The central obstacle the researchers set out to understand is bioavailability. Long-chain alkanes are hydrophobic compounds with extremely low water solubility, which means that even when a microbe possesses the right enzymes, the substrate may remain physically out of reach, locked inside oily droplets or solid phases that cells cannot easily contact. This limitation has long frustrated efforts to predict and enhance the biodegradation of petroleum residues in contaminated soils and shorelines. Short-chain alkanes, by contrast, dissolve to a useful extent and are comparatively easy for microbes to assimilate. Understanding how a cell surmounts the accessibility barrier for a C20 molecule therefore carries implications well beyond basic microbiology, touching on the design of bioremediation strategies for sites where heavy hydrocarbon fractions dominate the pollution load.

To tackle the question, the team grew ICBD2 with n-eicosane supplied at 5 millimolar as the sole source of carbon and energy, and compared the resulting cells with bacteria grown on acetate, a simple and highly soluble carbon source. The strain grew robustly on the alkane, reaching a turbidity at 600 nanometers of approximately 1.0, a clear demonstration that it could not merely tolerate the compound but thrive on it. That growth performance alone marks ICBD2 as a valuable isolate, but the real story lay in what the cells did to themselves in order to make the alkane usable.

The first adaptation was geometric. When grown on n-eicosane, the bacteria reduced their cellular surface area and simultaneously increased their surface hydrophobicity relative to acetate-grown controls. Both changes serve the same strategic purpose: they maximize direct contact between the cell envelope and the hydrophobic substrate. A smaller, more hydrophobic cell presents a surface that adheres readily to oily droplets, effectively letting the bacterium dock onto its food rather than waiting for dissolved molecules to diffuse its way. Hydrocarbon adhesion of this kind is a recognized hallmark of efficient oil degraders, and the new measurements show that ICBD2 tunes this property in direct response to the alkane in its environment.

Beneath that visible shift in cell behavior, the researchers documented a profound reorganization of the lipid architecture of the cell envelope. Bacteria grown on n-eicosane increased the saturation and reduced the chain length of their membrane fatty acids, the lipid molecules that form the cytoplasmic membrane bilayer. They made a parallel adjustment in their cell wall mycolic acids, the very long-chain fatty acids that characterize the envelope of Rhodococcus and its relatives in the actinobacterial lineage, which also includes the mycolata such as Mycobacterium and Corynebacterium. Saturated, shorter lipids pack together more tightly than unsaturated, longer ones, so the net effect of these changes is a more rigid and more stable cellular structure. In practical terms, the bacterium thickens and stiffens its armor while pressing that armor against the hydrocarbon it intends to consume.

This dual remodeling is chemically elegant because it addresses two problems at once. A rigidified membrane resists the destabilizing effects of direct contact with hydrophobic solvents, which can otherwise dissolve or disrupt lipid bilayers. At the same time, the shortened and saturated fatty acids and mycolic acids alter the physicochemical character of the envelope in ways that favor adhesion to the alkane phase. The mycolic acid layer, which forms an outer lipid shell covalently anchored to the arabinogalactan of the cell wall, is a distinctive feature of Rhodococcus biology, and the finding that its composition shifts in response to a long-chain alkane underscores how central this unusual wall is to the ecology of hydrocarbonoclastic actinobacteria.

The genetic underpinnings of the catabolic machinery proved equally striking. Sequencing and analysis of the ICBD2 genome revealed an unusually rich arsenal of alkane-oxidizing genes distributed across the chromosome. The strain carries five copies of alkB, encoding alkane monooxygenases that target alkanes of different chain lengths, together with almA and ladA, genes associated with the oxidation of long-chain alkanes. It also harbors seven cytochrome monooxygenase genes of the cyp family and three genes encoding Baeyer–Villiger-type monooxygenases, ethA, pamO and PA1538, enzymes that can insert oxygen atoms adjacent to ketone groups during the later stages of hydrocarbon catabolism. This redundancy and breadth suggest an organism evolutionarily prepared to handle a wide spectrum of petroleum constituents rather than a narrow substrate range.

Gene expression measurements during growth on n-eicosane showed which members of this arsenal the cell actually deploys. Transcripts of alkB1, alkB2 and almA increased significantly when the alkane was the carbon source, indicating that these three monooxygenases form the functional core of the long-chain alkane oxidation pathway in ICBD2. In a telling counterpoint, the expression of kasAB, a gene pair associated with the elongation of fatty acid chains, decreased during growth on the alkane. That downregulation dovetails precisely with the observed shortening of membrane fatty acids and cell wall mycolic acids: the cell throttles back the biosynthetic machinery that makes long lipids and thereby shifts the composition of its envelope toward the shorter, more saturated profile that the alkane-grown lifestyle demands. The coordination between transcriptional regulation and measurable lipid chemistry is one of the most compelling technical results of the study.

The authors emphasize that this is the first time the adaptive response of Rhodococcus to growth on a long-chain alkane has been presented at both structural and metabolic levels simultaneously. Previous work on alkane degradation has often focused either on the enzymology of terminal oxidation or on general phenomena such as biosurfactant production, without connecting the genome, the transcriptome and the physical chemistry of the envelope in a single experimental system. By integrating growth data, cell surface measurements, fatty acid and mycolic acid profiling, and gene expression analysis, the Chilean-German team has assembled a coherent mechanistic narrative of how a Gram-positive hydrocarbon degrader reorganizes itself around a difficult substrate.

The practical stakes of the work are considerable. Petroleum contamination of coastal soils is a persistent global problem, and the heaviest, least bioavailable fractions are typically the last to disappear and the hardest to remediate. Strains such as ICBD2, equipped with multiple alkane monooxygenases and an envelope that actively reconfigures to seize hydrophobic substrates, are natural candidates for bioaugmentation and biostimulation approaches at affected sites. The molecular markers identified here, from the induction of alkB1, alkB2 and almA to the saturation and shortening of envelope lipids, could serve as indicators of active long-chain alkane degradation in the field, helping practitioners verify that a bioremediation treatment is actually working. As the authors conclude, uncovering these mechanisms of adaptation to long-chain alkanes is a crucial step toward harnessing them for the cleanup of low-bioavailability petroleum hydrocarbons, turning the quiet chemistry of a Chilean soil bacterium into a tool for environmental repair.

Subject of Research: Membrane and cell wall adaptation of Rhodococcus erythropolis ICBD2 to long-chain alkane degradation

Article Title: Rhodococcus erythropolis ICBD2 membrane and cell wall adaptation to long-chain alkane degradation

Article References: Esparza-Correa, T., Durán, R. E., Baéz-Matus, X., Neumann-Schaal, M., Wolf, J., Nouioui, I., Mast, Y., Álvarez, S. A., & Seeger, M. (2026). Rhodococcus erythropolis ICBD2 membrane and cell wall adaptation to long-chain alkane degradation. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-026-13991-y

Image Credits: AI Generated

DOI: 10.1007/s00253-026-13991-y

Keywords: Rhodococcus erythropolis, bioremediation, long-chain alkane, n-eicosane, hydrocarbon degradation, alkane monooxygenase, alkB, almA, fatty acids, mycolic acids, cell envelope adaptation, petroleum contamination

The core of the argument is observational. Modern facilities are revealing that galaxies in the early universe were not the chaotic, shapeless protogalaxies that many theorists once expected. Instead, a substantial population of galaxies at high redshift appears dynamically mature, with rotating disks, concentrated star-forming regions and structural regularities that resemble, in broad strokes, the Hubble types we see nearby. The report emphasizes that this is a conceptual shift: if ordered structures were already in place when the cosmos was young, then the processes that shape galaxies, from the inflow of fresh gas to the turbulence driven by young stars, must operate quickly and efficiently, and the Hubble sequence itself becomes a fossil record of those processes rather than a late-time curiosity.

To understand why this matters, it helps to recall what the Hubble sequence actually encodes. Elliptical galaxies are triaxial, pressure-supported systems dominated by old stellar populations, while spirals are thin, rotationally supported disks with ongoing star formation organized into arms. Lenticulars occupy the transition zone. For decades, astronomers treated this ordering as an evolutionary sequence of sorts, though Hubble himself was careful to deny that the tuning fork implied a temporal path. Modern astrophysics has replaced that naive picture with a hierarchical one, in which galaxies grow through the accretion of gas and the merging of smaller systems, and morphology reflects the balance between those external drivers and the internal physics of the baryonic gas.

The technical language that has grown around this subject is now central to the field. Astronomers distinguish between the stellar mass surface density profiles of galaxies, their sizes measured at fixed stellar mass, their Sérsic indices, which quantify how centrally concentrated the light is, and their kinematics, the rotation velocities and velocity dispersions that reveal whether a galaxy is disk-like or dispersion-dominated. Each of these quantities can, in principle, be measured for galaxies whose light has traveled for more than ten billion years before reaching our telescopes. The report highlights how combining rest-frame optical imaging from JWST with cold-gas and dust observations from ALMA allows researchers to connect the stellar structure of early galaxies to the fuel reservoirs from which their stars form.

One of the most striking threads in the recent literature, and one that the report weaves through its discussion, concerns the abundance of disk galaxies at high redshift. Kinematic surveys of star-forming galaxies at redshifts between roughly one and three, the epoch when cosmic star formation peaked, showed that many of them are turbulent, thick disks with high gas fractions, supported partly by rotation and partly by random motions. Those studies, led in large part by near-infrared integral field spectroscopy on ground-based telescopes, established that disks existed early but were far more turbulent than their present-day counterparts. JWST has now pushed such structural and kinematic characterization to even higher redshifts, closer to the era of first galaxy assembly, and the emerging picture is one of surprisingly organized systems rather than a universal chaos.

Equally important is the population of compact, dense star-forming galaxies that dominated the high-redshift universe. Studies of their size evolution have shown that galaxies of a given stellar mass were typically much smaller in the past, and that the most massive systems assembled their dense cores first, a phenomenon often described as inside-out growth. Tacchella’s own earlier work contributed to this picture, demonstrating that star formation in massive galaxies appears to self-regulate: periods of intense star formation deplete or expel the gas supply, the galaxy temporarily quenches, and then renewed gas accretion restarts the cycle. Such cycles leave imprints on the structural properties of galaxies, linking morphology directly to the physics of feedback, the process by which supernova explosions, stellar winds and accreting black holes heat or eject the gas from which stars would otherwise form.

The report also situates these observations within the framework of modern simulations. Numerical models of galaxy formation, run on some of the largest supercomputers available, now resolve the interstellar medium of individual galaxies within a cosmological context, allowing theorists to predict how gas accretion from the cosmic web, turbulence driven by stellar feedback, and gravitational instabilities combine to set a galaxy’s size, thickness and spiral structure. Recent work cited in the report examines how such simulations reproduce the morphological diversity of galaxies across cosmic time, and where they still fall short. The comparison between simulated and observed morphologies is no longer a qualitative exercise; quantitative metrics, including non-parametric measures of concentration, asymmetry and clumpiness, as well as machine-learning classifiers trained on labeled images, allow statistical comparisons over thousands of galaxies.

That statistical approach is becoming essential as the data volumes grow. JWST surveys are imaging hundreds of thousands of galaxies in the rest-frame optical, the wavelength range where the older stellar populations and the overall structural skeleton of a galaxy are best traced. ALMA, meanwhile, maps the cold molecular gas and dust that fuel and obscure star formation, revealing the raw material from which the Hubble types are built. Combining the two gives a multiwavelength view in which morphology can be decomposed into its physical ingredients: a rotationally supported stellar disk, a turbulent gas layer, a bulge assembled through early collapse or mergers, and a halo of dark matter that sets the gravitational stage. The report argues that it is precisely this decomposition that turns morphology from a descriptive label into a diagnostic of the underlying baryon cycle.

The implications run in two directions. Looking backward, the presence of dynamically mature disks and massive, compact galaxies at high redshift places strong constraints on how efficiently baryons were assembled into ordered structures in the first billion years, constraining models of early gas accretion and the role of feedback in the youngest galaxies. Looking forward, the report suggests that the classical Hubble sequence should be understood as the late-time outcome of physical processes that were already operating when the universe was young: disks that formed early and survived, bulges that grew through mergers and secular evolution, and quiescent systems whose star formation was shut down as their gas supplies were exhausted or heated. In that reading, the tuning fork is not a museum piece but a summary of galaxy physics, one that JWST and ALMA are now reading out at every epoch of cosmic history.

A century after Hubble drew his famous diagram, the galaxies themselves have become the message. The structures we classify, spirals, ellipticals, lenticulars and their high-redshift progenitors, encode the accretion histories, feedback cycles and dynamical states of the gas and stars within them. As Tacchella’s report makes clear, the coming decade of observations, with deeper JWST imaging, wider ALMA mapping and ever more sophisticated simulations, will turn that encoding into a quantitative test of galaxy-formation theory, ensuring that the Hubble sequence remains not a relic of 1920s astronomy but a living framework, continuously revisited and refined across cosmic time.

Subject of Research: Galaxy morphology and the Hubble sequence as a probe of galaxy formation across cosmic time

Article Title: Beyond Hubble: revisiting the Hubble sequence across cosmic time

Article References: Tacchella, S. (2026). Beyond Hubble: revisiting the Hubble sequence across cosmic time. Nature Astronomy. https://doi.org/10.1038/s41550-026-02989-1

Image Credits: AI Generated

DOI: 10.1038/s41550-026-02989-1

Keywords: galaxy morphology, Hubble sequence, JWST, ALMA, high-redshift galaxies, galaxy disks, star formation, gas accretion, stellar feedback, galaxy evolution, early universe, cosmological simulations

Most massive stars in the universe are not loners. Decades of surveys of massive main-sequence stars have shown that the overwhelming majority are found in binary or higher-order multiple systems, and that these partnerships profoundly shape how the stars live and die. Binaries strip each other’s outer layers, exchange mass, spin each other up and, in the most violent cases, merge — producing some of the most energetic events in astronomy, including gravitational-wave sources detected by observatories such as LIGO and Virgo. Yet despite their ubiquity, the question of how massive binaries form in the first place has remained one of the most stubborn puzzles in star formation research.

Three main pathways have been proposed. In the disk fragmentation scenario, a single massive protostar surrounded by a massive accretion disk becomes gravitationally unstable, and the disk breaks apart to form a companion. In core fragmentation, a single dense cloud core splits early on into two separate condensations that each collapse into a star while still bound together. The third possibility, stellar capture, involves two stars formed independently in the same crowded region that happen to pass close enough for their mutual gravity to bind them. Each scenario leaves a distinct fingerprint in the geometry and dynamics of the resulting binary, particularly in the eccentricity of the orbit and the alignment between the orbital plane and the disks of gas feeding the young stars.

The trouble has always been observation. Measuring the three-dimensional orbit of a binary system requires detecting the tiny apparent shift of one component relative to the other across multiple observing epochs — the orbital proper motion. For massive protostars, which are deeply embedded in dusty cocoons that block visible light and which orbit slowly because of their large masses and wide separations, this measurement demands exquisite angular resolution, sensitivity and patience. As a result, direct orbital reconstructions of massive binaries in their infancy have been essentially nonexistent, leaving theorists to argue over plausible scenarios without decisive observational constraints.

The team behind the new work, led by Yao Wang and Yichen Zhang of Shanghai Jiao Tong University together with an international collaboration, overcame this obstacle by combining years of high-resolution observations from several of the world’s most powerful telescopes. They used the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array (JVLA) to image the system at wavelengths ranging from submillimetre to centimetre across multiple epochs, allowing them to track the relative positions of the two protostellar components with extraordinary precision. Complementary infrared imaging from the James Webb Space Telescope and the European Southern Observatory’s Very Large Telescope provided an additional view of the embedded pair and its surroundings, piercing the dust that hides the nursery.

The multi-epoch data revealed the unmistakable signature of orbital motion: the two components, separated by roughly 200 astronomical units — about 200 times the Earth–Sun distance — are visibly moving around each other. That detection opened the door to a full three-dimensional orbital reconstruction. But the team did not stop at astrometry. They also modeled the multi-wavelength continuum emission from each component to estimate the masses and the properties of the circumstellar disks, analyzed the kinematics of hydrogen recombination lines — spectral lines emitted by ionized gas close to each protostar that trace Keplerian motion — and examined radio jet observations that helped pin down the orientation of the disks relative to the orbit.

When all of these pieces were fitted together using Bayesian orbital modeling, a striking picture emerged. The preferred orbital solutions are highly eccentric, with the pair’s current trajectory lying close to a parabola — the razor’s edge between a bound elliptical orbit and an unbound hyperbolic escape. In other words, the two protostars appear to have been caught at the delicate moment when their first gravitational encounter is only barely holding them together. Even more tellingly, the circumstellar disks around both components are strongly misaligned with the orbital plane, tilted far from the flat configuration expected if the two stars had formed together from a single rotating structure.

Both properties — the near-parabolic eccentricity and the severe disk–orbit misalignment — are difficult to produce in the standard disk-fragmentation or core-fragmentation pictures, which tend to yield binaries on more circular orbits with disks broadly aligned with the orbital plane. Instead, they fall out naturally from the core-merger scenario. In this picture, the two protostars began their lives in separate, initially unbound cloud cores within the same star-forming region. As the cores drifted through the dense cluster environment, they converged on a near-parabolic encounter. During this close passage, dynamical friction and gravitational torques from their gas envelopes dissipated enough orbital energy to leave them barely bound, while the encounter itself scrambled the orientations of their disks, tilting them out of any common plane.

The idea that stellar encounters in young clusters can sculpt binary architectures is not new — astronomers have long studied how flybys perturb protoplanetary disks and how dynamics in cluster cores can harden or soften binaries. What makes this result remarkable is that it offers direct, quantitative evidence that such a process has operated on a massive protobinary caught in the act. IRAS 07299−1651, with its pair of massive twin disks and its razor-thin orbital binding, looks less like a binary that was born together and more like one that was assembled after the fact, stitched together by gravity during a single fateful pass. It is a snapshot of binary assembly in real time, preserved in the geometry of the system for observers to decode.

The implications ripple outward across stellar astrophysics. If core-merger encounters represent an important channel for forming eccentric massive binaries, then the population of massive binaries on eccentric orbits — including many of those that will eventually interact, exchange mass or merge — may owe their existence not to shared birth but to later dynamical matchmaking. This affects predictions for the rates of massive binary interactions, the formation of gravitational-wave progenitors and the statistics of stripped stars and X-ray binaries. More broadly, the study demonstrates that with multi-epoch, multi-wavelength observations and modern orbital fitting techniques, astronomers can now reconstruct the three-dimensional choreography of forming massive star systems, turning what was once pure theory into a measurable, evolving picture. The team has also released the reduced ALMA and JVLA continuum images and hydrogen recombination line data cubes through the Zenodo repository, ensuring that other researchers can scrutinize and build upon this rare glimpse of two young giants caught mid-encounter, their futures still hanging on a gravitational knife’s edge.

Subject of Research: The three-dimensional orbital architecture and core-merger formation pathway of the massive protobinary IRAS 07299−1651.

Article Title: An eccentric massive protobinary assembled via a core-merger parabolic encounter

Article References: Wang, Y., Zhang, Y., Fedriani, R., Tanaka, K. E. I., Rosero, V., Yang, K., Andersen, M., Beltrán, M. T., Bonfand, M., Cheng, Y., De Buizer, J. M., Di, Y., Garay, G., Gorai, P., Li, Z.-Y., Yang, Y.-L., & Tan, J. C. (2026). An eccentric massive protobinary assembled via a core-merger parabolic encounter. Nature Astronomy. https://doi.org/10.1038/s41550-026-02953-z

Image Credits: AI Generated

DOI: 10.1038/s41550-026-02953-z

Keywords: massive star formation, protobinary, orbital eccentricity, IRAS 07299−1651, ALMA, JVLA, core merger, disk misalignment, hydrogen recombination lines, protostellar disks, stellar dynamics, Nature Astronomy