Module 6: Limitations to Growth

Created by

Kiera Christensen

Cards (28)

biofilms: assemblage of bacterial cells to a surface, enclosed in adhesive matrix secreted by cell
steps of biofilm formation:
attachment to solid surface
polymerization as medium flows across
expansion: formation of water channels
at low temperatures enzyme rate slows and cell membrane solidifies
are low temperatures lethal?
no, reversible
at high temperatures proteins denature, membrane becomes too fluid and doesn't contain contents
are high temperatures lethal?
yes when higher than optimal growth temp
what adaptations to thermophiles have?
heat-stable proteins and saturated fatty acids in lipids
what domains are thermophiles in?
bacteria and archaea, some eukarya but limited by organelles
what adaptations do psychrophiles have?
cold-stable enzymes and unsaturated fatty acids in lipids
what domain are psychrophiles in?
bacteria, archaea and eukarya
only intracellular ph 6-8 is compatible with life
how do acidophiles reach intracellular ph? 
pump out protons (low ph)
what domains are acidophiles in?
bacteria, archaea and fungi
how do alkalophiles reach intracellular ph?
pump out OH
what domains are alkalophiles in?
bacteria and archaea
xerophiles: adapted to low water availability
halophiles: adapted to high salinity
osmophiles: adapted to high solute concentration
how do halophiles and osmophiles balance osmotic pressure? 
accumulate compatible solutes in cytoplasm
growth in the presence of oxygen doesn't mean oxygen is used in metabolism
organisms that grow in presence of O2 have to deal with by-products, toxic and highly reactive
superoxide dismutase removes superoxide radicals
aerotolerant anaerobes: grow in any O2 conditions
aerobes: require O2
micro-aerophilic: require minimal O2
anaerobes: don't require O2
what enzymes remove hydrogen peroxide (hydroxyl radicals)?
catalase and peroxidase
why does lactic acid bacteria use peroxidase?
generates NAD+ for fermentation