Bacterial Chemotaxis in Relation to Neurobiology
Bacteria have a simple sensory system and they exhibit behavioral re sponses. Since they are monocellular organisms it is legitimate to ask whether the study of such a system can be relevant to neurobiology, which, by its nature, involves interaction between many cells. The answer is that relevant information has already been uncovered, which may be helpful in studies on neural networks, and this chapter attempts to describe some of the findings in bacteria and their relationships to more complex systems. To a first approximation the understanding of a brain involves two ex treme problems. On the one hand there is the wiring problem, and on the other hand there is the problem of the However, the neuron is not simply a switch. It is a relatively complex cell that adds enormously to the capacity of the brain because it is by itself able to perform a great deal of information processing. If the brain is considered to be analogous to a giant computer, the neuron must be'considered closer to a pocket calculator than fl simple switch. In such a system, therefore, a fundamental under standing of the role of the individual cell will not only be important per se but will also help in understanding the design of the wiring diagram. If one is willing to accept that the chemistry of the individual neuron is relevant to an understanding of the overall system, it remains to decide whether the study of a bacterial cell is relevant to the understanding of the neuron. The answer to this question can be answered in part by historical precedent. At the biochemical level it has been proved repeatedly that all cells have characteristics in common. The same question of relevance of the bacterial system has been asked in relation to the genetic code, carbohydrate metabolism, energy sources, transport properties, etc. In each case the