Seeds of Stevia rebaudiana Bertoni as a Source of Plant Growth-Promoting Endophytic Bacteria with the Potential to Synthesize Rebaudioside A

In this study, a new strain of Pantoea vagans, SRS89, was isolated from surface-sterilized stevia seeds. The isolate was evaluated using morphological, molecular, and biochemical methods. The bacterium was 1.5 μm long, yellowish in color, and classified as Gram-negative. Whole genome sequencing of our strain revealed the presence of a 4,610,019 bp chromosome, and genome annotation resulted in the detection of 4283 genes encoding 4204 putative coding sequences. Phylogenic analysis classified the genome of our strain close to the MP7 and LMG 24199 strains of P. vagans. Functional analysis showed that the highest number of genes within the analyzed bacterium genome were involved in transcription, amino acid transport and metabolism, and carbohydrate transport and metabolism. We also identified genes for enzymes involved in the biosynthesis of carotenoids and terpenoids. Furthermore, we showed the presence of growth regulators, with the highest amount noted for gibberellic acid A3, indole-3-acetic acid, and benzoic acid. However, the most promising property of this strain is its ability to synthesize rebaudioside A; the estimated amount quantified using reversed-phase (RP)-HPLC was 4.39 mg/g of the dry weight of the bacteria culture. The isolated endophytic bacterium may be an interesting new approach to the production of this valuable metabolite

Seeds of Stevia rebaudiana\textit{Stevia rebaudiana} Bertoni as a source of plant growth-promoting endophytic bacteria with the potential to synthesize rebaudioside A

In this study, a new strain of Pantoea vagans, SRS89, was isolated from surface-sterilized stevia seeds. The isolate was evaluated using morphological, molecular, and biochemical methods. The bacterium was 1.5 μm long, yellowish in color, and classified as Gram-negative. Whole genome sequencing of our strain revealed the presence of a 4,610,019 bp chromosome, and genome annotation resulted in the detection of 4283 genes encoding 4204 putative coding sequences. Phylogenic analysis classified the genome of our strain close to the MP7 and LMG 24199 strains of P. vagans. Functional analysis showed that the highest number of genes within the analyzed bacterium genome were involved in transcription, amino acid transport and metabolism, and carbohydrate transport and metabolism. We also identified genes for enzymes involved in the biosynthesis of carotenoids and terpenoids. Furthermore, we showed the presence of growth regulators, with the highest amount noted for gibberellic acid A3, indole-3-acetic acid, and benzoic acid. However, the most promising property of this strain is its ability to synthesize rebaudioside A; the estimated amount quantified using reversed-phase (RP)-HPLC was 4.39 mg/g of the dry weight of the bacteria culture. The isolated endophytic bacterium may be an interesting new approach to the production of this valuable metabolite

Identification and control of endophytic bacteria during in vitro cultures of Staphylea pinnata L.

This study focused on the identification and elimination of endophytic bacterial contaminations during in vitro propagation of European bladdernut (Staphylea pinnata). Axillary shoots were propagated on Murashige and Skoog medium with 20 mg ∙ dm−3 FeEDDHA, 5 μM BA and 0.5 μM NAA at 20/18°C (day/night) and a 16-h photoperiod. Clouding by endophytic bacterial colonies was observed where shoots contacted the media. Bacteria were isolated and separated by repeated streaking as two strains. Gram staining revealed that both strains were Gram-negative. The colonies were very precisely identified as Acinetobacter johnsonii, strain ATCC 17909, and Methylobacterium rhodesianum, strain DSM 5687, using VITEK®2—a rapid bacterial identification system—and the 16S rRNA gene sequencing method. The agar disc-diffusion test proved that both bacterial strains were susceptible to 13 antibiotics (out of 25 tested), derived from the groups of fluoroquinolones, aminoglycosides and tetracyclines. Doxycycline or gentamicin (100–300 mg ∙ dm−3) was added to the S. pinnata shoot propagation medium to eliminate bacteria. Gentamicin 100 mg ∙ dm−3 showed the best effect, inhibiting the growth of endogenous bacteria (63%) when applied in the medium for 4 weeks. After the following transfer to media without antibiotics, shoots developed axillary buds and bacterial colonies were not observed

Endophytic bacteria from in vitro culture of Leucojum aestivum L. a new source of galanthamine and elicitor of alkaloid biosynthesis

International audienceAbstract Leucojum aestivum is known for its ability to biosynthesize alkaloids with therapeutic properties, among which galanthamine used for the treatment of Alzheimer's disease. New sources of this alkaloid are still being explored. In this study, a novel strain PLV of endophytic bacterium Paenibacillus lautus was isolated from in vitro L . aestivum plants. We report the whole genome sequence of that strain and its capacity to produce alkaloids and growth regulators. The effect of elicitation with autoclaved bacteria on the production of alkaloids was examined. Ten alkaloids were identified in bacteria extracts: galanthamine, lycorine, ismine, lycoramine, haemanthamine, tazettine, galanthine, homolycorine, 1,2-dihydrochlidanthine, and hippeastrine. The mean contents of galanthamine and lycorine were 37.51 µg/g of dry weight (DW) and 129.93 µg/g of DW, respectively. Moreover, isolated P . lautus strain synthesized: indole-3-acetic acid, t-zeatin, c-zeatin, kinetin, gibberellin A 1 , abscisic acid, salicylic acid, benzoic acid. In vitro elicitation of cultures with P . lautus increased dry biomass, stimulated galanthamine and lycorine production, contributed to 8,9-desmethylenebis (oxy)-7,9 dimethoxy-crinan biosynthesis, change pigments content, and antioxidant enzymes activities. Our findings for the first time point out that galanthamine can be synthesized by an microorganism. Moreover isolated strain can be used as a new elictor of Amaryllidaceae alkaloids biosynthesis