Biotransformation of secondary metabolites from medicinal plants by bacteria has been studied extensively in the recent years. One of the potential sources for screening bacteria is plant endophytic bacteria. In this study, we isolated and screened endophytic bacteria for transformation of ginsenoside Rb1 of Ngoc Linh ginseng collected at village number 2, Tra Linh commune, Nam Tra My district, Quang Nam province. There are 45 strains isolated form rhizobium (24 strains), petioles (8 strains) and leaves (13 strains). After screening, there are 27 strains positive with β-glucosidase test, an enzyme which catalyses the hydrolysis of terminal non-reducing residues in β-glucosides-aglycone linkage of ginsenoside Rb. By evaluating the β-glucosidase activity and identification via 16S rRNA sequence, we choosed four high β-glucosidase acitivity strains SVK32 (Enterobacter sp.); SVK34 (Serratia sp.); SVK37 (Ochrobactrum sp.) and SVK44 (Arthrobacter sp.) for futher study on biotransformating of ginsenoside Rb1 into ginsenoside Rd and Rg3.

4-Pyridoxolactonase from Mesorhizobium loti MAFF303099 has been overexpressed in Escherichia coli. The recombinant enzyme was purified and was crystallized by the sitting-drop vapour-diffusion method using PEG 4000 and ammonium sulfate as precipitants. Crystals of the free enzyme (form I) and of the 5-pyridoxolactone-bound enzyme (form II) grew under these conditions. Crystals of form I diffracted to 2.0 Å resolution and belonged to the monoclinic space group C2, with unit-cell parameters a = 77.93, b = 38.88, c = 81.60 Å , = 117.33 . Crystals of form II diffracted to 1.9 Å resolution and belonged to the monoclinic space group C2, with unit-cell parameters a = 86.24, b = 39.35, c = 82.68 Å , = 118.02. The calculated V M values suggested that the asymmetric unit contains one molecule in both crystal forms.

Coral bleaching is probably caused by the loss of endosymbiotic algae from the host tissue or disturbance of the microbial community composition of corals. In particular, bacteria inhabiting the surface mucus layer of corals are supposed to mediate coral health, but their role in coral bleaching has not been fully clarified. In the present study, we collected mucus samples from bleached and healthy Fungia sp. colonies in Nha Trang bay to investigate biodiversity and bacterial community composition using 16S rRNA gene amplicon next-generation sequencing. The results indicated rich biodiversity and significant changes in bacterial communities between bleached and healthy corals. Two phyla, Proteobacteria and Bacteroidetes, making up approximately 80% of the total bacterial abundance, were predominant in both bleached and healthy samples. Three phyla, Actinobacteria, Planctomycetes, and Cyanobacteria identified as minor taxa, were low in abundance in both samples. However, there were significant differences in bacterial communities at the genus level. Three bacterial genera, Erythobacteria, Synechcococcus CC9902, and Candidatus Actinomarina, involved in coral health protection, were mostly determined in the healthy coral samples. Whereas, five genera, Algicola, Fusibacter, Halodesulfovibrio, Marinifilum, and especially the genus Vibrio, were mainly detected in the bleached corals with a notable increase in relative abundance. Moreover, analysis of alpha and beta diversity (NMDS) also confirmed that there were significant changes in bacterial composition between the bleached and healthy corals (p-value <0.05). These findings suggest that the disturbance of the bacterial community composition living on coral is one of the factors causing coral bleaching, beside environmental factors like pH, temperature, and dissolved oxygen.