Light, time and micro-organisms

-3 > pts > -9
Kiloseconds to gigaseconds. The fourth time domain


Although the border of the fourth time domain corresponds fairly closely with the doubling time of Escherichia coli in log phase, the fastest biological events to be discussed in this context are predominantly developmental.

Developmental adaptations: photosystem stoichiometry adjustment and complementary chromatic adaptation.

The imbalance in distribution of absorbed excitation energy that initiates the physiological, and relatively rapid redox response of LHC II phosphorylation has a long-term, developmental counterpart in adjustment of photosystem stoichiometry. The response is to the same signal, and the adjustment in both cases is one of greater balance in light capture by the two photosystems in order that their rates of electron transfer may remain equal, a requirement of their being coupled electrochemically in series.

Recent results from the author's laboratory support the idea that redox signals from the plastoquinone pool of chloroplasts initiate changes in photosystem stoichiometry in parallel to their effects in regulation of phosphorylation of LHC II.

Is a decision made about the appropriate level of adaptational response?

If physiological and developmental responses that achieve broadly the same effect can be distinguished and, at the same time, are initiated by a single environmental signal, how is the appropriate level of response selected?


Biological adaptations

Bifurcated signalling: physiology versus development

How internal time reference may arbitrate between physiological and developmental adaptation