Bacterial Shape, Size, Appendages and Lifestyles L2

Question 1

who were the two people who made microscopes

Answer 1

Hooke and Leeuwenhoek

Question 2

describe Hooke’s microscope

Answer 2

compound microscope (2 lenses)
low magnification
discovered/named cells

Question 3

describe Leeuwenhoek’s microscope

Answer 3

used a small lens
specimen sat on needle
much higher magnification

Question 4

who was the first person to see microbes

Answer 4

Leeuwenhoek’s

Question 5

what are the two types of microscopy and what are their resolutions

Answer 5

light: 200nm- can be stretched to 10nm using super-resolution methods
electron: 10 million

Question 6

what are the two types of electron microscopes and how do they differ

Answer 6

scanning and transmission electron
scanning has a coil that allows 3D image to develop

Question 7

give 3 examples of light microscopy techniques and how they work

Answer 7

1. phase contrast
   - uses refraction and interference of light by structure in specimen to create high contrast, high resolution images without staining- good for living specimens - endospores
2. florescent
   - uses florescent stains to form image
3. confocal
   - uses laser to scan multiple Z-planes producing numerous 2D, high res images at different depths that can be constructed into 3D image
   - useful for biofilms which are thick

Question 8

describe process of Gram staining

Answer 8

1. stain with crystal violet (bacteria go purple)
2. wash with iodine
3. wash with alcohol (decolour some bacteria)
4. stain with safranin (bacteria go pink)

Question 9

which bacteria go purple and which bacteria go pink

Answer 9

purple: gram positive
pink: gram negative

Question 10

describe structure of gram pos and neg

Answer 10

pos: one membrane, thick cell wall made from peptiglycan
neg: two cell walls- outer and cytoplasmic, walls made from little peptiglycan which is why stain appears pink not purple

Question 11

what is the function of cell wall in bacteria

Answer 11

1. Important for protection against osmotic and environmental stresses, defines shape and helps with uniform cell division and
2. Target for immune defenses (e.g., lysozyme)
3. Target for many antibiotics (e.g., penicillin)

Question 12

what appears in the middle of a dividing cell

Answer 12

septum

Question 13

what does penicillin target

Answer 13

formation of cell wall
bacteria unable to make it and will lyse

Question 14

when can bacteria survive without cell wall

Answer 14

when intra and extracellular conditions are isosmotic

Question 15

describe bacteria that can survive without cell walls and what are they referred to as

Answer 15

referred to as L-form
they are fragile and slow to divide
resistant to penicillin
can rebuild the wall and retain membranes

Question 16

what does GFP stand for and where can it be found

Answer 16

Green Fluorescent Protein
jelly fish

Question 17

how can GFP be used in microscopy

Answer 17

the gene for GFP has been sequenced
the GFP is added onto tail of gene of interest forming hybrid protein containing protein of interest and GFP
it will glow

Question 18

what is a negative of GFP

Answer 18

Many fusion proteins malfunction and localization may be misleading

Question 19

how did fluorescent microscopy reveal complexity of bacterial cell

Answer 19

discovered FtsZ: contractile ring in bacteria allowing binary fission
GFP added to gene that coded for FtsZ, it glowed green under microscope
being able to visualise it meant it could be tracked

Question 20

what is the proteinaceous S-layer

Answer 20

outermost layer that is a crystalline lattice structure of a single protein that serves as a protective barrier like a sieve

Question 21

what are capsules

Answer 21

substances that surround bacterial cells made from polysaccrides and sometimes covalently attached to cell wall.
important in biofilms and can help in the avoidance of immune response

Question 22

give three examples of surface appendages and describe them

Answer 22

pili and fimbriae and flagella
protein polymers important in adhesions and attachment
Important in pathogenesis
Immunogenic
Support gene transfer by conjugation
“Twitching” motility

Question 23

what is the differenc between pili and fimbriae

Answer 23

pili are longer and there are fewer of them

Question 24

describe flagella

Answer 24

it is a roatatory motor that generates movement
helical in structure

Question 25

what are endospores

Answer 25

form from bacteria that have been starved
they are resistant to heat, solvents, lysosomes
turn back into bacteria when favourable conditions return

Question 26

describe creation of endospores

Answer 26

start from mother bacteria which is starved creating asymmetric divisions forming endospore
mother bacteria dissipates

Question 27

flouresent microscopy can be used to study endospores by adding red or green flouresent protein to sigma factors
which sigma factors are found in which cell
(sigma factors cause endospores to form)

Answer 27

mother: sigma factor E- identified with red dye
endospore: sigma factor F- identified with green dye

Question 28

what are biofilms

Answer 28

communities of different species held together by a matrix (polysaccrides, proteins nucleic acids)
cells often differentiate
biofilms promotes adhesion and resistance