Lecture 1: Bacterial Structure and Function

Question 1

What is Bacteria?

Answer 1

• Single celled organisms
• Contain both RNA and DNA
• They reproduce by binary fussion
• Cytoplasm with no nucleus
• Ribosomes -> metabolic activity
• Colonize your skin, mouth, hair, gut, and genital tract (pretty much everywhere)

Question 2

3 Ways Bacteria can be Described

Answer 2

1. Shape
2. Gram Stain
3. Morphology

Question 3

Types of Bacteria Shape

Answer 3

• Cocci (circles)
• Bacilli (oval)
• Curved (squiggles)
• Spiral (wavy)

Question 4

Types of Gram Stain

Answer 4

1. Gram +’ve: Thick, purple
2. Gram -‘ve: Thin, pink

Question 5

How is Bacteria named by genus and species?

Answer 5

“Kings Play Chess On Fancy Green Squares”
Kingdom, Phylum, Class, Order, Family Genus, Species
- Genus name capitalized, species name not capitalized
*Both italicized

Question 6

Gram Negative Stain

Answer 6

• Have a outer membrane
• Thin peptidoglycan layer
• Stain pinkish

Question 7

Gram Positive Stain

Answer 7

• Thick peptidoglycan layer; that is cross-linked between N-acetyl Glutamine and N-acetyl Muramic acid
• Stain purplish

Question 8

Characteristics of the Cell Membrane

Answer 8

• Energy production
• Nutrient processing
• Transport of nutrients and waste
• Selective transport of molecules
• Site of secretion of toxins and enzymes
• Osmotic barrier

Question 9

What bacterium cannot be classified as either gram positive or gram negative?

Answer 9

Mycobacterium (known as acid fast bacteria)
ex. Mycobacterium tuberculosis
- Have thick membrane capsule and mycolic acid cell wall that make them impermeable to most things

Question 10

Notable Acid-fast Bacilli (Mycobacteria)

Answer 10

• Mycobacterium tuberculosis (TB), Mycobacterium leprae (leprosy)

Question 11

Characteristics of Mycoplasma spp.

Answer 11

• Genus: Mycoplasma
• Simplest of bacteria: do not have a peptidoglycan layer
• Only a lipoprotein membrane (can’t be stained)
• Do not stain at all (gram stain or any other stain)

Question 12

3 Medically Relevant Gram Positives cocci (GPC)

Answer 12

• Streptococci
• Staphylococci
• Single cocci

Question 13

Staphylococcus Characteristics

Answer 13

• “Grape-cluster berry”
• Gram positive bacteria are found on skin but also highly pathogenic organisms
• 2 major groups:
  
  • Coagulase positive Staphylococcus: S. aureus
  • Coagulase negative Staphylococcus: all NON S.aureus (less than +’ve)

Question 14

What is the medical relevance of Gram Positives cocci Staphylococcus aureus?

Answer 14

• Can cause infections: several medically serious infections
• But also part of the normal flora of various areas of the body
• Always important when found in sterile site
• Methicillin Resistant S. aureus (MRSA) is a super bug

Question 15

Common coagulase negative staphylococcus

Answer 15

• S. epidermidis, S. hominus, S. warneri, S. hemolyticus, S. capitis

Question 16

What is the medical relevance of Gram Positives cocci Staphylococcus species?

Answer 16

• Gram positive usually found in the mouth and the oropharynx
• Typically organisms of low virulence
• Classified based on how the organisms grow on blood agar (5% blood in the agar)

Question 17

Alpha hemolysis

Answer 17

Partial lyses of blood cells in the agar (agar goes green)
Example: Viridans Streptococci, Streptococcus pneumoniae

Question 18

Beta-hemolysis

Answer 18

Complete lysis of blood cells in the blood agar
Example: Streptococcus pyogenes (Group A), Streptococcus agalactaea (Group B), others - Group C, Group F, Group G

Question 19

Gamma-hemolysis

Answer 19

Blood cells not lysed (not rly hemolysis)
Example: Enterococci spp. (Group D)

Question 20

Common Gram Positive Bacilli

Answer 20

• Bacillus anthracis, Bacillus cereus, Listeria monocytogenes, Clostridium difficile, Clostridium perfringens, Clostridium tetani, Clostridium botulinum, Propionibacterium acnes

Question 21

What is Listeria monocytogenes?

Answer 21

(Food borne outbreaks from reheating food)
- Found in almost all soft cheeses, and deli meats
- Can cause many problems with birth and pregnancy
- Grows well at 40 celsius - cold amplification

Question 22

What is Clostridium spp.

Answer 22

• All anaerobes (oxygen free)
• Organisms form spores, allowing them to remain in the environment for long periods of time
• Causes many infections
• Prodigious toxin producers - their primary virulence factor

Question 23

Notable Clostridium spp.

Answer 23

Clostridium difficile, Clostridium tetani, Clostridium botulinum, and Clostridium perfringens

Question 24

Characteristics of Gram Negative Bacilli

Answer 24

• Found in a # of sites including fresh water, the gastrointestinal tract
• Can lead to a very serious infections at a number of sites including in blood, wound infections, and pneumonia
• Major issue with these is their resistance to antibodies

Question 25

Notable Gram Negative Bacilli

Answer 25

• Escherichia coli
• Pseudomonas aeruginosa
• Klebsiella pneumoniae
• Proteus mirabilis

Question 26

Characteristics of Gram Negative Cocci

Answer 26

• Organisms found in the oral flora and mucosal surfaces including the genital tract
• Colonize the oral flora, but can also cause meningitis, pneumonia, bacteremia, and sexually transmitted infection

Question 27

Notable Gram Negative Cocci

Answer 27

• Neisseria gonorrhoea
• Neisseria meningitidis
• Neisseria spp.