B. Sc. First Year Semester I
          Paper I – Fundamentals of Microbiology
                  Unit 2: 
                TAXONOMY
                   Dr. Jadhav P. N.
                Associate Professor and Head,
                Microbiology Department,
                   Deogiri College,
                    Aurangabad
      Figure: Bacterial Morphology
      Physiological and metabolic characteristics
      •  Some physiological and metabolic characteristics are very 
         useful in classifying and identifying microorganisms because 
         they are directly related to the nature and activity of microbial 
         enzymes and transport proteins.
      •  Some most important physiological and metabolic 
         characteristics used in microbial taxonomy are nutritional 
         types, cell wall components, carbon and nitrogen sources, 
         energy metabolism, osmotic tolerance, oxygen relationships, 
         temperature relationships, salt requirements and tolerance, 
         secondary metabolites, storage inclusions, etc.
   Table: Some taxonomically useful physiological and metabolic 
         characteristics and their variations
         Ecological characteristics
    • Ecological characteristics, i.e., the characteristics of relationship of 
     microorganisms to their environment significantly contribute in 
     microbial taxonomy.
    • It is because even very closely related microorganisms may vary 
     considerably with respect to their ecological characteristics.
    • For convenience, microorganisms inhabiting freshwater, marine, 
     terrestrial, and human body environments differ from one another 
     and from those living in different environments.
    • However, some of the most important ecological characteristics used 
     in microbial taxonomy are 
        - life cycle patterns
        - the nature of symbiotic relationship
        - pathogenic nature
        - variations in the requirements for temperature, pH, oxygen, and 
    osmotic        concentrations.