micro exam 1

only focus topics

Who are the CDC and what do they focus on?

The Centers for Disease Control and Prevention (CDC) and other world health organizations are intensely focused on Emerging Infectious Diseases. 

Describe four different factors that are responsible for the recent increase in EIDs and provide at least one microbial example for each factor. 

People (HIV/Influenza)  → Environment (West Nile) → Animals (Ebola/Rabies/Hanta)  → Microbes. (E. coli/MRSA)

Which factor do you think will be the biggest contributor to EIDs in the future?

Microbial Evolution - Changes in genes due to adaptation to the environment (Ex: influenza)

Gram-Positive vs Gram-Negative

Know the following about the Gram stain:

Steps used to prepare a slide for staining

-Prepare a thin smear

-Heat fixation (adhere the cells)

-Do not leave under heat for too long as cells will shrink

Know the following about the Gram stain:

Steps used in the Gram stain itself, including the appearance of cells at each step.

-Cover smear with Crystal Violet for 1 min, then rinse with water to remove dye

-Cover smear with Iodine for 1 min, then rinse with water to remove dye

-Depolarize with Alcohol decolorizer for 3 seconds, then rinse with water

-Counterstain with Safranin for 1 min, then rinse

-Blot with bibulous paper

Know the following about the Gram stain:

Why the Gram stain is a differential stain and not a simple stain.

The Gram stain is a differential stain because it uses multiple stains/reagents to distinguish between different types of bacteria based on their cell wall structure.

Know the following about the Gram stain:

How cell wall composition results in the differential staining results.

Gram positive = Purple

Gram negative = Pink

Substrate-level phosphorylation

phosphate is directly transferred to ADP → ATP

Oxidative phosphorylation

electrons → ETC → proton gradient → ATP

Photophosphorylation

light → ETC → proton gradient → ATP

Why would a microbe rely on a less efficient metabolic process like anaerobic respiration or fermentation to produce energy?

A microbe may use anaerobic respiration or fermentation when oxygen is unavailable.

• Anaerobic respiration: uses an electron acceptor other than O₂.

• Fermentation: does not use an electron transport chain.

• They produce less ATP, but allow the microbe to keep producing energy and survive without oxygen.

Based on the properties of prokaryotic cells, provide an argument with supporting evidence for the endosymbiotic theory.

The endosymbiotic theory explains that bigger cells engulfed smaller prokaryotic cells that would later evolve and function as organelles due to forming a symbiotic relationship with the host. Eukaryotes became more complex from engulfing prokaryotes and using their special abilities, such as photosynthesis, and those prokaryotes are now known as organelles. 

Compare and contrast carbohydrate catabolism and energy production in the following (nutritional requirements for different classes of organisms) 

Pseudomonas, an aerobic chemoheterotroph

Uses organic chemicals for energy, organic compounds for carbon, and O₂ for aerobic respiration. Produces lots of ATP.

Compare and contrast carbohydrate catabolism and energy production in the following (nutritional requirements for different classes of organisms) 

Spirulina, an oxygenic photoautotroph

Oxygenic photoautotroph: Uses light for energy and CO₂ for carbon. Performs photosynthesis and produces O₂.

Compare and contrast carbohydrate catabolism and energy production in the following (nutritional requirements for different classes of organisms) 

Ectothiorhodospira, an anoxygenic photoautotroph

Anoxygenic photoautotroph: Uses light for energy and CO₂ for carbon. Performs photosynthesis without producing O₂.

Be able to describe the nutritional requirements for the different classes of organisms and give microbial examples of each.

1. Photoautotrophs – Use light for energy and CO₂ as their carbon source. Example: Spirulina.

2. Photoheterotrophs – Use light for energy and organic compounds as their carbon source. Example: Rhodopseudomonas.

3. Chemoautotrophs – Use chemicals for energy and CO₂ as their carbon source. Example: Nitrosomonas.

4. Chemoheterotrophs – Use organic chemicals for both energy and carbon. Example: Pseudomonas.

Easy way to remember:
Photo = light
Chemo = chemicals
Auto = CO₂
Hetero = organic compounds