Practice question

Vegetative Dictyostelium amoebae inhabit leaf litter and topsoil as professional phagocytes whose primary nutritional source is bacteria. They extend actin-rich pseudopods engulfing Klebsiella or Escherichia coli into food vacuoles where lysosomal digestion occurs. Folic acid secreted by bacteria also acts as growth-phase chemoattractant sensed via G protein-coupled receptors. When bacterial lawns deplete, cells arrest division and switch chemotactic preference from folate to pulsatile cAMP. Yeasts, algae, or organic debris support limited survival but bacteria provide optimal proteins, vitamins, and signals sustaining rapid proliferation before developmental program initiates.