Biological cells sense external chemical stimuli in their environment using
cell-surface receptors. To increase the sensitivity of sensing, receptors often
cluster, most noticeably in bacterial chemotaxis, a paradigm for signaling and
sensing in general. While amplification of weak stimuli is useful in absence of
noise, its usefulness is less clear in presence of extrinsic input noise and
intrinsic signaling noise. Here, exemplified on bacterial chemotaxis, we
combine the allosteric Monod-Wyman- Changeux model for signal amplification by
receptor complexes with calculations of noise to study their
interconnectedness. Importantly, we calculate the signal-to-noise ratio,
describing the balance of beneficial and detrimental effects of clustering for
the cell. Interestingly, we find that there is no advantage for the cell to
build receptor complexes for noisy input stimuli in absence of intrinsic
signaling noise. However, with intrinsic noise, an optimal complex size arises
in line with estimates of the sizes of chemoreceptor complexes in bacteria and
protein aggregates in lipid rafts of eukaryotic cells.Comment: 15 pages, 12 figures,accepted for publication on Physical Review