Module 3

Question 1

how do bacterial populations grow

Answer 1

binary fission

Question 2

how can a bacterial cell grow and divide

Answer 2

by using osmotic pressure against its cell wall

Question 3

describe causes of senescence in binary fission

Answer 3

one pole of the cell will always be made up of older material

can inherit damaged DNA

Inherit damaged proteins

Activation of damage defense systems (M) rather than growth systems (G)

Question 4

difference between anabolism and catabolism

Answer 4

anabolism: the building of components such as DNA and protein

catabolism: the breakdown of molecules to obtain energy

Question 5

physical requirements for growth of bacteria

Answer 5

temperature, water, pH, pressure all influence enzymatic activity and structure of proteins

oxygen levels differ per microbe

Question 6

list the types of aerobes/anaerobes

Answer 6

Obligate aerobes
□ Aerobic respiration
□ Oxygen is the terminal electron acceptor in the ETC

Facultative anaerobe
□ Don’t need O2 for growth, but grow better in its presence

Aerotolerant anaerobe
Can tolerant O2 but do not use it
□ Fermentative process

Strict Anaerobe
□ Oxygen is toxic
□ Fermentation
□ Anaerobic respiration

Microaerophile
□ Damages by atmospheric levels of oxygen (20%) but still require 2-10% of atmosphere oxygen for growth

Question 7

what are reactive oxygen species and why are they bad for cells

Answer 7

cellular proteins transfer electrons to O2 leaving extra paired or un[paired electrons forming reactive species that can damage proteins, lipids and nucleic acids in the cell

Question 8

describe the metabolic groupings

Answer 8

energy source:
-chemotrophic
-phototrophic

carbon source
-autotrophic: CO2
-mixotrophic: CO2 and organic compounds
-heterotrophic: organic compounds

electron source
-lithotrophic: inorganic compounds
-organotrophic: organic compounds

Question 9

how do bacteria establish infection

Answer 9

bacteria must constantly adapt their metabolic processes in order to balance biosynthesis with sufficient ATP biogenesis, using those nutrients available from the host environment

Question 10

what are persister cells

Answer 10

Escape effects of antibiotics without genetic change

Phenotypic variants that occur in low numbers in a population

Dramatically shift metabolism to remain just viable, but not growing
-Not metabolically active so antibiotics cant target them
-Once antibiotic is gone shift back to a metabolic state

Question 10

difference between persister and resistant cells

Answer 10

resistant cells include a genetic shift and do grow in the presence of antibiotics, persister cells do not do this

Question 11

how do bacteria communicate

Answer 11

through quorum sensing: an accumulation of signalling molecules that enables a single cell to sense the number of bacteria and respond by changing metabolic activity

Question 12

what are autoinducers and how do they work

Answer 12

signalling molecules in quorum sensing

small go back into bacterial cell to elicit response, large bind to receptors on cell surface to start a signalling cascade in the cytoplasm

Question 13

gram + quorum sensing strategies vs gram -

Answer 13

+: autoinducer binds to outside of cell
-signal cascade
-changes in gene expression

-: autoinducer enters the cell
-changes in gene expression

Question 14

describe quorum sensing and virulence

Answer 14

Bacteria are able to upregulate expression of virulence genes in the presence of high concentrations of autoinducers (which its concentration is dependent on the bacterial population density)
-genes that enhance survival (biofilm, toxins, motility)

Question 15

using quorum sensing to make a biofilm

Answer 15

cells must coordinately upregulate expression of polysaccharide synthesis and down regulate genes involved in motility

Question 16

phases of bacterial growth

Answer 16

lag phase
exponentiial phase
stationary phase
death phase

Question 17

methods of controlling microbial growth

Answer 17

Antisepsis
○ The inhibition of microorganisms on, or in, living tissue

Sanitization
○ A reduction of total microbial population to levels considered safe by public health standards

Disinfection is a substantial reduction of total microbial population and destruction of pathogens (not including spores)

Sterilization
○ All living cells, spores, viruses, and prions are either destroyed or removed from the treatment environment

Question 18

methods of sterilization and disinfection

Answer 18

physical: heat, radiation

mechanical: filtration

chemical: chemical agents

Question 19

3 principles of antibiotics

Answer 19

antibiotics do not work on viruses

antibiotics may be bactericidal or bacteriostatic

an antibiotic must be selectively toxic

Question 20

what do antibiotics target/what are some common processes targeted

Answer 20

metabolic pathways and cell growth mechanisms

folate synthesis and cell wall synthesis

Question 21

tetrahydrofolic acid is essential for

Answer 21

synthesizing nucleotides and amino acids

Question 22

what is opsonization and what are opsonins

Answer 22

the process of enhancing phagocytosis through the coating of a bacterium with opsonins

opsonins can be a antibodies or complements

Question 23

structure of the innate immune system

Answer 23

barriers (physical, chemical, microbial)

cells (NK, dendritic, macrophage, neutrophils)

processes (phagocytosis, inflammation, opsonization)

Question 24

what are the three C3 pathways that leads to increase inflammation and phagocytosis

Answer 24

○ Antibodies to the pathogen (classical pathway)

○ A host protein that binds to mannose on the pathogen’s surface (Lectin pathway)

○ Through direct interaction of C3 with repeating bacterial motifs on the pathogen surface that leads to cleavage generating C3b (alternative pathway)

Question 25

what is the membrane attack complex (MAC)

Answer 25

The complement system can assemble into a membrane attack complex (MAC) in the cell membrane of pathogen cells, forming pores/holes that cause the cells to lyse

The MAC is particularly effective against Gram- pathogens because it can insert through the outer membrane and destabilize the cytoplasmic membrane

Question 26

how do natural killer cells kill target cells

Answer 26

by secreting proteins that trigger target cells to commit suicide by apoptosis

Question 27

innate to adaptive immune response

Answer 27

inflammation: infected area flooded with cytokines and chemokines that attract and activate phagocytic cells

cells devour and display aicrobial antigens so that lymphocytes can activate a specific response