Cell-to-cell communication between unicellular organisms

3 examples of cell-to-cell communication between unicellular organism

1. yeast

2. bacteria

3. cellular slime molds

how do yeast normally reproduce?

asexually by budding

problem with asexual reproduction?

does not allow for genetic variety wince offspring are identical to parent

occasionally, yeast cells will want to find another yeast cell to mate with. how?

using chemical signals and receptors

2 mating types of yeast

“a” and “alpha”

pheromones

chemical signals used to attract a mate

a yeast cell that wants to mate must figure out if any other yeast cells nearby (that are of different type). what will an “a” type yeast do?

release “a” type pheromones that will diffuse away from “a” yeast and will hopefully bind to “a” receptors on “alpha” yeast if any nearby

releasing these pheromones is an example of __________ signaling

paracrine

receptors bind on the _______ side so that the yeast knows where to go

closer

a yeast cell that wants to mate must figure out if any other yeast cells nearby (that are of different type). what will an “alpha” type yeast do?

will release “alpha” pheromones, which will bind to receptors on “a” cells. then yeast will start to extend their cytoplasm on side of cell where pheromones bound to their receptors (shmoo).

shmoo

cytoplasmic extensions

shmooing

process of the cells growing toward each other

shmooing results in

the fusion, or mating, of two cells of opposite type

new cell is __ploid

diploid

the new diploid a/alpha cell contains _________ of both cells

all the genes

purpose of fusion of yeast cells is

genetic variety

bacteria cannot do much harm unless they act as a group:

coordinated attack

quorum-sensing bacteria

release chemical signals which can bind to receptors on other bacteria (and even on themselves) and let them know whether or not enough bacteria are present to be able to launch a coordinated attack

how could quorum sensing be used to fight bacteria that aren’t easily killed by most antibiotics?

scientists can block receptors on bacteria which will prevent coordinated attack, since they won’t be able to detect each other

why are they Kingdom Protista

because they are amoeba-like unicellular protists

how do cellular slime molds communicate when food is plentiful?

they exist separately/independently as a unicellular protist

how do cellular slime molds communicate when food is scarce?

• slime molds start to secrete cAMP into the extracellular fluid (distress signal)

• this extra cAMP attracts other slime molds to the area and they also release cAMP

• slime molds aggregate to form a slug-like organism (capable of faster movement) and will look for a better food supply

  • like Voltron coming together to be more powerful

• when more suitable place is found, fruiting body develops

  • releases spores (which become gametes) which become individual cellular slime mold cells upon fertilization

chemotaxis

attraction of slime molds to the cAMP chemical signal

basic order after fruiting body

fruiting body→spores→gametes→fertilization→new unicellular slime mold cell