Quantitative proteomics reveals the crucial role of YbgC for Salmonella enterica serovar Enteritidis survival in egg white.

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a food-borne bacterial pathogen that can cause human salmonellosis predominately by contamination of eggs and egg products. However, its survival mechanisms in egg white are not fully understood, especially from a proteomic point of view. In this study, the proteomic profiles of S. Enteritidis in Luria-Bertani (LB) broth containing 50% and 80% egg white, and in whole egg white were compared with the profile in LB broth using iTRAQ technology to identify key proteins that were involved in S. Enteritidis survival in egg white. It was found that there were 303, 284 and 273 differentially expressed proteins in S. Enteritidis after 6 h exposure to whole, 80% and 50% egg white, respectively. Most of up-regulated proteins were primarily associated with iron acquisition, cofactor and amino acid biosynthesis, transporter, regulation and stress responses, whereas down-regulated proteins were mainly involved in energy metabolism, virulence as well as motility and chemotaxis. Three stress response-related proteins (YbgC, TolQ, TolA) of the tol-pal system responsible for maintaining cell membrane stability of Gram-negative bacteria were up-regulated in S. Enteritidis in response to whole egg white. Interestingly, deletion of ybgC resulted in a decreased resistance of S. Enteritidis to egg white. Compared with the wild type and complementary strains, a 3-log population reduction was observed in △ybgC mutant strain after incubation in whole egg white for 24 h. Cellular morphology of △ybgC mutant strain was altered from rods to spheres along with cell lysis in whole egg white. Furthermore, deletion of ybgC decreased the expression of tol-pal system-related genes (tolR, tolA). Collectively, these proteomic and mutagenic analysis reveal that YbgC is essential for S. Enteritidis survival in egg white.

Isolation and Analysis of the Cppsy Gene and Promoter from Chlorella protothecoides CS-41.

Phytoene synthase (PSY) catalyzes the condensation of two molecules of geranylgeranyl pyrophosphate to form phytoene, the first colorless carotene in the carotenoid biosynthesis pathway. So it is regarded as the crucial enzyme for carotenoid production, and has unsurprisingly been involved in genetic engineering studies of carotenoid production. In this study, the psy gene from Chlorella protothecoides CS-41, designated Cppsy, was cloned using rapid amplification of cDNA ends. The full-length DNA was 2488 bp, and the corresponding cDNA was 1143 bp, which encoded 380 amino acids. Computational analysis suggested that this protein belongs to the Isoprenoid_Biosyn_C1 superfamily. It contained the consensus sequence, including three predicted substrate-Mg(2+) binding sites. The Cppsy gene promoter was also cloned and characterized. Analysis revealed several candidate motifs for the promoter, which exhibited light- and methyl jasmonate (MeJA)-responsive characteristics, as well as some typical domains universally discovered in promoter sequences, such as the TATA-box and CAAT-box. Light- and MeJA treatment showed that the Cppsy expression level was significantly enhanced by light and MeJA. These results provide a basis for genetically modifying the carotenoid biosynthesis pathway in C. protothecoides.

Sequestration of phosphorus from wastewater by cement-based or alternative cementitious materials.

Cement-based and alternative cementitious materials were tested in the laboratory for their capability of removing phosphate from wastewater. The results demonstrated that both Langmuir and Freundlich adsorption isotherms were suitable for describing the adsorption characteristics of these materials. Among the four types of filter media tested, the cement-based mortar A has the highest value of maximum adsorption (30.96 mg g(-1)). The P-bonding energy (KL) and adsorption capacity (K) exhibited a positive correlation with the total content of Al2O3 and Fe2O3 in each mortar. The maximum amount of P adsorbed (Qm) and adsorption intensity (1/n) exhibited a positive correlation with the CaO content in each mortar. For three of them, the P-removal rates were in excess of 94 percent for phosphorus concentrations ranging from 20 to 1000 mg L(-1). The underlying mechanisms were examined using field emission scanning microscopy (FESEM), coupled with energy-dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD). The results reveal that the removal of phosphate predominantly followed a precipitation mechanism in addition to weak physical interactions between the surface of adsorbent filter media and the metallic salts of phosphate. The use of cement-based or alternative cementitious materials in the form of ground powder shows great promise for developing a cost-effective and environmentally sustainable technology for P-sequestration and for wastewater treatment.