Biomineralisation Flashcards
dissolution involves
breaking bonds
activation energy barriers
overcome electrostatic repulsion
eliminate hydration shell
remove ligands
form new interface (nucleation)
mineral nucleation and growth
step 1; nucleation
nucleus of new phase within old phase
SI>0
mineral nucleation and growth
step 2; growth of initial phase
ions adsorb (join the party)
very hydrated- tiny crystal lattice
before it is crystalline
easier to get to transitional phase
mineral nucleation and growth
step 3; growth of crystalline phase
initial phase is template
or dehydration
SI<0
Q<Ksp
undersaturated with respect to the mineral -dissolve more
SI>0
supersaturated with respect to the mineral
will not dissolve
Induced biomineralisation
formed as by-product of metabolic activity
out side cell
metabolic waste (o2, HS)
enzymatically medicated change in redox state
nucleation on cell surface
controlled biomineralization
cytoplasm or cell wall
microorganism controls all stages of mineralisation- physiological prepose
need high enough SI
requires energy
Induced biomineralization
what does metabolism effect
pH and saturation state
and can induce biomin
Induced biomineralization
cell surface reactivity
ionized surface lowers interfacial energies for nucleation
lowers activation energy barrier
Induced biomineralization
Ferrihydrite
Fe adsorbed to EPS
bacteria serve as nucleation site
cells encrusted with ferrihydrite
Facilitated by chemohetero or chemoauto iron mineralization
Leptothrix
induced biomineralization
chemohetero iron mineralisation
Controlled biomineralization
mechanism
-seal off site from enviro (intercellular or in the cell)
-transport ions in until supersaturated
-nucleation controlled by ligands
-crystals grow in cell (ordered)
Controlled biomineralization
Magnetite
magnetic, magnetotactic bacteria
unique shape
intercellular, linearly arranged, crystal perfect, arranged in chains
