Chapter 6 Microbial Growth Flashcards
Microbial “Growth”
- increase in population of microbes
- result of growth is a discrete colony
- reproduction>growth
Colony
aggregation of cells arising from a single parent
Growth Requirements
- nutrients for energy + for building organic molecules
- common nutrients: c, o, n, h
- microbes obtain nutrients fr various sources
organisms that require CARBON SOURCE for energy
Autotrophs + Heterotrophs
organisms that require energy source
Chemotrophs + Phototrophs
Autotrophs
require CO2
-food producers, dont need to eat
Heterotrophs
require organic compound (carbon-containing compounds)
-must obtain food fr other sources
organisms that require light + CO2
Photoautotrophs (plants, algae, cyanobacteria)
organisms that require chem compounds + CO2
Chemoautotrophs (uses specific chem compounds like hydrogen, sulfur, + nitrifying bacteria + some archaea)
organisms that require light and organic compound
Photoheterotroph (food consumers but can also use light)
organism that require chem compound + organic compound
Chemoheterotroph (animals, fungi, protazoa, bacteria, yeast, archaea)
4 types of oxygen requirements for bacteria
1 Obligate Aerobes
2 Obligate Anaerobes
3 Facultative Anaerobes
4 Aerotolerant Anaerobes
Obligate Aerobes
- O is essential for life
- aerobic resp ONLY
Obligate Anaerobes
- O is deadly
- toxic forms of O are highly reactive + excellent oxidizing agents
- O causes irreparable damage to cells bc missing key enzymes
-fermentation ONLY!
Facultative Anaerobes
- can survive in O
- will use cellular respiration if O is present,
- can switch to fermentation if O is NOT present
-both fermentation + aerobic resp
Aerotolerant Anaerobes
- tolerate presence of O bc they have enzymes
- fermenters
aerobes and facultative anaerobes have these enzymes that help tolerate toxic oxygen species
superoxide dismutase + catalase
Superoxide Dismutase
neutralizes oxygen radicals which are toxic
ex)
O2- > O2
O2 + 2H+ > H2O2
Catalase
neutralize peroxide
ex)
H2O2 > 2H2O + O2
peroxide > water and oxygen
4 forms of Toxic Oxygen
1 singlet oxygen
2 superoxide radicals
3 peroxide anion
4 hydroxyl radical
-unstable forms of oxygen that has extra electrons that they are trying to get rid of
Catalase Test
- determines if bacteria has enzyme catalase
- hydrogen peroxide is added to bacteria. if bubble/foams, then positive for catalase
ex) staph cocci vs strep cocci: staph is catalase pos.
4 Microbe Types based on Temp Requirements
[ -5 to 20C] PSYCHROphiles
[ 15 to 45C] MESOphiles
[ 43 to 80C] THERMOPHILES
[67 to 105C] HYPERTHERMOphiles
most pathogenic bacteria based on temp
Mesophiles [15 to 45C]
pH requirements for microbes
- organisms are sensitive to changes in acidity
- H+ and OH- interfere with H bonding
3 Microbe Types based on pH Requirements
Neutrophiles (most human pathogens)
Acidophiles
Alkalinophiles
Water requirements for microbes
- water is required to dissolve enzymes + nutrients
- water is important reactant in many metabolic rxn
- when water is not present, bacteria may undergo sporation
2 physical effects of water on microbes
1 osmotic pressure
2 hydrostatic pressure
Osmotic Pressure
- pressure exerted on a semipermeable membrane by a soln containing solutes that cannot freely cross
- water can freely cross
- water will follow salt/ions
Hypotonic Soln
lower solute concentration
Hypertonic Soln
higher solute concentration
Obligate + Facultative Halophiles
organisms that live in high salt concentration
Biofilms
- complex relationships among numerous organisms
- from slime layer + fimbraea
- form on surfaces as a result of quorum sensing
- many organisms in a biolfilm are more harmful than a colony of a single type
Biofilm Extracellular Matrix
- adhere cells to one another
- allows attachment to a substrate
- sequester nutrients
- may protect individuals in the biofilm
Inoculum/Inoculation
introduction of microbes from one place to another medium
-for collecting environmental, clinical, and stored specimens
Culture
act of cultivation microbes
Obtaining Pure cultures
- cultures composed of cells arise from a single progenitor [CFU-colony forming unit]
- aseptic technique
- isolation technique
2 Isolation Techniques
streak plates
pour plates
Pour Plate Method
-dilution of sample by factors of 10 1mL of initial sample into 9mL of broth 1mL of diluted sample into 9mL of broth repeat and then 1mL of diluted sample into 9mL warm agar
6 types of Culture Media
1 Selective Media 2 Differential Media 3 Defined Media 4 Complex Media 5 Anaerobic Media 6 Transport Media
Differential Medium: Blood Agar
-checks for pathogenic form of strepto cocci (Beta-Hemolysis, Alpha-Hemolysis, Gamma-Hemolysis)
- beta (positive hemolysis of rbc)
- alpha (some clearing, greenish, partial hemolysis, causes pneumonia)
- gamma (no hemolysis, no clearings, found in oral cavity)
Hemolysis
destruction of red blood cells
MacConkey
- selective+differential media
- selects for Gram-Neg bacteria
- differentiates bw Gram-Neg for Lactose Fermentation
MacConkey
- selective+differential media
- selects for Gram-Neg bacteria (gram-pos will not grow)
- differentiates bw Gram-Neg for Lactose Fermentation (medium turns yellow if positive for fermentation)
Preservation of Cultures
- refrigeration (stores for short period of time)
- deep-freezing (stores for years)
- lyophilization or freeze-drying (decades)
Bacterial Growth
- binary fission
- increasing number of bacterial cells
Generation Time
time required for bacterial cell to grow and divide
- amt of time for 1 cell to grow into 2 cells
- dependent on chem + physical conditions
- varies among different bacterial species
Arithmetical Growth
constant increase. straight line
Logarithmic Growth
. grow at an exponential level each time their generation time is up. curved, to steep line
Microbial Growth Curve
Lag Phase
Log (exponential) Phase
Stationary Phase
Death (decline) Phase
Chemostat
- type of bioreactor
- fresh medium is continuously added while culture liquid is continuously removed to keep culture volume constant
- can control the growth rate of microbes by changing the rate w which the medium is added
Serial Dilution + Viable Plate Count
ways to measure microbial reproduction
Metabolic Activity
- distinguishes live and dead cells
- indirect methods of measuring microbial reproduction
Lag Phase
bacteria is floral sensing
-in new environment, learning what nutrients + amino acids are available.
Log Phase
-number of bacteria grows exponentially until there is no more room to grow.
Stationary Phase
maxed out, no more room for growth
