Abstract
Mangrove plant endophytic bacteria are prolific sources of bioactive secondary metabolites. In the present study, twenty-three endophytic bacteria were isolated from the fresh roots of the mangrove plant Rhizophora apiculata. The identification of isolates by 16S rRNA gene sequences revealed that the isolated endophytic bacteria belonged to nine genera, including Streptomyces, Bacillus, Pseudovibrio, Microbacterium, Brevibacterium, Microbulbifer, Micrococcus, Rossellomorea, and Paracoccus. The ethyl acetate extracts of the endophytic bacteria’s pharmacological properties were evaluated in vitro, including antimicrobial, antioxidant, α-amylase and α-glucosidase inhibitory, xanthine oxidase inhibitory, and cytotoxic activities. Gas chromatography–mass spectrometry (GC-MS) analyses of three high bioactive strains Bacillus sp. RAR_GA_16, Rossellomorea vietnamensis RAR_WA_32, and Bacillus sp. RAR_M1_44 identified major volatile organic compounds (VOCs) in their ethyl acetate extracts. Genome analyses identified biosynthesis gene clusters (BGCs) of secondary metabolites of the bacterial endophytes. The obtained results reveal that the endophytic bacteria from R. apiculata may be a potential source of pharmacological secondary metabolites, and further investigations of the high bioactive strains—such as fermentation and isolation of pure bioactive compounds, and heterologous expression of novel BGCs in appropriate expression hosts—may allow exploring and exploiting the promising bioactive compounds for future drug development.
Highlights
Plant endophytic bacteria are live and thrive inside plants without causing harmful effects to their host plants [1]
The obtained results in the present study reveal that the endophytic bacteria from Rhizophora apiculata are potential sources of biological compounds and further investigations, e.g., isolation of active pure compounds and heterologous expression of novel biosynthesis gene clusters of secondary metabolites should be performed in order to explore and exploit the novel bioactive compounds for drug development
Twenty-three endophytic bacteria belonging to nine genera (i.e., Microbulbifer, Streptomyces, Bacillus, Rossellomorea, Micrococcus, Paracoccus, Microbacterium, Pseudovibrio, and Brevibacterium) were isolated from the fresh roots of R. apiculata
Summary
Plant endophytic bacteria are live and thrive inside plants without causing harmful effects to their host plants [1]. The endophytic bacteria provide numerous benefits to their host plants, including promoting the growth of host plants, enhancing the resistance of host plants against diseases, and increasing the tolerance of host plants to stressful environmental conditions [2,3,4]. Mangrove plants growing under such frequent and sporadic environmental changes provide special ecological niches for diverse endophytic microbial communities [7]. The variable environmental conditions in mangrove ecosystems may serve as excellent selectors for structurally distinct secondary metabolites with intriguing pharmacological effects. Along with their host plants, endophytic bacteria have been reported to be a rich source of secondary metabolites with promising pharmacological properties [8,9,10,11]. Many compounds exhibit potent biological activities and may be considered as lead compounds for further drug developments
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