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The appearance of ice I in the smallest possible clusters and the nature of its phase coexistence with liquid water could not thus far be unraveled. The experimental and theoretical infrared spectroscopic and free-energy results of this work show the emergence of the characteristic hydrogen-bonding pattern of ice I in clusters containing only around 90 water molecules. The onset of crystallization is accompanied by an increase of surface oscillator intensity with decreasing surface-to-volume ratio, a spectral indicator of nanoscale crystallinity of water. In the size range from 90 to 150 water molecules, we observe mixtures of largely crystalline and purely amorphous clusters. Our analysis suggests that the liquid-ice I transition in clusters loses its sharp 1st-order character at the end of the crystalline-size regime and occurs over a range of temperatures through heterophasic oscillations in time, a process without analog in bulk water.

Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in [Formula: see text] surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during [Formula: see text] surface oxidation.

Subsurface chlorophyll maximum layers (SCMLs) are nearly ubiquitous in stratified water columns and exist at horizontal scales ranging from the submesoscale to the extent of oligotrophic gyres. These layers of heightened chlorophyll and/or phytoplankton concentrations are generally thought to be a consequence of a balance between light energy from above and a limiting nutrient flux from below, typically nitrate (NO3). Here we present multiple lines of evidence demonstrating that iron (Fe) limits or with light colimits phytoplankton communities in SCMLs along a primary productivity gradient from coastal to oligotrophic offshore waters in the southern California Current ecosystem. SCML phytoplankton responded markedly to added Fe or Fe/light in experimental incubations and transcripts of diatom and picoeukaryote Fe stress genes were strikingly abundant in SCML metatranscriptomes. Using a biogeochemical proxy with data from a 40-y time series, we find that diatoms growing in California Current SCMLs are persistently Fe deficient during the spring and summer growing season. We also find that the spatial extent of Fe deficiency within California Current SCMLs has significantly increased over the last 25 y in line with a regional climate index. Finally, we show that diatom Fe deficiency may be common in the subsurface of major upwelling zones worldwide. Our results have important implications for our understanding of the biogeochemical consequences of marine SCML formation and maintenance.

Johne's disease (JD), a chronic, infectious enteritis caused by Mycobacterium avium subsp. paratuberculosis (MAP), affects wild and domestic ruminants. There is no cure or effective prevention, and current vaccines have substantial limitations, leaving this disease widespread in all substantial dairy industries causing economic, and animal welfare implications. Mycobacteriophages (MPs) have been gaining interest in recent years and are proposed as a promising solution to curtailing MAP infection. Using a well-validated infection model, we have demonstrated the preventative potential of MPs to protect dairy calves against MAP infection. Calves were supplemented daily with a phage cocktail from birth till weaning at 2 m of age and inoculated with MAP at 2 wk of age. Infection status was measured for 4.5 mo through blood, fecal, and postmortem tissue samples. Our findings highlight the remarkable efficacy of orally administered MPs. Notably, fecal shedding of MAP was entirely eliminated within 10 wk, in contrast to the infected control group where shedding continued for the entirety of the trial period. Postmortem tissue culture analysis further supported the effectiveness of MPs, with only 1 out of 6 animals in the phage-treated group testing positive for MAP colonized tissues compared to 6 out of 6 animals in the infected control group. Additionally, plaque assay results demonstrated the ability of phages to persist within the intestinal tract. Collectively, these results underscore the potential of orally administered MP cocktails as a highly effective intervention strategy to combat JD in dairy calves and by extension in the dairy industry. [ABSTRACT FROM AUTHOR]

Peroxisome proliferator-activated receptor gamma (PPARG) is a master transcriptional regulator of adipocyte differentiation and a canonical target of antidiabetic thiazolidinedione medications. In rare families, loss-of-function (LOF) mutations in PPARG are known to cosegregate with lipodystrophy and insulin resistance; in the general population, the common P12A variant is associated with a decreased risk of type 2 diabetes (T2D). Whether and how rare variants in PPARG and defects in adipocyte differentiation influence risk of T2D in the general population remains undetermined. By sequencing PPARG in 19,752 T2D cases and controls drawn from multiple studies and ethnic groups, we identified 49 previously unidentified, nonsynonymous PPARG variants (MAF < 0.5%). Considered in aggregate (with or without computational prediction of functional consequence), these rare variants showed no association with T2D (OR = 1.35; P = 0.17). The function of the 49 variants was experimentally tested in a novel high-throughput human adipocyte differentiation assay, and nine were found to have reduced activity in the assay. Carrying any of these nine LOF variants was associated with a substantial increase in risk of T2D (OR = 7.22; P = 0.005). The combination of large-scale DNA sequencing and functional testing in the laboratory reveals that approximately 1 in 1,000 individuals carries a variant in PPARG that reduces function in a human adipocyte differentiation assay and is associated with a substantial risk of T2D.

Gene transcription is a fundamental cellular process carried out by RNA polymerase (RNAP). Transcription initiation is highly regulated, and in bacteria, transcription initiation is mediated by sigma (σ) factors. σ recruits RNAP to the promoter DNA region, located upstream of the transcription start site (TSS) and facilitates open complex formation, where double-stranded DNA is opened up into a transcription bubble and template strand DNA is positioned inside RNAP for initial RNA synthesis. During initial transcription, RNAP remains bound to σ and upstream DNA, presumably with an enlarging transcription bubble. The release of RNAP from upstream DNA is required for promoter escape and processive transcription elongation. Bacteria sigma factors can be broadly separated into two classes with the majority belonging to the σ70 class, represented by the σ70 that regulates housekeeping genes. σ54 forms a class on its own and regulates stress response genes. Extensive studies on σ70 have revealed the molecular mechanisms of the σ70 dependent process while how σ54 transitions from initial transcription to elongation is currently unknown. Here, we present a series of cryo-electron microscopy structures of the RNAP-σ54 initial transcribing complexes with progressively longer RNA, which reveal structural changes that lead to promoter escape. Our data show that initially, the transcription bubble enlarges, DNA strands scrunch, reducing the interactions between σ54 and DNA strands in the transcription bubble. RNA extension and further DNA scrunching help to release RNAP from σ54 and upstream DNA, enabling the transition to elongation. [ABSTRACT FROM AUTHOR]

Bone regulates its mass and quality in response to diverse mechanical, hormonal, and local signals. The bone anabolic or catabolic responses to these signals are often received by osteocytes, which then coordinate the activity of osteoblasts and osteoclasts on bone surfaces. We previously established that calcium/calmodulin-dependent kinase 2 (CaMKII) is required for osteocytes to respond to some bone anabolic cues in vitro. However, a role for CaMKII in bone physiology in vivo is largely undescribed. Here, we show that conditional codeletion of the most abundant isoforms of CaMKII (delta and gamma) in mature osteoblasts and osteocytes [Ocn-cre: Camk2d/Camk2g double-knockout (dCKO)] caused severe osteopenia in both cortical and trabecular compartments by 8 wk of age. In addition to having less bone mass, dCKO bones are of worse quality, with significant deficits in mechanical properties, and a propensity to fracture. This striking skeletal phenotype is multifactorial, including diminished osteoblast activity, increased osteoclast activity, and altered phosphate homeostasis both systemically and locally. These dCKO mice exhibited decreased circulating phosphate (hypophosphatemia) and increased expression of the phosphate-regulating hormone fibroblast growth factor 23. Additionally, dCKO mice expressed less bone-derived tissue nonspecific alkaline phosphatase protein than control mice. Consistent with altered phosphate homeostasis, we observed that dCKO bones were hypo-mineralized with prominent osteoid seams, analogous to the phenotypes of mice with hypophosphatemia. Altogether, these data reveal a fundamental role for osteocyte CaMKIId and CaMKIIγ in the maintenance of bone mass and bone quality and link osteoblast/osteocyte CaMKII to phosphate homeostasis. [ABSTRACT FROM AUTHOR]