The recent years have seen the emergence of the microbiomes as important axes of human health and disease. Microbial communities abound in various regions of the human body, notably the gut, skin and the oral cavity. Microbial communities are increasingly being used for industrial fermentations and wastewater treatment.

Many algorithms and tools have been developed to study microbial communities, particularly the metabolic interactions that drive and sustain these microbial communities. **In this tutorial, we seek to provide a brief overview of the key modelling paradigms that have been used to study microbiomes, particularly focussing on two broad classes of methods: (a) constraint-based modelling, that attempts to model microbial metabolic networks in terms of the fluxes of various constituent reactions, and (b) graph-based modelling, which models microbial interactions as part of a complex graph capturing the exchange of several metabolites between the constituent organisms, and consequently, shed light on the nature of the interactions between the organisms.

In this tutorial, we will introduce the participants to the fundamental concepts of metabolic modelling with a special emphasis on microbial communities. Following this, we will delve deeper into different types of techniques to understand interactions in a microbial community. Lastly, we will showcase some representative tools and methods, which will enable the participants to apply the theories to real-life examples and understand the nature of interactions between different kinds of organisms in community settings.
At the end of the tutorial, the participants will have an understanding of:

• Broad applications of metabolic modelling to model microbiome
• Databases and resources for microbiome modelling
• Key constraint-based methods that can be used to understand microbiome
• Key graph-based methods that can aid in understanding metabolic exchanges
• Tools for microbiome modelling such as COBRA toolbox (specific algorithms) or MetQuest