EXAM 2: Growth Flashcards
Growth
An increase in size, population, or development of an organism
Nitrogen Fixation
The chemical processes by which atmospheric nitrogen is assimilated into organic compounds
Biofilm
A dynamic, heterogeneous, community of microorganisms adhered to an artificial surface
Defined media
A nutrient media in which all the chemical compounds are known
Complex media
A uncharacterized nutrient media with undefined ratios of essential elements
Selective media
A nutrient media that inhibits the growth of particular types of organisms
Differential media
A nutrient media that allows for the identification of particular types of organisms
Lyophilize
To freeze dry
Binary fission
A type of asexual reproduction utilized by prokaryotes that results in subdivision of a single organism into two or more separate organisms
Generation Time
Time required for a bacterial cell to grow and divide
Understand how organisms are divided into nutritional categories based on carbon and energy source
Two groups of organisms based on source of carbon
Autotrophs - utilize CO2
Heterotrophs - catabolize organic compounds
Two groups of organisms based on source of energy
Chemotrophs - use organic compounds
Phototrophs - acquire energy from light
Mixtures:
Photoautotrophs: use CO2 as a carbon source and acquire energy from environmental light (plants)
Chemoautotrophs: use CO2 as a carbon source & catabolize organic molecules for energy
Photoheterotrophs: Photosynthetic organisms that acquire energy from light and acquire nutrients from catabolism of organic compounds
Chemoheterotrophs: use organic compounds for both energy and carbon
Compare the oxygen requirements of aerobes, anaerobes, facultative anaerobes, aerotolerant anaerobes and microaerophiles
Aerobes: oxygen is essential
Anaerobes: oxygen is deadly
Facultative anaerobes: metabolic efficiency reduced in the absence of oxygen. Can undergo aerobic & anaerobic respiration
Aerotolerant anaerobes: do not use aerobic metabolism, but tolerate oxygen by having some enzymes that detoxify poisonous oxygen forms
Microaerophiles: require oxygen levels of 2% –10%
–Can compare all of these when looking at an FTM, fluid thioglycollate medium (gets rid of all oxygen)
Discuss the elements required for growth and how they are utilized
- Most common nutrients contain CHNOPS
1. Trace elements - only required in small amounts
2. Growth factors - necessary organic chemicals that cannot be synthesized by certain organisms
3. Nitrogen requirements
Often growth limiting - anabolism often ceases due to insufficient nitrogen - All cells recycle nitrogen from AAs and nucleotides
Discuss how physical parameters, such as temperature, pH, osmolarity and pressure affect microbial growth
Temperature: Denaturation through disruption of H bonds in proteins (loss of function)
- Low temp: membranes rigid & fragile, no kinks
- High temp: membranes fluid, kinks present
Categories of microbes based on temperature
Psychrophiles (~-5-20 degrees C)
Mesophiles (~15-45 degrees C) (important bc we’re 98F)
Thermophiles (~45-80 degrees C)
Hyperthermophiles (~65-105 degrees C)
pH: Organisms sensitive to acidity changes; H+ and OH- interfere with H bonding
- talk ab acidophiles, neutrophiles and alkaliphiles
Osmolarity: Most cells die in absence of water; Microbes require water to dissolve enzymes & nutrients
Pressure:
Osmotic pressure
- Pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross membrane
Hydrostatic pressure
- Water exerts pressure in proportion to its depth
- Barophiles depend on pressure to maintain their 3D functional shape
Explain the importance of aseptic and pure culture technique. Provide examples
Prevents contamination of sterile objects
- Washing of hands
- PPE such as gloves and masks
Necessary for isolation of a specific microorganism, especially in the diagnosis of disease. Pure culture technique allows us to isolate one species & know that it’s colony came from one and only one progenitor → CFU
2 common isolation techniques:
Streak plates
Pour plates
Differentiate between the types of media used in the culture of microorganisms and discuss their importance
Defined media -A nutrient media in which all the chemical compounds are known
Complex media - A uncharacterized nutrient media with undefined ratios of essential elements
Selective media - A nutrient media that inhibits the growth of particular types of organisms
Differential media - A nutrient media that allows for the identification of particular types of organisms
Anaerobic media - contains a reducing agent that removes free oxygen from the environment
Transport media - medium used to remove clinical specimens from one location to another while preserving the relative abundance of organisms and preventing contamination of the specimen or environment.
Describe the process by which bacteria reproduce
Bacteria reproduce via binary fission
1. Cell replicates its DNA
2. Cell stretches its membrane and cell wall
3. Septum is formed, which has one copy of the DNA on either side
4. Cross wall is completely formed between the two daughter cells
5. Splits via cytokinesis!
Explain logarithm growth and the phases of the microbial growth
Logarithmic growth: 2n growth (n is the number of generations), uses a semi-log graph
Generation time: the time required for a bacterial cell to grow and divide
phases of microbial growth:
Lag phase: cells are adjusting to their new environment and are synthesizing macromolecules needed for efficient growth
Log phase: Adapted to media, replication occurring faster than death
Stationary phase: reached carrying capacity of the media, some nutrients are rate limiting
Death (decline) phase: nutrients exhausted by products of metabolism built up in the medium, death occurs faster than replication
Compare various methods of measuring microbial reproduction
of colonies = to # of CFUs in the original large sample
Direct methods—–
Serial dilution: the stepwise series of dilutions of a liquid culture
Viable plate count: counting/calculating CFUs
Membrane filtration: membrane filtered cells grow, and then count/calculate CFUs.
Most probable #: serial dilution performed, pH indicator is added to tubes, color change indicates the presence of acid and presence of growth
Microscopic/Electronic counters: counts the number of bacteria with microscope or electric counter, counts cell #’s
Indirect methods—-
Turbidity: Presence of microorganisms blocks the passage of light (spectrophotometer). Generally, the greater the bacterial population, the more turbid a broth
Dry weight: Organisms are filtered from their culture medium, dried, and weighed
Genetic sequences: Isolate DNA sequences of unculturable prokaryotes to estimate the # of these microbes
