Highly efficient and sustainable removal of Cr (VI) in aqueous solutions by photosynthetic bacteria supplemented with phosphor salts.

Photosynthetic bacteria have flexible metabolisms and strong environmental adaptability, and require cheap, but plentiful, energy supplements, which all enable their use in Cr(VI)-remediation. In this study, the effects of culture conditions on the total Cr removal rate were investigated for a newly identified strain of Rhodobacter sphaeroides SC01. The subcellular distribution and Cr(VI) reduction ability of four different cellular fractions were evaluated by scanning electron microscopy and transmission electron microscopy. Experiments indicated that the optimal culture conditions for total Cr removal included a culture temperature of 35 °C, pH of 7.20, an NaCl concentration of 5 g L-1, a light intensity of 4000 lx, and an initial cell concentration (OD680) of 0.15. In addition, most Cr was found in the cell membrane in the form of Cr (III) after reduction, while cell membranes had the highest Cr(VI) reduction rate (99%) compared to other cellular components. In addition, the physical and chemical properties of SC01 cells were characterized by FTIR, XPS, and XRD analyses, confirming that Cr was successfully absorbed on bacterial cell surfaces. CrPO4‧6H2O and Cr5(P3O10)3 precipitates were particularly identified by XRD analysis. After screening supplementation with five phosphor salts, Cr(VI) reduction due to bioprecipitation was improved by the addition of Na4P2O7 and (NaPO3)6 salts, with the Cr(VI)-reduction rate combined with Na4P2O7 addition being 15% higher than that of the control. Thus, this study proposes a new Cr(VI)-removal strategy based on the combined use of photosynthetic bacteria and phosphor salts, which importantly increases its potential application in treating wastewater.

Nitric oxide induces monosaccharide accumulation through enzyme S-nitrosylation.

Nitric oxide (NO) is extensively involved in various growth processes and stress responses in plants; however, the regulatory mechanism of NO-modulated cellular sugar metabolism is still largely unknown. Here, we report that NO significantly inhibited monosaccharide catabolism by modulating sugar metabolic enzymes through S-nitrosylation (mainly by oxidizing dihydrolipoamide, a cofactor of pyruvate dehydrogenase). These S-nitrosylation modifications led to a decrease in cellular glycolysis enzymes and ATP synthase activities as well as declines in the content of acetyl coenzyme A, ATP, ADP-glucose and UDP-glucose, which eventually caused polysaccharide-biosynthesis inhibition and monosaccharide accumulation. Plant developmental defects that were caused by high levels of NO included delayed flowering time, retarded root growth and reduced starch granule formation. These phenotypic defects could be mediated by sucrose supplementation, suggesting an essential role of NO-sugar cross-talks in plant growth and development. Our findings suggest that molecular manipulations could be used to improve fruit and vegetable sweetness.

Antiviral and antitumor activities of the lectin extracted from Aspidistra elatior.

Lectins, a group of highly diverse proteins of non-immune origin and are ubiquitously distributed in plants, animals and fungi, have multiple significant biological functions, such as anti-fungal, anti-viral and, most notably, anti-tumor activities. A lectin was purified from the rhizomes of Aspidistra elatior Blume, named A. elatior lectin (AEL). In vitro experiments showed that the minimum inhibitory concentrations of AEL against the vesicular stomatitis virus, Coxsackie virus B4, and respiratory syncytial virus were all the same at about 4 µg/mL. However, AEL was ineffective against the Sindbis virus and reovirus-1. AEL also showed significant in vitro antiproliferative activity towards Bre-04, Lu-04, HepG2, and Pro-01 tumor cell lines by increasing the proportion of their sub-G1 phase. However, AEL failed to restrict the proliferation of the HeLa cell line. Western blotting indicated that AEL induced the upregulation of cell cycle-related proteins p53 and p21. The molecular basis and species-specific effectiveness of the anti-proliferative and anti-viral potential of AEL are discussed.

Extraction, purification and characterization of polysaccharides from Hawk tea.

In the present study, the extraction, purification and characterization of polysaccharides from Hawk mature leaf tea (HMP) were investigated. The optimal extraction parameters were obtained by using a Box-Behnken design as follows: extraction temperature 88.9 °C, extraction time 128.2 min and ratio of water to solid 11.4 mL/g. The crude HMP was sequentially purified by chromatography of DEAE-52, and two purified fractions, HMP-1 and HMP-2, were obtained. HMP-1 and HMP-2 were mainly composed of arabinose, galactose, glucose and mannose with the molecular weight of 133 and 100 kDa, respectively. For antioxidant activities in vitro, HMP-1 had strong 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity and ferric reducing activity power (FRAP). These results provide a scientific basis for the further use of polysaccharides from this traditional herb tea.