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Micro

Microbial Growth

QuestionAnswer
identify bacteria by... what they can grow on, what nutrients/conditions growth occurs, and the characteristic by-products produced
to identify bacteria, organisms MUST be in a... pure culture
sterile completely free of microbes
aseptic technique procedures that minimize unintentional introduction of microorganisms to media (cultures) or from cultures to surrounding environment
colony pile of cells descended from a single cell (is a clump of cells)
petri dish container to which agar is added to obtain a pure culture
agar plate (plate) agar-containing petri dish
microbial growth refers to... an increase in cell number, not in cell size
bacteria grow and divide by... binary fission
psychrophile bacteria that grow at an optimum temperature between -5 C and 15 C, found in North pole, ocean depths (seldom cause food spoilage) (i.e. listeria in hot dogs)
psychrotroph bacteria that grow at an optimum temperature between 20 C and 30 C, but grows well at all temperatures (responsible for most low temperature food spoilage)
mesophile bacteria that grow at an optimum temperature between 25 C and 45 C - optimum temp. commonly 37 C, adapted to live in animals' bodies (most bacteria - most pathogens and common spoilage organisms)
thermophile optimum temperature between 45 C and 70 C or 50 to 60 C (grow in sunlit soil, compost piles, and hot springs), some can form extremely heat resistant endospores
hyperthermophile optimum temperature between 70 C and 110 C, optimum growth at 80 C or higher (i.e. Archaebacteria - most live in volcanic and ocean vents
obligate aerobe requires oxygen (disadvantage... oxygen dissolves poorly in water) (i.e. Pseudomonas - common nosocomial pathogen)
obligate anaerobe cannot multiply in the presence of oxygen and are harmed by the presence of toxic forms of oxygen (Clostridium bacteria - cause tetanus and botulism)
facultative anaerobe grows best if oxygen is present, but can also grow without it (E. coli, Staphylococcus, yeasts, and many intestinal bacteria)
microaerophile requires small amounts of oxygen, but higher concentrations are inhibitory (sensitive to toxic forms of oxygen) (i.e. Campylobacter)
aerotolerant anaerobe (obligate fermenter) indifferent to oxygen, can't use oxygen (can break down toxic forms of oxygen) (i.e. Lactobacillus carries out fermentation regardless of oxygen presence)
neutrophile multiplies in the range of pH 5 to 8 (molds and yeast can grow in a wider range, but prefer pH between 5 and 6) (includes human pathogens)
acidophile grows optimally at a pH below 5.5 (i.e. Lactobacillus produces lactic acid, tolerates mild acidity)
alkalophile grows optimally at a pH above 8.5 (pH of 7 to 12 or higher) (i.e. Vibrio cholerae and Alkaligenes faecalis - pH 9 and the soil bacterium Agrobacterium - pH 12)
extreme or obligate halophiles require very high salt concentrations (20 to 30 %) (bacteria in Dead Sea, brine vats)
halophile requires moderate to large salt concentrations (ocean water contains 3.5 % salt) (most bacteria in oceans)
cold-temperature associated issues in bacteria freezing cells, kills them because of cell lysis (crystal ice punches holes in cell membrane which is bad when thawing), enzymes need low temperature
thermophile adaptations have isoprenes, not phospholipids in membrane, proteins have disulfide bonds (extra) to make it strong, proteins hold DNA together (so it doesn't denature) - proteins = heat shock/chaperone proteins, can be found in hot tubs
acidity inhibits most microbial growth and is used frequently for food preservation (i.e. pickling)
alkalinity inhibits microbial growth, but not commonly used for food preservation
hypertonic solutions high osmotic pressure removes water from the cell, causing shrinkage of cell membrane (plasmolysis) (used to control spoilage and microbial growth - sugar in jelly, salt on meat)
hypotonic solutions low osmotic pressure causes water to enter the cell (most cases, cell wall prevents excessive entry of water) (microbe may lyse or burst if the cell wall is weak) (osmotic lysis)
facultative halophiles do not require high salt concentrations for growth, but tolerate 2% salt or more
chemoheterotrophs obtain carbon from their energy source: lipids, proteins, and carbohydrates
chemoautotrophs and photoautotrophs obtain carbon from carbon dioxide
problems associated with acidity and alkalinity break proteins, denature, destroy membranes, and release contents in humans... bacteria have special proteins and pH pumps to get rid of the acid/base
osmotic pressure solutions bacteria are resistant to osmotic stress because they have cell wall
barophile like extreme pressure and most are obligate
bacteria that live at high radiation levels... have back-up chromosome if one is damaged due to radiation
carbon is the cell makes up 50% of the dry weight and is the structural backbone of all organic compounds
nitrogen in the cell makes up 14% of the dry cell weight and is used to form amino acids, DNA, and RNA
sources of nitrogen protein (most bacteria), ammonium (found in organic matter), nitrogen gas (obtain nitrogen directly from atmosphere - nitrogen fixing bacteria), and nitrates (salts that dissociate to give NO3-)
sulfur in the cell used to form proteins and some vitamins (thiamin and biotin)
sources of sulfur protein (most bacteria), hydrogen sulfide, and sulfates (salts that dissociate to give SO42-)
phosphorus in the cell used to form DNA, RNA, ATP, and phospholipids
sources of phosphorus mainly inorganic phosphate salts and buffers
other elements potassium, magnesium, and calcium (as enzyme cofactors), calcium (cell wall synthesis in Gram positive bacteria)
trace elements used as enzyme cofactors, commonly found in tap water (iron, copper, molybdenum, and zinc)
organisms that use molecular oxygen... produce more energy from nutrients than anaerobes
singlet oxygen extremely reactive form of oxygen, present in phagocytic cells
superoxide free radical (O2-) extremely toxic and reactive form of oxygen. All organisms growing in atmospheric oxygen must produce an enzyme superoxide dismutase (SOD) to get rid of them
SOD enzyme that gets rid of superoxide free radicals and is made by aerobes, facultative anaerobe, and aierotlerant anaerobes, but not anaerobes or microaerophiles
hydrogen peroxide peroxide ion is toxic and the active ingredient of several antimicrobials (i.e. benzoyl peroxide)
2 enzymes that break down hydrogen peroxide catalase (converts to water and oxygen) and peroxidase (converts to water)
requirements of culture medium must be sterile, contain appropriate nutrients, and must be incubate at appropriate temperature
unique properties of agar melts above 95 C, once melted, does not solidify until it reaches 40 C, cannot be degraded by most bacteria, polysaccharide made by red algae, originally used as food thickener
chemically defined media nutrient material whose exact chemical composition is known (not widely used, and expensive
Created by: Nicolekr