INTRODUCTION

Less than 50 years of molecular biology have documented that a few thousand genes suffice to construct prokaryotic life forms, which could be argued to be the most successful of all life forms throughout all biological evolution. These were the first to appear, and most likely the last to sustain as living organisms on earth. Molecular biology has also taught us that one explanation for the success of bacteria is the continuous evolution of not only new traits, but also of new regulatory elements, making these organisms very adaptable to a range of environments and to shifts between these. Expression of a large fraction of the genes in modern bacterial genomes is controlled at several levels – from the very specific metabolite-directed derepression scheme to global regulatory loops controlling the overall state of the cell and its interactions with the environment. Through complex webs of signal-transduction events bacteria sense their environment, and react to a large number of factors by finetuning expression of a large number of genes in apparently ‘intelligent’ ways.

It is therefore an almost logical extrapolation to assume that these simple, but highly regulated, organisms may also possess the capacity to engage in multicellular system constructions, in which features of co-ordinated organizational designs develop. The embryonic development of compartmentalized organisms with different organs and tissues from the undifferentiated fertilized egg-cell may have its parallel in prokaryotic organisms forming highly structured communities with distributed functionality based on a programmed, progressive differentiation process.