Lignocellulose bio-refinery provides a feasible approach for the sustainable supply of fuels and fine chemicals. The cover image depicts the engineered industrial yeast Ogataea (Hansenula) polymorpha, which Gao et al. engineered to convert lignocellulose into free fatty acids (a biofuel precursor) and 3-hydroxypropionic acid (a monomer of degradable plastics) via the co-utilization of glucose and xylose.

See Gao et al.

A team led by Boxun Lu has shown that RNAs with expanded CAG repeats can form gel-like condensates and suppress global protein synthesis by sequestering the translation elongation factor eEF2. The cover image depicts the process of RNA gel formation and degradation by lysosomes in the cytoplasm of a neuron.

See Pan et al. and Yang

The biological role of free nitric oxide (NO) as messenger in the cardiovascular system has long been recognized, despite its rapid scavenging by blood. The cover image illustrates that NO–ferroheme is a signaling species in its own right, which enables it to perform NO-like bioactivity in the bloodstream.

See Kleschyov et al.,DeMartino et al. and Emil Martin

Antimicrobial peptides are an important part of the eukaryotic innate immune system for combating invading bacteria. The cover image illustrates the finding that insects such as the fruit fly Drosophila produce the antimicrobial peptide drosocin, which bears an O-glycosylation (reflected in the eye of the fruit fly here) that is critical for its ability to interact with the ribosome and inhibit bacterial protein synthesis.

See Wilson et al. and Mankin et al.

The heterodimeric bacterial ABC transporter CydDC acts as a heme transporter to promote the assembly and maturation of cytochrome bd, a pharmaceutically relevant drug target. The image depicts heme and CydDC embedded in the bacterial membrane.

See Safarian et al.

Proteus mirabilis bacteria natively form a centimeter-scale bullseye colony pattern on solid agar via collective motility, called ‘swarming’. The image depicts the patterns of P. mirabilis strains engineered with genetic circuits that modify swarming in response to sensed inputs, serving as a visible environmental record.

See Doshi et al.

Ferroptosis, a form of iron-dependent cell death, is caused by lipid peroxidation in cellular membranes. The cover image depicts the endoplasmic reticulum (blue tubular network) outside the nucleus (blue sphere) in a cell undergoing lipid peroxidation during ferroptosis, indicated by the flames.

See von Krusenstiern et al.

Quorum sensing — whereby cells decide their collective fate on the basis of their population density — is usually associated with bacteria. The cover shows a centimeter-sized colony of mouse cells that began as embryonic stem cells and survived differentiation by quorum sensing at a centimeter scale. Darker regions correspond to denser cell layers (brightfield image, ~1 cm × 1 cm).

See Daneshpour et al.

An engineering approach was developed to control cellular functions via regulating the formation and physical properties of synthetic condensates. The image depicts the programmable synthetic biomolecular condensates for the modulation of transcription, plasmid partitioning and protein circuits.

See Dai et al.

Glutamine synthetase is the only enzyme known to produce glutamine in mammals. The cover depicts N 5-methylglutamine, a metabolite previously undescribed in mammals that is synthesized by glutamine synthetase in peri-central hepatocytes and in β-catenin-mutant liver cancer (green).

See Villar et al.

The nematode Caenorhabditis elegans is an excellent model system for studying the neurotransmitter serotonin, including its biosynthesis, metabolic fate and function in animal behavior and physiology. The cover depicts a transgenic C. elegans male in which the nuclei of cells that express the serotonin-biosynthesis enzyme tryptophan hydroxylase have been fluorescently labeled.

See Yu et al.

The DeltaMAX protein is an evolved variant of the natural ligand DLL4 and contains mutations that enhance its affinity for Notch receptors. The image depicts activation of a Notch receptor (magenta) by the engineered ligand DeltaMAX (green). The nucleus of the signal receiver cell is glowing to indicate potent activation.

See Gonzalez-Perez et al.