Prospecting the plant growth–promoting activities of endophytic bacteria Cronobacter sp. YSD YN2 isolated from Cyperus esculentus L. var. sativus leaves

Purpose Plant growth–promoting (PGP) bacteria are an environment-friendly alternative to chemical fertilizers for promoting plant growth and development. We isolated and characterized a PGP endophyte, YSD YN2, from the leaves of Cyperus esculentus L. var. sativus. Methods Specific PGP characteristics of this strain, such as phosphate solubilization ability, potassium-dissolving ability, siderophore and indole-3-acetic acid (IAA) production, and salt tolerance, were determined in vitro. In addition, positive mutants were screened using the atmospheric and room temperature plasma (ARTP) technology, with IAA level and organic phosphate solubility as indices. Furthermore, the effect of the positive mutant on seed germination, biomass production, and antioxidant abilities of greengrocery seedling was evaluated, and the genome was mined to explore the underlying mechanisms. Results The strain YSD YN2 showed a good performance of PGP characteristics, such as the production of indole acetic acid and siderophores, solubilization ability of phosphate, and potassium-dissolving ability. It was recognized through 16S rRNA sequencing together with morphological and physiological tests and confirmed as Cronobacter sp. The strain exposed to a mutation time of 125 s by ARTP had the highest IAA and organic phosphate (lecithin) concentrations of 9.25 mg/L and 16.50 mg/L, 50.41% and 30.54% higher than those of the initial strain. Inoculation of mutant strain YSD YN2 significantly increased the seed germination, plant growth attributes, and the activities of peroxidase (POD) and superoxide dismutase (SOD), respectively, but decreased the content of malondialdehyde (MDA) significantly compared with the control. Furthermore, genome annotation and functional analysis were performed through whole-genome sequencing, and PGP-related genes were identified. Conclusion Our results indicated that the mutant strain YSD YN2 with PGP characteristics is a potential candidate for the development of biofertilizers.

Co-administration of vitamin D3 and Lacticaseibacillus paracasei DG increase 25-hydroxyvitamin D serum levels in mice

Purpose Subclinical vitamin D (vitD) deficiency enhances the predisposition to a myriad of acute and chronic pathologies in many people worldwide. Due to the scarcity of vitD-rich foods, the consumption of supplements or fortified foods can be required to maintain healthy serum levels of 25-hydroxyvitamin D [25(OH)D], and the major circulating form of vitD that is commonly measured in serum to determine the vitD status. Since the vitD absorption seems to resemble that of lipids, improved emulsification in the gut could favor vitD permeation through the enterocyte membrane. Contextually, we hypothesized that a microorganism with cholecalciferol (vitD3)-solubilization properties may potentially result in enhanced serum vitD levels. Methods and results Six probiotic strains were screened for their ability to create a stable suspension of vitD3 in water: Lacticaseibacillus paracasei DG, L. paracasei LPC-S01, L. paracasei Shirota, L. rhamnosus GG, Limosilactobacillus reuteri DSM 17938, and Lactobacillus acidophilus LA5. The DG strain displayed the strongest vitD3 solubilization ability and, consequently, were used in an in vivo trial where a commercial preparation of vitD3 in refined olive oil was administered by gavage to CD-1 mice with or without the concurrent administration of L. paracasei DG. ELISA measurements showed that the DG strain significantly increased the serum levels of 25(OH) D when administered once a day for 1 week in association with the vitD3 supplement. Conclusion This preliminary pre-clinical study suggests that the combined administration of L. paracasei DG with an oil-based cholecalciferol supplement could contribute to the maintenance of the adequate 25(OH) D serum levels in people at risk of vitD deficiency.