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93 Cards in this Set
- Front
- Back
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What is a colony?
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A visible mass of microbial cells arising from one cell or from a group of the same microbes.
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What are the groups of microbes classified on the basis of preferred temperature range?
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Psychrophiles
Mesophiles Thermophiles Hyperthermophiles Psychotrophs |
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What is a psychrophile?
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-A cold-loving microbe
-Temperature range of -10-20°C -Optimum growth around 15°C |
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How does temperature affect growth of microbes?
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-Most bacteria grow only within a limited range of temperatures and grow poorly at the high and low temperature extremes in their range.
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What is the estimated difference of degrees between the maximum and minimum growth temperatures of bacteria?
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30°C
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What is a mesophile?
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A moderate-temperature loving microbes
Temperature range 10-50°C Optimum temperature range of 25-40°C |
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What is a thermophile?
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Heat loving microbes
-Temp range of 40-70°C Optimum temp 50-60°C |
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What is a psychrotroph?
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psychrophile hat can withstand slightly warmer temps and know as food spoilers
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What are hyperthermophiles?
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Extreme thermophiles-archaea that have an optimum growth temp of 80°C or higher
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What is nitrogen fixation?
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the process of an organism using gaseous nitrogen directly from the atmosphere
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What is plasmolysis?
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The shrinkage of the cell's cytoplasm caused by osmotic loss of water
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How do obligate and facultative halophiles differ?
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Obligate halophiles require high salt concentrations to survive. Facultaive halophiles don't require high salt concentrations but are still able to grow in high salt concentrations
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Other than it properties as a buffer, what is the advantage of using phosphate salts as buffers in growth media?
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Phosphate is non-toxic and can be used as an essential nutrient.
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Approximately what percentage of the dry weight is carbon in the typical bacterial cell?
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50%
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Approximately what percentage of the dry weight is nitrogen in the typical bacterial cell?
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Nitrogen 14%
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Approximately what percentage of the dry weight are sulfur and phosphorus in the typical bacterial cell?
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4% combined
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What is an aerobe?
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Microbe requiring molecular oxygen for growth
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What is an anaerobe?
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Microbe that does not require molecular oxygen for growth.
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What is a facultative anaerobe?
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aerobic bacteria that have developed or retained the ability to continue growing in the absence of oxygen; however their efficiency in producing energy decreases
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What is an obligate anaerobe?
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bacteria that is unable to use molecular oxygen for energy-yeilding reactions and may even be harmed by it.
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What is superoxide dismutase (SOD)?
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An enzyme that destroys superoxide by nuetralizing it.
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What is an aerotolerant anaerobe?
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microbe that cannot use oxygen for growth, but can tolerate it.
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What are microaerophiles?
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Microbes that are aerobic, however they grow only in oxygen concentrations lower than those in the air
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What are organic growth factors?
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Essential organic compounds an organism is unable to synthesize and must be obtained from the enviroment.
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What is a biofilm?
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a microbial community that usually forms a slimy layer on a surface
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What is the matrix (slime) that biofilm reside in, primarily made of?
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Polysaccharides, but also contains DNA and proteins
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What is a hydrogel?
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A complex polymer containing many times its dry weight in water
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What is quorum sensing?
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cell-to-cell communication
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What is it that allows bacteria to coordinate their activity and group together into communities that provide benefits not unlike those of multicellular organisms?
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quorum sensing
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How is it advantagious for microbes to live in biofilms?
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microbes can share nutrients, are sheltered from harmful factors in the environment, such as desiccation, antibiotics and the body's immune system. In addition, they may be able to transfer genetic information by conjugation.
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What is a colony?
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a visible mass of microbial cells arising from one cell or from a group of the same microbe
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Describe the deep-freezing process.
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a pure culture of microbes is placed in a suspending liquid and quick-frozen at temperatures ranging from -54°C to -95°C. The culture can later be thawed and cultured even years later.
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Describe lyophilization (freeze-drying).
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a suspension of microbes is quickly frozen at temperatures ranging -54° C to -72°C, and the water is removed by a high vacuum (sublimation).
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How is growth defined when discussing bacteria?
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an increase in bacterial numbers, not an increase in the size of the individual cell.
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Describe budding.
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bacteria can reproduce by forming a small initial outgrowth (a bud) that enlarges until its size approaches that of the parent cell, and then it seperates.
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Define generation time
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the time required for a cell to divide (and it's cells to double)
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What is the generation time for most bacteria?
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1-3 hours
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________ scales are used to graph bacterial growth.
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logarithmic
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What is the lag phase? How long can it last?
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The period of little or no cell division.
1 hour or several days. |
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What is happening to a cell during the lag phase
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its undergoing a period of intense metabolic activity involving synthesis of enzymes and various molecules.
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What is happening during the log phase?
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cells are dividing and entering a period of growth or logarithmic increase.
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What's another name for log phase?
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exponential growth phase
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When are cells most active metabolically?
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Log phase
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What is the stationary phase?
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when growth rate slows and the number of microbial deaths equl the number of new cells.
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What are the phases of growth?
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Lag, Log, Stationary and Death
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What is the death phase?
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When the number of deaths exceeds the number of new cells.
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What is the most frequently used method of measuring bacterial populations?
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Plate count
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What is plate count?
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A method of determining the number of bacteria in a sample by counting the number of colony-forming units on a solid medium.
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How are plate counts recorded?
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Colony-forming units (CFU)
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Name a pro and a con of using plate counts to measure microbial growth.
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Pro-it measures the number of viable cells
Con-it takes time. |
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What is serial dilution used for?
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To insure colonies measured will be within a measurable range.
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What is a Capnophile?
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A microbe that grows better at a high concentrations of CO2
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What enzyme acts upon hydrogen peroxide to convert it into water and oxygen?
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catalase
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What enzyme acts open hydrogen peroxide to convert it into 2 water molecules?
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peroxidase
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What is the hydroxyl radical?
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intermediate form of oxygen (and probably the most reactive) formed in the cytoplasm by ionizing radiation
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What is reducing media and why is it used?
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Media containing ingredients that chemically combine with dissolved oxygen and deplete the oxygen supply in culture medium. Used for anaerobic bacteria.
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What is agar?
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a solid medium used to grow microbial cultures mad of a complex polysaccharide derived from a marine alga
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Describe a chemically define medium.
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A medium whose exact chemical composition is known.
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What is complex media?
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media made up of nutrients including extracts from yeasts, meat, or plants, or digest of proteins from these and other sources whose exact chemical composition can vary from batch to batch
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What is selective media used for?
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to suppress the growth of unwanted bacteria and encourage growth of desired microbes
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What is differential media used for?
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to make it easier to distinguish colonies of the desired organism from other colonies growing on the same plate.
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What is a enrichment culture and why is it used?
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A selective medium (usually liquid) designed to increase very small numbers of the desired microbe to detectable numbers.
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What is complex media called when its in liquid form? What is it called when its in solid form?
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liquid- nutrient broth
solid-nutrient agar |
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What is singlet oxygen?
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normal molecular oxygen that has been boosted into a higher-energy state and is extremely reactive
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What are superoxide radicals?
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formed in small amounts during normal respiration of organisms that use oxygen as a final electron acceptor, forming water.
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Whats a synonym for superoxide radicals?
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superoxide anions
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What is the peroxided anion?
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toxic anion formed from reaction of superoxide dismutase nuetralizes superoxide radicals.
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What are the 3 physical requirements for microbial growth?
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Temp, pH and osmotic pressure
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What is the pH range most bacteria grow best in?
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6.5-7.5
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Why is that a number of foods, such as sauerkraut, pickles and many cheeses, are preserved from spoilage?
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very few bacteria grow at a pH below 4
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What is an acidphile
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bacteria that is remarkably tolerant of acidity. Some can go as little as a pH of 1
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79
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cob
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How much water composition is required for microbial growth?
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80-90%
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What happens when a cell is placed in a hypertonic solution?
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plasmolysis
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How can honey or salt have a medicinal use?
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Their high salt or sugar concentrations create a hypertomic solution causin plasmolysis
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Would a hypertonic solution create a high or low osmotic pressure?
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high
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What is an extreme halophile
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a microbe that has adapted to high salt concentrations
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What is an obligate halophile?
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mircroorganism that requires high salt concentrations for growth
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Organisms from the saline waters as the Dead Sea often require what percent of salt solution?
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30%
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When using an inoculating loop to transfer obligate halophiles, what may have to do?
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Dip loop in to saturated salt solution
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What is a facultative halophile?
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an organism that does not require high salt concentration but are able to grow at salt concentrations up to 2%. A few species can tolerate 15% salt
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Where do Chemohetrotrophs derive their energy from?
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organic materials such as proteins, lipids and carbs.
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Where do Chemoautotrophs derive their energy from?
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Carbon dioxide
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Where do photoautotrophs derive their energy from?
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Carbon dioxide
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How do most bacteria meet their nitrogen requirements
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decomposing protein-containing material and reincorporating the amino acids
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Where can bacteria get the their required Nitrogen
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nitrogen from ammonium ions (NH4) or nitrates (compounds that dissociate to give the nitrate ion NO3), decomposing protein containing material or nitrogen fixation
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Which organisms use nitrogen fixation?
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photosynthesizing cyanobacteria
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Some cyanobacteria live in symbiosis with what?
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legumes such as clover, soybeans, alfalfa, beans, and peas
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What are trace elements?
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mineral elements such as iron, copper, molybdenum, and zinc that are essential for functions of certain enzymes, usually as cofactors
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What is a cofactor
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the nonprotein component of an enzyme
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What is Iron needed for in humans? For plants?
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Humans need it to make catalase and for hemoglobin. Plants use it to make chloroform.
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Where do most bacteria get sulfur from
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SO4, Hydrogen Sulfide and amino acids
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What are some examples of facultative anaerobes
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yeast and e.coli
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