass and packaging Sterilize
2.1.2 nonionizing radiation Ultraviolet light Not as penetrating need direct contact Wavelength of 40 - 390nm
2.2 Temperature
2.2.1 Heat Moist Heat Boiling water Kills most non-spore forming pathogens Does not kill endospore Pasteurization A mild heating method Used by Pasteur to kill organisms that caused wine to sour Destroys disease causing organisms but not endospores Batch Methods 63° C for 30 min Flash Methods Rapid cooling Does not alter nutrition value Lowers bacterial counts UHT Ultra high- temperature treatments 134°C for 1-2 sec Allow storage of milk without refrigeration Sterilized Autoclaving Kills all microorganisms and endospores 121°C 20 min most practiical method Used for culture media, surgical equipments, rubber goods Dry heat Flaming 1870°C Used inthe lab for loops, test tubes Incineration 800°C to 6500°C Good for things that have no futher use Best method of disposal Hot -air sterilization in ovens Sterilizes Used on dry materials, oily substances Bulky items require longer times 150-180°C for 24 hrs
2.2.2 Low Temperature Cold 5°C Bacteriostatic Slow down enzyme action Freezing -10°C Bacteriostic, usually not bacteriocidal Can rupture cells by expandingg water Prevent spoilage for longer time
2.3 Dessication
2.3.1 Not effective endospores
2.3.2 Cell remain viable and begain to grow when water is present
2.3.3 lack of water prevents enzyme from working
2.4 Osmotic Presure
2.4.1 Plasmolysis Cause water to leave cell
2.4.2 Hypertinic solution Concentrated salt or sugar solution
2.4.3 inhibits bacterial growtth
3 Chemical Methods
3.1 Phenols and Phenolics
3.1.1 First used by Lister Sprayed in
3.1.2 Disrupts plasma membrane
3.1.3 Denatures protein
3.1.4 Inactives enzymes
3.1.5 Triclosan a bisphenol in antibecterial soaps slowly remove Broad-spectrum activity and effective against fungi
3.1.6 Chlorhexidine Chlorine and two phenol rings An antiseptic used in hospitals Not sporicidal
3.2 Alcohols
3.2.1 effective by wiping off dirt and microbes of off sking
3.2.2 Antiseptic
3.2.3 Ethanol 70% most effective and isopropanol rubbing alcohol
3.2.4 Not effective against endospore
3.2.5 dissolves membrane lipids
3.3 Heavy Metals
3.3.1 Bscteriostatic or bactericidal depending on concentration
3.3.2 Does not kill endospore
3.3.3 Mercury Thimerosol- antiseptic
3.3.4 Silver Silver nitrate put into newborns eyes to protect from gonorrhea Used in dressing and burn creams
3.3.5 Arsenic
3.3.6 Copper Copper sulfate used to kill algae in water
3.3.7 Selenium kill fungi Used to treat skin fungal infection
3.4 Surfactants
3.4.1 Disrupt the cell membrane
3.4.2 reduce the surface tension of water
3.4.3 Detergents and soaps
3.5 Peroxygens
3.5.1 Hydrogen peroxide Poor antiseptic for open wounds Broken down by catalase to water and oxygen Used with acidic solutions to steriliz delicate
3.5.2 Ozone o3 reactive form of oxygen Produce by passing oxygen via electrical discharges Used to disinfect the air, water, industrial air conditioners, and cooling tower
3.5.3 Disinfectant
3.5.4 Mild antiseptic
3.6 Halogens
3.6.1 Chlorine Active ingredient in bleach can sterilize Disinfects water
3.6.2 Iodine Antiseptic Iodophor mixed with organic molecule for slow release cleanse wounds or prep surgery Betadine dissolve in alcohol
3.7 Aldehydes
3.7.1 Gluteraldehyde Kills vegetative cellss and endospore in 3hrs Good sterilant for heat-sensitive medical equipment cross-linking with microbial protein
3.7.2 Formaldehyde Inactive viruses and toxins Found in embalming fluid Carcinogen
3.8 Alkylating Reagents
3.8.1 Denaturing proteins
3.8.2 Ethylene Oxide Very flammable is mixed with CO2 to reduce fire and explosions Kills bacteria, endospores, virus, and mold Sterilizes Gas at room temperature
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