We provide a kinetic model for signal processing in photo- and chemotaxis in the archaeon H. salinarum suggesting an essential role of receptor cooperativity, antagonistic reversible methylation, and a CheY-dependent feedback on transducer demethylation.
It is based on feedback control of the transducer voltage using a digital resistive network RG.
The two other types of control are based on the electrical characteristics of the piezoelectric transducer (electrical feedback).
The last control strategy takes into account both the current and the power of the piezoelectric transducer (power feedback).
Feedback of CheY on transducer demethylation is based on direct experimental evidence by [ 38] who showed that the normal Halobacterium-type methanol release pattern (a positive peak in response to both attractant and repellent stimulation) is converted into an E. coli-like pattern (a negative peak in response to attractant stimulation and positive in response to repellent).
Three key functional characteristics were measured: (1) the maximum equivalent pressure output (MEPO) of the transducer; (2) the feedback gain margin (GM), which describes the maximum allowable gain before feedback occurs; and (3) the tympanic-membrane damping effect (DTM), which describes the change in hearing level due to placement of the transducer on the eardrum.
Presumptive mechanisms of functional coupling might be conformational coupling of different transducer types, or feedback by modulating the methyl-esterase and methyl-transferase activity at transducers other than the actually stimulated transducers.
The advantage of this technique is absence of current transducers for current feedback control loop.
The use of an electrodynamic actuator to generate damping forces, controlled by feedback from acceleration and force transducers, may help to overcome these limitations and provide additional benefits.
Our analysis reveals three important features of these systems: 1), multiple step signaling cascades improve sensitivity to low doses by an effect distinct from signal amplification; 2), some feedback architectures act as signal transducers converting stimulus strength into response duration; and 3), feedback deactivation acts as a dose-dependent switch between transient and sustained responses.
