spores

vegetative cell

active stage of bacterial cell

sensitive to heat

endospore

state after vegetative

resistant to extreme environment

spores

• resting or dormant cell

• metabolically inactive

• produced during unfavorable conditions

sporulation

process of formation of spores

0.2 um

average size of spore in diameter

germination of spore

• return of favorable nutritional conditions

• activation

• production of single vegetative cell

2 types of bacterial spores

endospore

exospore

endospore

produced WITHIN the bacterial cell

exospore

produced OUTSIDE the cell

very few bacteria produces these

5 major layers of endospores

• exosporium

• spore coat

• cortex

• spore wall

• core

exosporium

outermost layer covering the spore coat

made up of lipoprotein and some carbohydrate

spore coat

thick double layered membrane that encloses the cortex

cortex

thickest layer of the spore envelope

lies outside the spore wall

core

spore protoplast

innermost part

gel-like dehydrated state (10-25%)

spore wall

innermost layer surrounding the core

spoluration

begins when environmental conditions become unfavorable

stage 0: normal vegetative cell

normal condition of cell prior to sporulation

nucleoid subjects the cell to sporulation

stage 1: axial filament formation

bacterial chromosome becomes long thread-like called axial filament

stage 2: asymmetric septation and formation of forespore

cell divides asymmetrically as the cell membrane undergoes in-folding near one end to produce a double membrane structure called forespore (daughter cell)

stage 3: engulfment of forespore

mother cell membrane grows continously towards and around the forespore and engulfs it

stage 4: cortex synthesis

forespore starts forming primordial cortex between the two membranes

stage 5: coat deposition

an outer shell called coat is deposited outside the cortex forming a coat layer

stage 6: maturation

the endospore matures

stage 7: release of endospore

mother cell undergoes lysis and releases a matured endospore into the environment

bacterial endospores

germinate to vegetative cells

they either need to remain dormant for some time or get activated before germination

activation

spore coat must be damaged by agents

• heat

• abrasion

• acid

initiation

once activated, spore will initiate germination

triggered by binding of endospore receptors with the effector molecules present in the medium