Microbial ecology is undergoing a revolution, with significant implications for microbiology, ecology, and ecosystem science. The rapid accumulation of molecular data is revealing vast microbial diversity, novel functions, and abundant uncultivated microbial groups. However, the application of theory in microbial ecology is currently limited, and the full potential of this revolution will not be realized without theory-driven research. Established ecological theory must be tested in microbial systems to ensure its applicability. Microorganisms, though small, are abundant and play essential roles in biogeochemical cycles. Their phylogenetic and physiological diversity is greater than that of animals and plants, and their interactions are more complex. Understanding microbial ecology is a major intellectual challenge, with practical implications for managing ecosystems and mitigating climate change. Despite this, theory application in microbial ecology is lacking, as it is required most. Theory is essential for classifying, interpreting, and predicting microbial processes. It provides quantitative insights into microbial interactions with their environments. Theoretical models can inform policy and management, as seen in epidemiological models for disease control. However, microbial systems offer unique opportunities for testing ecological theory, as they are more controlled and manipulable than plants or animals. Two factors limit the development of theory in microbial ecology: a lack of data and a cultural disconnect from ecological theory in microbiology. The application of molecular techniques has highlighted the need for theory-driven research. Existing ecological theory may not apply directly to microorganisms, but it can be tested and adapted. Theoretical approaches, such as species abundance curves, are essential for estimating microbial diversity. Ecological theory must be adapted to microbial systems, considering their unique characteristics, such as asexual reproduction, high dispersal, and rapid growth. Theoretical models can help understand microbial diversity, spatial patterns, and temporal dynamics. The application of ecological theory to microbial systems can enhance our understanding of microbial ecology and improve management of natural ecosystems. Theoretical approaches, such as adaptive dynamics and game theory, can help explain microbial behavior and interactions. Ecological theory is also relevant to microbial community structure, evolution, and ecosystem function. The integration of ecological theory with microbial ecology is essential for advancing our understanding of microbial processes and their role in ecosystems. The development of a coherent theoretical framework for microbial ecology is crucial for addressing the challenges facing human society.Microbial ecology is undergoing a revolution, with significant implications for microbiology, ecology, and ecosystem science. The rapid accumulation of molecular data is revealing vast microbial diversity, novel functions, and abundant uncultivated microbial groups. However, the application of theory in microbial ecology is currently limited, and the full potential of this revolution will not be realized without theory-driven research. Established ecological theory must be tested in microbial systems to ensure its applicability. Microorganisms, though small, are abundant and play essential roles in biogeochemical cycles. Their phylogenetic and physiological diversity is greater than that of animals and plants, and their interactions are more complex. Understanding microbial ecology is a major intellectual challenge, with practical implications for managing ecosystems and mitigating climate change. Despite this, theory application in microbial ecology is lacking, as it is required most. Theory is essential for classifying, interpreting, and predicting microbial processes. It provides quantitative insights into microbial interactions with their environments. Theoretical models can inform policy and management, as seen in epidemiological models for disease control. However, microbial systems offer unique opportunities for testing ecological theory, as they are more controlled and manipulable than plants or animals. Two factors limit the development of theory in microbial ecology: a lack of data and a cultural disconnect from ecological theory in microbiology. The application of molecular techniques has highlighted the need for theory-driven research. Existing ecological theory may not apply directly to microorganisms, but it can be tested and adapted. Theoretical approaches, such as species abundance curves, are essential for estimating microbial diversity. Ecological theory must be adapted to microbial systems, considering their unique characteristics, such as asexual reproduction, high dispersal, and rapid growth. Theoretical models can help understand microbial diversity, spatial patterns, and temporal dynamics. The application of ecological theory to microbial systems can enhance our understanding of microbial ecology and improve management of natural ecosystems. Theoretical approaches, such as adaptive dynamics and game theory, can help explain microbial behavior and interactions. Ecological theory is also relevant to microbial community structure, evolution, and ecosystem function. The integration of ecological theory with microbial ecology is essential for advancing our understanding of microbial processes and their role in ecosystems. The development of a coherent theoretical framework for microbial ecology is crucial for addressing the challenges facing human society.