Flashcards in Lecture 5: Microbial Growth Deck (40)
What is Cell growth?
Increase in cell number
-Growth = reproduction
What is binary fission?
Division of 1 cell into 2 cells
-Divides through elongation and septum formation
What is generation time?
Time required for binary fission
-30min to 6hrs typically
What factors affect generation time?
-Nutrient availability and temperature
-Specific to different microbial species
What is the Divisome?
Collection of FTS Proteins embedded in cytoplasmic membrane that direct cell division in prokaryotes
What does FTS stand for?
Filamenting Temperature Sensative
What proteins make up the Divisome?
What does the FtsZ protein do?
Forms ring around center of the dividing cell
-Related to tubulin
What does the ZipA protein do?
Connects FtsZ ring to Cytoplasmic Membrane
What does the FtsA protein do?
Attracts the other Fts proteins to form the divisome
What does the Ftsl Protein do?
-Synthesizes peptidoglycan for the newly formed cell walls in order to complete separation
Good for new antibiotics or Drug design
-Target this (Or any) protein = prevent bacterial growth
What is the MreB protein?
Part of cell morphology
-Forms cellular cytoskeleton
Absent in Coccoid bacteria
Present in Rod-shaped bacteria
What kind of growth does a microbial population experience? What are the applications of this?
-Cells double EACH generation (1->2->4->8 etc)
-So the rate increases each generation
Applicable to standards for bacterial counts in food
What are the different phases of the growth cycle for a bacterial population in a CLOSED SYSTEM (No nutrients in and No waste products out)?
What is the lag phase of microbial growth?
Low (but positive) growth rate
-Recovering from transfer to nutrient agar (lab conditions but also wild)
What is the Exponential Phase of Microbial Growth?
Big jump in growth rate
-Maximal rate, all cells dividing
What is the Stationary Phase of Microbial growth?
Net Growth rate = 0
-Nutrients begin depleting and waste products accumulating
Also known as "Cryptic Growth"
-# of cells dividing = # of cells dying
What is the death phase of microbial growth?
Growth Rate Negative
What is a Continuous Culture? What is an Example?
Continuous Culture is an open system
Example is Chemostat
-Nutrient Rich broth in
-Waste products out
What are some controls and applications of a continuous culture?
-Dilution rate (How fast in/out)
-Ecology and physiology
What are the methods for measuring microbial growth?
-Cell counts (Both living/dead)
-Plate counts (living)
-# of colonies that form = # of cells in sample
What are the advantages/disadvantages of Microscopic Counts for measuring microbial growth?
-Difficult with low cell number and/or motile cells
What are the advantages/disadvantages of Viable Counts for measuring microbial growth?
-Counts only viable cells
-Possible errors (Cell clumps, plating inconsistencies)
What is the Turbidimetric Method for measuring Microbial growth?
Using light shined through vials with sample and measuring with spectrophotometer
-Cell mass = Cell Number
What are the advantages/disadvantages for using the Turbidimetric method for measuring microbial growth?
-Non-destructive (don't have to throw away sample)
-Possible errors (cell clumps + Biofilms)
What are the cardinal temperatures?
Minimum: below this temp = no growth
Optimal: at this temp = fastest growth
Maximum: above this temp = cell death
Differ for each species of microorganism
-Limited Temp (25-40 degrees Celsius)
-Proteins within each microbe function at specific temp
What are the different temperature classifications for microbes that live in different environments?
Psychrophile = (< 15 degrees C)
Mesophile = Moderate
Thermophile = (> 45 degrees C)
Hyperthermophile = (>80 degrees C)
Anything that isn't a Mesophile = Extremophile
What kind of Microbe lives in the cold? Where are they found?
-Slow growing in pockets of water
-Deep Oceans, Glaciers, Polar Regions
What kinds of molecular adaptations have Psychrophioles developed for their environment?
Cytoplasmic membrane contains much more Unsaturated/Short Chain Fatty Acids
-This causes the membrane to be more loosely packed and fluid at low temperatures
-Cold Shock Proteins
-Antifreeze for cell
-Ice that forms inside cell will cause PHYSICAL damage