ETHYL ALCOHOL REDUCTION OF SALMONELLA TYPHIMURIUM IN POULTRY FEED

This study was designed to evaluate the effect of ethyl alcohol as a potential treatment for reduction of Salmonella populations in poultry feed. Growth rate of S. typhimurium in tryptic soy broth was significantly reduced by addition of greater than 0.3% volume/volume of ethyl alcohol and growth was completely inhibited by addition of 5% ethyl alcohol. Ethyl alcohol concentrations of 20% volume/weight and greater significantly reduced initial S.typhimurium populations in poultry feed (for 20% treated, 2.31 ± 0.31 vs 3.39 ± 0.29 for untreated; P < 0.05). When feed treatment was administered either before or after inoculation of S. typhimurium with 60% ethyl alcohol or 0.04% buffered propionic acid, populations in feeds treated after inoculation were decreased to a nondetection level (< 1.0 log₁₀ CFU/g) by ethyl alcohol treatment but not by other treatments. Ethyl alcohol treatment may have the potential for reducing Salmonella spp. contamination in poultry feed.     

Rapid identification of lettuce seed germination mutants by bulked segregant analysis and whole genome sequencing

Lettuce (Lactuca sativa) seeds exhibit thermoinhibition, or failure to complete germination when imbibed at warm temperatures. Chemical mutagenesis was employed to develop lettuce lines that exhibit germination thermotolerance. Two independent thermotolerant lettuce seed mutant lines, TG01 and TG10, were generated through ethyl methanesulfonate mutagenesis. Genetic and physiological analyses indicated that these two mutations were allelic and recessive. To identify the causal gene(s), we applied bulked segregant analysis by whole genome sequencing. For each mutant, bulked DNA samples of segregating thermotolerant (mutant) seeds were sequenced and analyzed for homozygous single‐nucleotide polymorphisms. Two independent candidate mutations were identified at different physical positions in the zeaxanthin epoxidase gene (ABSCISIC ACID DEFICIENT 1/ZEAXANTHIN EPOXIDASE, or ABA1/ZEP) in TG01 and TG10. The mutation in TG01 caused an amino acid replacement, whereas the mutation in TG10 resulted in alternative mRNA splicing. Endogenous abscisic acid contents were reduced in both mutants, and expression of the ABA1 gene from wild‐type lettuce under its own promoter fully complemented the TG01 mutant. Conventional genetic mapping confirmed that the causal mutations were located near the ZEP/ABA1 gene, but the bulked segregant whole genome sequencing approach more efficiently identified the specific gene responsible for the phenotype.     

Mannose binding lectin plays a crucial role in innate immunity against yeast by enhanced complement activation and enhanced uptake of polymorphonuclear cells

Background  

Mannose binding lectin (MBL) is an important host defence protein against opportunistic fungal pathogens. This carbohydrate-binding protein, an opsonin and lectin pathway activator, binds through multiple lectin domains to the repeating sugar arrays displayed on the surface of a wide range of clinically relevant microbial species. We investigated the contribution of MBL to antifungal innate immunity towards C. parapsilosis in vitro.     

Bioproduction of p-Hydroxystyrene from Glucose by the Solvent-Tolerant Bacterium Pseudomonas putida S12 in a Two-Phase Water-Decanol Fermentation

Two solvent-tolerant Pseudomonas putida S12 strains, originally designed for phenol and p-coumarate production, were engineered for efficient production of p-hydroxystyrene from glucose. This was established by introduction of the genes pal and pdc encoding l-phenylalanine/l-tyrosine ammonia lyase and p-coumaric acid decarboxylase, respectively. These enzymes allow the conversion of the central metabolite l-tyrosine into p-hydroxystyrene, via p-coumarate. Degradation of the p-coumarate intermediate was prevented by inactivating the fcs gene encoding feruloyl-coenzyme A synthetase. The best-performing strain was selected and cultivated in the fed-batch mode, resulting in the formation of 4.5 mM p-hydroxystyrene at a yield of 6.7% (C-mol of p-hydroxystyrene per C-mol of glucose) and a maximum volumetric productivity of 0.4 mM h⁻¹. At this concentration, growth and production were completely halted due to the toxicity of p-hydroxystyrene. Product toxicity was overcome by the application of a second phase of 1-decanol to extract p-hydroxystyrene during fed-batch cultivation. This resulted in a twofold increase of the maximum volumetric productivity (0.75 mM h⁻¹) and a final total p-hydroxystyrene concentration of 21 mM, which is a fourfold improvement compared to the single-phase fed-batch cultivation. The final concentration of p-hydroxystyrene in the water phase was 1.2 mM, while a concentration of 147 mM (17.6 g liter⁻¹) was obtained in the 1-decanol phase. Thus, a P. putida S12 strain producing the low-value compound phenol was successfully altered for the production of the toxic value-added compound p-hydroxystyrene.The demand for so called “green” production of chemicals is rapidly increasing due to the declining availability of fossil fuels and the urgency to reduce CO₂ emissions (10, 30). However, this bioproduction may be hindered by the toxicity of the product of interest, such as substituted aromatics, to the production host (1, 2, 12, 29). One way to cope with this product toxicity is to deploy solvent-tolerant microorganisms as biocatalysts (5, 28). Of special interest among these solvent-tolerant hosts are Pseudomonas putida strains that have been engineered to produce a variety of compounds such as p-hydroxybenzoate (25, 33), p-coumarate (19), and (S)-styrene oxide (22). In our laboratory, we study and employ the solvent-tolerant P. putida S12. This strain is well suited for the production of substituted aromatic chemicals (18, 19, 33, 38) thanks to its extreme solvent tolerance (5, 35) and metabolic versatility toward aromatics (14, 16, 34).An example of an industrially relevant but extremely toxic aromatic is p-hydroxystyrene (4-vinyl phenol) (23). This compound is widely used as a monomer for the production of various polymers that are applied in resins, inks, elastomers, and coatings. Ben-Bassat et al. (2, 3, 23) reported p-hydroxystyrene production from glucose in Escherichia coli. In this strain, phenylalanine/tyrosine ammonia lyase (PAL/TAL; encoded by pal) from Rhodotorula glutinis and p-coumaric acid decarboxylase (PDC; encoded by pdc) from Lactobacillus plantarum were introduced for the conversion of l-tyrosine into p-hydroxystyrene via p-coumarate. The maximum concentration of p-hydroxystyrene was limited to 3.3 mM due to the toxicity of the product to the E. coli host (3, 23). To alleviate product toxicity, a two-phase fermentation with 2-undecanone as the extractant was performed. This approach resulted in a modest 14.2 mM p-hydroxystyrene in the organic phase and 0.5 mM p-hydroxystyrene in the water phase (2). Toxicity-related adverse effects on p-hydroxystyrene production may also be avoided by dividing the whole process into three stages: production of l-tyrosine from glucose by E. coli, conversion of l-tyrosine into p-coumarate by immobilized PAL-overexpressing E. coli cells, and chemical decarboxylation of p-coumarate into p-hydroxystyrene (29).In this report, we address and strongly enhance the bio-based production of p-hydroxystyrene from glucose by employing the solvent-tolerant P. putida S12 as a host. Previously, two strains, P. putida S12 C3 (19) and P. putida S12 TPL3 (38), have been constructed for the production of the l-tyrosine-derived aromatics p-coumarate and phenol, respectively. These strains were highly optimized for aromatics production, resulting in a heavily increased metabolic flux toward l-tyrosine. Therefore, they are suitable platform strains for the production of other l-tyrosine-derived aromatics (33). The bifunctional enzyme PAL/TAL (EC 4.3.1.25) from Rhodosporidium toruloides and the enzyme PDC (EC 4.1.1.-) from L. plantarum were introduced into these strains to allow the conversion of l-tyrosine into p-hydroxystyrene (Fig. ​(Fig.1).1). These minor modifications resulted in an efficient biocatalyst for the production of the value-added compound p-hydroxystyrene from glucose.Open in a separate windowFIG. 1.Schematic overview of the biochemical pathway for p-hydroxystyrene production. TAL, tyrosine ammonia lyase; FCS, feruloyl-coenzyme A synthetase. The cross indicates the disruption of fcs, disabling p-coumarate degradation.     

Estimating specific inherent optical properties of tropical coastal waters using bio-optical model inversion and in situ measurements: case of the Berau estuary,East Kalimantan,Indonesia

Specific inherent optical properties (SIOP) of the Berau coastal waters were derived from in situ measurements and inversion of an ocean color model. Field measurements of water-leaving reflectance, total suspended matter (TSM), and chlorophyll a (Chl a) concentrations were carried out during the 2007 dry season. The highest values for SIOP were found in the turbid waters, decreasing in value when moving toward offshore waters. The specific backscattering coefficient of TSM varied by an order of magnitude and ranged from 0.003 m² g⁻¹, for clear open ocean waters, to 0.020 m² g⁻¹, for turbid waters. On the other hand, the specific absorption coefficient of Chl a was relatively constant over the whole study area and ranged from 0.022 m² mg⁻¹, for the turbid shallow estuary waters, to 0.027 m² mg⁻¹, for deeper shelf edge ocean waters. The spectral slope of colored dissolved organic matter light absorption was also derived with values ranging from 0.015 to 0.011 nm⁻¹. These original derived values of SIOP in the Berau estuary form a corner stone for future estimation of TSM and Chl a concentration from remote sensing data in tropical equatorial waters.     

二甲基亚砜毒性研究

二甲基亚砜（Dimethyl sulfoxide DMSO）是一种含硫有机化合物,被誉为＂万能溶剂＂,广泛用作溶剂和反应试剂。在医药工业中,DMSO可直接用作某些药物的原料及载体。DMSO本身有消炎止痛,利尿,镇静等作用,亦誉为＂万灵药＂,常作为止痛药物的活性组分添加于药物之中。DMSO也是一种渗透性保护剂,能够降低细胞冰点,减少冰晶的形成,减轻自由基对细胞损害,改变生物膜对电解质、药物、毒物和代谢产物的通透性。DMSO作为组蛋白去乙酰化酶抑制剂（Histone Deacetylases-inhibitor HDACi）的一种,同样具有恢复组蛋白的乙酰化与去乙酰化平衡,抑制细胞程序性死亡,修复DNA双螺旋结构,抗放射性损伤,抗炎症反应及抗癌作用。鉴于其应用广泛,本文就其物理特性及毒性研究做一综述。     

岱海流域土地利用动态模拟及生态系统服务价值测算

北方内陆湖泊面积萎缩严重,岱海作为典型的内陆湖之一,其面积变化尤为显著.为研究岱海湖面积变化及岱海流域生态系统服务价值(Esv)的动态趋势,本研究运用CA-Markov模型,基于1989-2018年6期的土地利用数据,预测2026年的土地利用状况,并采用当量因子法,对岱海流域ESV进行评估.结果 表明:岱海湖若不进行生...