Microbiology, Developmental Genetics and Evolution

The major elementary components of development in higher forms, that is, cellular division, cellular differentiation and epigenetic homeostasis, are well established in microorganisms. Their existence and functional significance in modern microbes suggest that they may all have arisen in primitive unicellular forms and may have provided the "pre-adaptive" basis for the transition to multicellularity. Regardless of whether the developmental mechanisms in unicellular and multicellular organisms are parts of a single evolutionary sequence or represent parallel evolutionary advances, modern experimental analyses emphasize their essential similarities. Nuclear differentiation, the regulation of genetic activities by modifications at particular chromosomal sites, may prove to be an important unifying concept. In any case, broad comparative studies on a variety of forms, selected for their suitability in exploring particular problems, should cross-illuminate each other and provide eventually the foundation for a "synthetic" developmental biology.