Micro-organisms undergo developmental responses when faced with stressful environmental conditions such as starvation, overcrowding, or limitation of some needed substance. For example, researchers observe major changes in cell physiology and gene expression during the stationary phase in most bacteria.

However, some groups of bacteria exhibit particularly dramatic developmental responses to stresses. Bacillus subtilis forms endospores - specialized resting cells viable for thousands of years and resistant to ultraviolet radiation and boiling. Transcriptional regulators and sigma factors that control key steps in the developmental process mediate these changes. Myxobacteria responds to environmental stress by forming biofilms and multicellular fruiting bodies containing spores. These developmental processes exhibit many complexities which make them excellent model systems for understanding higher cells.
Researchers also study development in eukaryotic microorganisms, especially fungi. Experiments in microbial development give the graduate student the opportunity to explore frontier areas of molecular research such as transcription factors, signal transduction pathways, subcellular localization pathways, and the adaptation of cells to specialized environments. These experiments lie at the cutting edge of biology and provide unique opportunities to make important scientific discoveries.