archaea membrane desc.
-lipids are ether-linages not ester linkages
-attached to glycerol (diether) + phosphate =glycerol phosphates
-lipids are not fatty acids but phytanyl (isoprene unit) = bulky
-bilayer (biphytanyl or crenarchaeol)- common in thermophiles vs monolayer (phytanyl)
archaea cell envelope options
1) pseudomurein
2) methanochondrotin + s-layer (inner)
3) S layer
4) protein sheath + s layer (inner)
pseudomurein
-N -acetylglucosamine (like pepti.) + N-acetylalosaminuronic acid linked by B (1,3) linage - lysozyme insensitive
- peptide link to minuronic acid and peptide cross-link form
archaeallum uses ____
ATP not PMP to spin
archaeal hami is what>
similar to pili
extends but has 3 prong hook at the end and brances
bacterial growth curve is plotted on ____
log scale so exponential phase is linear
bacterial growth curve parts
-lag -nutrients are taken in, enzymes are made, and replication
-exponential (log) -popn growth is doubling -organisms dependent
-stationary- out of nutrients, growth slows, endospores created
-decline/death -rupture of PM, destruction of DNA
growth refers to ____
popn growth rather than growth of individual cells
generation doubling time (def.)
- time required for the population to double in size
- varies depending on species of microorganism and
environmental conditions - range is from 10 minutes for some bacteria to several
days for some eukaryotic microorganisms
growth outside lab
- almost always slower than optimal
- progression through stages is not linear
- virtually always part of a mixed culture
- frequently part of a biofilm
Asexual reproduction (def.)
Sexual reproduction (def.)
-new cells from one set of chromosomes yields daughter cells which are genetic clones of parent
-combination of genetic material from two organisms yields new organism
microbial growth by _____
-asexual reproduction
-microbial “pseudosexual” reproduction
types of asexual reproduction
- Binary fission
- Budding
- Fragmentation- long part often fungi that breaks off into different parts
types of pseudosexual reproduction
- Conjugation
- Transformation
- Transduction
pseudosexual reproduction (def.)
the combination of genetic material from different organisms but not required for growth of the cell
the most common way for bacteria to divide
binary fission
binary fission steps
1) cell elongation
2) septum formation: barrier between two cells with peptidoglycan
3) pinching: completion of septum; formation of walls + cell separation
DNA replication in binary fission
1) binding of DNAA to oriC initiates replication
2) Blocking of oriC regions by SepA; cell elongation
3) segregation of chromosomes
4) Z-ring formation-part of the septum
5) cell division
cytokinesis steps
- Replication of cytoplasmic contents (ribosomes, inclusions, etc.)
- Septation occurs (cross walls between daughter cells)
- Site is selected by FtsZ (exactly in the center of the
cell) - Z ring is assembled
- Z ring is linked to plasma membrane
- Cell wall biosynthetic machinery is synthesized
- Constriction of cell and septum formation
The E-coli divisome (Z-ring)
- 10,000 FtsZ molecules polymerize into ring at the
center of the cell - Ring is tethered to plasma membrane by ZipA and FtsA
- Localizes peptidoglycan biosynthesis machinery to the center of the cell -> requires ATP
How does the cell know where the center is?
Min C,D,E
Z-ring localization
1) Min CD prevents Z-ring from forming (found all over the cell)
2) When cell is ready to divide, Min E comes to the center (no MinCD in the center of the cell so Z-ring forms)
3) Ftz ring + divisome complex
4) septum forms
5) loss of MinE so Min CD formed again
Peptidoglycan synthesis occurs in ____
middle of cell anchored by Ftz ring
general peptidoglycan biosynthesis
- Synthesis of the building blocks
- Synthesis of the disaccharide-peptide repeat unit (a.a added one at a time except last d-ala which are added at the same time)
- Translocation from cytoplasm to periplasm
- Transglycosylation (loss of pyrophosphate-linking repeat unit)
- Transpeptidation (DAP forms cross link with Ala of pentapeptide and removes 2nd d-ala to form tetrapeptide)
