Background: Leguminous plants alter patterns of gene expression in response to symbiotic colonization and infection by their cognate rhizobial bacteria, but the extent of the transcriptomic response has rarely been examined below the species level. Here we describe the identification of 12 rhizobial biotypes of Ensifer meliloti, which form nitrogen-fixing nodules in the roots of alfalfa (Medicago sativa L.), followed by a comparative RNA-seq analysis of four alfalfa cultivars each inoculated with two E. meliloti strains varying in symbiotic performance and phylogenetic relatedness. Results: Rhizobial biotypes were identified on the basis of their symbiotic performance, particularly shoot dry weight. Differentially expressed genes (DEGs) and metabolic pathways were determined by comparing the RNA-seq data with that of the uninoculated control plant. Significant differences were found between DEGs generated in each cultivar with the inoculation of two rhizobial strains in comparison (P < 0.01). A total of 8111 genes was differentially expressed, representing~17.1% of the M. sativa genome. The proportion of DEGs ranges from 0.5 to 12.2% for each alfalfa cultivar. Interestingly, genes with predicted roles in flavonoid biosynthesis and plant-pathogen interaction (NBS-LRR) were identified as the most significant DEGs. Other DEGs include Medsa002106 and genes encoding nodulins and NCR peptides whose expression is specifically induced during the development of nitrogenfixing nodules. More importantly, strong significant positive correlations were observed between plant transcriptomes (DEGs and KEGG pathways) and phylogenetic distances between the two rhizobial inoculants. Conclusions: Alfalfa expresses significantly distinct sets of genes in response to infection by different rhizobial strains at the below-species levels (i.e. biotype or strain). Candidate genes underlying the specific interactions include Medsa002106 and those encoding nodulins and NCR peptides and proteins in the NBS-LRR family.

BackgroundGroup B streptococcus (GBS) is a leading cause of serious infections in infants. The extensive use of tetracycline has led to the selection of specific resistant and infectious GBS clones. The sequence type (ST) 10 GBS strain, causing invasive infections in infants, is becoming prevalent in China. We aimed to understand the clinical and microbiological characteristics of this GBS strain.MethodsWe conducted a retrospective study on infants with invasive GBS disease from the largest women’s and children’s medical center in Shanxi and collected data between January 2017 and October 2020. GBS isolates were analyzed by capsule serotyping, genotyping, antibiotic resistance, and surface protein genes.ResultsAll ST10 isolates belonged to serotype Ib; type Ib/ST10 strains were responsible for 66.7% (14/21, P &lt; 0.05) of infant invasive GBS infections during the period and all resulted in late-onset (LOD) and late LOD disease (14/14). Infants with type Ib/ST10 GBS disease had significantly higher rates of meningitis (9/14, 64.3%, p &lt; 0.05) and clinical complications (5/14, 35.7%, p &lt; 0.05). The Ib/ST10 GBS isolates had limited genetic diversity, clustered in the CC10/bca/PI-1 + PI-2a genetic lineage, showed resistance to erythromycin, lincomycin, and fluoroquinolones and sensitivity to tetracycline, and possessed genes ermT, ermB, and amino acid changes in gyrA and parC.ConclusionsThe probable clonal expansion can result in severe infections in infants and ongoing emergence of multi-drug resistant isolates. Continued monitoring for type Ib/ST10 GBS infections is warranted.

Alfalfa (Medicago sativa) is a highly valuable perennial forage legume that suffers from autotoxicity, which decreases plant resistance, reduces soil fertility, causes serious soil-borne diseases, and promotes ecological imbalance. We evaluated the effects of autotoxicity on the seed germination of 22 alfalfa varieties, and then elucidated the oxidative damage and lipid peroxidation in two alfalfa varieties with contrasting autotoxicity tolerances. The technique for order of preference by similarity to ideal solution (TOPSIS) method was used to rank the germination of the 22 alfalfa varieties when exposed to six autotoxic concentrations (0, 0.025, 0.075, 0.125, 0.175, and 0.225 g∙mL−1). We found WL656HQ and 3105C to be autotoxicity-tolerant and autotoxicity-sensitive varieties, respectively. The germination index mainly affects the comprehensive allelopathic index of WL656HQ and 3105C, which were the simple vigor index and radicle length according to the random forest model, respectively. 3105C eliminates reactive oxygen species (ROS) via antioxidant enzymes and antioxidants under T1 (0.025 g∙mL−1), but the oxidative stress system and the oxidative scavenging system cannot maintain the balance under T2 (0.125 g∙mL−1), causing oxidative bursts. In comparison, WL656HQ used its oxidative scavenging system (peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR)) to maintain its redox dynamic balance by removing excess ROS at all concentrations. In conclusion, the positive and negative indicators of autotoxicity for the two varieties were ascorbate (ASA) and hydroxyl free radicals (OH•), and proline (Pro) and dehydroascrobate (DHA), respectively. The most sensitive autotoxic concentrations of 3105C and WL656HQ were T2 (0.125 g∙mL−1) and T1 (0.025 g∙mL−1), respectively.

Crooked Ag2Te nanotubes were prepared through homogeneous precipitation and the photoelectric properties of the film-based photodetector were investigated.

The association between low density lipoprotein cholesterol (LDL-C) and all-cause mortality has been examined in many studies. However, inconsistent results and limitations still exist. We used the 1999–2014 National Health and Nutrition Examination Survey (NHANES) data with 19,034 people to assess the association between LDL-C level and all-cause mortality. All participants were followed up until 2015 except those younger than 18 years old, after excluding those who died within three years of follow-up, a total of 1619 deaths among 19,034 people were included in the analysis. In the age-adjusted model (model 1), it was found that the lowest LDL-C group had a higher risk of all-cause mortality (HR 1.708 [1.432–2.037]) than LDL-C 100–129 mg/dL as a reference group. The crude-adjusted model (model 2) suggests that people with the lowest level of LDL-C had 1.600 (95% CI [1.325–1.932]) times the odds compared with the reference group, after adjusting for age, sex, race, marital status, education level, smoking status, body mass index (BMI). In the fully-adjusted model (model 3), people with the lowest level of LDL-C had 1.373 (95% CI [1.130–1.668]) times the odds compared with the reference group, after additionally adjusting for hypertension, diabetes, cardiovascular disease, cancer based on model 2. The results from restricted cubic spine (RCS) curve showed that when the LDL-C concentration (130 mg/dL) was used as the reference, there is a U-shaped relationship between LDL-C level and all-cause mortality. In conclusion, we found that low level of LDL-C is associated with higher risk of all-cause mortality. The observed association persisted after adjusting for potential confounders. Further studies are warranted to determine the causal relationship between LDL-C level and all-cause mortality.

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Research on rhizobium diversity has paved the way for diversification of rhizobial germplasm resources. Seventy-three endophytic bacterial isolates were collected from seven tissues of five alfalfa cultivars in three geographic locations in Gansu, China. Restriction fragment length polymorphism (RFLP) fingerprinting of 16S rRNA and analysis of concatenated sequence of three housekeeping genes (atpD, glnII, and recA) and two symbiotic genes (nodC and nifH) were used for strain identification. Results showed that the endophytic strains were genetically diverse at different taxonomic levels, and Ensifer meliloti (31) and Agrobacterium radiobacter (12) are common Medicago sativa endophytic bacteria in Gansu, China. The nifH genes (97%–98% sequence identity) of E. meliloti strains were more diverse than the nodC genes (99%–100% sequence identity), even though the strains evolved from a common ancestor. The degree of dispersion of symbiotic phenotypes of E. meliloti strains on M. sativa ‘Gannong No. 3’, ‘Gannong No. 9’, and ‘Qingshui’ was much less than that on M. sativa ‘Longzhong’ and ‘WL168HQ’. This suggested that the symbiotic efficiency of E. meliloti strains on the former three alfalfa cultivars was similar but on the latter two was discrepant. Their symbiotic efficiency differed primarily according to alfalfa cultivars and, to a lesser extent, to the tested strains, indicating the difference in the sensitivity of different alfalfa cultivars to rhizobial strains.