Saran's Learn Microbiology

TYPES OF BACTERIA ·        A few different criteria are used to classify Bacteria. The organisms can be distinguished by a)      The nature of their cell walls (Gram positive bacteria and Gram negative bacteria) b)   Their shapes (Coccus, Bacillus, Spirilla, Box, Filamentous, Appentaged and Pleomorphic) c)      Gaseous requirements or Respiration (Aerobic bacteria and Anaerobic bacteria) d)      Nutritional pattern (Autotrophic bacteria and Heterotrophic bacteria) Table – 8.1: Difference between Gram positive bacteria and Gram negative bacteria S. No Features Gram Positive Bacteria Gram Negative Bacteria 1 Gram staining Appears in Violet colour Appears in Pink colour 2 Examples Staphylococcus , Streptococcus , Lactobacillus , Clostridium and Bacillus . Neisseria, Escherichia coli , Salmonella, Vibrio, Klebsiella, Rhizobium and Azospirillum

  SHAPE AND ARRANGEMENT OF BACTERIA Shape and Arrangement of Bacteria (Source: microbiologyinfo.com)             The basic bacterial shapes are (a) Coccus (spherical), (b) Bacillus (rod-shaped), and (c) Spiral (twisted), (d) Filamentous bacteria, (e) Box shaped bacteria, (f) Appentaged bacteria and (g) Pleomorphic bacteria can assume several shapes. a) SPHERICAL BACTERIA (COCCUS) ·        Cocci (or Coccus for a single cell) are round cells which are spherical or ovoid in shape, sometimes slightly flattened when they are adjacent to one another (plural - Cocci). Arrangement of Coccus i.       Diplococcus – Cocci arranged in pairs ( Streptococcus pneumoniae , Moraxella catarrhalis , Enterococcus sp. and Neisseria gonorrhea ) ii.   Streptococcus – Cocci arranged in form of chains (string like) ( Streptococcus pyogenes and Streptococcus mutans ). iii.    Tetrads – Cocci arranged in packets of four cells, as the cell di