Glutathione S-Transferase(GST)Identified from Giant Kelp Macrocystis pyrifera Increases the Copper Tolerance of Synechococcus elongatus PCC 7942

The glutathione S-transferases gene family plays an important regulatory role in growth and development,and responses to environmental change.In this study,six complete GST genes(Mp GST1,Mp GST2,Mp GST3,MpGST4,Mp GST5,and Mp GST6)were cloned from the gametophytes of brown alga Macrocystis pyrifera.Subsequent bioinformatics analysis showed that these six genes encoded proteins with 202,216,288,201,205,and 201 aa,respectively.Moreover,Mp GST3 differs from the other GST genes.Phylogenetic analysis suggested that MpGST3 belongs to the Ure2p type GST.Domain analysis suggested that the other GSTs from M.pyrifera belong to the soluble GST family and form an independent branch with the GSTs found in the other macroalgae,suggesting that a new GST type was formed during macroalgal evolution.GST genes were upregulated in M.pyrifera when 2.5 mg L^(-1)Cu ions were added to the medium.Six GST genes were integrated into the genome of Synechococcus elongatus PCC 7942,and their functions were verified by measuring light absorbance,photosynthetic pigment content,and photosynthetic parameters of the transformed strains under 0.3 mg L^(-1)Cu ion stress.The results showed much higher levels of various parameters in the transformed strains than in the wild strain.The transformed strains(with the MpGST genes)showed significantly enhanced resistance to Cu ion stress,while the wild strain almost died.The results of this study lay a theoretical foundation for further research on the Cu ion stress resistance function of GSTs in M.pyrifera.

Simultaneous production of hydrogen and volatile fatty acids from anaerobic digestion of Macrocystis pyrifera biomass residues

The Macrocystis pyrifera biomass residues(MPBRs) after extraction of algin could be applied in anaerobic fermentation. The effects of different pretreatment conditions, substrate concentrations and initial pH values on hydrogen and volatile fatty acid(VFA) production during the anaerobic fermentation of MPBRs were evaluated. The optimal pretreatment conditions, substrate concentration, initial pH values were determined as thermo-alkaline pretreatment at 100 °C with 0.1 mol/L NaOH, 40 g/L and 7.0, respectively. Under these conditions, the maximum hydrogen production was 11.38 mL/g(volatile solids, VS), which was approximately 23 times higher than that of untreated MPBRs. Furthermore, the maximum total volatile fatty acid(TVFA) yield was found to be 0.055 g/g(VS) and the VFA mainly consisted of acetic and butyric acids. The results indicate that the yield of TVFA is positively correlated with hydrogen production, and the MPBRs could produce hydrogen and TVFA simultaneously. In addition, thermo-alkaline pretreatment is proven to be the best method for hydrogen and VFA production.

Litopenaeus vannamei immunestimulated with Macrocystis pyrifera extract:improving the immune response against Vibrio campbellii

Objective:To examine the immune responses of Litopenaeus vannamei after different treatments with a hot water extract of Macrocystis pyrifera(M.pyrifera)and a subsequent challenge with Vibrio campbellii(V.campbellii).Methods:A total of 184 adult white shrimp that were infected with V.campbellii(1×10^(6) CFU/shrimp)were immunostimulate by the hot-water extract from M.pyrifera via either injection(10μg)or immersion(350 mg/L),the experimental controls were injected with either saline solution or V.campbellii(1×10^(6) CFU/shrimp).The bacterial DNA depuration rate,antimicrobial activity and total hemocyte count were evaluated in hemolymph samples at 2,6,12,24,48 and 72 h post-infection.Results:Injected shrimp(10μg M.pyrifera extract)demonstrated the best clearance of bacterial infection,with 82%survival at 72 h post-infection(cellular response).Hemolymph from the immersed organisms had the best antimicrobial activity against Escherichia coli growth;specifically,the most efficient antimicrobial activity was observed at 24 h post-infection.Both types of immunostimulated shrimp had similar total hemocyte counts at 24 h post-infection(1.63-1.59 million/mL);however,after 72 h,injected shrimp had higher total hemocyte counts than immersed animals(2.59 v.s.0.56 million/mL).Conclusions:The injection of the M.pyrifera hot-water extract facilitated a more efficient response to V.campbellii infection due to the stimulation of the hemocytes of the shrimp.In other words,the cellular immune response was more efficient to eliminate bacterial infection than the humoral response in shrimp.