Module 6: Nutrient Limitation

• inclusions store nutrients
• energy sources are stored by sulfur globules and polyphosphate
• sulfur globules can be oxidized to sulfate if hydrogen sulfide is low in environment
• polyphosphate stores phosphate
• carbon is stored as PHA/PHB or glycogen
• adaptations to limited nutrients are active processes that use energy
• hibernation: changes metabolism during stationary phase
• what are the gene changes in hibernation?

  increase in RpoS sigma factor alters gene expression for survival
• what are the morphological changes in hibernation?

  cell division, smaller and rounder cells, more rigid cell envelope
• what are the nucleoid changes in hibernation?

  compact DNA and increase protective proteins
• what are the metabolic and translational changes in hibernation?

  decrease metabolic rate and protein synthesis
• seed method: differentiation to resting cell type
• giardia form cysts that don't grow until ingested by host
• endospore formation is irreversible asymmetirc cell division
• what is endospore formation triggered by?

  both limiting nutrients and high cell density
• how does endospore formation occur?

  mother cell engulfs forespore, sequential gene regulation forms spore
• spore structure: dehydrated core with heat resists cytoplasm stores genome
• how many membranes does a spore have?

  inner and outer membrane
• inner spore membrane has germinant receptor proteins
• what are the germ cell wall and cortex made of?

  peptidoglycan
• spore coat: protein matrix resistant to some chemicals
• spore germination occurs in favorable conditions sensed by receptor protein
• what is spore germination usually triggered by?

  nutrients of low molecular weight
• communal method: group response to enhance survival
• what is the communal method in myxobacteria?

  aggregate to form fruiting body that creates and disperses spores
• cyanobacteria form multiple vegetative cell types depending on condition (heterocysts, akinetes, and homogonia)
• heterocysts: nitrogen fixation, stops phototrophic oxygen generation and carbon fixation
• heterocysts form thickened cell wall to protect O2 sensitive nitrogenase
• akinetes: reduced metabolic activity in light/phosphate limiting conditions
• akinetes contain carbon and nitrogen storage molecules, thickened cell wall
• homogonia: dispersal and symbiosis, motile filaments formed by cell division without biomass increase
• bacteria predators: viruses, predatory bacteria and eukaryotes
• strategies to avoid predation:

  • filamentation, increasing size
  • biofilm formation
  • communication with other cells
  • toxin release
  • motility (swim away)
  • size reduction
  • change cell wall structure, harder to digest
• UPEC differentiation into long filaments in response to byproduct produced by predator