Analyzing Microbial Core Communities, Rare Species, and Interspecies Interactions Can Help Identify Core Microbial Functions in Anaerobic Degradation

Anaerobic degradation (AD) technology converts organic waste into renewable energy (biogas), biofertilizer, and other green products. The conversion process relies on the actions of a microbial community consisting of taxonomically diversified species that interact in close cooperation. However, the identity of the microorganisms involved and their metabolism, role in AD processes, and interspecies cooperation are largely unknown, impeding identification of links between operational variables and performance parameters. Emerging microbial concepts and tools for data interpretation can help address broad-scale questions about the variability and mutuality of AD microbial communities, often with the ultimate objective of enhancing understanding of microbial functionality. In this chapter, we summarize known AD core communities and explore the existence of cores linked to process types. Based on this, we offer insights into terminologies such as core community, rare taxa, and keystone species in engineered systems which, although frequently used in AD studies, require clearer definition. We then consider how these microbial groups are influenced by different deterministic and stochastic factors in AD processes, and assess whether network-based analyses for detection of keystone species that co-exist in AD processes can assist in interpreting results from sequencing data. We conclude by discussing possible future insights into the prevalence of microorganisms with specific functional traits or an abundance of certain functional genes, among a wide range of processes (core functionality), which can broaden understanding and help in designing productive biogas processes.