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AAT Bioquest

What are the different ways of the classification of bacteria?

Posted April 19, 2023


Answer

Bacteria may be classified using many different classification systems. 

  1. Based on the cell wall:
  • Peptidoglycan cell wall – Gram-positive bacteria
  • Lipopolysaccharide cell wall – Gram-negative bacteria
  1. Based on shape:
  • Coccus – Unicellular, spherical shaped, remaining as a single cell or aggregating together in various configurations
  • Bacillus - Rod-shaped or cylindrical, remaining singly or in pairs
  • Spirilla or spirochete – Spiral with multiple curvatures in its structure and terminal flagella
  • Vibrio - Comma-shaped or curved and represented by a single genus
  1. Based on mode of respiration:
  • Aerobic – Break down glucose molecules completely in the presence of oxygen to yield energy
  • Anaerobic – Break down glucose partially in the absence of oxygen to yield reduced energy
  1. Based on mode of nutrition:
  • Phototrophs – Gain energy from light
  • Autotrophs – Obtains carbon only from carbon dioxide to prepare its own food 
  • Heterotrophs – Source carbon from organic compounds
  • Chemotrophs – Gain energy from chemical compounds
  1. Based on number of flagella: 
  • Atrichos – No flagella
  • Monotrichous – One flagellum attached at one end of the cell
  • Lophotrichous – Multiple flagella attached at one end of the cell
  • Amphitrichous – Multiple flagella attached to both ends of the cell
  • Peritrichous – Flagella evenly distributed around and covering the entire cell
  1. Based on optimum temperature for growth: 
  • Psychrophiles –15 °C or below
  • Psychotrophs – 20°C to 30°C
  • Mesophiles - 37°C
  • Thermophiles – Above 45°C
  • Hyperthermophiles – Above 80°C
  1. Based on optimum pH requirements for growth: 
  • Acidophiles – Acidic pH
  • Alkaliphiles – Alkaline pH
  • Neutrophiles – Neutral pH 6.5 to 7.5
Additional resources

Classification of Bacteria and Archaea: past, present and future

MycoLight™ Fluorimetric CTC Live Bacteria Quantification Kit