Exploring the Divergence of Functional and Evolutional Interactions between Fungi and Bacteria

概要

Appended Form No. 3(Doctor)

Abstract of Thesis
Affiliation

Doctoral Program in Life and Agricultural Sciences
Degree Programs in Life and Earth Sciences
Graduate School of Science and Technology

Student ID Number

202037006

Name

ABEYSINGHE KALUHATH GAYAN DAKSHITHA DE ABREW

Thesis Title

Exploring the Divergence of Functional and Evolutional
Interactions between Fungi and Bacteria
(糸状菌と細菌の機能的進化的相互作用の多様性の解析)

Abstract of Thesis

Fungi and bacteria comprise a large fraction of biomass in the soil and since they interact with
each other, bacterial-fungal interactions are crucial for understanding the microbial ecosystem
which is closely related to agriculture, medicine and the environment. It is evident that the
interactions between numerous microbes promote the activation of cryptic biosynthetic
pathways leading to the production of various secondary metabolites and other bioactive
compounds that confer defense functions, cell to cell communication and other interactive
dynamics. Currently, researchers striving to learn the dynamics of microbiota employ
coculturing which is proven to be a lucrative method to resemble at least a few conditions
existing among the microbial interactions in the natural environment, that could potentially
facilitate the production of novel bioactive compounds like antimicrobials.

Our recent study described the distinctive nature of the mutualistic relationship between the
filamentous fungus Aspergillus nidulans and gram-positive bacterium Bacillus subtilis
depicting evidence to show their spatial and metabolic interactions that facilitates the
communication in between species to explore untraversed environmental niches and obtain

nutrients. Confronting this interactive nature, the current study was comprised of co-culturing
of 36 environmental fungal species and 22 bacterial species to further investigate the interaction
dynamics in the co-cultures. Parameters such as the effect on the fungal growth, the affinity of
the bacterial cells to the fungal hyphae, bacterial cell dispersal distance and the velocity of
movement of bacteria were analyzed to define the phenotypic interaction specificity. Depending
on the nature of interactions, the combinations were then classified into genres of positive,
negative, and neutral. In depth analysis of the diversity of interaction specificity even among
the species of Aspergillus species with Bacillus subtilis revealed that specific antagonism
demonstrated in Aspergillus niger was directed primarily through Pyranonigrin A. Subsequently,
selected combinations were subjected to LCMS/MS analysis and transcriptomic analysis to
visualize their genomic potential and expression in coexistence compared to their monoculture
state which would assist in defining the factors that help establish and maintain the relationships
of the microbes in the microbial network setting.

This study intended to impart insights to the ecological context of interactions of the
environmental microbiota and utilization of the metabolic capacity of the chemically prolific
microorganisms. ...