No abstract

Iron is prone to change its form and speciation in phases. Thus, several methods have been developed to estimate iron partitioning in the mineral phases of soils. However, the accuracy of these methods to evaluate the iron contribution from minor phases, such as actinolite, almandine, biotite, chlorite, epidote, hornblende, muscovite, and Fe-diospide, remains low. Furthermore, most of the current iron speciation research is focused on bulk samples, and only applies to soil samples that are mostly composed of clays or clay minerals, without a wide-ranging evaluation of soil particles with different grain sizes. In this study, we classified several iron phases using a mineral liberation analyzer on desert soil particles with diameters ranging from silt- to fine-sand (5–20 µm, 20–45 µm, 45–63 µm, 63–75 µm, and > 75 µm). The iron containing minor phases were identified, the modal mineral abundances were determined via matching with the standard energy dispersive spectra library, and a particle size analysis was performed using mineral processing tools on each of the examined 40,000 particles. The iron partition results were ultimately established based on the standard iron concentration in the mineral phases and the modal mineral abundances. This new method could be automated, thereby facilitating high efficiency identification of iron-containing phases that would allow, for the first time, the generation of a dataset for iron partitioning in soil particles. This method allows the identification of minor iron phases in soil particles, and permits in situ mapping of iron mineralogy in fine sand- to silt-sized soil particles. Not restricted by single mineral particles, this method considers multi-phase complex particles. Thus, it largely improves the accuracy for estimating the iron partition parameter.

Diphtheria is a respiratory disease caused by Corynebacterium diphtheriae. While the toxin-based vaccine has helped control outbreaks of the disease since the mid-20th century there has been an increase in cases in recent years, including systemic infections caused by non-toxigenic C. diphtheriae strains. Here we describe the first study of gene essentiality in C. diphtheriae, providing the most-dense Transposon Directed Insertion Sequencing (TraDIS) library in the phylum Actinobacteriota. This high-density library has allowed the identification of conserved genes across the genus and phylum with essential function and enabled the elucidation of essential domains within the resulting proteins including those involved in cell envelope biogenesis. Validation of these data through protein mass spectrometry identified hypothetical and uncharacterized proteins in the proteome which are also represented in the vaccine. These data are an important benchmark and useful resource for the Corynebacterium, Mycobacterium, Nocardia and Rhodococcus research community. It enables the identification of novel antimicrobial and vaccine targets and provides a basis for future studies of Actinobacterial biology.

The sources of the sediments in distinct areas of the Chinese Loess Plateau (CLP) are still disputed, starting with the particle formation in the original desert areas, as well as the neighboring river systems. The formation of loess particles in the southern CLP was investigated using Scanning Electron Microscopy (SEM) and combined material modal composite analysis. Here, we determined the mineralogy in the Duanjiapo (DJP) section on the southernmost CLP and the last glacial‐interglacial samples on the central and north CLP. The results reveal that the samples plot along the N‐S transect, which is very likely the result of differential weathering. The SEM observations of the internal textures of soil aggregates from DJP suggest that precipitation mediated dissolution led to the formation of the fine particle fraction (5–10 μm). The most dissolution was observed for the hornblende particles. The further evolution of these smaller particles followed a decrease (2.6–0 Ma) in the grain size up section. Our record of the changes in and trend of the hornblende concentrations suggests an imbalance in the budget of the hornblende influx via sub‐aerosol wind transport versus the mineral dissolution, which provides robust evidence for a sediment provenance in the deserts north and west of CLP. Understanding the sediment source is critical to trace Asian monsoon evolution. The hornblende record suggests a coeval change in the trends of the summer monsoon and winter monsoon, and this contemporaneous change may not support the recently proposed Pacific Walker Circulation mechanism in the interpretation of Asian monsoon.

Biogenesis of the bacterial outer membrane is key to survival and antibiotic resistance. Central to this is the beta-barrel assembly machine (Bam) complex and its associated chaperones, which are responsible for outer membrane protein (OMP) transport and insertion. The Escherichia coli Bam complex consists of two essential subunits, BamA and BamD, and three non-essential lipoproteins, BamB, BamC and BamE. Optimal Bam function is further dependent on the non-essential chaperones DegP, Skp and SurA. Despite intensive study, the specific function of these non-essential Bam-associated proteins remains unknown. Here, we analysed knockout strains for each gene by phenotypic screening, conservation analysis and high-throughput genetics. We reveal that Bam activity is affected by outer membrane lipid composition and that enterobacterial common antigen is essential in the absence of the chaperone SurA. We also show that components of peptidoglycan are conditionally essential with Bam accessory lipoproteins and that DNA replication is perturbed in the absence of BamB. Together, our data indicates potential mechanisms for coordination of OMP biogenesis with processes such as LPS and peptidoglycan biogenesis, and DNA replication.