Lecture 6 Flashcards
(90 cards)
Which of the following uses sunlight for energy and CO2 for a carbon source ?
Photoautotrophs
What species differentiates into fruiting bodies ?
Myxococcus xanthas
INTRODUCTION
Microbes have both the fastest and slowest growth rates of known organisms
- Some hot springs bacteria double in as little as 10 min
* Some deep-sea sediment microbes take as long as 100 years
What determines the differences in growth rate?
- Nutrition
- Temperature
- pH
- Osmolarity
ENVIRONMENTAL LIMITS ON GROWTH
What are “normal” growth conditions?
From our human frame of reference “normal” is defined as: sea level, 20-40C, near neutral pH, salt concentration 0.9%, and ample nutrients
Any ecological niche outside this window is labeled “extreme” and organisms inhabiting them are called ____
Extremophiles. (Like temp. & pressure)
• Extremophiles may evolve to survive multiple extreme environments
• Extremophiles may provide insight into the workings of extraterrestrial microbes we may one day encounter (astrobiology)
MICROBES ARE COMMONLY CLASSIFIED BY THIER ENVIRONMENTAL NICHE
[pic with important info]
GROWTH AND TEMPERATURE
Every organism has an optimum temperature at which it grows most quickly
Also, minimum and maximum temperatures that define the limits of growth
Fastest growth rate occurs at temp where all proteins work most efficiently as a ______
Group
*as it starts
Optimum —-> normal
Rising temperatures cause critical enzymes or cell structures (e.g. cell membrane) to ____
Fail
At _______ temperatures enzymatic processes become too sluggish and the cell membrane becomes too rigid
Cold
*move a lot slower
The relationship between growth rate constant and temperature obeys ______ equation
Arrhenius
k= Ae ^ Ea/RT
General result – growth rate roughly ____ every 10C rise in temperature
Doubles
______ breaks down at upper and lower limits of growth
Arrhenius
[pic]
The typical temperature growth range spans the organisms optimal growth temperature by ____
30 - 40 C
* Some organisms have a smaller range
_______ principles limit a cell’s growth to a
narrow temperature range
Thermodynamic
• Heat increases molecular movement with proteins
• Too much or too little movement will interfere with enzymatic reactions
MICROBES ARE CLASSIFIED BY GROWTH TEMPERATURE
Mesophiles :
~15-45 C, typical lab strains
[pic]
PSYCHROPHILES (0-20 C)
(Grow in extreme cold temps)
Optimum growth
~15 C
Proteins are more ____
Flexible
Require less ____ (heat) to function
Energy
Membranes are more ____
Fluid
Have antifreeze proteins and other ____ That depress the freezing point
Cryoprotectants
THERMOPHILES (40-80 C)
Hyperthermophiles
65-121 C
Enzymes are more stable – don’t unfold as easily
Low amounts of glycine
