MT2 Content Flashcards
How is selective permeability achieved?
- substrate-specific carrier proteins (permeases)
- Dedicated nutrient-binding proteins patrolling periplasmic space
- Membrane-spanning protein channels/pores
ABC Transporters
-powered by ATP
-found in all 3 domains of life
-gram - employ peiplasmic binding proteins
-gram + & archaea employ substrate-binding proteins on external surface of cytoplasmic membrane
2 main types of ABC Transporters
-Uptake: taking things in, critical for transporting nutrients
-Effflux: pump shit out, generally used as multidrug efflux pumps
Growth Cycle
- Growth: increase in # of cells
- Binary fission: cell division when cell doubles in size
- Septum: Partition of cells, creating 2 daughter cells
Planktonic growth
-growth as suspension
Sessile growth
-attached to surface
-can develop into biofilms
Biofilms
-forms in stages
-planktonic cells attach
-sticky matrix forms
Microbial Mats
-multilayered sheets w/ diff. organisms in each layer
Closed Culture
-limited nutrients
-also called batch culture
Bacterial Growth Curves
- Lag phase: no increase in number of living cells (takes a while to adapt)
- Log phase: exponential increase in # of living bacterial cells
- Stationary phase: plateau in # of living cells; death rate = birth rate
- Death phase: exp. decrase in living cells
Continuous Culture
-all cells in pop. achieve steady state
-chemostat constantly adds & removes equal amounts of culture medium (ensures log growth)
Biofilms
-surface attached communities
-can be constructed by 1 or multiple species
-can form on range of surfaces
-difficult to dislodge
-protect bacteria from chemicals
Biofilm development involves?
-adherence of cells to a substrate
-formation of microcolonies
-formation of complex channeled communities that generate new planktonic cells
Biofilm Life Cycle
- Attachment to monolayer by flagella
- Microcolonies
- Exopolysides (EPS) production
- Mature biofilm
- Dissolution & dispersal
Molecular constitution of biofilms
-EPS (polysaccharides in gram + and cellulose in gram -)
-proteins
-eDNA
Quorum Sensing
-how bacteria communicate
-triggered by c-di-GMP
-AHL is signalling molecule in gram -
Cardinal Temperatures
-min, max, & optimum temps at which an organism grows
Psychrophile
-low, found in cold env.
Mesophile
-midrange, most commonly studied
Thermophile
-high, found in hot env.
Hyperthermophile
-very high, found in very hot habitats
Water Activity
-how much water is available for use
-measured as ratio of solution’s vapour pressure relative to that of pure water
-inversely related to osmolarity
Osmophiles
-live in env. where sugar is high as a solute
Xerophiles
-organisms able to grow in very dry env.
Compatible solutes
-presence does not inhibit organism’s biochem
-usually made by bacteria to protect internal water when placed in hypertonic media
Strict Aerobes
-can only grow in O2
Microaerophiles
-grow only at lower O2 levels
Strict anaerobes
-die in the least bit of O2
Aerotolerant anaerobes
-grow in O2 while having fermentation-based metabolism
Facultative anaerobes
-can live w/ or w/o O2
-possess ability for both anaerobic & aerobic
DNA Binding Regulatory Proteins
-control initiation of transcription at gene promoters
Sigma Factor
-helps RNA pol. bind to certain DNA sequences & add specificity to RNA pol.
-housekeeping ones are for genes that are always expressed
-alternative ones do other genes
Stringent Response
-when nutrient scarcity leaves many ribosomes idle
-triggers ppGpp synth.
-binds to RNA pol., and lower’s it’s ability to transcribe RNA
-decrease in growth
Alarmones
-produced by RelA when ribosomes stall (stress signal)
-ppGpp & pppGpp
-help bacteria with stress
-slow down/stop certain cellular processes
Morphogenesis
-transition to stalked cell
-triggered by c-di-GMP in C. crescentus
Autoinducer
-membrane permeable second messenger that allows cells to regulate gene expression based on density of cells in env.
-allows for quorum sensing
Flagellar Motion
-CCW = smooth swimming/run
-CW = tumbling
