Abstract:Abstract:As cell factories，lactic acid bacteria are widely used in food，agriculture，pharmaceutical and other industries．Acid stress is one the important survival challenges encountered by lactic acid bacteria both in fermentation process and in the gastrointestinal tract．Recently，the development of systems biology and metabolic engineering brings unprecedented opportunity for further elucidating the acid tolerance mechanisms and improving the acid stress resistance of lactic acid bacteria． This review addresses physiological mechanisms of lactic acid bacteria during acid stress．Moreover，strategies to improve the acid stress resistance of lactic acid were proposed．

Abstract:[Objective] To study the immunological cross-reactivity and cross-protection characteristics of OmpU in Vibrio species. [Methods] The ompU genes from 10 Vibrio strains were cloned, sequenced, followed by bioinformatics analysis. Western blot and whole-cell ELISA assay were used respectively to determine immunological cross-reaction feature and subcellular location of OmpU with rabbit serum against recombinant OmpU from V. parahaemolyticus ATCC17802, V. alginolyticus ATCC33787, V. vulnificus ATCC27562, V. mimicus ATCC33653 and V. cholera Vb0. Finally, the cross-protective property of recombinant OmpU (V. cholera-derived) was evaluated through vaccination and subsequent challenge with heterogeneous virulent Vibrio strains in mice. [Results] The similarities of OmpU proteins of Vibrio ranged from 73.0 to 100% intra-species, and from 58.6 to 89.0% inter-species. Furthermore, homologous epitopes were found in OmpU and shared by different species of Vibrios. Western blot of rabbit serum against recombinant OmpU showed cross-recognition intra- and inter-species. Bands were observed ranging from 35 to 40 kDa. Whole-cell ELISA assay further confirmed that the antiserum of recombinant OmpU from V. parahaemolyticus ATCC17802, V. vulnifgicus ATCC27562 and V. mimicus ATCC33653 recognized the tested Vibrio species, implying that epitopes of OmpU were located on the cell surface. Recorded relative percent survival of the vaccinated group varied from 43.0 to 100%, showing that mice were protected from Vibrio infection after immunization with OmpU protein. [Conclusion] OmpU was a conserved antigen among tested Vibrio species and might be a universal vaccine candidate for the prevention of Vibriosis.

Abstract:Abstract: [Objective] In this study, we investigated the cross-protection of Lactobacillus casei ATCC? 393TM under multi-stress conditions. [Methods] Cells pre-adapted to mild conditions (heat, H2O2, acid or bile salts) were then treated at lethal temperature (>60 oC) or hydrogen peroxide stress (>5 mmol/L). Furthermore, the changes of survival rate, intracellular pH and membrane fatty acid under lethal conditions with or without acid adaption were compared. [Results] The cross-protection in Lactobacillus casei ATCC 393TM were affected by different stress conditions cell encountered. Acid pre-adaption, especially hydrochloride treatment, would increase the resistance of cells to lethal heat and peroxide stresses significantly, with the survival rate of 305-fold and 173-fold, respectively. Further study suggested that the effect of acid pre-adaption might be related to the regulation on intracellular pH and the saturation of cell membrane. [Conclusion] In this study, hydrochloride adaption was the best inducer for the cross-protection of Lactobacillus casei ATCC 393TM to maintain relatively stable physiological status of cells. The results above supplied a novel way to investigate the relationship between different protective mechanisms in L. casei under different kinds of stresses.

Abstract:Abstract：[Objective] We evaluated the cross-protective effect of a 39-kDa adhesive protein (Cp39), recombinant adhesive protein (rCp39), and capsular proteins from in vitro and in vivo grown avian P. multocida in mice. [Methods] The Cp39 was purified by electroelution from capsular proteins of in vivo grown strain C48-3. The rCp39 was expressed in E. coli B21 as a soluble protein by IPTG inducing, and purified with pMALTM protein fusion and purification system. Mice of each group were subcutaneously immunized twice with 100μg of rCp39, Cp39 or capsular proteins from in vivo or in vitro grown strain C48-3 with in complete or incomplete Freund adjuvant at 2-week intervals. Five mice of each group were challenged with 100 LD50 of avian P. multocida strain C48-3 or rabbit P. multocida strain C51-3 two weeks after the second immunization, while the antibody response specific for rCp39 was determined by ELISA. [Results] SDS-PAGE indicated that the Cp39 protein was expressed in vitro and in vivo grown P. multocida. Mice immunized with rCp39, native Cp39 or capsular proteins from in vivo and in vitro grown strain C48-3 were protected completely against the challenge with the homologous strain C48-3, while 60-80% protection was demonstrated in the mice against the challenge with the heterologous strain C51-3. [Conclusion] In conclusion, rCp39 is a cross immunoprotective antigen of P. multocida capsular serogroup A strains, and might be a useful vaccine candidate against fowl cholera.