The genus Streptomyces is a unique subgroup of actinomycetes bacteria that are well-known as prolific producers of antibiotics and many other bioactive secondary metabolites. Various environmental and physiological signals affect the onset and level of production of each antibiotic. Here we highlight recent findings on the regulation of antibiotic biosynthesis in Streptomyces by signaling molecules, with special focus on autoregulators such as hormone-like signaling molecules and antibiotics themselves. Hormone-like signaling molecules are a group of small diffusible signaling molecules that interact with specific receptor proteins to initiate complex regulatory cascades of antibiotic biosynthesis. Antibiotics and their biosynthetic intermediates can also serve as autoregulators to fine-tune their own biosynthesis or cross-regulators of disparate biosynthetic pathways. Advances in understanding of signaling molecules-mediated regulation of antibiotic production in Streptomyces may aid the discovery of new signaling molecules and their use in eliciting silent antibiotic biosynthetic pathways in a wide range of actinomycetes.

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This is the first study to examine the nonlinear dynamic behavior of a microtweezer under electrostatic forces by taking into account viscoelastic effects and linear and nonlinear thermal stresses. The van der Waals (vdW) forces and Casimir intermolecular forces have been included in order to consider more realistic assumptions. Hamilton's principle is applied to derive the nonlinear equations governing the system. A nonlinear partial differential equation has been converted into an ordinary nonlinear differential equation using the Galerkin method. The equations are numerically solved and the results are analyzed at different values of the effective parameters, such as the coefficients of the Casimir force and the vdW forces. Results indicate that the increase in the small size parameter and Casimir and vdW forces results in a decrease in the equivalent stiffness and, therefore, a decrease in the pole's voltage. In addition, the viscoelastic behavior causes a significant change in the stability behavior of the microbeams, and with an increase in damping, the resonance frequency increases by about 33%. Therefore, it is essential to take into account the effect of viscous damping when designing a microtweezer.