Bacterial observations: a rudimentary form of intelligence?

Genome sequencing has revealed that signal transduction in bacteria makes use of a limited number of different devices, such as two-component systems, LuxI-LuxR quorum-sensing systems, phosphodiesterases, Ser-Thr (serine-threonine) kinases, OmpR-type regulators, and sigma factor-anti-sigma factor pathways. These systems use modular proteins with a large variety of input and output domains, yet strikingly conserved transmission domains. This conservation might lead to redundancy of output function, for example, via crosstalk (i.e. phosphoryl transfer from a non-cognate sensory kinase). The number of similar devices in a single cell, particularly of the two-component type, might amount to several dozen, and most of these operate in parallel. This could bestow bacteria with cellular intelligence if the network of two-component systems in a single cell fulfils the requirements of a neural network. Testing these ideas poses a great challenge for prokaryotic systems biology.