OAT

OAT calculates average nucleotide identity (ANI) between genome sequences to improve species demarcation in Bacteria and Archaea.

Key Features:

• OrthoANI algorithm: Implements OrthoANI to incorporate orthology into ANI calculations.
• Genome fragmentation and orthologous pairing: Fragments both genome sequences and considers only orthologous fragment pairs when computing nucleotide identities.
• Resolves ANI asymmetry: Eliminates reciprocal ANI asymmetry observed in standard ANI calculations (differences sometimes >1%).
• Correlation with BLASTn-based ANI: Shows high correlation with BLASTn-derived ANI while typically yielding ~0.1% higher values.
• Improved accuracy and speed: Provides a faster and more accurate means of calculating ANI compared with standard approaches.
• Replaces DDH limitations: Addresses limitations of DNA–DNA hybridization (DDH) by using genome-sequence-based similarity measures for taxonomic demarcation.

Scientific Applications:

• Species demarcation: Enables robust species boundaries in Bacteria and Archaea based on genome sequence similarity.
• Taxonomic classification: Supports genome-based taxonomic assignments and microbial systematics.
• Evolutionary analysis: Facilitates comparative and evolutionary analyses using nucleotide identity metrics.
• Species identification and genome comparisons: Supports precise genome sequence comparisons for species identification.

Methodology:

Uses the OrthoANI algorithm by fragmenting both genome sequences, identifying orthologous fragment pairs, and calculating average nucleotide identity, with comparisons against BLASTn-based ANI.