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Classification of Microorganisms
- 1. Nutritional
- 2. Temperature
- 3. Gas (O2)
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Autotrophs
- 1. Photoautotroph- photosynthesize
- 2. Chemoautotroph- oxidize chemical compounds
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Photoautotrophs
- microbes that photosynthesize (derive energy from light and transform it into chemical energy that could be used in cell metabolism)
- ex: Green sulfur bacteria, cyanobacteria
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Chemotrophs
- microbes that oxidize chemical compounds
- neither sunlight nor organic nutrients
- oxidize inorganic compounds such as hydrogen gas, Hydrogen sulfide, iron, sulfur to obtain the necessary energy to produce their own organic compounds)
- ex: 1. Methanogens 2. vent bacteria
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Chemoheterotroph
- derive both carbon and energy from organic compound (aerobic respiration)
- ex: 1. Saprobes 2. Parasites
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Temperature requirements (Optimal)
Optimal- the small intermediate between the minimum and maximum which promotes the fastest rate of growth and metabolism
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Psychrophiles
- optimum temp of 15oC, it is an obligate in respect to the cold and cannot grow above 20oC
- -20o to 15o C
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Mesophiles
- gtow at intermediate temperatures (include most pathogens)
- 10o to 50o C
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Thermophiles
- grow at temperatures higher than 45oC
- 45o to 80o C
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Facilitative Psychrophiles
- grow slowly at a lower temperature, but have an optimum temp above 20o C
- concern- they can grow in refrigerated food and cause food borne illness
- ex: 1. Staphylococcus aureus 2. Listeria monocytogenes
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Thermoduric microorganisms
- can survice short exposure to high temperatures, but are normally mesophiles
- can be contaminants of heated and pasteurized foods
- ex: 1. Bacillus 2. Clostridium
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Clostridium botulism
- spore forming anaerobe that commonly inhabits soil and water and occasionally, the intestianal tract of animals
- factors in food processing that lead to botulism dependent on several factors
- concern-- spores present on vegetables or meat at the time of gathering and are difficult to remove by washing alone
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1. Obligate aerobe
2. Obligate anaerobe
3. Facultative anaerobe
4. Aerotolerant anaerobe
5. Microaerophiles
6. Capnophiles
- 1. Obligate aerobe- requires O2
- 2. Obligate anaerobe- O2 kills them
- 3. Facultative anaerobe- can grow with or without O2
- 4. Aerotolerant anaerobe- resists O2
- 5. Microaerophiles- 4-6% O2
- 6. Capnophiles- 3-10% O2
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Defenses against oxygen
- build up of singlet oxygen and the oxidation of membrane lipids and other molecules can damage and destroy a cell
- Superoxide ion, peroxide, and hydroxyl radicals are other metabolic by products of oxygen
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Anaerobic Infections in large intestine
- during abdominal surgery
- traumatic injuries to include gas gangrene and tetanus
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Anaerobe infections (Clostridium tetani)
- in soil and gastrointestinal tracts of animals
- spores usually enter body through accidental puncture wounds, burns, the umbilicus, frostbite, and crushed body parts
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Growing anaerobes
requires special media, methods of incubation, and handling chambers that exclude oxygen
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Clostrium
- produces toxins that kill surrounding tissues, providing the bacterium with more nutrients and increasing the size of the anaerobic environment necessary for Clostrium to grow
- pain, gas gangrene (blackening of the infect muscle, skin and production of bubbles that may break out with a frothy brownish fluid)
- shock, kidney failure, and death can follow often withing a week of infection
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Capnophiles
- 1. Neisseria
- 2. Brucella
- 3. Streptococcus pneumoniae
- (3-10% CO2 incubation)
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Microaerophiles
- 1. soil
- 2. water or
- 3. human body
- (small amounts of O2) (not exposed to the atmosphere)
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Aerotolerant anaerobes
- not harmed by O2--> alternative mechanisms for breaking down peroxidde and superoxide
- ex: 1. Lactobacilli 2. Streptococci
- use manganese ions or peroxidases to do this
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Metabolism of Microbes
- 1. Anabolism
- 2. Carabolism
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Anabolism
- building complex organic molecules from simpler ones

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Catabolism
breakdown of complex organic molecules into simpler ones
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Enzymes
- protein compounds
- catalysts (speed up chemical reactions)
- only lower energy of activation (do not create reactions)
- substrate specific
- coded by a specific gene
- affected by pH and temperature
- shape determines function
- provide active sites for substrates
- many enzymes need cofactors or coenzymes to work effectively
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Cofactor and Coenzymes
- cofactors- inorganic ions (Mg, Fe)
- many enzymes need cofactors to work effectively
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Inhibition
- EA ( enzyme active site) can be blocked by the presence of inhibitors
- drug affecting inhibitors (Sulfa drugs):
- kill bacteria by working as competitive inhibitors of EA in the synthesis of folic acid from para-amino-benzoic acid (PABA)
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Competitive inhibition
substance resembles normal substrate competes w/substrate for active site
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Feedback Inhibition
- concentration of product at the end of a pathway blocks the action of a key enzyme

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Enzyme repression
- stop further synthesis of an enzyme somewhere along its pathway
- any process where it keeps an enzyme to be made
- as the level of the end product of a pathway has been built to excess, the genetic apparatus responsible for replacing these enzymes is automatically repressed
 
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Enzyme Induction
- Process that allow the enzyme to be made
- enzymes appear when suitable substrates are present
- induced by a substrate (a carbohydrate-note lactose)
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Cellular Respiration (Glycolysis)
Glycolysis occurs in the CYTOPLASM both prokaryotes and eukaryotes
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Cellular Respiration (Krebs Cycle)
- Krebs Cycle- cytoplasm of prokaryotes
- mitochondria of eukaryotes
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Cellular Respiration (Electron Transport Chain ETC)
- ETC- cell membrane of prokaryotes
- mitochondrial membrane of eukaryotes
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Energy Strategies in microorganisms
- 1. Aerobic respiration
- 2. Anarobic respiration
- 3. Fermentation
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1. Aerobic Respiration
- 3 main cathabolic pathways:
- 1. Glycolysis, 2. KC 3. ETC
- uses O2 as the main electron acceptor at the end of the ETC
- main energy pathway of strict aerobes and facilitative anaerobes
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Differences in ETC
the lack of cytochromes, catalase, and peroxidases in anaerobes may limit their ability to process free oxygen and contributes to its toxic effect on them
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2. Anaerobic respiration
- in organisms that can utilize and O2 containing salt as the final electron acceptor in the ETC
- ex: nitrate, nitrite, sulfates, or carbonates)
- used by:
- 1. Strict Anaerobess
- 2. Facultative Anaerobes
- 3. Microaerophiles
- 4. Aerotolerant anaerobes
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3. Fermentation
- incomplete oxidation of glucose and other carbohydrates (limited ATP production)
- main products of fermentation:
- 1. Ethanol (alcoholic fermentation)
- 2. Organic acids ( mixed acidic fermentation) lactic, propionic, butyric, formic, acetic acids
- Anaerobic fermentation:
- 1. Souring milk (Streptococcus, Lactobacillus)
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