MIC 206: Lab 04 & 05 - Effects of temperature and osmotic pressure & Measuring microbial growth/pH

What does FTM stand for?

Fluid thioglycollate medium

What does fluid thioglycollate medium (FTM) do

Determines growth characteristics of microorganism based on its oxygen requirements

How much agar does fluid thioglycollate medium (FTM) contain and why

0.075% agar to slow down atmospheric oxygen diffusion throughout the broth

What is the reducing agent for fluid thioglycollate medium and what does it do

Thioglycolic acid creates an anaerobic environment deeper in the tube, allowing anaerobic bacteria in the absence of oxygen

What does thrioglycolic acid do

Reducing agent that creates anaerobic environment deeper in tube

What is resazurin in fluid thioglycollate medium

A REDOX indicator that turns pink in presence of oxygen and colorless when oxygen is absent

What could disrupt the oxygen gradient in a fluid thioglycollate media (FTM)

Shaking the tube and old media

What are the results of fluid thioglycollate media

Organisms are either obligate aerobic, obligate anaerobic, facultative anaerobic, microaerophiles

What are obligate aerobic

Require oxygen for respiration

What are obligate anaerobic

Grows only in absence of oxygen (oxygen is lethal)

What are facultative anaerobic

Grows in presence or absence of oxygen. Densest growth at the top

What is microaerophiles

Survive only in lower atmospheric levels of oxygen

What are environmental growth factors

Oxygen requirements, temperature, osmotic pressure, and pH

What are environmental conditions

External factors that will affect microbial cell physiological processes, leading to changes (increase or decrease) in the growth rate

What happens when environmental conditions are extreme

It can lead to the inhibition of growth and death of the individual cell and population level of the microbes

What does each microbe have in terms of growth

Optimum conditions for growth

What are physiological processes within microbes governed by

Protein catalysts known as enzymes

What happens outside of the optimum condition

Activity of the enzyme will be lower, which will lower the growth of microbes

What happens when a microbe is in its optimum condition versus outside of its optimum condition

In optimum conditions: enzymes will fold correctly
Outside optimum conditions: proteins will misfold causing cell death

What happens outside of the optimum condition for growth

Activity of enzyme and growth lowers

What does thermal energy play a crucial role for in term of growth

Thermal energy play a crucial role in movement of molecules, structure, and function of cell’s proteins and membranes

If liquid water is present, what else is possible to be present

Microbes

What are the temperature classification of microbes

Psychrophile, mesophile, thermophile, extreme thermophile

What is the temperature of a psychrophile

-5 to 20 degrees c

What is the temperature of a mesophile

15 to 45 degree c

What is the temperature of a thermophile

40 to 80 degree c

What is the temperature of a extreme thermophile

80 to 121 degree c

What are the optimum growth temperature for microbes for each temperature category

Psychrophiles: 8, Mesophiles: 35, Thermophiles: 65, Extreme thermophiles: 95

What is an isotonic solution

Solute concentration is the same on the inside as outside. Equal movement of solute and water

What is a hypotonic environment (most environments)

High solute inside the cell. Water will move into the cell and solutes move out. This results in cell swelling
(think: hypothermia → too much cold →hypotonic → too much inside cell)

What is a hypertonic environment

High solute outside the cell. Water will move out of the cell and solutes move in. Results in plasmolysis and cell death. This is how you preserve food and are halophiles (loves salt)

How do bacteria reproduce and what is it?

Asexually through a process called binary fission → where a single cell splits into 2 equally sized cells

How do bacteria populations grow

In a predictable pattern, resulting in growth curve with 4 phases of growth

What are the 4 growth phases of a growth curve

Lag phase, Log phase, Stationary phase, and Death phase

What is prodigiosin?

A pigment that allows colonies to be red (what causes the red color in the bathtub)

What are the 3 methods of measuring the growth of a population of microbes

Microscopic counts: counting 1, 2, 3… very impractical and inaccurate
Standard plate counts: using serial dilutions to reduce number of microbes to a countable number
Optical density (absorbance): uses light scattering to determine size of a microbial population

What does optical density (OD) equal to

Absorbance (abs)

What does turbidity mean and what does more turbidity mean in regards to OD or ABS

Turbidity is cloudiness and more turbidity = more growth = higher optical density or absorbance value

Can optical density/absorbance distinguish between living and nonliving organisms

No

What does homogenize mean? (like when it says homogenize your sample)

To mix together into a single entity by shaking it up

What instrument is this?

Plastic pipette

What instrument is this? How do you use it?

Cuvette → line the smooth side of the cuvette up with the arrow (don’t forget the top)

What instrument is this?

Spectrophotometer

What is pH

A measure of hydrogen ion (H+) concentration or the degree to which a substance is acidic or basic

What is an acidophiles

Prefers pH of 5.5 and below → low pH < 7

What is an alkaliphiles

Prefer pH of 8.5 and above → high pH > 7

What is a neutrophiles

Prefer pH of 5.5 - 8.8 → neutral pH = 7