A Multiphasic Approach for the Identification of Endophytic Bacterial in Strawberry Fruit and their Potential for Plant Growth Promotion

Abstract

This study used a multiphasic approach, characterized by the simultaneous use of culture-dependent and culture-independent methods, to investigate endophytic bacterial communities in strawberry (Fragaria ananassa) fruit. A total of 92 bacterial endophytes were isolated and initially grouped by their repetitive extragenic palindromic (rep)-PCR banding pattern and biochemical features. Phylogenetic analysis of the 16S rRNA gene sequences of 45 representatives showed that the isolates belonged to the species Bacillus subtilis (eight isolates), Bacillus sp. (seven isolates), Enterobacter sp. (seven isolates), Enterobacter ludwigii (six isolates), Lactobacillus plantarum (six isolates), Pseudomonas sp. (five isolates), Pantoea punctata (three isolates), and Curtobacterium citreum (three isolates). Nucleic acids were extracted from the strawberry fruit and subjected to 16S rRNA gene directed polymerase chain reaction denaturing gradient gel electrophoresis (16S rRNA PCR-DGGE). The species B. subtilis, Enterobacter sp., and Pseudomonas sp. were detected both by isolation and DGGE. The DGGE fingerprints of total bacterial DNA did not exhibit bands corresponding to several of the representative species isolated in the extinction dilution (L. plantarum, C. citreum, and P. punctata). In contrast, bands in the DGGE profile that were identified as relatives of Arthrobacter sp. and one uncultivable Erythrobacter sp. were not recovered by cultivation techniques. After isolation, the nitrogen fixation ability and the in vitro production of indole-3-acetic acid (IAA) equivalents and siderophores were evaluated. A high percentage of isolates were found to possess the ability to produce siderophores and IAA equivalents; however, only a few isolates belonging to the genera Pseudomonas and Enterobacter showed the ability to fix nitrogen. Plant growth promotion was evaluated under greenhouse conditions and revealed the ability of the Bacillus strains to enhance the number of leaves, shoot length, root dry weight, and shoot dry weight. The activity of the bacterial isolate identified as B. subtilis NA-108 exerted the greatest influence on strawberry growth and showed a 42.8% increase in number of leaves, 15.26% for high shoot, 43.5% increase in root dry weight, and a 77% increase in shoot dry weight when compared with untreated controls.

Lactic Acid Bacteria in Durum Wheat Flour Are Endophytic Components of the Plant during Its Entire Life Cycle

“…According to the 16S rRNA gene-based high-throughput sequencing, L. plantarum was the endophytic lactic acid bacterial species found in both cultivars at all the phenological stages, grain, and flour. This finding reinforced the concept that L. plantarum has a strong ecological or metabolic adaptability to different habitats (58,59). Mesophilic lactobacilli (e.g., L. coryniformis) were mainly isolated in the first phenological stages.…”

Bacterial endophytes in agricultural crops and their role in stress tolerance: a review

“…Unlike phytopathogens, such bacteria do not normally cause any substantial disease symptoms, and occurrence of endophytes is not associated with morphological changes of plant tissues such as caused by root-nodule symbionts. Endophytes colonize plant apoplast, including the intercellular spaces of the cell walls and xylem vessels of plant roots, stems and leaves, and they are also found in tissues or flowers (Compant et al, 2011), fruits (de Melo Pereira et al, 2012) and seeds . Population densities of endophyte bacteria are extremely variable in different plants and tissues and have been shown to vary from hundreds to reaching as high as 9 × 10 9 of bacteria per gram of plant tissue (Jacobs et al, 1985;Misaghi, Donndelinger, 1990;Chi et al, 2005).…”

Nitrogen-Fixation by Endophytic Bacteria in Agricultural Crops: Recent Advances

“…In addition, endophytic bacteria colonize niches that are more conducive to forming mutualistic relationships with plants [51], for example, providing fixed N to the plant and getting photosynthate in return [52][53][54]. Following the rhizospheric colonization, endophytic bacteria can colonize various plant organs such as roots, stem, leaves, flowers, fruits, and seeds [55][56][57][58][59][60][61], indicating different capacities of endophytic bacteria to colonize various plant compartments. They can even colonize legume nodules [62] and tubercles of mycorrhizal fungi [63].…”