CH. 4 Bacterial Culture, Growth & Development Flashcards
Why is it important to study microbial growth?
To understand the physical and chemical factors influence the extent of growth and compare the growth in nature vs. lab environment
What is required for microbial growth?
CHONPS (macronutrients)
C - carbon (provides the skeleton)
H - hydrogen
O - oxygen
N - nitrogen (proteins/nucleic acids)
P - phosphorous (phospholipids)
S - sulfur (methionine, cysteine)
Cations - K, Mg, Fe, Ca (cofactors/signaling molecules)
Micronutrients (small trace amount) - Co, Cu, Mn, Mo, Ni, Z
Growth factors: vitamins. amino acids. blood serum, etc.
What is complex media?
Possess many pre-formed, nutrients cells can readily assimilate
*Nutrients provide primarily by protein source
*Nutrient-rich but poorly defined components
What is a defined medium?
Chemical composition is known; cells must synthesize all required molecules
*Requirements for fastidious bacteria (long list of nutrients)
What are essential nutrients?
Nutrients that cannot be synthesized (MUST be supplied)
How does an auxotroph differ from a prototroph?
Prototrophs: have all of the metabolic capabilities for their growth; known as a wild type
Auxotroph: is deficient in a metabolic pathway for its growth
What is enrichment culture?
Provide conditions to enhance the growth of specific bacterial types
*Often these may be present at low numbers in an environmental sample
How is a microbe defined as a heterotroph or autotroph?
Defined as a heterotroph: consumption of the organic compounds to gain carbon
Defined as an autotroph: consumption of carbon through photosynthesis or lithotrophy (inorganic) and making organic compounds
What are the two types based on energy source and how is the energy obtained by each?
The two types of growth types are either from carbon (hetero-/auto-) or electrons which are from inorganic/organic source (litho-/organo-)
Describe the following in terms of carbon source, energy, & electron source: chemoautotroph, chemoheterotroph, chemolithotroph, chemoorganotroph, photoautotroph, & photoheterotroph
Chemoautotroph uses inorganic energy sources to synthesize organic compounds from carbon dioxide
Chemoheterotroph utilizes organic energy to obtain carbon dioxide
Chemolithotroph oxidizes inorganic chemicals
Chemoorganotroph oxidizes organic compounds
Photoautotroph generates energy through light absorption which is used to make carbon dioxide
Photoheterotroph obtain energy from the catabolism of organic compounds and light absorption
*Chemoorganotrophs & Chemoheterotroph are synonymous
*Chemolithotrophs & Chemoautotrophs are synonymous
How does the growth of bacteria on rich media compare to growth on minimal media? Why is there a difference?
Bacteria grow more slowly on defined media because the organisms must synthesize more of their own components than a rich media
What is generation time? What is the equation for determining the number of generations? What is the mean growth rate constant (k) represent?
Generation Time: length of time for a cell to divide (and population to double)
Equation: log10(Nt/N0)/0.301
The growth rate constant (k) represents the rate of exponential growth (generations/time)
How does growth in pure culture differ from the growth of a microbe in nature?
Microbes in nature usually exist in complex communities (having multiple species) while in pure culture, it focuses on one species
Draw a hypothetical growth curve for a bacterial culture growing in a liquid medium and indicate the different stages of growth. What is occurring during each stage?
Lag Phase - no growth (temporarily), acclimation to surroundings, & synthesis affected by inoculum age & size, media composition, and physical factors
Log Phase - most metabolically, active state; fastest growth; cell sizes increases
Stationery Phase - nutrient limited; growth rate = death rate, cell size decreases
Death Phase - lack of nutrients & pH changes leading to exponential decline in cell numbers
Differentiate the following: batch culture and fed‐batch culture; how is a fed‐batch culture set up and maintained?
Fed-batch culture has an increase in cell # growth compared to batch growth. Batch culture is a culture system that contains limited amounts of nutrients.
Fed-batch culture is set up and maintained by adding extra nutrients during the middle of cultivation until the end of the fermentation system
