Cellular Differentiation

• Differentiation

  1. Resting cells (endospores): forms to resist environmental stress
  2. Swarmer cells: cell forms that are specifically designed for dispersal within niches
  3. Heterocysts: cells with specific functions
  4. Nitrogen-fixing nodules: for symbiotic relationships
• Endospore formation

  Endospores: simplified forms of bacteria formed to resist environmental stress

  • for survival; dissemination of species
• Endospore Formation in Bacillus Life Cycle

  Has vegetative growth and stationary phase

  1. Septum formation: asymmetric cell division
  2. a forespore will form from the mother cell
  3. Engulfment: spore coat surrounds the forespore
  4. Late Sporulation: formation of coat, outer forespore membrane, cortex, and inner forespore membrane
  5. Mother cell lysis: forespore detaches from MC
  6. Germination
  7. (Vegetative Cycle) Binary fission occurs
• Stages of Sporulation


  1. DNA replication and Division sites shift to polar positions

  2. One of the division sites form a septum

  a. Forespore chromosome is transported to the forespore by the SpoIIIE DNA translocase

  Engulfment: membrane of MC migrates around the forespore (phagocytosis manner)

  a. Proteinaceous coat assembles around the forespore

  3. Forespore is enclosed within MC cytoplasm delimited by two membranes

  a. inner: original forespore membrane; b. outer: derived from MC
• 4. Cortex made up of peptidoglycan is formed between the inner and the outer forespore membranes

  a. SASPs (small acid soluble proteins) bind the chromosome

  5. Coat assembly is complete; forespore chromosome is compacted and saturated by SASPs

  6. DPA (dipicolinic acid) synthesized in MC is loaded to the forespore

  7. Mother cell lyses; forespore released

  a. conditions permit germination
• Spore Formation in Fungi

  • can be part of asexual or sexual
  • for dispersion: provide genetic link
• Fungi Life Cycle

  • Plasmogamy: fusion of two haploid cells forming a heterokaryotic cell
  • Karyogamy: fusion of two nuclei to form diploid cells that form a zygote
  • Germination: forms multi-cellular mycelium
• Cyst formation in Protozoa

  Cysts: dormant forms of protozoa (single-celled eukaryotes); for transmission