L11 Overview of the Microbial World

Question 1

Most animals harbor a complex bacterial community called the ___.

Answer 1

Microbiota

Question 2

What are some of the functions of the microbiota?

Answer 2

1. Organ development
2. Digestion of food
3. Synthesis of vitamins
4. Prevention of bacterial infection

Question 3

Which part of the GI microbiota is most dense?

Answer 3

Lower gut

Question 4

What are the 6 major shapes of bacteria?

Answer 4

1. Circle
2. Rod
3. Spirilum
4. Spirochete
5. W/appendages (stalk, hypha)
6. Filamentous

Question 5

What are 6 major methods used to identify bacteria?

Answer 5

1. Ability to grow on various distinct media
2. Measure metabolism of sugars used during, and the organic products of, fermentation
3. Growth on antibiotics
4. Gram stain
5. Determine whether peroxidases or superoxide dismutases are present (can the bacteria perform oxidative metabolism?)
6. Identify genes specific to a given pathogen

Question 6

What colors do gram + and gram - bacteria stain?

Answer 6

Gram +: purple

Gram -: pink

Question 7

Describe the process of invasion by microbes after exposure to the pathogen.

Answer 7

1. Adherence to skin or mucosa
2. Invasion through the epithelium
3. Colonization and growth, production of virulence factors
4. Toxicity/Spread
5. Disease

Question 8

What are some barriers to entry and adherence?

Answer 8

1. Lysozyme in tears/secretions
2. Normal flora
3. Skin
4. Rapid pH change from stomach to SI
5. Flushing of urinary tract
6. Lungs
7. Blood proteins

Question 9

What are some direct consequences of pathogen adherence?

Answer 9

1. Activation of immune system (adaptive and innate)
2. Uptake into a specialized double membrane intracellular compartment via endocytosis
3. Cytoskeletal rearrangement and formation of a specialized lesion and entry into the host cell

Question 10

True or false - certain pathogens have preferred niches.

Answer 10

True

Question 11

What happens when a commensal bacterium enters a location in the body that it does not normally occupy?

Answer 11

It can be pathogenic.