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Micro
Microbial Growth
| Question | Answer |
|---|---|
| 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
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