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Microbiology Chap. 4
Dynamics of Prokaryotic Growth
| Question | Answer |
|---|---|
| Robert Koch (1843-1910) | The greatest contributor to methods of cultivating bacteria, primarily interested in identifying disease-causing bacteria. |
| Fannie Hess 1882 | suggested using agar (perfect solidifying agent) |
| Biofilm | Polysaccharide-encased community of microorganism |
| Chemically Defined Medium | Bacteriological growth medium composed of precise mixtures of known pure chemicals; generally used for specific experiments when nutrients must be precisely controlled |
| Complex Medium | Bacteriological medium that contains protein digests, extracts, or other ingredients that vary in their chemical composition |
| Differential Medium | Bacteriological medium that contains an ingredient that can be changed by certain bacteria in a recognizable way; used to differentiate organisms based on their metabolic traits |
| Exponential (Log) Phase | Stage of graowth in which cells divide at a constant rate; generation time is measured during this period of active multiplication |
| Facultative Anaerobe | Organism that grows best if O2 is available, but can grow without it |
| Generation Time | The time it takes for a population to double in number |
| Obligate Aerobe | Organism that requires molecular oxygen (O2) |
| Obligate Anaerobe | Organism that cannot multiply, and is often killed, in the presence of O2 |
| Plate Count | Method to measure the concentration of viable cells by determining the number of colonies that arise from a sample added to an agar plate |
| Pure Culture | A population of organisms descended from a single cell and therefore separated from all other species |
| Selective Medium | Bacteriological medium to which additional ingredients have been added that inhibit the growth of many organisms other than the one being sought |
| Binary fission | Process by which prokaryotes generally multiply, the increase in cell numbers is exponential |
| Microbial growth | An increase in the number of cells in a population |
| Generation/Doubling Time | The time it takes for a population to double in number |
| Exponential growth equation | Nt=No X 2n |
| Nt | the relationship between the number of cells in a population at a given time |
| No | the original number of cells in the population |
| n | the number of divisions those cells have undergone during that time |
| Stages of binary fission | 1.DNA attached to cytoplasmic membrane 2.Cell enlarges and DNA duplicates 3.DNA is partitioned into each future daughter cell and cross wall forms 4.Cell divides into two cells 5.Cells separate |
| Biofilms | have a characteristic architecture with open channels through which nutrients and waste products can pass |
| Examples of biofilm | the slipperiness of rocks in a stream bed, the slimy "gunk" that coats kitchen drains, toilet bowl scum, dental plaque on teeth |
| Why would bacteria in a biofilm be more resistant to harmful chemicals? | the structure of the biofilm shields the microbes growing within it |
| Describe a situation in which the activities of one species benefit another. | the metabolic wastes of one species may serve as a nutrient for another |
| Colony | a mass of cells descended from the original one, (about 1 million cells are required for a colony to be easily visible to the naked eye) |
| Agar | a polysaccharide extracted from marine algae used to solidify a liquid culture medium |
| Streak-plate method | the simplest and most commonly used technique for isolating bacteria (the object is to reduce the number of cells being spread with each successive series of streaks, effectively diluting the sample) |
| Percentage of prokaryote that can be cultivated in the laboratory | one percent (1%) |
| Growth Curve | a pattern of stages that a population follows while growing in a closed system |
| 5 stages of the Growth Curve | 1.Lag phase 2.Exponential/Log phase 3.Stationary phase 4.Death phase 5.Phase of prolonged decline |
| Open System/Continuous Culture | nutrients must be continuously added and waste products removed to maintain cells in a state of continuous growth |
| Lag Phase | "tooling up"-during this time they synthesize macromolecules required for multiplication, including enzymes, ribosomes, and nucleic acids, and they generate energy in the for of ATP |
| Exponential/Log Phase | cells divide at a constant rate and their numbers increase by the same percentage during each time interval |
| Time in which bacteria are most susceptible to antiobiotics and other chemicals | during the exponential/log phase |
| Primary metabolites | compounds synthesized during the log phase |
| Secondary metabolites | during the late log phase cell begin synthesizing a new group of metabolites (commercially, the most important of these are antibiotics, which inhibit the growth of or kill other organisms) |
| Stationary Phase | cells no longer have supplies of energy and nutrients adequate for sustained growth (cell population remains constant because dying cells provide nutrients to fuel the growth of other cells) length of time varies from a few hours to days |
| Death Phase | period when the total number of viable cells in the population decreases as cells die off at a constant rate |
| Phase of Prolonged Decline | marked by a very gradual decrease in the number of viable cells in the population, lasting for days to years (survival of the fittest) |
| Colony Growth | cells on the outside are multiplying, ones in the center are dying off, and the cells in between may be in stationary phase |
| Chemostat | keeps a culture in a continuous stage of growth by by providing nutrients to the medium and eliminating waste through an outlet |
| Extremophiles | love living in harsh environments, most are members of the Domain Archaea |
| Environmental factors that influence microbial growth | temperature, oxygen availability, pH, and water availability |
| Optimum growth temperature | the temperature at which the organism multiplies most rapidly |
| Psychrophiles | between -5C and 15C (usually found in Arctic and Antarctic regions and in lakes fed by glaciers) |
| Psychrotophs | between 20C and 30C but grow well at lower temps (important in cause of food spoilage) |
| Mesophiles | between 25C and 45C (include E. coli & most other common bacteria) Disease-causing bacteria, which are adapted to growth in the human body, typically have an optimum between 35C and 40C. |
| Thermophiles | between 45C and 70C (commonly occur in hot springs and compost heaps, also found in artificially created thermal environments such as water heaters) |
| Hyperthermophiles | 70C or greater (usually members of the Archaea) The highest recorded was found at 121C from the wall of a hydrothermal vent deep in the ocean. |
| Anaerobic | containing little or no oxygen |
| Shake tubes | determine the oxygen requirements of some organisms |
| Obligate aerobes | have an absolute requirement for oxygen (they use it to transform energy in the process of aerobic respiration) |
| Obligate anaerobes | cannot multiply if any O2 is present and are often killed (transform energy by fermentation or anaerobic respiration) Include members of the genus Bacteroides (large intestines) Clostridium botulinum botulism. |
| Facultative anaerobes | grow better if O2 is present, but can also grow without it (use aerobic respiration if O2 is available, but use fermentation or anaerobic respiration in it absence> |
| Microaerophiles | require small amounts of O2 for aerobic respiration 2% to 10% (higher concentrations are inhibitory)An example is Helicobacter pylori (causes gastric and duodenal ulcers) |
| Aerotolerant anaerobes/ aka Obligate fermenters | are indifferent to O2 (they can grow in its presence, but they do not use it to transform energy)Called obligate fermenters because they do not use aerobic or anaerobic respiration (Streptococcus pyogenes- strep throat) |
| Toxic forms of O2 | 1.Superoxide O2- 2.Hydrogen peroxide H2O2 |
| Superoxide dismutase | cells must have these enzymes to convert these toxic derivatives to non-toxic forms (degrades superoxide to produce hyrdrogen peroxide) |
| Catalase | breaks down hydrogen peroxide to H2O and O2 |
| Neutrophiles | live and multiply within the range of pH 5 to pH 8 |
| Urease | produced by H. pylori (splits urea in the stomach into carbon dioxide and ammonia, the ammonia neutrolizes the stomach acid in the bacterium's immediate surroundings) |
| Acidophiles | grow optimally at a pH below 5.5 |
| Alkalophiles | grow optimally at a pH above 8.5 (it appears that alkalophiles maintatin a relatively neutral internal pH by exchanging internal sodium ions for external protons) |
| Plasmolysis | a phenomenon that causes the cytoplasm to dehydrate and shrink from the cell wall |
| Halotolerant | bacteria that can tolerate high concentration of salt, up to approximately 10% NaCl |
| Halophiles | organisms requiring high levels of sodium chloride to grow (many marine bacteria are mildly halophilic) |
| Extreme halophiles | certain members of the Archaea, requiring 9% sodium chloride or more (extreme halophiles are found in environments such as the salt flats of Utah and the Dead Sea) |
| Major elements | elements that make up cell constituents (these include carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, magnesium, calcium, and iron) |
| Heterotrophs | use organic carbon (medically important, using organic sources such as glucose) |
| Autotrophs | use inorganic carbon in the form of carbon dioxide (play a critical role in the cycling of carbon in the environment because they convert inorganic carbon (CO2) to an organic form, the process of carbon fixation) |
| Nitrogen fixation | process unique to prokaryotes (some prokaryote are able to use nitrogen gas (N2), converting it to ammonia, which can be incorporated into cellular material) |
| Limiting nutrients | phosphorus and iron (they are present at the lowest concentration relative to need) |
| Trace elements | are required in very minute amounts by all cells (they include cobalt, zinc, copper, molybdenum, and manganese, which are required for enzyme function) |
| Growth factors | low molecular weight compounds required by a particular bacterium |
| Fastidious | bacteria such as Neisseria that require many growth factors |
| Phototrophs | organisms that harvest the energy of sunlight (plants, algae, and photosynthetic bacteria) |
| Chemotrophs | organisms that obtain energy by oxidizing chemical compounds (mammalian cells, fungi, and many types of bacteria oxidize organic compounds such as sugars, amino acids, and fatty acids) |
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