Isolation and characterization of indigenous endophytic bacteria associated with leaves of switchgrass (Panicum virgatum L.) cultivars

Abstract

Aims: To isolate and characterize indigenous bacterial endophytes from cultivars of switchgrass and study their antimicrobial and growth promoting potential. Methods and Results: The diversity, molecular and biochemical characterizations of indigenous and culturable bacterial endophytes residing in leaves of switchgrass have not been studied previously. This study describes the characterization of 31 bacterial endophytes from three switchgrass cutlivars: Cave-in Rock, Blue Jacket and Tecumseh. Molecular and phylogenetic analysis based on the 16S rRNA sequence grouped the endophytes into eight different taxa that shared high homology of 98-99% with other known sequences. Bacterial endophytes were identified as Microbacterium testaceum, Curtobacterium flaccumfaciens, Bacillus subtilis and Bacillus pumilus, Pseudomonas fluorescens, Sphingomonas parapaucimobilis, Serratia sp. and Pantoea ananatis. Some endophytes were detected in switchgrass seeds and in plants that originated from seeds collected a year earlier, confirming vertical transmission to the next generation of the host. Selected endophytes produced cellulases and were capable of solubilizing inorganic phosphorus. Analysis of cell-free culture filtrate of selected strains using direct infusion orbitrap mass spectrometry confirmed the presence of several well-characterized lipopeptide toxins and phytohormones. Re-inoculation of the roots of switchgrass seedlings with endophytes singly or combined confirmed their migration to the upper aerial parts of the plant. Conclusions: Our findings suggest that switchgrass leaves harbour a diversity of bacterial endophytes, some of which could potentially be applied as growth promoting bacteria. Significance and Impact of the Study: This is the first report on the characterization of indigenous bacterial endophytes and their potential use as biofertilizers.

Pantoea agglomerans productora de biosurfactante aislada de rizosfera de pastos Tanzania y Llanero

“…Canada by Gagne-Bourgue et al (2013), confirming the vertical transmission to the next generation of hosts, the above is consistent with our findings because only one species as best producer of BS in the rhizosphere of grasses Tanzania and Llanero identified.…”

“…Reportamos trece cepas de P. agglomerans con 99% de identidad, como ya se dijo las especies de Pantoea sp., se han reportado como endófitos de diversos cultivos, en los que destaca Pantoea ananatis aislada de hojas y semillas de Panicum virgatum conocido como pasto "Varilla" en Canadá por Gagne-Bourgue et al (2013), confirmando así la transmisión vertical a la siguiente generación de hospederos, lo anterior concuerda con nuestros hallazgos dado que solo se identificó una especie como mejor productora de BS en la rizosfera de los pastos Tanzania y en Llanero.…”

Pea Protein Alginate Encapsulated Bacillus subtilis B26, a Plant Biostimulant, Provides Controlled Release and Increased Storage Survival

“…The B.subtilis strain B26, previously isolated from switchgrass and fully characterized [15], was maintained on Luria Broth (LB) (1.0% Tryptone, 0.5% Yeast Extract, 1.0% NaCl) with glycerol (25% final volume) and stored at-80°C. B. subtilis B26 was revived on LBA (1.5% Agar) plates.…”

“…To ensure that B26 successfully and systemically colonized timothy and Brachypodium, bacteria cell numbers and DNA copy numbers were determined in the root and shoot tissues of the inoculated and the control plants. Surface sterilized tissue samples (200 mg) were homogenized, serially diluted in modified phosphate buffer and plated on LBA, following established procedures [15]. Plates were incubated at 37°C for 24 hr.…”

“…We previously demonstrated that Bacillus subtilis strain B26, is a growth enhancer of switchgrass (Panicum virgatum L.) and Brachypodium distachion seedlings [15,16]. The strain's ability to migrate from the roots to aerial parts of the plant and thus behaving as a competent endophyte [17] was also demonstrated.…”