(B) Lecture 11: Intro to Bacteriology

Question 1

Prokaryotes

Answer 1

• smallest, simplest and most abundant cells on Earth
• include Bacteria + Archaea
• NO nucleus + NO complex organelles

Question 2

Bacteria growth

Answer 2

• reproduce by binary fission (grow fast)

4 phases of growth
- lag (get nutrients)
- logarithmic growth (FAST - doubling_
- stationary (run out of nutrients- waste)
- death

Generation/doubling time in logarithmic phase

Question 3

Bacteria shape classification

Answer 3

• Coccus (sphere)
• Rod (bacillus)
• Spirillum

Question 4

Bacterial classification by O2 use

Answer 4

Obligate aerobe
Obligate anaerobe
Facultative anaerobe
Aeroteolerant anaerobe
Microaerophile

Question 5

Obligate aerobe

Answer 5

require oxygen for growth

Question 6

Obligate anaerobe

Answer 6

oxygen is toxic for growth

Question 7

Facultative aerobe

Answer 7

can use oxygen is present but can also grow without oxygen

Question 8

Aerotolerant anaerobe

Answer 8

doesn’t use oxygen but oxygen is not toxic

Question 9

Microaerophile

Answer 9

grows best with LOW levels of oxygen

Question 10

Naming of bacteria

Answer 10

Genus comes first capitalized then species is not capitalized

Question 11

Basic bacterial cellular structure

Answer 11

• nucleoid: houses genetic material (not nucleus b/c not membrane-bound)
• ribosomes: make protein
• plasmid
• cytoplasmic membrane
• cytoplasm
• cell wall
• cell envelope

Question 12

Gram stain

Answer 12

2 types of bacteria

1. Warm slide w/ sample up on a flame
2. Add crystal violet
3. Add iodine - helps purple stick in cell wall
4. Wash slide w/ alcohol
   - gram + = thick cell wall = keeps purple
   - gram - = thin cell wall = purple washes
5. add safranin
   - stains gram -

Acid fast (myobacteria) don’t stain

• Gram-positive = PURPLE
• Gram-negative = PINK

Question 13

Purple and pink in gram stain

Answer 13

PURPLE = Gram-positive
PINK = Gram-negative

Question 14

Gram + vs Gram -

Answer 14

Gram-positive = cell wall/peptidoglycan is very THICK
- purple dye gets trapped in cell wall

Gram-negative = THIN cell wall (2 separate membranes)
- outer layer made of LPS

Question 15

Bacterial cell walls

Answer 15

• called peptidoglycan
• RIGID structure
• prevents osmotic lysis
• glycan backbone (G + M alternate)
• peptide cross-linkage btwn glycan cells

humans don’t have these cell walls, so they are good to target w/ antibiotics

Question 16

Lipopolysaccharide (LPS)

Answer 16

ONLY in gram-negative bacteria

Endotoxin

• O-specific polysaccharide (aka O-antigen): antigenic + highly variable
• core polysaccharide

Lipid A is main part : disaccharide + fatty acid groups
- recognized by INNATE immune system
- recognized by Toll-like receptors
- induces inflammation
- can lead to septic shock due to cytokine storm

Question 17

Nucleoid

Answer 17

• NOT the nucleus (bacteria do not have a nucleus)
• NO surrounding membrane
• single, circular chromosome (most)
• haploid genomes (one set of chromosome)

Question 18

Plasmids

Answer 18

• extra-chromosomal genetic elements
• usually not required for bacterial growth
• often encode for FITNESS factors (ex. antibiotic resistance, selective adv.)
• can be transferred from bacteria to bacteria

Question 19

Human microbiota

Answer 19

• internal organs are usually sterile
• surface tissues have lots of microbes - open to environment (ex. large intestine has most of microbes in body)

Question 20

Where are most microbes in the body found?

Answer 20

In the large intestine

Question 21

Host-microbe relationships

Answer 21

• Commensalism
• Mutualism
• Parasitism

Question 22

Commensalism

Answer 22

one benefits without helping or hurting the other

Question 23

Mutualism

Answer 23

BOTH benefit (host and microbe)

Question 24

Parasitism

Answer 24

One benefits (usually microbe) at expense of the other (usually host)

Question 25

What makes bacterial pathogen successful?

Answer 25

• colonization
• invasion/toxicity
• immune evasion
• transmission

w/o toxicity + immune evasion, a lot of bacteria won’t cause disease

they produce virulence factors - contribute to disease

Question 26

Virulence factors

Answer 26

Surface
- LPS (endotoxin)
- flagella
- pili and adhesins
- capsules
- secretion systems

Secreted
- EXOTOXINS (bacterial infection is localized but systemic response)

Question 27

Flagella

Answer 27

• structures that allow some bacteria to be MOTILE (CHEMOTAXIS)

CLOCKWISE = random direction/tumble
COUNTERCLOCKWISE = FORWARD (produces run and goes toward attractant)

Question 28

Pili

Answer 28

a.k.a. fimbrae

Primarily involved in ATTACHMENT to:
- surfaces
- host tissue
- other bacteria

Question 29

Capsules

Answer 29

• usually made of (exo)polysaccharides
• attachment to host tissues
• PROTECTION FROM HOST IMMUNE SYSTEM
• can sometimes be used in vaccines
• formation of biofilms (bind to cell surface of bacteria + make colonies to form exopolysaccharides = forms biofilms)

Question 30

Biofilms

Answer 30

Stages
- attachment
- microcolony development
- biofilm development
- maturation

Question 31

Endospores

Answer 31

ONLY in gram-POSITIVE

• highly differentiated cells formed within parent cell
• HIGHLY RESISTANT TO HEAT, HARSH CHEMICALS + RADIATION
• a “dormant” stage of life cycle
• most common in soil, bacillus and clostridium

Question 32

Exotoxins

Answer 32

• SECRETED from bacteria

Includes
1. hemolysins (lyse red blood cells)
2. toxins that function inside host cells
3. extracellular enzymes (destroy proteins, DNAses, lipids, non-specific virulence factors)
4. Superantigens (activate T cells = cause toxic shock)

Some exotoxins (inactivated) can be used as vaccines

Question 33

Intracellular pathogen

Answer 33

taken up and survive within phagocytic cells

• some force their own uptake into epithelial cells
• allows BACTERIA TO HIDE from different component of immune system