Characterization of a novel psychrophilic and halophilic β-1, 3-xylanase from deep-sea bacterium, Flammeovirga pacifica strain WPAGA1

β-1, 3-Xylanase is one of the most important hydrolytic enzymes to prepare oligosaccharides as functional foods in seaweed industry. However, less than five β-1, 3-xylanases have been experimentally expressed and characterized; moreover, none of them is psychrophilic and salt tolerant. Here, we mined a novel β-1, 3-xylanase (Xyl512) from the genome of the deep-sea bacterium Flammeovirga pacifica strain WPAGA1 and biochemically characterized it in detail. The Xyl512 did not contain any carbohydrate-binding module; the catalytic domain of it belonged to the glycoside hydrolase family 26. The optimum temperature and pH of the purified β-1, 3-xylanase was 20 °C and pH 7.0 in the condition of no NaCl. However, they shifted to 30 °C and 7.5 with 1.5 mol/L NaCl, respectively. In this condition (1.5 mol/L NaCl), the overall activity was 2-fold as high as that without NaCl. Based on the residue interactions and the electrostatic surfaces, we addressed the possible mechanism of its adaption to low temperature and relative high NaCl concentration. The Xyl512 showed significantly reduced numbers of hydrogen bonds leading to a more flexible structure, which is likely to be responsible for its cold adaptation. While the negatively charged surface may contribute to its salt tolerance. The β-1, 3-xylanase we identified here was the first reported psychrophilic and halophilic one with functionally characterized. It could make new contributions to exploring and studying the β-1, 3-xylanase for further associated investigations.

A transcriptome resource for the deep-sea bacterium Shewanella piezotolerans WP3 under cold and high hydrostatic pressure shock stress

Low temperature and high hydrostatic pressure (HHP) are two of the most remarkable environmental factors influencing deep-sea ecosystem. The adaptive mechanisms of microorganisms which live in these extreme environments to low temperature and high pressure warrant investigation. In this study, the global gene expression patterns of the deep-sea bacterium Shewanella piezotolerans WP3 in response to cold (0 °C) and HHP (50 MPa) shock were evaluated through DNA microarray analysis. Results revealed that 22, 66, and 106 genes were differentially expressed after WP3 was respectively exposed to cold shock for 30, 60, and 90 min. Of these genes, 16 genes were identified as common differentially expressed genes (DEGs). After 30 min and 120 min of HHP shock, 5 and 10 genes were respectively identified as DEGs. The hierarchical clustering analysis of the DEG pattern indicated that WP3 may employ different adaptive strategies to cope with cold and HHP shock stress. Taken together, our study provided a transcriptome resource for deep-sea bacterial responses to cold and HHP stress. This study also established a basis for further investigations on environmental adaptive mechanisms utilized by benthic bacteria.

Global transcriptome analysis of the heat shock response of the deep-sea bacterium Shewanella piezotolerans WP3

For microorganisms, heat shock is a major stressful condition. Heat shock is characterized by sudden temperature increases that damage important protein structures and interfere with essential cellular functions. In this study, global gene expression patterns of the deep-sea bacterium Shewanella piezotolerans WP3 in response to heat shock were studied by DNA microarray analysis. Overall, 438, 573, and 627 genes were found to be differentially expressed after heat shock for 30, 60, and 90min, respectively. Functional classification of differentially transcribed genes was performed using the Clusters of Orthologous Groups of Proteins database. Additionally, 361 genes were identified as common differentially expressed genes. These genes may comprise the core genes responsible for coping with heat shock stress of WP3. Moreover, comparative analysis of gene expression pattern in WP3 and other bacteria indicated the presence of different adaptive strategies. These data represent the first transcriptome resource for the response of this deep-sea bacterium to high-temperature stress. This study contributes to the understanding of the global adaptation mechanisms of benthic bacteria toward environmental stresses.

Enhanced phosphorus removal from wastewater by growing deep-sea bacterium combined with basic oxygen furnace slag

As one solid waste with potential for phosphorus removal, application of slags in water treatment merits attention. But it was inhibited greatly by alkaline solution (pH>9.5) and cemented clogging generated. To give one solution, phosphorus removal was investigated by combining deep-sea bacterium Alteromonas 522-1 and basic oxygen furnace slag (BOFS). Results showed that by the combination, not only higher phosphorous removal efficiency (>90%) but also neutral solution pH of 7.8-8.0 were achieved at wide ranges of initial solution pH value of 5.0-9.0, phosphorus concentration of 5-30mg/L, salinity of 0.5-3.5%, and temperature of 15-35°C. Moreover, sedimentary property was also improved with lower amount of sludge production and alleviated BOFS cementation with increased porosity and enlarged particle size. These results provided a promising strategy for the phosphorus recovery with slags in large-scale wastewater treatment.

Bioremoval and recovery of Cd(II) by Pseudoalteromonas sp. SCSE709-6: Comparative study on growing and grown cells

Comparison of the bioremoval and recovery of Cd(II) by growing and grown marine bacterium Pseudoalteromonas sp. SCSE709-6 was performed in batch systems. Bioremoval with growing cells (Sorption I) showed better performance at low Cd(II) concentrations, whereas bioremoval with grown cells (Sorption II) had significant advantages in both removal efficiency and time consumption at high Cd(II) concentrations. The optimal pH was higher for Sorption I than for Sorption II for achieving the maximum Cd(II) removal efficiency. Complete desorption was achieved using either Na2EDTA or HNO3 as eluent. Cd(II) adsorbed on grown cells had higher tendency to be desorbed. Na2EDTA was a preferable eluent for the recycling biomaterials, whereas HNO3 performed better for the final security disposal of sludge. For Sorption II, both Langmuir and Freundlich isotherms well explained the biosorption behavior, and the pseudo-second-order model better expressed biosorption and desorption kinetics.