lab 5 Flashcards
brownian motion
jiggling not true motility
s. ep
non motile
b. su
motile
rod shaped cells clearly moving
in the stab tube was also motile
b.su is an obligate aerobe, greatest metabolic activity at the top of the tube where there is oxygen, and the cells show net movement upwards toward the top of the tube. show chemotaxis or aerotaxis towards Oxygen
flagella can be stained
flagella is to thin to be seen with a brightfield microscope
so must first be thickened with a mordant: tannic acid
(know monotrichous, amphitrichous, lophotrichous, and peritrichous)
motility using growth media
motility tubes contained a rich nutrient medium, much like t soy but a lower concentration of agar. semi solid medium should keep non motile bacteria in place along the stab line and motile bacteria should be able to swim through the semi solid medium into other parts of the tube
to make bacteria visible the motility medium also contained an indicator dye that turns red in the presence of metabolically active bacteria called 2,3,5-triphenyltetrazoliumchloride
capsules are a characteristic of many
pathogenic bacteria
virulent
able to cause disease
cells with capsules
avirulent
cells without capsules
not able to cause disease
however does not mean that all bacteria with capsules cause disease
benefits cells might derive from having a capsule
resisting drying or slowing the diffusion of oxygen into the cell
help microorganisms stick to surfaces and are important in helping bacteria establish biofilms
biofilm is an
aggregation of bacteria on a solid surface
capsule is composed of
thick layer of polysaccharide and or glycoprotein and it contains a great deal of water
the chemical nature of the capsule makes it difficult to stain so a diff method of staining is required to view capsules (capsules resist stains)
two steps: basic - crystal violet and acidic-nigrosin
capsule appears colourless
inside clear capsule is a stained cell
we did capsule stain on
N. capsulatum
refer to page 64 for details
only gram positive bacteria form true endospores
however does not mean all gram positive bacteria form endospores
bacillus forms endospores
endospores
made when cells run out of nutrients
once spores have been released you can’t tell if they are true endospores or not , spores that were formed on the inside of a mother cell or simply some other particle on the slide that retained the green stain
endospore stain
blue green coloured, subterminal endospore
pink cells (stained with safranin)- counterstain
heat is a mordant to help the stain malachite green penetrate the spore wall
water acts as a destain-washing the water soluble malachite green out of the cell but no out of the thick walled endospore
go to page 67
you cannot see flagella on the
hanging drop slide
hanging drop slide
see how the cells behave in a three dimensional liquid environment
