Lecture 4 Microbial Growth and Nutrient

Question 1

Why is understanding microbial nutrition important?

Answer 1

Crucial for comprehending how microorganisms obtain energy and nutrients, allowing us to study their physiology, metabolic processes, and role in the environment

Question 2

What are different methods used to grow microorganisms, and how are they selected?

Answer 2

Culture media
liquid vs. solid media, complex vs. defined, selective vs. differential cultures.

Axenic vs Enrichment media

Continuous vs Batch culture

Question 3

What are macronutrients and micronutrients, and what role do growth factors play in microbial nutrition?

Answer 3

Macronutrients are required in larger amounts (C, O, N, K)
, while micronutrients are needed in trace amounts (Cu, Co, Zn, Fe,) metals

Growth factors, things that the cell cannot produce such as vitamins and amino acids, are essential for microbial growth

Question 4

What is the Great Plate Count Anomaly, and what factors contribute to it?

Answer 4

many dead cells

cells could not grow on media (environment conditions)

some organisms grew faster tthan others

VBNC

Question 5

What are the environmental factors influencing microbial growth?

Answer 5

Temperature, pH, water activity, oxygen/redox potential, pressure, radiation

Question 6

What are organisms that like nutrient rich environments called?

Answer 6

oligotrophs

Question 7

organisms that like nutrient low rich environments called?

Answer 7

copiotrophs

Question 8

Different organisms that have low water activity…

Answer 8

halophile
-high salt concentration

osmophile
-high solute concentration

xerophile
-dry environment

Question 9

How does water activity impact microbial growth, and what are some adaptations to low water activity?

Answer 9

influences solute activity and concentration

water potential should be positive in cells (hypertonic to solution)

if less water is coming in, they will decrease their Aw, increasing internal solute concentration so that solutes will come into the cell.

Question 10

How does redox potential relate to microbial growth, and what are examples of microbes with different oxygen preferences?

Answer 10

Redox potential describes electron availability. Microbes exhibit preferences such as aerobes, anaerobes, and facultative anaerobes.

Question 11

How do organisms adapt to high-pressure environments, and what mechanisms provide resistance to ionizing radiation?

Answer 11

Barotolerant and piezophilic organisms adapt to high pressure. Resistance to radiation involves DNA repair and protein protection mechanisms.

Question 12

Adaptions to temperature

Answer 12

cold (increase fluidity)
-more a helices than b
-short fatty acids, more space
-poly unsaturated
-cryoprotectants: inhibit crystal ice formation
- cold shock proteins: chaperone proteins

Hot (resist denaturing)
-long, saturated fatty acids
-amino acid substitutions create more heat resistant folds
- ionic bonds between acidic and basic amino acids resist unfolding
-production of solutes: help stabilize proteins