Abstract
Medicinal plants are of interest to researchers and scholars due to their capability to host endophytes which are known to produce specialized metabolites that display therapeutic properties. Endophytes are defined as microorganisms, specifically fungi and bacteria, that colonize plant tissues without causing harm to their hosts. Bacterial endophytes promote growth and development within their plant hosts through nutrient acquisition mechanisms as well as aid plants against harsh environmental stresses and pathogenic attack, through the secretion of bioactive secondary metabolites. The in-depth relationship between bacterial endophytes and their host plants is still inadequately understood, making bacterial endophytes the focus of this study. This study aimed to characterize two endophytic Pantoea strains, namely Pantoea sp. strain MHSD2 and Pantoea sp. strain MHSD4 which were previously isolated from Pellaea calomelanos. Morphological and phylogenetic analysis were used to characterize the two strains, moreover, evaluating them for tannic acid degradation potential. Furthermore, the two strains differed in the utilization of the substrate N-acetyl-β-d-mannosamine, with strain MHSD4 having a positive reaction to the substrate and strain MHSD2 unable to metabolize the substrate. While employing genotypic characterization, multilocus sequencing (MLSA) data showed that the endophytic Pantoea species under study shared a high genetic relatedness with P. agglomerans from different environmental sources and that the concatenated phylogenetic tree was more robust at delineating the two species. The whole genome of strain MHSD4 was sequenced, assembled, and annotated. Biochemical and physiological data revealed that strain MHSD4 indicated an absence of the catalase enzyme contrary to other Pantoea species. The draft genome size and G+C content of strain MHSD4 indicated that it was within the ranges of its genus and the genomic data also indicated presence of copper resistance genes potentially useful for bioremediation. The data obtained in this study provided successful characterization of endophytic Pantoea species and initiated the investigation of tannic acid degradation as a potential biotechnological potential. This study has contributed in the identification of endophytic lifestyle, plant growth promotion and copper resistance and homeostasis genes.
Keywords: Bacterial endophytes, characterization, multilocus sequence analysis (MLSA), whole genome sequencing, Pantoea sp. strain MHSD4