Microbiology notes week of Oct 10
Microbiology notes week of Oct 10 MICR 3050
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This 22 page Class Notes was uploaded by Madeline Notetaker on Wednesday October 12, 2016. The Class Notes belongs to MICR 3050 at Clemson University taught by Dr. Rudolph in Fall 2016. Since its upload, it has received 3 views.
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Date Created: 10/12/16
Microbial Growth in Natural Environments • microbial • microbial growth depends environments on – are complex – Nutrient supply – constantly changing – tolerance of environment – often contain low – inhibitory substances (ex: nutrient herbicides, toxins) concentrations (oligotrophic • most microbes grow environment) attached to surfaces as biofilms – Change behavior when they 1 are in a biofilm Biofilm Formation • microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA to form the extracellular polymeric substance (EPS) Single species rare in are nature- usually lots of species- yellow and purple 2 • Heterogeneous community Biofilms – metabolic differences – location • provide protection • microbial interactions – metabolic exchange – DNA uptake – Quorum sensing • Communication • density dependent! Have to have enough • Ex: streptococcus pneumonae – Produce protein that goes out of biofilm, get to high concentrations that causes cells to become competent (can take up DNA) and triggers them to start producing antibiotic to kill other bacteria in biofilm and take their DNA • Ex: vibrio ficherie – In fish and squid light organs, glowing may protect them from predators, bacteria in high enough numbers produces protein that is released, so much released that gradient is reversed, turning on genes for 43 bioluminescence Problems Associated with Biofilms • Medical – form on medical devices – Immune system and antibiotics cant get rid of it – cause disease • dental caries • Pneumonia • Industrial – interfere with fluids distribution- pipes – Corrosion potential 4 • Like on boats, rusting, oil Chapter 8.1, 8.3 – 8.4, 8.6 Control of Microorganisms in the Environment 1 Microbial Control Methods 2 Frequently Used Terms • sterilization – destruction or removal of all viable organisms • disinfection – killing, inhibition, or removal of pathogenic organisms – disinfectants • agents, usually chemical, used for disinfection • usually used on inanimate objects 3 • sanitization – reduction of microbial population to levels deemed safe (based on public health standards) • antisepsis – prevention of infection of living tissue – antiseptics • chemical agents that kill or inhibit growth of microorganisms when applied to tissue • chemotherapy – use of chemicals to kill or inhibit growth of microorganisms within host tissue 4 Antimicrobial Agents -cide – suffix indicating that agent kills – germicide • kills pathogens and many nonpathogens but not necessarily endospores • bactericides, fungicides, algicides, and viricides -static – suffix indicating that agent inhibits growth • bacteriostatic and fungistatic 5 Conditions Influencing the Effectiveness of an Antimicrobial Agent • population size • population composition • concentration or intensity of the agent • duration of exposure • temperature • local environment 6 Filtration (Mechanical Removal) • reduces microbial population or sterilizes solutions that are heat-sensitive – membrane filters with defined pore size • also used for air – surgical masks – cotton plugs on culture vessels – high-efficiency particulate air HEPA-filter – laminar flow biological safety cabinets 7 Physical Methods to Control Microbes 1. Heat moist and dry 2. Low temperature 3. Radiation 8 Moist Heat • destroys bacteria, fungi, and viruses • degrades nucleic acids, denatures proteins, and disrupts membranes • 3 types: – boiling • will not destroy endospores, so does NOT necessarily sterilize – Autoclaving • If done appropriately, can sterilize – Pasteurization 9 • A type of disinfection 10 Autoclave Effective against all types of microbes (sterilization) Pressure = 15 psi Temp. = 121 degress C (steam) Time = 15 to 20 min Validation process – autoclave, incubate, 11observe for growth of Pasteurization • controlled heating at temperatures well below boiling – used for wine, milk, and other beverages • kills pathogens present and slows spoilage – reduces the total load of organisms present • process does not sterilize 13 Dry Heat Sterilization • less effective than moist heat sterilization – requires higher temperatures and longer exposure times – items subjected to 160–170 C for 2 to 3 hours • oxidizes cell constituents and denatures proteins 14 Dry Heat Incineration 15 Low Temperatures §Freezing – stops microbial reproduction due to lack of liquid water – some microorganisms killed by ice crystal disruption of cell membranes §Refrigeration – Slows microbial growth and reproduction 16 Ultraviolet (UV) Radiation • most bactericidal wavelength is 260 nm • causes thymine dimers in DNA • limited to surface sterilization – does not penetrate glass, plastic, dirt films, etc. 17 Ionizing Radiation • agent that penetrates deep into objects • cold sterilization – antibiotics – medical supplies – Food 18
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