Classification and identification of bacteria: current approaches to an old problem. Overview of methods used in bacterial systematics.

Most of the bacterial species are still unknown. Consequently, our knowledge about bacterial ecology is poor and expectations about specialized species with novel enzymatic functions or new products are high. Thus, bacterial identification is a growing field of interest within microbiology. In this review, suitability of developments for identification based on miniaturized biochemical and physiological investigations of bacteria are evaluated. Special emphasis is given to chemotaxonomic methods such as analysis of quinone system, fatty acid profiles, polar lipid patterns, polyamine patterns, whole cell sugars, peptidoglycan diaminoacids, as well as analytical fingerprinting methods and cellular protein patterning. 16S rDNA sequencing introduced to investigate the phylogenetic relationships of bacteria, nucleic acids hybridization techniques and G + C content determination are discussed as well as restriction fragment length polymorphism (RFLP), macrorestriction analysis and random amplified polymorphic DNA (RAPD). The importance of the different approaches in classification and identification of bacteria according to phylogenetic relationships are demonstrated on selected examples.