Principles and Practice of Bacterial Taxonomy--a Forward Look

Abstract

SUMMARYTaxonomy is divisible into three parts: (1) classification, (2) nomenclature, (3) identification. There are rules of nomenclature but none for classification or identification. S i x principles are postulated for classification of bacteria and three ways of making identifications are discussed. Both classification and identification depend on characterization of the bacterium, but each makes different use of the individual feature. In classification equal weight is given to each independent character; in identification characters are weighted, some as important (distinguishing), others less so. Exception is taken to the retroactive application of the rules of nomenclature, and the unrealistic starting date (1753) of bacterial nomenclature is criticized. Names act merely as labels and it is suggested that a sequential code should be used, not only as a substitute for a name, but as a means of conveying information about the characters of the organism.

Heretical Taxonomy for Bacteriologists

“…Because all taxonomists have different ideas on the subject it is necessary to remind readers what I mean by taxonomy (Cowan, 1965a). I distinguish it from systematics, which embraces all facets of biology intended to lead to the greater organization of organisms (Cowan, 1968).…”

New Strategies for the Selective Isolation of Industrially Important Bacteria

“…Although these measures are to be welcomed, the criteria for recognition of species and higher taxa can still be expected to vary between different taxonomists and microbial groups. The philosophy of taxonomists is still reflected in the subdivisions they create ('lumpers' or 'splitters') and the group on which they work (Cowan, 1965). Procedures used to distinguish new from established taxa must be based on sound taxonomic principles.…”

Microbial Identification

“…Some characters are almost invariably positive or negative, but characters of such constancy are usually shared by similar organisms and, although they are' important in characterizing an organism, have little value in distinguishing it from its neighbours. On the results of a limited number (up to ten) of selected cytological and physiological tests, Cowan & Steel (1961, 1965 found that most organisms encountered in clinical bacteriology could be placed in a genus or group of genera; this constituted the first stage of identification with their diagnostic tables.…”

“…If the diagnostician has ready access to an electronic computer he could use an almost infinite number of characters, but with tables he is restricted by memory or is limited by his ability to recognize similarities and differences when making comparisons simultaneously. These limitations led to the construction of the Determinator and the compilation of tables suitable for use with it (Cowan & Steel, 1960, 1965.…”

“…Of the three approaches to identification (Cowan, 1965), the third or progressive method aims to determine a few fundamental characters so that an isolate can be placed in one genus or small group of genera; other appropriate tests are then carried out so that specific identification can be made. Additional tests for the better identification of a species, variety or biotype may be required.…”