General Bacteriology

Question 1

Describe bacteria.

Answer 1

-unicellular
-lack membrane bound organelles & nucleus

Question 2

Describe eukaryotes VS prokaryotes.

Answer 2

Question 3

Describe bacteria size, shape, & arrangement.

Answer 3

-1 um in diameter
-smaller size = lg surface to vol ratio
-spherical bacterium = 2um diameter
-eukaryotic = 20um diameter
-pleomorphism (cocci, rods/bacilli, spirals)

Question 4

Describe bacterial taxonomy & phylogeny.

Answer 4

-polyphasic taxonomy
>phenotypic, genotypes, phylogenetic
-bacterial phylogeny = evolutionary relationship between bacteria
-species = taxonomic unit

Question 5

Describe bacterial cell wall.

Answer 5

-peptidoglycan = unique to prokaryotes
-function: rigid, protection (mechanical & osmotic lysis)
-differences in structure & chemical composition = pathogenicity & staining properties

Question 6

Describe bacterial cell wall staining properties.

Answer 6

1. Gram staining = differentiates bacteria by chemical & physical properties of cell wall (detecting peptidoglycan)
2. Ziehl neelsen (acid fast) = presence of my colic acid in cell wall (mycobacterium)

Question 7

Describe gram pos, gram neg, & mycobacteria.

Answer 7

1. Gram pos (purple) thiccer peptidoglycan
   -lipoteichoic acid = antigenic
   -resistance to physical disruption & drying
2. Gram neg (red)
   -LPS
   -lipid A = endotoxin (activates immune system & harmful effects)
   -polysaccharide chain = antigenicity
   -low resistance to physical disruption & drying
3. Mycobacteria = mycolic acid as virulence factor

Question 8

Describe flagella.

Answer 8

-bacterial surface in gram neg
-locomotion, bacterial motility
-arrangement ID bacteria
-endoflagella in periplasmic space = cork screw motility

Question 9

Describe pili/fimbriae.

Answer 9

-hair like appendage on bacterial surface
-antigencity
-attachment pili = adherence to host tissue
-conjugation pili = transfer of genetic material

Question 10

Describe capsule.

Answer 10

-polysaccharide outer layer
-functions:
>nutrient reserve
>protection from adverse environment
>adhere to host cell surface
>evade phagocytosis

Question 11

Describe endospores.

Answer 11

-cryptobiotic state of dormancy
-durable
-survive in adverse environment (long periods)
-formed intracellularly (free spores)
-made by clostridium & bacillus when exposed to adverse conditions like nutrition depletion

Question 12

Describe sporulation VS germination.

Answer 12

1. Sporulation
   -formation of spores from vegetative bacterial cells during unfavorable environmental conditions
2. Germination
   -return of dormant spores to vegetative growth induced by nutrients (non nutrient agents)

Question 13

Describe exceptions to general bacterial populations.

Answer 13

1. Mycoplasma - no cell wall (peptidoglycan)
2. Leptospira - 2 circular chromosomes
3. Borrelia burgdorferi - linear chromosomes

Question 14

Describe bacterial metabolism.

Answer 14

-replication by binary fission (asexual)
-growth curve:
>lag = increase cell size, active metabolism (no division)
>exponential phase (log) = cells multiple max rate
>max stationary phase = exhaustion of nutrition or toxic product accumulation, growth stops (balance of growth & death rate)
>decline/death phase

Question 15

Describe the factors required for bacterial growth.

Answer 15

-different nutrients for species
-source of metabolic energy: fermentation, respiration, photosynthesis
-diff temp (mesophiles mostly) & oxygen

Question 16

Describe bacterial virulence factors.

Answer 16

-exo & endotoxins
-superantigens
-biofilms
-quorum sensing

Question 17

Describe exo VS endotoxins.

Answer 17

1. Exotoxins = proteinaceous toxins made by bacteria (heat labile)
2. Endotoxins = cell wall components that induce inflammation by stim immune system (heat stable)

Question 18

Describe superantigens.

Answer 18

-exotoxins cause dysfunction of IS
-activation via variable region of B chain of TCR (not antigen specificity) = no immune protection
-T cell prolif & cytokine release
-nausea, vomiting, fever, shock
-ex: staph, strep

Question 19

Describe biofilms.

Answer 19

-bacterial pop adhere to each other or surface = bi polymer matrix - exchange nutrients & make LPS

Question 20

Describe quorum sensing.

Answer 20

-bacteria make sm signal molecules (autoinducers) to communicate
-when pop reaches defined density = changes in behavior, appearance & metabolism

Question 21

Describe transfer of virulence factors.

Answer 21

-between bacteria thru conjugation, transformation, or transduction
-horizontal gene transfer mediated by outer membrane vesicles
-plasmid & bacteriophages carry genes for antibiotic resistance, toxins, capsules, fimbriae

Question 22

Definitions!

Answer 22

-pathogen = infectious agent (microorganism that can cause disease by colonization of host)
-pathogenesis = biological mech that lead to disease
-pathogenicity = ability of microorganism to damage host
-infection = invasion & multiplication of pathogens in individual or pop
-virulence = capacity of pathogen to damage host
-virulence factors = properties found in isolates that cause disease but aren’t found in isolates of same species that lack ability to cause disease
-predisposition = what predisposes an animal to an infectious disease
-infectious disease = disease caused by microorganisms
infection doesnt mean disease - all communicable diseases are infectious but not vice versa

Question 23

Describe the diff types of pathogens.

Answer 23

*less than 5% of microbes are pathogenic
-majority extracellular
-obligate intracellular (host cell to replicate)
-facultative intracellular
-opportunistic

Question 24

Describe the infectious disease triangle.

Question 25

Describe the seq of events in pathogenesis.

Answer 25

1. Host
2. Overcome host defense
3. Compete w normal microbiota to adhere to host tissue & colonize host systems
4. Multiply
5. Exert damage to host

Question 26

Describe the consequence of host pathogen interaction.

Answer 26

-Inflammation
-local tissue damage (toxin or IS)
-toxemia (structural/functional)
-acute or chromic systemic disease