Growth and Division Flashcards
Types of culture media
-Defined media
-complex media
Defined Media
-also known as minimal media
-made with purified chemicals so that exact composition is know: Glucose, amino acids, salts, buffer, vitamins.
Complex Media
-also known as undefined media
-made with digests of animal or plant products: yeast extract, casein (milk protein), soybeans, and beef extract
Growth Media: Defined Media
-works well for species with high biosynthetic capacity, as they have the ability to produce all of the amino acids, nucleotides, from basic carbon and nitrogen sources
Growth Media: Complex Media
-often required for species with numerous nutritional requirements
-many animal pathogens never grow outside the animal and so are never required to synthesize many required biosynthetic building blocks
Growth Media: Media used for Isolating/Identifying organisms within a mixed population
-common in clinical labs for identifying pathogens
Growth Media: Selective Media
-Contains compounds that inhibit the growth of certain organisms while allowing others to grow
Growth Media: Differential Media
-contains compounds that cause different colony appearance of different organisms. Often dyes that signal the presence of specific biochemical reactions.
Types of Growth Media
-Solid
-Liquid
Liquid medium
-allows for rapid and contrast mixing, so all cells are experiencing identical conditions at all times
-simple recovery and concentration of cells by filtering or centrifugation
Solid medium
-allows for isolation of individual colonies
-counting of individuals
-observation of colony phenotype differences
-isolation of pure culture
Bacterial Cell Division
Binary fission results in symmetric cell division.
Steps in Cell Division
-DNA replication and segregation (begins before start of division)
-Cytokinesis
-Synthesizing the new cell wall
What is Cytokinesis and what happens in this step of Cell Division?
-Splitting the cytoplasm in two septum formations
-choosing the center of the cell
-divisome formation
-invaginating the membrane
What happens in the synthesize step of cell division?
-polymerizing peptidoglycan strands
-cell shape determination
What is Fts?
-Fts protein
-stands for filamentation temperature sensitive
- a homolog of tubulin found in eukaryotic cells
-forms a hoop-shaped filament around the center of the cell
-linked to cytoplasmic membrane by Zip A and Fts A
What is GTP hydrolysis by and what does it do?
-GTP is hydrolysis by Fts Z drives filament shortening and thus membrane invagination
What is Fts I directly involved in?
-peptidoglycan synthesis in the septum
What are used to finding the Cell Center?
Min proteins
What does Min E do?
-oscillates from pole to pole, driving Min C and Min D away from the poles
What do Min C and Min D do?
-Because of Min E they are also constantly oscillating from one pole to the other
-inhibit divisome formation
-forms where Min protein concentration is lowest, at the cell center
What does the name Min come from?
-Minicell formation
What does Min D do?
-oscillates from pole to pole every 20 seconds.
How can you measure population growth?
-Direct Count/total count
-Viable Count
Direct Count/total count
-with Petroff-Hausser counting chamber
Viable Count
-using serial dilutions and either spread or pour plates
-serial dilutions to obtain a cell suspension that can be accurately counted
-statistically significant counts are found between 30-300 colonies/plate
-TMTC or TFTC
Monitoring Population Growth
-measure turbidity or optical density with a spectrophotometer
Growth of Bacterial Populations
-Exponential = Logarithmic!
Population Growth
-we plot growth on semi-log scales (log of cells/ml versus time)
-A standard measure of growth RATE is doubling time = generation time
Growth Phases in BATCH culture
-Lag
-Exponential/Logarithmic (log)
-Stationary
-Depth
Growth in Continuous Culture
-Chemostat
-Steady State
-Applications
-dilution rate=flow rate/volume of container
Factors Affecting microbial growth
-medium: complex (undefined) vs minimal (defines)
-Medium: liquid vs solid media
-Temperature
-pH
-Osmotic Strength (NaCl and Halophiles)
-Oxygen level
Temperature
-cardinal temperatures (minimal, optimum, and maximum)
Cardinal Temperature: Minimum
-membrane gelling
-transport processes so slow that growth cannot occure
Cardinal Temperature: Optimum
-enzymatic reactions occurring at maximal possible rate
Cardinal Temperature: Maximum
-protein denaturation
-collapse of the cytoplastic membrane
-thermal lysis
Temperature: Classes of Organisms
-Psychrophile (4 degrees Celsius)
-Mesophile (39 degrees Celsius)
-Thermophile (60 degrees Celsius)
-Hyperthermophile (88 degrees Celsius)
-Hyperthermophile (106 degrees Celsius)
pH
-Acidophile
-Alkalophile
-Neutrophiles
Acidophiles
-increasing acidity
-6 pH or lower
-H+ 10^-6 or higher (10^5)
-OH- 10^-8 or lower (10^9)
Alkalophile
-increasing alkalinity
-8 pH or higher
-H+ 10^-8 or lower (10^9)
-OH- 10^-6 or high (10^5)
Neutrophiles
-pH 7
-pure water
-H+ 10^7
-OH- 10^-7
What is the pH of medium cells?
-maintain internal pH between 6-8
-we frequently put buffers in artificial medium to maintain constant pH.
Osmotic Strength
-nonhalophile: Escherichia Coli
-halotolerant: Staphylococcus Aureus
-halophile: Aliivibrio Fischer
-extreme halophile: Halobacterium
Oxygen Levels of Organisms
-Aerobes (21% O2)
-Obligate (strict anaerobes)
-Facultative (aerobic or anaerobic)
-Microaerophiles (0% O2< x < 21% O2)
-Aerotolerant anaerobes
Growth of Anaerobes
-strict anaerobes frequently in anerobic (anoxic) chamber
-Aerotolerant anaerobes can be in anoxic jars (chemical removal O2)
Oxygen Levels
-Toxic forms of oxygen
-produced during metabolism in the presence of oxygen
Cellular enzymes for removal of toxic forms of oxygen
-catalase
-peroxidase
-superoxide dismutase
-superoxide dismutase/catalase in combination
-superoxide reductase
