MICRO-ORGANISMS 29 



to the same system; frequently one system will gain acceptance in 

 several countries. In any event, the system and the code of nomencla- 

 ture under which a microbiologist operates will determine which name 

 is correct. All other names then become synonyms. Thus, under the 

 system for classification of bacteria used most widely in the United 

 States, as given in Bergey's manual (4), Pseudomonas ps&udomattei 

 (Whitmore) Haynes is the correct name for the micro-organism that 

 has also been known as Malleomyces pseudomallei, Pfeijferella pseudo- 

 mallei, Bacillus pseudo-mallei, Flavobacterium pseudonnallei, Actino- 

 bacillus pseudomallei. Bacillus whitmori, Sclerothrix whitmori, and 

 Loefflerella whilmori. 



An American microbiologist who wishes to know the correct name 

 of a bacterium or an actinomycete should refer to the seventh edition 

 of Bergey's manual (4) , unless he knows of a more recent authoritative 

 treatise about the group under consideration that supersedes it. Until 

 the Index Bergeyana is published, the sixth edition of Bergey's manual 

 must be relied upon for the most complete listing of synonyms and 

 other historical data about viruses, bacteria, and rickettsiae. Refer- 

 ences are given for other categories of micro-organisms where they are 

 discussed in this bulletin. 



As defined previously, taxonomy is the science of classification. In 

 biology, classification is the systematic arrangement of living things 

 into groups. Living things can be divided into the plant and animal 

 kingdoms. Each kingdom may be divided into two or more smaller 

 segments, which themselves ma} T be fragmented. This procedure is 

 repeated down to the single cell. In botanical sciences, these resulting 

 groups in descending rank below kingdom are division, class, order, 

 family, genus, species, and various subspecific and infrasubspecific 

 categories. Every species belongs to a genus, every genus to a family, 

 every family to an order, and so on up to one of the kingdoms. 



It is evident that such a scheme as outlined expresses relationships of 

 the organisms fitted into it. The primary objective of taxonomy is to 

 establish the phylogenetic or evolutionary relationships of living 

 things. The phylogenetic relationships of some micro-organisms, 

 notably bacteria, actinomycetes, and viruses, are not so readily deter- 

 mined as they are among higher forms of life. Because of this defici- 

 ency in knowledge, schemes for their classification have at best been 

 only quasi-phylogenetic, Year by year taxonomic investigations pro- 

 vide greater^ insight to taxonomists, so that the true relationships of 

 micro-organisms of all types are becoming better known. 



Once a system of classification for a group of micro-organisms is 

 devised, it can be used to identify an unknown. After making certain 

 that the unknown is pure, or uncontaminated, it must be characterized. 

 This is generally done by determining its morphological, cultural, and, 

 if appropriate, physiological properties. In the classification and 

 identification of the more highly developed micro-organisms, such as 

 molds, morphological characterization is relied upon to a large extent. 

 An important part of the morphological characterization of the higher 

 forms pertains to sexual and asexual spores. Such cultural charac- 

 teristics as growth patterns and temperature responses may also be 

 helpful. Among the lower forms, such as bacteria, morphological 

 and cultural distinctions are inadequate and physiological character- 



