introduction to bacteriology

Question 1

what are the 3 domains of life?

Answer 1

bacteria

archaea

eukarya

Question 2

when did prokaryotes come to be? eukaryotes

Answer 2

prokaryotes
around 4-3.5 billion years ago

eukaryotes
around 2-1.5 billion years ago

Question 3

what’s unique about archaea (in comparison to bacteria)?

Answer 3

can live in extreme environments

don’t cause human diseases (they are not pathogenic)

Question 4

what are prokaryotes?

Answer 4

the smallest, simplest, and most abundant cells on Earth

includes bacteria and archaea

lacks a nucleus and other complex organelles
— they have no membrane bound organelles

Question 5

describe the 4 phases of growth bacteria undergo

Answer 5

LAG
- cellular activity
—- cells increase in size, but no cell division
—- bacteria “re-wires” metabolism

LOGARITHMIC GROWTH
- cell divides by binary fission and doubles in numbers after each generation time
- high metabolic activity because DNA, RNA, cell wall components, and other substances necessary for growth are generated by division
- appears like a steep incline

STATIONARY
- population growth starts to decline because of depletion of available nutrients and accumulation of waste products
—- increased competition for nutrients and cells become less metabolically active
—- in this phase, spore forming bacteria produces endospores and pathogenic bacteria produce virulence factors that help them survive harsh conditions and cause disease
- appears like a plateau on the graph, no overall population growth

DEATH
- as nutrients become less available and waste increases, number of dying cells rises
- as dying cells lyse, they spill their contents into the environment, making these nutrients available to other bacteria
- appears as a sharp decline

Question 6

what are endospores?

Answer 6

highly differentiated cell that is formed within a vegetative or mother cell. the vegetative cell is mainly referred to as a sporangium.

they are highly resistant to heat, desiccation, radiation, chemicals, and some disinfectants

ensures the survival of a bacteria during harsh environmental conditions e.g. overpopulation, nutrient deficiency, or unfavorable climatic conditions

a “dormant” stage of the life cycle

most common in soil

endospores of bacillus and clostridium genera are the best studied

Question 7

which bacteria can form endospores?

Answer 7

only gram+ and only a few can do it

Question 8

what are virulence factors?

Answer 8

bacteria-associated molecules that are required for a bacterium to cause disease while infecting eukaryotic hosts such as humans

produced by the pathogen

Question 9

what is generation time aka doubling time?

Answer 9

time it takes for one generation to divide into daughter cells

varies for species - some grow fast (e.g. DT = 10 minutes) or slow (e.g. DT = 24 hours)

Question 10

what are the 3 types of bacterial shapes?

Answer 10

bacillus
- rod shaped

coccus
- spherical

spirillum
- spiral-shaped or curved

Question 11

what is bacillus?

Answer 11

bacteria that are rod shaped

Question 12

what is coccus?

Answer 12

bacteria that are spherical

Question 13

what is spirillum?

Answer 13

bacteria that are spiral-shaped or curved

Question 14

what are obligate aerobes?

Answer 14

requires oxygen for growth

Question 15

what are obligate anaerobes?

Answer 15

oxygen is toxic for growth

Question 16

what are facultative anaerobes?

Answer 16

can use oxygen if present, but can also growth without oxygen

Question 17

what are aerotolerant anaerobes?

Answer 17

don’t use oxygen – but oxygen isn’t toxic!

Question 18

what are microaerophiles?

Answer 18

grows best with low levels of oxygen

Question 19

in order, what’s the taxonomic ranks for classifying bacteria

Answer 19

Donkey Kong Picks Cheese Over Family, Gains Super Strength

domain

kingdom

phylum

class

order

family

genus – should be capitalized and italicized

species – should be italicized

strain (diversity within species!)

Question 20

among bacterial species, what’s notorious for their diversity? how diverse is this specie?

Answer 20

E COLI

only 60% of it is identical to other E coli

(humans 99.5% identical with each other!)

Question 21

why is there diversity within bacterial species?

Answer 21

due to bacteria’ short life cycle, high reproduction rate, and ability to adapt to environmental changes

Question 22

who developed the staining technique?

Answer 22

Hans Christian Gram

Question 23

what are the staining colours of the 2 major types of bacteria?

Answer 23

gram+
—- purple (bc more dense with peptidoglycan)

gram -
—- pink (bc less dense with peptidoglycan)

Question 24

what happens when gram staining is conducted on mycobacteria? why?

Answer 24

appears neutral - neither positive nor negative

due to thick, waxy cell wall that resists destaining/decolourization with the acid and alcohols used in gram staining – ability called acid fast and is found in mycobacteria

but it’s actually gram +

Question 25

what is acid-fast?

Answer 25

a physical property of certain bacteria and cells that allows them to resist decolorization by acids during laboratory staining --- a thick, waxy cell wall

Question 26

what are mycoplasmas?

Answer 26

small, spherical, self-replicating bacteria they have a plasma membrane, ribosomes, and a genome -- but no cell wall gram-

Question 27

differentiate between mycobacteria and mycoplasmas?

Answer 27

mycoplasma has no cell wall and thus, no distinct shape

Question 28

describe the process of staining -- note the colour at each stage

Answer 28

1. flood the heat-fixed smear with crystal violet for 1 minute ---- all cells become purple 2. add iodine solution for 1 minute ---- all cells remain purple 3. decolourize with alcohol briefly - about 20 minutes ---- gram+ cells are purple; gram- cells are colourless 4. counterstain with safranin for 1-2 minutes ---- gram+ cells are purple; gram- cells are pink/red

Question 29

what's the purpose of counter staining in the staining process?

Answer 29

to help differentiate the cell types before this step, gram+ cells are purple and gram- cells are colourless adding safranin, a pink stain, stains gram-, making it pink. has no visible effects because gram +'s purple colour is much darker

Question 30

describe the structure of bacterial cell walls

Answer 30

rigid structure prevents osmotic lysis contains peptidoglycan --- larger amounts in gram+ --- glycan backbone which is made up of alternate, repeating N-acetylglucosamine (G) and N-acetylmuramic (M) disaccharide units ------ cross-linkages between M sugars since it's not found in eukaryotes, it's a common target of antibiotics

Question 31

what component of most bacteria prevents osmotic lysis?

Answer 31

their cell wall

Question 32

differentiate between gram+ and gram- bacterial cell wall

Answer 32

gram- organisms have less extensive cross-linking in their peptidoglycan layer, making it LESS RIGID gram - has a thinner peptidoglycan layer and has an outer membrane in addition to the cytoplasmic membrane present in all bacteria. the space between the outer membrane and the inner cytoplasmic membrane is called the periplasm space. on it's outer membrane, is a a layer of lipopolysaccharides (endotoxins)

Question 33

what makes up the glycan backbone of peptidoglycan in bacterial cell walls

Answer 33

alternate, repeating N-acetylglucosamine (G) and N-acetylmuramic (M) disaccharide units

Question 34

what is the periplasm space?

Answer 34

the space between the outer membrane and the inner cytoplasmic membrane in gram- bacteria

Question 35

what are lipopolysaccharides?

Answer 35

found on the outer membrane of gram- bacteria part of it is endotoxin, toxic substances that can cause inflammation and fever

Question 36

what are the components of the lipopolysaccharide? describe them

Answer 36

O-specific polysaccharide aka O-antigen - found at the end - antigenic and highly variable (different bacteria makes different O-antigens) - plays a role in colonization, resistance to the immune system, and virulence core polysaccharide - links the O-antigen to the lipid A lipid A - disaccharide and fatty acid group - recognized by the innate immune system -- if they over-respond, it can lead to a cytokine storm which then results in septic shock! - it's the endotoxic part - hydrophobic, how it's able to attach to the membrane

Question 37

describe nucleoids and its genetic material

Answer 37

where genetic material is found in prokaryotes like other organelles in prokaryotes, it had no membrane it's genetic material is generally in the form of single, circular chromosomes -- some bacteria will have multiple, linear chromosomes haploid genome like in all prokaryotes! -- one set of chromosomes -- allows bacteria to evolve very fast since favourable mutations are chosen easily

Question 38

what are plasmids

Answer 38

extra-chromosomal genetic elements usually, not required for bacterial growth often encode for 'fitness' factors -- e.g. antibiotic resistance can be transferred from bacteria to bacteria (horizontal gene transfer) -- transferring antibiotic resistance -- leading to superbugs

Question 39

describe the human microbiota (-- where can bacteria be found in humans? where can it not?)

Answer 39

surface tissues have extensive populations of microbes internal organs are usually sterile - but bacteria can some times be found here the collective "genome" of the human microbiota contains more than 100 times as many genes as our genome

Question 40

what is commensalism?

Answer 40

a relationship where one benefits without helping or hurting the other

Question 41

what is mutualism?

Answer 41

a relationship where both benefits

Question 42

what is parasitism?

Answer 42

a relationship where one benefits at the expense of the other the microbe/pathogen is generally the one benefitting from the host -- parasites are usually eukaryotes!

Question 43

what does a bacterial pathogen need to do to be successful?

Answer 43

colonization invasion/toxicity immune evasion - nearly all pathogens have mechanisms to evade the immune system transmission

Question 44

what are some virulence factors of bacteria?

Answer 44

SURFACE -- lipopolysaccharides (LPS) aka endotoxins -- flagella -- pili and adhesions -- capsules -- secretion systems (complexes that allow bacteria to secrete stuff) SECRETED -- exotoxins

Question 45

what are pili and adhesions?

Answer 45

surface structures involved in attachment to surfaces, host tissues, other bacteria pili are similar to fimbriae, both attach to things plaque is loaded with many bacterial species -- the pili helps them stick to teeth and gums

Question 46

what's a flagella?

Answer 46

structure that allows some bacteria to be motile uses chemotaxis it can run (smooth movement) via counterclockwise rotation and tumble (bumpy movement) via clockwise rotation

Question 47

what's a capsule?

Answer 47

usually made of exopolysaccharides attachment to host tissues protection from host immune system can sometimes be used in vaccines important for formation of biofilms, slimy, glue-like substance

Question 48

what are exotoxins?

Answer 48

soluble proteins excreted by bacteria that can damage host ---- hallmark of a toxin-mediated disease some exotoxins (inactivated) can be used as vaccines -- e.g. tetanus

Question 49

what are the classes of exotoxins?

Answer 49

hemolysis - destroys RBCs (not WBCs) toxins that function inside host cells - e.g. E.Coli, diphtheria extracellular enzymes - destroys tissues (e.g. proteases) superantigens - turns on adaptive immune system

Question 50

describe bacterial intracellular pathogens

Answer 50

taken up and survive within phagocytic cells -- e.g. macrophages some 'force' their own uptake into epithelial cells allows bacteria to hide from different components of the immune system

Question 51

what are stages of biofilms?

Answer 51

attachment - initial contact between bacteria and surface microcolony development - begins to grow exopolysaccharide biofilm development - bacteria begins growing very slowly and becomes very resistant to antibiotic treatments maturation - tip of film: releases bacteria to complete biofilm life cycle (attach to new surface) dissolution/dispersal

Question 52

what are biofilms?

Answer 52

in nature, most bacteria live on biofilm structures (e.g. teeth) organized structures/channels for nutrients to enter & waste products to exit -- the real problem implanted devices (e.g. urinal stint) develop infections very quickly & cannot be killed w/ antibiotics → must remove & replace it

Question 53

what type of bacteria is more resistant?

Answer 53

gram - is more resistant than gram +

Question 54

what are superbugs?

Answer 54

bacteria, fungi, or other microorganisms that are resistant to many antibiotics and other drugs used to treat infections

Question 55

how are most commensals actually mutualistic?

Answer 55

no intention of helping the other, but helps as a byproduct e.g. bacteria in human gut!

Question 56

what type of bacteria can't be visualized well using the gram stain technique?

Answer 56

mycobacteria - acid fast mycoplasma - no cell wall