About half of the known bacterial species perform chemotaxis that gains them access to sites that are optimal for growth and survival. The motility apparatus and chemotaxis signaling pathway impose a large energetic and metabolic burden on the cell. There is almost no limit to the type of chemoeffectors that are recognized by bacterial chemoreceptors. For example, they include hormones, neurotransmitters, quorum-sensing molecules, and inorganic ions. However, the vast majority of chemoeffectors appear to be of metabolic value. We review here the experimental evidence indicating that accessing nutrients is the main selective force that led to the evolution of chemotaxis., This work was supported by the Spanish Ministry for Science and Innovation/Agencia Estatal de Investigación 10.13039/501100011033 (grants PID2020-112612GB-I00 to TK, PID2019-
103972GA-I00 to MAM, and PID2020-116261GB-I00 to JAG), Consejo Superior de Investigaciones Científicas (CSIC) (grant 2023AEP002 to MAM), and the Junta de Andalucía (grant P18-FR-1621 to TK)

Peptide assembly is attractive not only to develop biotechnological tools and smart nanomaterials, but also to treat pathologies in new ways. This Review focuses on recent progress made in the exciting area pertaining the interaction between peptide assemblies and proteins. Earlier works aimed to identify proteins able to bind peptide assemblies for therapeutics’ delivery and biocompatible scaffolds. Recent advancements cover more applications that go beyond tissue regeneration and biomaterials. On one hand, self-assembling peptides interacting with proteins can inhibit pathological amyloid fibrillation, or boost the immune response to vaccines. On the other, they have been exploited to promote protein crystallization, also for therapeutics’ delivery. As research advances in this exciting area, it opens the way towards a qualitative leap in the clinical translation of supramolecular medicinal chemistry to creatively tackle unmet challenges of modern disease treatment and prevention., The authors acknowledge Francesca Prochilo and Elisa Prelli at the University of Trieste for administrative assistance. This study was supported by FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades (Spain) projects P18-FR-3533 and A-FQM-340-UGR20. J.A.G. is supported by the Spanish Ministry of Science and Innovation/FEDER funds grant PID2020-116261GB-I00/AEI/10.13039/501100011033. M.C.M.T. acknowledges grant PRE2018-083773 funded by MCIN/AEI/10.13039/501100011033 and FSE “El FSE invierte en tu futuro”, Spain. Open Access Funding provided by Università degli Studi di Trieste within the CRUI-CARE Agreement. Open Access funding provided by Università degli Studi di Trieste within the CRUI-CARE Agreement.

Supramolecular gels are unique materials formed through the self-assembly of molecular building blocks, typically low molecular weight gelators (LMWGs), driven by non-covalent interactions. The process of crystallization within supramolecular gels has broadened the scope of the traditional gel-phase crystallization technique offering the possibility of obtaining crystals of higher quality and size. The broad structural diversity of LMWGs allows crystallization in multiple organic and aqueous solvents, favouring screening and optimization processes and the possibility to search for novel polymorphic forms. These supramolecular gels have been used for the crystallization of inorganic, small organic compounds of pharmaceutical interest, and proteins. Results have shown that these gels are not only able to produce crystals of high quality but also to influence polymorphism and physicochemical properties of the crystals, giving rise to crystals with potential new bio- and technological applications. Thus, understanding the principles of crystallization in supramolecular gels is essential for tailoring their properties and applications, ranging from drug delivery systems to composite crystals with tunable stability properties. In this review, we summarize the use of LMWG-based supramolecular gels as media to grow single crystals of a broad range of compounds., We are grateful for funding to the European Commission (HORIZON-MSCA-PF-2022, project 101110492), to the Ministerio de Ciencia, Innovación y Universidades (Spain) MCIN/AEI/10.13039/501100011033 (PID2020-118498GB-I00 and PID2020-116261GB-I00), to the FEDER/Junta de Andalucia-Consejeria de Transformación Económica, Industria, Conocimiento y Universidades (Spain) (P18-FR-3533), and to the Engineering and Physical Research Council (EP/S035877/1). Funding for open access charge: Universidad de Granada/CBUA.

The ability of bacteria to adapt to changing environmental conditions largely depends on transmembrane receptors that sense signal molecules and generate responses such as chemotaxis, changes in gene expression, or alterations in second-messenger levels. Although these receptors differ significantly in function, they share a common mode of activation that involves signal molecule interaction with sensor domains. A major challenge in microbiology lies in the limited knowledge of ligands that stimulate receptors. Here, we review recent advances in this field, including the occurrence of multi-modular sensor domains, the identification of co-component signal transduction systems, evidence for sensor domain evolution from transporters, and the use of binding pocket sequence motifs to identify sensor domain ligands., This work was supported by the Spanish Ministry of Science and Innovation/FEDER funds Grant PID2020-116261GB-I00/AEI/10.13039/501100011033 (JAG). SMR is grateful to the Andalusian Regional Government through the Endocrinology and Metabolism Group (CTS-202) and to University of Granada “Plan Propio de Investigación de la UGR” (PP2022.PP.18). ACA is grateful to Junta de Andalucía (PY20_00149). We are grateful to the European Synchrotron Radiation Facility (ESRF), Grenoble, France, for providing time through proposal MX2353 and MX2454, and the staff at ID30-A3 beamlines for assistance during data collection. We are also grateful to the Spanish Synchrotron Light Facility (ALBA), Barcelona, Spain, for providing time through proposals 2021085252 and 2022086950, and the staff at XALOC beamline for assistance during data collection. We deeply thank Ma Carmen López-Sánchez for technical assistance.