Characterization of Endophytic Microbiomes of Medicinal Plants for their Antimicrobial Activities

Authors

Ganesh Khadka, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Earth Systems Science

First Advisor's Name

Krishnaswamy Jayachandran

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Kateel G. Shetty

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Amir Khoddamzadeh

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Yuk-Ching Tse-Dinh

Fourth Advisor's Committee Title

Committee member

Keywords

Endophyte, Fungi, Bacteria, antimicrobials, diversity

Date of Defense

11-10-2022

Abstract

Emerging new infectious diseases and developing antimicrobial resistance are serious global health threats. New approaches are needed for the discovery and development of new antimicrobial compounds with novel modes of action to overcome the problem of resistant microbial pathogens. There has been increasing interest in the discovery of endophytes, an important component of plant microbiome that live within plant tissues as potential key sources of novel antimicrobial compounds. Medicinal plants are generally considered excellent sources of bioactive compounds produced by endophytes. South Florida with its unique sub-tropical humid climate has botanical gardens, private orchards, and nurseries with vast collections of sub-tropical and tropical medicinal plants species. These plant species can be potential sources of endophytes capable of producing novel antimicrobial compounds. Moreover, increasing loss of biodiversity is a threat to the survival of these native medicinal plant species in South Florida. Therefore, discovering endophytic fungi and bacteria and their biodiversity in native medicinal plants such as Petiveria alliacea (Guinea hen weed), Annona glabra (Pond apple), Agave americana (Century plant), and Conocarpus erectus (Buttonwood mangrove) is crucial for understanding their roles in ecosystems and for the discovery of novel antimicrobials against human, plant, and animal pathogens. Characterization of microbiomes of these four medicinal plant species were conducted using cultural, biochemical, and molecular approaches. Pure cultures of bacterial and fungal endophytes were isolated from different parts of native medicinal plants and was screened for antagonistic activity against bacteria and fungi using dual culture technique. Culture extracts from endophytes showing antagonistic activity were collected and screened for antimicrobial activity against common human and plant pathogens such as Escherichia coli ATTC 25902, Staphylococcus aureus ATTC 14775, Bacillus subtilis NRRL 5109, Candida albicans ATTC 10231 and Aspergillus fumigatus NRRL 5109. Phylogenetic identification of endophytes producing antimicrobial compounds were carried out using 16S rRNA and ITS gene sequence analysis. Characterization of antimicrobial compound/s present in the culture extracts were analyzed using chemical analysis method. Microbial biodiversity of endophytes was assessed using both cultural and molecular methods. Results indicated that the fungal endophytes isolated from all four native medicinal plant South Florida has potential to produce novel bioactive potential to kill or inhibit the growth of disease-causing strain of bacteria and fungi. Moreover, endophytic bacteria produced from medicinal plant of South Florida also contain bacterial endophytes that provide antibacterial properties. It was also found that there is diversity among the culturable and non-culturable fungal endophytes from medical plants of South Florida. Hence, Native medicinal plants of South Florida harbor the endophytic microbiomes capable of producing novel bioactive metabolites.

Identifier

FIDC010950

ORCID

0000-0003-2083-1250

Recommended Citation

Khadka, Ganesh, "Characterization of Endophytic Microbiomes of Medicinal Plants for their Antimicrobial Activities" (2022). FIU Electronic Theses and Dissertations. 5138.
https://digitalcommons.fiu.edu/etd/5138