This paper presents a comprehensive examination of bacterial taxonomy, subdividing it into three interconnected but distinct components: classification (organizing bacteria into hierarchical groups), nomenclature (assigning names to classified units), and identification (matching unknown organisms to known classified groups). Cowan outlines six foundational principles for bacterial classification: purpose, flexible subdivisions, uniformity of units, precise circumscription, adequate characterization, and appropriate weighting of characters. A central debate concerns character weighting: the Adansonian approach assigns equal weight to all characters in classification, while Kauffmann's approach emphasizes certain characters (particularly antigenic structure) more heavily. Cowan argues that equal weighting is appropriate for classification but differential weighting is practical for identification. The paper critiques the International Code of Bacterial Nomenclature's 1753 starting date and proposes alternative labeling systems using sequential codes that could convey organism characteristics more efficiently than traditional binomial names. Cowan emphasizes that classification should build upward from individual isolates through increasingly larger groupings based on fundamental similarities, including genetic material and biochemical characteristics, rather than assuming natural relationships implied by hierarchical systems.

Key findings

• Taxonomy comprises three distinct but interdependent components: classification, nomenclature, and identification, each with different purposes and requiring different approaches to character weighting
• Equal weighting of characters should be applied in classification (Adansonian principle) while differential weighting of important or distinguishing characters is practical and appropriate for identification
• The Nomenclature Code's retroactive application from 1753 is problematic; a starting date aligned with pure culture era would be more acceptable
• Sequential alphanumeric codes could replace traditional nomenclature as more efficient labels for conveying organism characteristics and accommodating the wide permutations of bacterial properties
• Adequate characterization of bacteria requires comprehensive multifaceted analysis including morphology, physiology, chemical composition, genetic factors, and antigenic structure