This chapter provides a comprehensive overview of the natural history of freshwater lake bacteria, focusing on their phylogenetic diversity, ecology, and distribution. The authors present a meta-analysis of published 16S rRNA gene sequences from freshwater lake environments, constructing phylogenetic trees and classifying bacterial lineages into phyla, lineages, clades, and tribes. They highlight the importance of Actinobacteria, Bacteroidetes, Cyanobacteria, and Proteobacteria in freshwater ecosystems, detailing their phylogenetic relationships, ecological roles, and distribution patterns. The chapter also discusses the challenges in culturing these bacteria and the use of molecular methods to study their diversity and function. The authors emphasize the need for a consistent and robust vocabulary to describe taxonomic units and the importance of understanding the ecological traits of different bacterial groups. They conclude by summarizing the key findings and providing insights into the future research directions in freshwater microbial ecology.This chapter provides a comprehensive overview of the natural history of freshwater lake bacteria, focusing on their phylogenetic diversity, ecology, and distribution. The authors present a meta-analysis of published 16S rRNA gene sequences from freshwater lake environments, constructing phylogenetic trees and classifying bacterial lineages into phyla, lineages, clades, and tribes. They highlight the importance of Actinobacteria, Bacteroidetes, Cyanobacteria, and Proteobacteria in freshwater ecosystems, detailing their phylogenetic relationships, ecological roles, and distribution patterns. The chapter also discusses the challenges in culturing these bacteria and the use of molecular methods to study their diversity and function. The authors emphasize the need for a consistent and robust vocabulary to describe taxonomic units and the importance of understanding the ecological traits of different bacterial groups. They conclude by summarizing the key findings and providing insights into the future research directions in freshwater microbial ecology.