Microbiology and immunology Flashcards
nucleoid
typically circular chromosomes, not membrane bound but restricted to an area called the nucleoid
other small self replicating dna molecules present in the cytoplasm- called plasmids
bacteria cell wall function
provides a rigid macromolecular layer- strength
protects cells from osmotic lysis and keeps cell shape
peptidoglycan present
structure of peptidoglycan
NAGNAMNAGNAM carbohydrate chains
vertical cross linking
transpeptidase- the enzyme that cross links the peptidoglycan chains- creating a rigid cell wall
gram positive vs gram negative
including staining
gram positive- thick layer of peptidoglycan ontop of plasma membrane (20-80nm) . traps crystal violet, therefore staining purple
gram negative- thin layer (5-10nm) of peptidoglycan in between plasma membrane and outer membrane.
Staining- crystal violet easily wiped away leaving a pink stain from the red safrin dye
what does chemotaxis mean
when bacteria move along a concentration gradient, towards chemical attractants (positive) or away from repellent (negative)
adherance factors - Fimbrae
adhesions/ aderance pilli
cause bacteria to stick to surfaces
Not all bacteria have them- they are an inherited trait
shorter and in higher numbers than flagella ( not involved in motility)
adherance factors- Pilli
Pilli, Pillus
attatchment to other bacteria
transfer genetic material - conjugation
a form of horizontal gene transfer
capsule vs slime layer
their two functions
capsule- glycocalx (jelly like polysaccaride) in a defines structure attatched firmly to cell wall
slime layer- disorgansied without cell shape and is loosely attatched
virulence- protect bacteria from being phagocytosed and immune cell engulfment. They prevent dessication.
bacterial endospores, their role and when they form
bacterial spores are formed in unfavourable growth conditions- under stress.
They then germinate in favourable conditions
they protect cells from stress, only present in some gram postive bacteria
High cell density and nutrient starvation= stress causing endospores
why are prokaryotes so dominant
they evolve and adapt fast- 13 minute doubling time
process of binary fission in prokaryotes
reproduce asexually
one cell into two cells
1) chromosomes replicate
2) one copy of origin at each end of the cell
3) replication finishes
4) two identical daughter cells result
closed batch culture system
limited amount of nutrients provided
standard method of studying microorganisms in culture
the method uses dictates what occurs, not the shape of the flask
what are the stages for a closed batch culture system
lag phase- getting biosynthetic reactions running, dependent on history of the innoculum
exponential phase- cells actively dividing, doubling in constant time
Stationary phase- cells stop growing, cryptic growth occuring (organsims surivive by eating the contents of the dead cells in the system)
Death phase- cell death, more cells are dying rather than growing
what can now growth indicate on a graph
that cell death and growth are in balance
what are the three things that microbes need to grow
carbon source- building blocks for the macromolecule synthesis
energy source- to drive anabolic and catabolic reactions
reducing power- energy/ electron carries NAD+ and NADP+
