Bacteria

Question 1

what are the different structural components of bacteria?

Answer 1

• capsule
• cell wall
• nucleoid
• plasmids
• plasma membrane
• ## ribosomes

Question 2

what can certain bacteria produce?

Answer 2

endospores (allow bacterial genome protection - in a dormant state when the environmental conditions are unfavourable)
inclusion bodies (bacteria in unstable environments store excess nutrients within inclusion bodies)

Question 3

what are bacterial sizes

Answer 3

0.5 micrometer to 5

Question 4

what are the shapes of bacteria

Answer 4

coccus, bacillus, vibrio, coccobacillus, spirilli, spirochete

Question 5

what is the capsule?

Answer 5

organisational layer located outside cell wall and composed of polysaccharides or proteins (glycoalyx)

Can get capsulated or non capsulated bacteria
Capsuled produce smooth colonies
Non capsulated produce rough colonies

Question 6

what do capsules protect the cell from?

Answer 6

drying
attachment of phages
antibacterials
phagocytic cells

Question 7

what is bacterial mode of nutrition?

Answer 7

absorptive

Question 8

what cellularity is bacteria?

Answer 8

multicellular, prokaryotic

Question 9

how do bacteria reproduce?

Answer 9

binary fission

Question 10

what is the major component of the bacterial cell wall

Answer 10

peptidoglycan

or murein

Question 11

what are the layers of peptidoglycan composed of?

Answer 11

long chains of alternating molecules of N-acetylglucosamine, and N-acetylmuramic acid

Question 12

how are tetra peptide chains linked in gram positive and negative?

Answer 12

gram positive = linked by pentaglycine cross bridges

Gram negative = directly cross linked

Question 13

what do antibiotics do to bacterial cell wall?

Answer 13

as peptidoglycan is unique to bacteria it is a good target - interfere with PG synthesis - weaken the cell wall and make cells more susceptible to effects of osmotic pressure

Question 14

what is the cell wall like in gram positive?

Answer 14

simple - thick layer of peptidoglycan with embedded teichoic acid external to the plasma membrane

Question 15

What is the cell wall like in gram negative?

Answer 15

complex- 3 layers -
thin layer of peptidoglycan
inner membrane
outer membrane containing lipopolysaccharides

Question 16

what are teichoic acids?

Answer 16

the PG layers are embedded with these TAs (CHO chains that extend - they stabilise PG by increasing its rigidity)

Question 17

what is embedded in the PG layers that increase its rigidity?

Answer 17

teichoic acids

Question 18

what is mycobacteriaceae?

Answer 18

have PG and TAs but also an additional external layer of waxy mycolic acids in the cell wall. - They’re called acid fast bacteria

Question 19

why are mycobacteriaceae called acid fast bacteria?

Answer 19

Because acid fast stains are used to penetrate the mycolin acid during staining - stain red by carbolfuschin

Question 20

what is the nucleoid?

Answer 20

DNA and DNA proteins are in the nucleoid. DNA interacts with nucleoid associated proteins that assist in the organisation and packaging of chromosome

Question 21

what are plasmids?

Answer 21

sometimes bacteria have extra chromosomal DNA which isn’t part of the chromosome - they are in plasmids which are small, circular dsDNA. - carry genes that confer advantageous traits

Question 22

what is the plasma membrane?

Answer 22

selectively permeable bilayer of mainly phospholipids formed with ester linkages, and proteins. The phospholipids and proteins move laterally within the plane as well as between phospholipid layers

Question 23

name and describe 3 types of membrane transport

Answer 23

1. Simple diffusion (passive) - high concentration to low - small molecules
2. Faciliated - uses selective protein carriers channels - charged and large molecules
3. Active transport - when cells move across a membrane against concentration gradient - requires ATP

Question 24

What are the colours of gram positive and negative on gram staining with crystal violet?

Answer 24

positive- purple

negative-pink

Question 25

what is the primary stain for the acid fast staining of mycobacteria?

Answer 25

carbolfuschin

Question 26

what is the order of reagents used in gram stain?

Answer 26

crystal violet, iodine, decolourizer, safranin

Question 27

the process of gram staining is based on the ability of the bacterial cell wall to what?

Answer 27

retain crystal violet dye during solvent treatment

Question 28

why do bacteria store nutrients in inclusion bodies in a polymerised form?

Answer 28

It reduces the build up of osmotic pressure as the cell accumulates solutes

Question 29

what are: volutin granules sulfur granules

Answer 29

volutin granules - inclusions that store polymerised inorganic phosphate that can be used in metabolism and assist in biofilm formation sulfur - in sulfur bacteria (thiobacillus) - store elemental sulfur for metabolism

Question 30

What are the characteristics of endospores?

Answer 30

- resistant to extreme temps and radiation - dont absorb gram stain - only endospore stain - dehydrated, no metabolic activity - dormant

Question 31

outline sporulation

Answer 31

Formation of septum in vegetative cell, septum divides.- DNA replicates. = foreshore 2. Membrane forms around the forespore 3. Protective cortex forms around forespore by laying down layers of calcium and dipicolinic acid between membranes 4. protein spore coat forms around cortex and mother DNA disintegrates 5. Maturation forming the outermost exosporium 6. Mother cell disintegrates and the endospore is released

Question 32

what is sporulation and why does this happen?

Answer 32

process of a vegetative cell turning into an endospore - this happens when nutrients are depleted or the conditions in environment are unfavourable

Question 33

what happens to endospores once living conditions improve?

Answer 33

undergo germination to re-enter a vegetative state

Question 34

name gram positive bacteria that produce endospores (5)

Answer 34

- B.anthracis (anthrax) - C.tetani = tetanus - C.botulinum = botulism - C.difficile - C.perfrinogens = gas gangrene

Question 35

what are filamentous appendages and what do they do?

Answer 35

protein appendages embedded within cell envelope - extend outward and allow interaction with environment - attach to other surfaces, transfer DNA or aid in movement

Question 36

what are 3 types of appendages

Answer 36

fimbriae pili flagella

Question 37

what are fimbriae

Answer 37

short, bristle like proteins projecting from the cell surface by the hundreds - enable cell to attach to surfaces e.g on host cell or for biofilm production

Question 38

what are pili | what is F pilus

Answer 38

longer, less numerous protein appendages aiding in attachment to surfaces. F pilus = sex pilus for transfer of DNA between cells - physical

Question 39

what are flagella

Answer 39

stiff, spiral filaments composed of flagellin protein subunits - move in aqueous environment and have propellers to dictate direction of bacteria

Question 40

what are the 4 types of flagella arrangements

Answer 40

1. monotrichous - singular flagellum at end of cell (polar) - vibrio cholera 2. amphitrichous - flagellum at each end - spirillum minus 3. lophotrichous- tuft at 1 end - pseudomonas aeruginosa 4. Peritrichous - cover entire surface - E.coli

Question 41

how do bacteria achieve directional movement?

Answer 41

by changing the rotation of their flagella

Question 42

flagella rotations

Answer 42

1- bundle when they rotate anti-clockwise resulting in a run 2. Rotate clockwise they are no longer bundled resulting in tumbles

Question 43

describe bacterial cell division (binary fission)

Answer 43

1. genome attached to membrane (by mesosomes) 2. chromosomes replicate and separate 3. septum formation 4. septum divides - 2 daughter cells separate that are identical to parent (diplococci, chains)

Question 44

describe gram staining

Answer 44

1. Crystal violet - primary stain added to specimen - stains cells purple or blue (pink) 2. Iodine - mordant makes dye less soluble so adheres to cell walls - they remain blue or purple 3. Alcohol - decolourizer washes away stain from gram negative cell wall. Gram pos remain their colour 4. Safranin - counterstain allows dye adherence to gram negative walls - gram negative appear pink