Metagenomics study of endophytic bacteria in Aloe vera using next-generation technology.

Next generation sequencing (NGS) enables rapid analysis of the composition and diversity of microbial communities in several habitats. We applied the high throughput techniques of NGS to the metagenomics study of endophytic bacteria in Aloe vera plant, by assessing its PCR amplicon of 16S rDNA sequences (V3-V4 regions) with the Illumina metagenomics technique used to generate a total of 5,199,102 reads from the samples. The analyses revealed Proteobacteria, Firmicutes, Actinobacteria and Bacteriodetes as the predominant genera. The roots have the largest composition with 23% not present in other tissues. The stems have more of the genus-Pseudomonas and the unclassified Pseudomonadaceae. The α-diversity analysis indicated the richness and inverse Simpson diversity index of the bacterial endophyte communities for the leaf, root and stem tissues to be 2.221, 6.603 and 1.491 respectively. In a similar study on culturable endophytic bacteria in the same A. vera plants (unpublished work), the dominance of Pseudomonas and Bacillus genera was similar, with equal proportion of four species each in root, stem and leaf tissues. It is evident that NGS technology captured effectively the metagenomics of microbiota in plant tissues and this can improve our understanding of the microbial-plant host interactions.

Diversity, antimicrobial and antioxidant activities of culturable bacterial endophyte communities in Aloe vera.

Twenty-nine culturable bacterial endophytes were isolated from surface-sterilized tissues (root, stem and leaf) of Aloe vera and molecularly characterized to 13 genera: Pseudomonas, Bacillus, Enterobacter, Pantoea, Chryseobacterium, Sphingobacterium, Aeromonas, Providencia, Cedecea, Klebsiella, Cronobacter, Macrococcus and Shigella. The dominant genera include Bacillus (20.7%), Pseudomonas (20.7%) and Enterobacter (13.8%). The crude and ethyl acetate fractions of the metabolites of six isolates, species of Pseudomonas, Bacillus, Chryseobacterium and Shigella, have broad spectral antimicrobial activities against pathogenic Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, Salmonella Typhimurium, Proteus vulgaris, Klebsiella pneumoniae, Escherichia coli, Streptococcus pyogenes and Candida albicans, with inhibition zones ranging from 6.0 ± 0.57 to 16.6 ± 0.57 mm. In addition, 80% of the bacterial endophytes produced 1,1-diphenyl-2-picrylhydrazyl (DPPH) with scavenging properties of over 75% when their crude metabolites were compared with ascorbic acid (92%). In conclusion, this study revealed for the first time the endophytic bacteria communities from A. vera (Pseudomonas hibiscicola, Macrococcus caseolyticus, Enterobacter ludwigii, Bacillus anthracis) that produce bioactive compounds with high DPPH scavenging properties (75-88%) and (Bacillus tequilensis, Pseudomonas entomophila, Chryseobacterium indologenes, Bacillus aerophilus) that produce bioactive compounds with antimicrobial activities against bacterial pathogens. Hence, we suggest further investigation and characterization of their bioactive compounds.

Antimicrobial and enzymatic activities of endophytic bacteria isolated from Mentha spicata (MINT)

Aims: This study is to isolate and characterize endophytic bacteria for potential industrial enzymes and antimicrobial activities against some human pathogens. Methodology and results: Mentha spicata, a local medicinal plant, was used to source for endophytes. The roots, stems and leaves of M. spicata were surface-sterilized to isolate the endophytic bacteria. The endophytic bacteria were subsequently characterized based on their 16S rRNA sequences. The endophytic bacteria were screened for both antimicrobial and enzymatic activities. We identified 15 isolates of 4 genus-Pseudomonas (7 species), Bacillus (3 species), Enterobacter (1 species) and Comamonas (1 species) with 97-100% similarity level. Isolates MSS-3 (Pseudomonas putida), MSR-4 (Pseudomonas pictorum), MSS-2 (Bacillus thuringiensis) and MSR-5 (Pseudomonas straminea) showed prominent antimicrobial activities against the pathogens tested with zones of inhibition between 6.3 to 15.3 ± 0.6 mm. All species examined have positive cellulase activities except Comamonas guangdongensis and only isolates of the Bacillus genus, Pseudomonas pictorum and P. argentinensis exhibited amylase activities. Conclusion, significance and impact of study: Our findings revealed potential therapeutic uses of the bioactive compounds of these bacteria endophytes against pathogens. Their enzymatic potential can also be of use in various industries.