This study determined bacterial genome sizes using DNA renaturation kinetics, a technique based on second-order reaction kinetics of single-stranded DNA reassociation. The researchers analyzed DNA from 36 bacterial species across 21 genera and 11 families. DNA was extracted, denatured, and renatured under controlled conditions, with genome sizes calculated from reaction rate constants and sedimentation coefficients. Genome sizes ranged from approximately 1.0 × 10⁹ to 7.0 × 10⁹ daltons. Results agreed well with previously determined values for Escherichia coli, Haemophilus influenzae, Salmonella, and Bacillus species. Notably, Pseudomonas species showed larger genomes (4.0-7.0 × 10⁹ daltons) than previously reported by chemical methods. The authors conclude that DNA renaturation is a reliable method for determining bacterial genome sizes and could provide a foundation for bacterial taxonomy and phylogenetic classification at higher taxonomic levels, complementing DNA base composition and nucleic acid homology studies.

Key findings

• DNA renaturation kinetics successfully determined genome sizes ranging from 1.0 to 7.0 × 10⁹ daltons across 36 bacterial species.
• Results validated previous measurements for E. coli (2.8 × 10⁹ daltons) and H. influenzae (0.8 × 10⁹ daltons), confirming method reliability.
• Pseudomonas species exhibited larger genomes (4.0-7.0 × 10⁹ daltons) than previously reported by chemical methods.
• The renaturation technique provides a reliable, standardized approach for genome size determination suitable for bacterial taxonomy and phylogenetic differentiation.