Bacterial Shape, Size, Appendages and Lifestyles L2 Flashcards
who were the two people who made microscopes
Hooke and Leeuwenhoek
describe Hooke’s microscope
compound microscope (2 lenses)
low magnification
discovered/named cells
describe Leeuwenhoek’s microscope
used a small lens
specimen sat on needle
much higher magnification
who was the first person to see microbes
Leeuwenhoek’s
what are the two types of microscopy and what are their resolutions
light: 200nm- can be stretched to 10nm using super-resolution methods
electron: 10 million
what are the two types of electron microscopes and how do they differ
scanning and transmission electron
scanning has a coil that allows 3D image to develop
give 3 examples of light microscopy techniques and how they work
- 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 - florescent
- uses florescent stains to form image - 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
describe process of Gram staining
- stain with crystal violet (bacteria go purple)
- wash with iodine
- wash with alcohol (decolour some bacteria)
- stain with safranin (bacteria go pink)
which bacteria go purple and which bacteria go pink
purple: gram positive
pink: gram negative
describe structure of gram pos and neg
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
what is the function of cell wall in bacteria
- Important for protection against osmotic and environmental stresses, defines shape and helps with uniform cell division and
- Target for immune defenses (e.g., lysozyme)
- Target for many antibiotics (e.g., penicillin)
what appears in the middle of a dividing cell
septum
what does penicillin target
formation of cell wall
bacteria unable to make it and will lyse
when can bacteria survive without cell wall
when intra and extracellular conditions are isosmotic
describe bacteria that can survive without cell walls and what are they referred to as
referred to as L-form
they are fragile and slow to divide
resistant to penicillin
can rebuild the wall and retain membranes
what does GFP stand for and where can it be found
Green Fluorescent Protein
jelly fish
how can GFP be used in microscopy
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
what is a negative of GFP
Many fusion proteins malfunction and localization may be misleading
how did fluorescent microscopy reveal complexity of bacterial cell
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
what is the proteinaceous S-layer
outermost layer that is a crystalline lattice structure of a single protein that serves as a protective barrier like a sieve
what are capsules
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
give three examples of surface appendages and describe them
pili and fimbriae and flagella
protein polymers important in adhesions and attachment
Important in pathogenesis
Immunogenic
Support gene transfer by conjugation
“Twitching” motility
what is the differenc between pili and fimbriae
pili are longer and there are fewer of them
describe flagella
it is a roatatory motor that generates movement
helical in structure
what are endospores
form from bacteria that have been starved
they are resistant to heat, solvents, lysosomes
turn back into bacteria when favourable conditions return
describe creation of endospores
start from mother bacteria which is starved creating asymmetric divisions forming endospore
mother bacteria dissipates
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)
mother: sigma factor E- identified with red dye
endospore: sigma factor F- identified with green dye
what are biofilms
communities of different species held together by a matrix (polysaccrides, proteins nucleic acids)
cells often differentiate
biofilms promotes adhesion and resistance
