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Organisms and The Environment > Microorganisms > Flashcards

Microorganisms Flashcards

1
Q

Brief history of microbes

A

Hooke: microscope
Nothing 150 years
Pasteur : disproved spontaneous generation…discovered germs
- Sterilised equipment
Koch: link between micro orgs and disease..wash hands
- Koch postulates

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2
Q

What are koch’s postulates

A
  • Koch postulates
    ○ Diseased animal will have bacteria not present in healthy animal
    ○ If reinfect healthy animal with that bacteria they will get same disease And same bacteria will be seen in the blood
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3
Q

What are the different ways to observe microorganisms

A
  • bright field microscopy
  • fluorescent microscopy
  • differential interface contrast microscopy
  • atomic force microscopy
  • confocal scanning laser microscopy
  • electron microscopy (transmission and scanning)
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4
Q

Bright field microscopy

A
  • staining can improve but kills cells

- phase contrast and dark field = 2 different filters that may allow to see more easily

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5
Q

Fluorescent microscopy

A
  • visualise cells that fluoresce e.g. chlorophyll, DAPI stain
  • stains dna of the cell
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6
Q

Differential interface contrast microscopy

A
  • form of light microscopy
  • uses polarised light (light in a single plane)
  • cellular structures appear more 3D
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7
Q

Confocal scanning laser microscopy

A
  • couples laser source to fluorescent microscope
  • focuses through specimen = reconstructs layers into 3D image
  • cells stained with fluorescent dye to make them distinct
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8
Q

Electron microscopy

A
  • uses electrons instead of visible light
  • electromagnets function as lenses
  • whole system operates in a vacuum

Split into transmission and scanning

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9
Q

Transmission electron microscopy

A
  • high mag
  • high res
  • see structures at molecular level
  • have to make very thin sections of specimen (electrons don’t penetrate into tissue well)
  • tissue has to be dead
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10
Q

Scanning electron microscope

A
  • shows external surfaces of cells
  • specimen coated in film of heavy metal e.g gold
  • electrons scatter from metal coating are collected/processes to form image
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11
Q

Why study microbes

A
  • fight disease
  • food preservation
  • agriculture e.g. nitrogen fixing bacteria
  • animal husbandry
  • fermentation in food
  • biofuels
  • biotechnology
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12
Q

Why microbes are useful in studies

A
  • all cells very similar = discoveries of microbes could be transferred to other organisms
  • don’t take up too much space
  • grow rapidly
  • easily manipulated
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13
Q

What are the different types of microorganisms

A
  • bacteria
  • archaea
  • Protozoa
  • algae
  • viruses
  • fungi
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14
Q

Different shapes of microorganisms cells

A 
○ Coccus
		○ Spirochete
		○ Rod
		○ Spirilla
		○ Stalk and hypha
		○ Filamentous bacteria
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15
Q

Why is morphology useful

A
  • Useful to identify species
    • Differences between people
      However:
    • shape of cell doesn’t tend to predict properties of cell
    • Many species of bacteria look identical
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16
Q

Advantages of cells being small

A
  • Small cells = larger SA:V ratio
    ○ Faster nutrient exchange per unit cell volume
    ○ Can grow faster
    ○ Support a larger population
    • Faster evolution
      ○ DNA replicated as cells divide
      ○ DNA replications cause mutations
      ○ High rate of division = higher rate of mutation (mutations are ‘raw material’ for evolution)
      ○ Allows for rapid adaptation to changing environments
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17
Q

What is the minimum cell size limit

A

0.15 micrometers

Otherwise cant fit everything inside

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18
Q

Describe a gram stain

A
  • Gram stain separates bacteria into positive or negative
    • Positive = purple
    • Negative = red/pink
    • Used as starting point for identifying bacteria
      Procedure:
    • Place bacteria on slide
    • Flood slide with crystal violet
    • Add iodine solution (stain pos purple)
    • Add ethanol briefly (too long will pop cells) (neg cells decolourised)
    • Add counterstain safranin (stains neg cells red)
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19
Q

What is a gram positive cell wall

A

Contains peptidoglycan layer

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20
Q

What is a negative gram cell wall

A

Cell wall, thin peptidoglycan and second membrane

- Second outer membrane prevents purple staining inner membrane which is why it goes red instead

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21
Q

What are endospores

A
  • Highly specialised
    • Only with certain species of bacteria
    • Highly resistant to heat, harsh chemicals, radiation etc.
    • Enable species to survive in very harsh conditions: produce one that survives until conditions good again
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22
Q

Describe sporulation

A
  • Vegetative cell = average cell (no reproduction or specialisation etc)
    • An essential nutrient is exhausted e.g. carbon or nitrogen
    • Vegetative cell stops growing
    • Triggers development of endospore within vegetative cell and is released once matured
    • Spores can remain dormant for years
    • Germinates into a vegetative cell once conditions stabilise
23
Q

Terminal endospore

A

Develops at very end of vegetative cell

24
Q

Subterminal endospore

A

Endospore not quite at end but not at middle

25
Q

Central endospore

A

Develop right in the centre of the cell

26
Q

Describe endospore structure

A
  • Strongly refractive and impermeable to almost all dyes
    • More layers than in vegetative cell
    • Exosporium: thin protein covering
    • Spore coat: layers of spore specific proteins
    • Cortex: loosely cross-linked peptidoglycan
    • Core: core wall, cell membrane, cytoplasm, nucleotide, ribosomes etc.
27
Q

Fimbriae

A
  • Enables cells to stick to surfaces and each other

Assist disease process

28
Q

Pilli functions

A
  1. Conjugation: genetic exchange between cells
    • Plasmid copied and sent to recipient cell
      2. Adhesion of pathogens to specific host tissues and subsequent invasion
      3. Can also be used in mobility
29
Q

What a re the 2 main types of bacteria cell locomotion

A
  1. Swimming
    - needs flagellum
    - in gram pos or neg
  2. Gliding
    - slow
    - needs contact with solid surface
    - bacteria will have ragid edge
30
Q

What are the 3 different attachments of flagella

A

Polar = attached atone or both ends
Tuft
Peritrichous = flagella all over

31
Q

How does gliding locomotion

A
  1. Cell connects with surface and slime pulls along

2. Pilli reach out along surface and pull

32
Q

Describe flagella structure

A
  • Helical
    • Wavelength is characteristic for given species
    • Composed of many copies of a protein called flagellin
    • Molecular motor that drives rotation of flagellin filament is embedded in cell membrane
33
Q

Describe the proton turbine model for flagella

A

○ motor Contains central rod Passed through a series of rings
○ Mot proteins line lower rings = acts as stators
○ Rod and rings rotate while the mot proteins stay still
- Proton turbine model:
○ Proton movement across membrane through mot complex
○ Protons flow through channel
○ Exert electrostatic forces on helically arranged charges on rings (spirals of alternating positive and negative charges: positive will attract negative proton and repelling negative atttractions = spinning motion)
○ Attraction between charges cause rotation

34
Q

Taxis

A

Movement towards something that will aid growth/growth away from toxins

35
Q

Chemotaxis

A

Responding to chemicals

36
Q

Photo taxis

A

Responding to light

37
Q

Why do cells have locomotion

A

To aid with taxis

Gives evolutionary advantage

38
Q

Myxobacteria and myxospores

A

○ Form multicellular structures = fruiting bodies
○ Fruiting body creates mysxospores (resistant to bad conditions, similar to endospores but not the same.) mysxospores related and germinate ( gram neg ). Wait till favourable conditions then turn vegetative
○ Fruiting bodies often colourful and morphologically elaborate
○ Vegetative cells release slime trails for gliding
○ Under favourable conditions vegetative cells aggregate. Do this via slime trails, that can identify and follow = radiating pattern of established slime trails. Slime trail gets thicker and more join. End up in big circle.
○ Aggregated myxobacteria differentiate into fruiting body

39
Q

Autotroph

A

Org that grows with co2 as sole carbon source

40
Q

Chemolithotrophs

A

Org that gets energy from oxidation of inorganic compounds
Only in prokaryotes
No competition from chemoorganotrophs (many compounds used are the waste products from chemoorganotrophs) : often live close together

41
Q

Chemoorganotrophs

A

Org that obtains energy from oxidation of organic compounds

Can be aerobic or anaerobic or both

42
Q

Heterotrophs

A

Org that requires organic carbon as carbon source

43
Q

Phototrophic

A

Orgs that obtain energy from light

44
Q

Symbiotic mutualities

A

Cooperative relationship between microbe and host

45
Q

Parasitic microbe

A

Antagonistic to host

Takes carbon and gives nothing back

46
Q

Saprotrophic

A

Host is dead

47
Q

What are the 3 types of prokaryotic photosynthetic orgs

A

Cyanobacteria, plants and algae

48
Q

Purple and green bacteria

A

Uses oxygenic photosynthesis

Inorganic compounds used instead of water as reducing power in photosynthesis

49
Q

What types of bacteria can fix nitrogen

A

Free living = require no host
Symbiotic
(Eukaryotes CANT)

50
Q

Why is nitrogen fixation important

A

Used for sewage and wastewater treatment

Removes toxic amines and ammonia

51
Q

What 2 groups of bacteria are fixing nitrogen

A

Nitrosomonas

Nitrobacter

52
Q

What’s humus

A

Mixture of organic materials that have resisted rapid decomposition
Mainly plants and microorganisms

53
Q

What is the most important contributor of CO2 to atmosphere

A

Microbial decomposition of dead organic materials and humus

Organisms and The Environment (9 decks)

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