A Sb(III)-specific efflux transporter from Ensifer adhaerens E-60.

Antimony is pervasive environmental toxic substance, and numerous genes encoding mechanisms to resist, transform and extrude the toxic metalloid antimony have been discovered in various microorganisms. Here we identified a major facilitator superfamily (MFS) transporter, AntB, on the chromosome of the arsenite-oxidizing bacterium Ensifer adhaerens E-60 that confers resistance to Sb(III) and Sb(V). The antB gene is adjacent to gene encoding a LysR family transcriptional regulator termed LysRars, which is an As(III)/Sb(III)-responsive transcriptional repressor that is predicted to control expression of antB. Similar antB and lysRars genes are found in related arsenic-resistant bacteria, especially strains of Ensifer adhaerens, and the lysRars gene adjacent to antB encodes a member of a divergent subgroup of putative LysR-type regulators. Closely related AntB and LysRars orthologs contain three conserved cysteine residues, which are Cys17, Cys99, and Cys350 in AntB and Cys81, Cys289 and Cys294 in LysRars, respectively. Expression of antB is induced by As(III), Sb(III), Sb(V) and Rox(III) (4-hydroxy-3-nitrophenyl arsenite). Heterologous expression of antB in E. coli AW3110 (Δars) conferred resistance to Sb(III) and Sb(V) and reduced the intracellular concentration of Sb(III). The discovery of the Sb(III) efflux transporter AntB enriches our knowledge of the role of the efflux transporter in the antimony biogeochemical cycle.

Sporadic Pb accumulation by plants: Influence of soil biogeochemistry, microbial community and physiological mechanisms.

Recent results revealed that considerable Pb accumulation in plants is possible under specific soil conditions that make Pb phytoavailable. In this review, the sources and transformations of Pb in soils, the interaction of Pb with bacteria and specifically the microbiota in the soil, factors and mechanisms of Pb uptake, translocation and accumulation in plants and Pb toxicity in living organisms are comprehensively elaborated. Specific adsorption and post-adsorption transformations of Pb in soil are the main mechanisms affecting the mobility, bioavailability, and toxicity of Pb. The adsorption ability of Pb largely depends on the composition and properties of soils and environmental conditions. Microbial impact on Pb mobility in soil and bioavailability as well as bacterial resistance to Pb are considered. Specific mechanisms conferring Pb-resistance, including Pb-efflux, siderophores, and EPS, have been identified. Pathways of Pb entry into plants as well as mechanisms of in planta Pb transport are poorly understood. Available evidence suggests the involvement of Ca transporters, organic acids and the phytochelatin pathway in Pb transport, mobility and detoxification, respectively.

Selenate regulates the activity of cell wall enzymes to influence cell wall component concentration and thereby affects the uptake and translocation of Cd in the roots of Brassica rapa L.

Selenium (Se) can be used to counteract cadmium (Cd) toxicity in plants. However, mechanisms underlying the alleviation of Cd toxicity by Se have not been completely elucidated, especially those by which Se reduces Cd translocation. A hydroponic experiment was performed to illustrate the regulatory mechanisms of Cd transport by selenate (Se (VI)) in pakchoi (Brassica rapa L., LvYou 102). The results showed that this plant had a high accumulation capacity for Cd, and Se(VI) addition restricted Cd translocation from roots to shoots. Se(VI) exposure stimulated the concentrations of pectins and hemicellulose II but reduced the concentration of hemicellulose I in the roots. In many cases, the enzymes pectin methylesterase, polygalacturonase, and ß-galactosidase were dose-dependently triggered by Se(VI) under Cd exposure, but root calcium concentration was significantly lowered (p < 0.05). Xyloglucan endoglycosidase (hydrolase) was triggered by Se(VI) under 2 mg L-1 Cd exposure and cellulase was generally activated by Se(VI) under Cd stress. The above results suggest that Se(VI) up-regulates pectin methylesterase activity, stimulates synthesis of pectins, and down-regulates root Ca concentration to release free carboxyl groups to combine Cd. In this study, the relationships between enzyme activity (e.g., peroxidase, superoxidase and ß-galactosidase), hydrogen peroxide, cell wall structure strengthening/loosening, and Cd toxicity affected by Se(VI) were also discussed.

The impact of mandatory mammographic breast density notification on supplemental screening practice in the United States: a systematic review.

PURPOSE: Dense breast tissue is an independent risk factor for breast cancer and lowers the sensitivity of screening mammography. Supplemental screening with ultrasound or MRI improves breast cancer detection rate but has potential harms. Breast density notification (BDN) legislation has been introduced in the United States (US) and its impact on supplemental screening practice is unclear. This study systematically reviewed current evidence to explore the impact of BDN on supplemental screening practice in the US. METHODS: Medline, PubMed, Embase, Cochrane and the Cinhal Library databases were searched (2009-August 2020). Studies were assessed for eligibility, data were extracted and summarised, and study quality was evaluated. RESULTS: Evidence from the included studies (n = 14) predominantly showed that BDN legislation increased the overall utilisation of supplemental screening by 0.5-143%. This effect was amplified if the notification included a follow-up telephone call informing women about additional screening benefits, and if the state's law mandated insurance cover for supplemental screening. Likelihood of supplemental screening was also influenced by history of breast biopsy and family history of breast cancer, race, age, socioeconomic status, density category, and physician's specialty and region. Some studies reported increases in biopsy rate (up to 4%) and cancer detection rate (up to 11%) after implementation of BDN legislation. CONCLUSION: BDN leads to increased use of supplemental screening. This has implications for women and the health system. These findings can help inform current and future screening programs, where breast density notification is currently implemented or being considered.