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microimm > introduction to bacteriology > Flashcards

introduction to bacteriology Flashcards

1
Q

what are the 3 domains of life?

A

bacteria

archaea

eukarya

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2
Q

when did prokaryotes come to be? eukaryotes

A

prokaryotes
around 4-3.5 billion years ago

eukaryotes
around 2-1.5 billion years ago

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3
Q

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

A

can live in extreme environments

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

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4
Q

what are prokaryotes?

A

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

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5
Q

describe the 4 phases of growth bacteria undergo

A

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

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6
Q

what are endospores?

A

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

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7
Q

which bacteria can form endospores?

A

only gram+ and only a few can do it

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8
Q

what are virulence factors?

A

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

produced by the pathogen

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9
Q

what is generation time aka doubling time?

A

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)

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10
Q

what are the 3 types of bacterial shapes?

A

bacillus
- rod shaped

coccus
- spherical

spirillum
- spiral-shaped or curved

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11
Q

what is bacillus?

A

bacteria that are rod shaped

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12
Q

what is coccus?

A

bacteria that are spherical

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13
Q

what is spirillum?

A

bacteria that are spiral-shaped or curved

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14
Q

what are obligate aerobes?

A

requires oxygen for growth

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15
Q

what are obligate anaerobes?

A

oxygen is toxic for growth

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16
Q

what are facultative anaerobes?

A

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

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17
Q

what are aerotolerant anaerobes?

A

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

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18
Q

what are microaerophiles?

A

grows best with low levels of oxygen

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19
Q

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

A

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!)

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20
Q

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

A

E COLI

only 60% of it is identical to other E coli

(humans 99.5% identical with each other!)

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21
Q

why is there diversity within bacterial species?

A

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

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22
Q

who developed the staining technique?

A

Hans Christian Gram

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23
Q

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

A

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

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

24
Q

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

A

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 +

25
Q

what is acid-fast?

A

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

26
Q

what are mycoplasmas?

A

small, spherical, self-replicating bacteria

they have a plasma membrane, ribosomes, and a genome – but no cell wall

gram-

27
Q

differentiate between mycobacteria and mycoplasmas?

A

mycoplasma has no cell wall and thus, no distinct shape

28
Q

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

A
  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
29
Q

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

A

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

30
Q

describe the structure of bacterial cell walls

A

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

31
Q

what component of most bacteria prevents osmotic lysis?

A

their cell wall

32
Q

differentiate between gram+ and gram- bacterial cell wall

A

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)

33
Q

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

A

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

34
Q

what is the periplasm space?

A

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

35
Q

what are lipopolysaccharides?

A

found on the outer membrane of gram- bacteria

part of it is endotoxin, toxic substances that can cause inflammation and fever

36
Q

what are the components of the lipopolysaccharide? describe them

A

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

37
Q

describe nucleoids and its genetic material

A

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

38
Q

what are plasmids

A

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

39
Q

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

A

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

40
Q

what is commensalism?

A

a relationship where one benefits without helping or hurting the other

41
Q

what is mutualism?

A

a relationship where both benefits

42
Q

what is parasitism?

A

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!

43
Q

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

A

colonization

invasion/toxicity

immune evasion
- nearly all pathogens have mechanisms to evade the immune system

transmission

44
Q

what are some virulence factors of bacteria?

A

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

SECRETED
– exotoxins

45
Q

what are pili and adhesions?

A

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

46
Q

what’s a flagella?

A

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

47
Q

what’s a capsule?

A

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

48
Q

what are exotoxins?

A

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

49
Q

what are the classes of exotoxins?

A

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

50
Q

describe bacterial intracellular pathogens

A

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

51
Q

what are stages of biofilms?

A

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

52
Q

what are biofilms?

A

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

53
Q

what type of bacteria is more resistant?

A

gram - is more resistant than gram +

54
Q

what are superbugs?

A

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

55
Q

how are most commensals actually mutualistic?

A

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

56
Q

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

A

mycobacteria - acid fast

mycoplasma - no cell wall

microimm (30 decks)

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