Description of two nitrogen-fixing bacteria,Geomonas fuzhouensis sp. nov. and Geomonas agri sp. nov., isolated from paddy soils

Two strictly anaerobic nitrogen-fixing strains, designated RG17^T and RG53^T, were isolated from paddy soils in China. Strains RG17^T and RG53^T showed the highest 16S rRNA gene sequence similarities to the type strain Geomonas paludis (97.9–98.4%). Phylogenetic tree based on 16S rRNA gene sequences showed that two strains clustered with members of the genus Geomonas. Growth of strain RG17^T was observed at 20–42 °C, pH 5.5–8.5 and 0–0.3% (w/v) NaCl while strain RG53^T growth was observed at 20–42 °C, pH 5.5–9.5 and 0–0.7% (w/v) NaCl. Strains RG17^T and RG53^T contained MK-8 as main menaquinone and C_15:1 ω6c, iso-C_15:0, and Summed Feature 3 as the major fatty acids. The genomic DNA G?+?C content of strains RG17^T and RG53^T were 61.6 and 60.7%, respectively. The digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values between the isolated strains and the closely related Geomonas species were lower than the cut-off value (dDDH 70% and ANI 95–96%) for prokaryotic species delineation. Both strains possessed nif genes nifHDK and nitrogenase activities. Based on the above results, the two strains represent two novel species of the genus Geomonas, for which the names Geomonas fuzhouensis sp. nov. and Geomonas agri sp. nov., are proposed. The type strains are RG17^T (=?GDMCC 1.2687^T?=?KTCC 25332^T) and RG53^T (=?GDMCC 1.2630^T?=?KCTC 25331^T), respectively.

     

Metabolic engineering of Escherichia coli for efficient osmotic stress-free production of compatible solute hydroxyectoine

Compatible solutes are key for the ability of halophilic bacteria to resist high osmotic stress. They have received wide attention from researchers for their excellent osmotic protection properties. Hydroxyectoine is a particularly important compatible solute, but its production by microbes faces several challenges, including low titer/yield, the presence of the byproduct ectoine, and the requirement of high salinity. Here, we aimed to metabolically engineer Escherichia coli to efficiently produce hydroxyectoine in the absence of osmotic stress without accumulating the byproduct ectoine. First, combinatorial optimization of the expression strength of key genes in the ectoine synthesis module and hydroxyectoine synthesis module was conducted. After optimization of the expression of these genes, 12.12 g/L hydroxyectoine and 0.24 g/L ectoine were obtained at 36 h in shake-flask fermentation with the addition of the co-substrate α-ketoglutarate. Further optimization of the addition of α-ketoglutarate achieved the sole production of hydroxyectoine (i.e., no ectoine accumulation), indicating that the supply of α-ketoglutarate is critically important for sole hydroxyectoine production. Finally, quorum sensing-based auto-regulation of intracellular α-ketoglutarate pool was implemented as an alternative to α-ketoglutarate addition by coupling the expression of sucA with the esaI/esaR circuit, which led to 14.93 g/L hydroxyectoine with a unit cell yield of 1.678 g/g and no ectoine accumulation in the absence of osmotic stress. This is the highest reported titer of sole hydroxyectoine production under salinity-free fermentation to date.     

Environmental Drivers and Spatial Prediction of the Critically Endangered Species <i>Thuja sutchuenensis</i> in Sichuan-Chongqing,China

Identifying the ecological environment suitable for the growth of Thuja sutchuenensis and predicting other potential distribution areas are essential to protect this endangered species. After selecting 24 environmental factors that could affect the distribution of T. sutchuenensis, including climate, topography, soil and Normalized Difference Vegetation Index (NDVI), we adopted the Random Forest-MaxEnt integrated model to analyze our data. Based on the Random Forest study, the contribution of the mean temperature of the warmest quarter, mean temperature of the coldest quarter, annual mean temperature and mean temperature of the driest quarter was large. Based on MaxEnt model prediction outputs, the potential distribution map not only identified areas that originally recorded T. sutchuenensis, such as Xuanhan County, Kai County and Chengkou County, but also identified highly suitable distribution areas where T. sutchuenensis may exist, including Wanyuan County, Sichuan Province, and the junction of Chongqing and Hubei Province. This provides a more explicit geographic range for ex situ conservation and reintroduction of T. sutchuenensis. Our results also indicate that, in addition to climate factors, topography and soil factors are also important environmental factors that affect distribution. This provides a theoretical basis for subsequent laboratory construction to simulate the indoor growth of T. sutchuenensis.     

Temporal shifts in the relative importance of climate and leaf litter traits in driving litter decomposition dynamics in a Chinese transitional mixed forest

Plant and Soil - To assess the direction and strength of climate and leaf litter trait effects on decomposition dynamics throughout the litter decomposition process. We performed a three-year-long...     

Construction of two regulatory networks related to salt stress and lignocellulosic synthesis under salt stress based on a Populus davidiana × P. bolleana transcriptome analysis

Plant Molecular Biology - Construction of ML-hGRN for the salt pathway in Populus davidiana?×?P. bolleana. Construction of ML-hGRN for the lignocellulosic pathway in Populus...     

Analysis of Grain Yield Formation Components of Extra Heavy-Panicle-Type Mid-Season Indica Hybrid Rice

Journal of Plant Growth Regulation - Rice is the most important food crop species of the developing world, and there are increasing concerns about food security to increase rice yields...     

Loss of Function Mutation of IOS1 in Arabidopsis Is More Sensitive to Salt Stress

Plant Molecular Biology Reporter - Plants are subjected to a variety of environmental stressors, including salinity, drought and pathogens, and have consequently developed a sophisticated sensing...     

Nerve Growth Factor is a Potential Treated Target in Tg(SOD1*G93A)1Gur Mice

Nerve growth factor (NGF) is a protective factor of neural cells; the possible relationship between the NGF and the pathogenesis of amyotrophic lateral sclerosis (ALS) hasn’t been completely known. In this study, we observed and analyzed the expression and distribution of NGF, as well as the possible relationship between the NGF expression and distribution and the neural cell death in both SOD1 wild-type (WT) and Tg(SOD1*G93A)1Gur (TG) mice applying the fluorescence immunohistochemistry method. The results showed that the expression and distribution of NGF in the anterior horn (AH), the lateral horn (LH), and the surrounding central canal (CC) significantly increased at the supper early stage of ALS (Pre-onset stage) and the early stage (Onset stage), but the NGF expression and distribution in the AH, the LH, and the surrounding CC significantly reduced at the progression stage. The astrocyte, neuron, and oligodendrocyte produced the NGF and the neural precursor cells (NPCs) produced the NGF. The neural cell death gradually increased accompanying with the reduction of NGF expression and distribution. Our data suggested that the NGF was a protective factor of neural cells, because the neural cells in the AH, the LH, and the surrounding CC produced more NGF at the supper early and early stage of ALS; moreover, the NPCs produced the NGF. It implied that the NGF exerted the protective effect of neural cells, prevented from the neural cell death and aroused the potential of self-repair in the development of ALS.

     

Expression of Cre recombinase in chondrocytes causes abnormal craniofacial and skeletal development

The cranial base synchondroses are growth centers that drive cranial and upper facial growth. The intersphenoid synchondrosis (ISS) and the spheno-occipital synchondrosis (SOS) are two major synchondroses located in the middle of the cranial base and are maintained at early developmental stages to sustain cranial base elongation. In this study, we report unexpected premature ossification of ISS and SOS when Cre recombinase is activated in a chondrocyte-specific manner. We used a Cre transgenic line expressing Aggrecan enhancer-driven, Tetracycline-inducible Cre (ATC), of which expression is controlled by a Col2a1 promoter. Neonatal doxycycline injection or doxycycline diet fed to breeders was used to activate Cre recombinase. The premature ossification of ISS and/or SOS led to a reduction in cranial base length and subsequently a dome-shaped skull. Furthermore, the mice carrying either heterozygous or homozygous conditional deletion of Tsc1 or Fip200 using ATC mice developed similar craniofacial abnormalities, indicating that Cre activity itself but not conditional deletion of Tsc1 or Fip200 gene, is the major contributor of this phenotype. In contrast, the Col2a1-Cre mice carrying Cre expression in both perichondrium and chondrocytes and the mice carrying the conditional deletion of Tsc1 or Fip200 using Col2a1-Cre did not manifest the same skull abnormalities. In addition to the defective craniofacial bone development, our data also showed that the Cre activation in chondrocytes significantly compromised bone acquisition in femur. Our data calls for the consideration of the potential in vivo adverse effects caused by Cre expression in chondrocytes and reinforcement of the importance of including Cre-containing controls to facilitate accurate phenotype interpretation in transgenic research.