Bacteria sense and respond to a wide range of physical and chemical signals. Central to sensing and responding to these signals are two-component systems, which have a sensor histidine kinase (SK) and a response regulator (RR) as basic components. Here we review the different molecular mechanisms by which these signals are integrated and modulate the phosphorylation state of SKs. Apart from the basic mechanism, which consists of signal recognition by the SK that leads to an alteration of its autokinase activity and subsequently a change in the RR phosphorylation state, a variety of alternative modes have evolved. The biochemical data available on SKs, particularly their molecular interactions with signals, nucleotides, and their cognate RRs, are also reviewed.

Macromolecules are essential cellular components in biological systems responsible for performing a large number of functions that are necessary for growth and perseverance of living organisms. Proteins, lipids and carbohydrates are three major classes of biological macromolecules. To predict the structure, function, and behaviour of any cluster of macromolecules, it is necessary to understand the interaction between them and other components through basic principles of chemistry and physics. An important number of macromolecules are present in mixtures with surfactants, where a combination of hydrophobic and electrostatic interactions is responsible for the specific properties of any solution. It has been demonstrated that surfactants can help the formation of helices in some proteins thereby promoting protein structure formation. On the other hand, there is extensive research towards the use of surfactants to solubilize drugs and pharmaceuticals; therefore, it is evident that the interaction between surfactants with macromolecules is important for many applications which includes environmental processes and the pharmaceutical industry. In this review, we describe the properties of different types of surfactants that are relevant for their physicochemical interactions with biological macromolecules, from macromolecules–surfactant complexes to hydrophobic and electrostatic interactions.

Pseudomonas putida strains are prevalent in a variety of pristine and polluted environments. The genome of the solvent‐tolerant P. putida strain DOT‐T1E which thrives in the presence of high concentrations of monoaromatic hydrocarbons, contains a circular 6.3 Mbp chromosome and a 133 kbp plasmid. Omics information has been used to identify the genes and proteins involved in solvent tolerance in this bacterium. This strain uses a multifactorial response that involves fine‐tuning of lipid fluidity, activation of a general stress‐response system, enhanced energy generation, and induction of specific efflux pumps that extrude solvents to the medium. Local and global transcriptional regulators participate in a complex network of metabolic functions, acting as the decision makers in the response to solvents.

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