Size, Shape and Arrangement of bacteria

this ppt describes about the various size ,shape and arrangement of bacteria with examples and pictures.

1. BACTERIAL CELL BY-ALPANA DAVE

2. HISTORY The word bacterium (Gk. Bakterion = little rod) Originally applied for rod shaped organism. Which belongs to the lowest order of the plant life or "microscopic unicellular plants without chlorophyll that reproduce by fission". Antony Von Leeuwenhoek discovered bacteria, named them as "tiny animalcules". He is called as "Father of Bacteriology". Ehrenberg (1829) coined the term bacteria for these microorganism.

3. Size of bacteria Great variation in size of bacteria. On an average each cell of bacterium measures 1.25 - 2 µm in diameter and 2-10 µm in length. The smallest rod shaped eubacterium is Dialister pneumosintes which measure in between 0.15- 0.3 µm in size. The biggest bacteria Beggiatoa mirabilis is about 16-45µ in diameter and 80µ in length.

4. Escherichia coli is a rod of about average size, 1.1 to 1.5 μm wide by 2.0 to 6.0 μm long. Mycoplasma------ about 0.3 μm in diameter. Nanobacteria and nanoarchaea ----- around 0.2 μm to less than 0.05 μm in diameter. Spirochetes---- can reach 500 μm in length. Photosynthetic bacterium Oscillatoria, which is about 7 μm in diameter (the same diameter as a red blood cell).

5. SHAPE & ARRANGEMENT Endless variety in terms of morphology. Usually three conventional shapes. Initial classification of bacteria was based on their shapes but now it is not used . The various shapes are as follows: (1) Ellipsoidal/Spherical/Cocci – simplest form of bacteria, appears like a minute sphere (0.5~ - 1.25~ in diameter) they lack flagella. On the basis of arrangements cocci are further classified as follows: 1. Micrococci: When a bacterium appears singly e.g . Micrococcus agitis, M. aureus.

6. 2. Diplococcus : remains in pairs, cells divide in one plane. e.g. Diplococcus pneumoniae. 3. Streptococci: remain attached to form rows or chains and cells divides in one planes. e.g. Streptocoocus lactis

7. 4. Tetracoccus : divides in two planes and remains in group of four, forming square. e.g. Neisseria and Micrococcus tetrogenus . 5. Sarcinae : when it divides in three planes and form cuboidal like structure. e.g. Sarcillae lutea

8. 6. Staphylococcus: formed by division in many planes , arranged randomly in a cluster like bunches of grapes e.g. Staphylococcus aureus

9. (2) Rod Shaped Bacteria or Bacillus The word bacillus originated from greek word, bacillii means rod or stick. There ends are rounded flat or pointed. There size ranges from 0.5-1.2~ in diameter and 3- 7~ in length. They may be flagellated or non-flagellated. Most of the bacteria causing disease in plants belongs to bacilli category .

10. They may be of following types: ( i ) Monobacillus : When they arrange singly. (ii) Diplobacillus: When they are present in a group of two,  appears in pairs after division  e.g. Diplobacillus pneumoniae (iii ) Streptobacillus : When they appear in chains e.g. Bacillus tuberculosis. (iv ) Palisade: Very rarely the bacillus arrange in a palisade arrangement

11. (3 ) Spiral or Helical greek word; spira means coiled. A single spirillum has more than one turn of helix. Generally they are found as free living, unicellular entity. There size ranges from 10-50~ in length and 0.5 - 3~ in diameter. They are flagellated e.g. Spirillum minus, S. volutans .

12. (4) Vibrio or Coma The bacteria of this group are like 'coma or small curved rod. They bear flagella at their end. Their size ranges from 1.5-l.7µm in diameter and upto 10µm in length e.g. Vibrio cholarae .

13. (5) Spirochaete These bacteria appears like a cork screw and atrichous . Their length is more as compared to their diameter. Their body is more flexible.

14. (6) Filamentous These type of bacteria are generally found in sewage water and the effluent of sugar industry. e.g . Sphaerotilus natalls . Basically they are rod shaped bacilli which grow in an elongated chain and are covered by a tubular envelope. Ferrous containing water generally contain filamentous bacteria e.g. Leptothrix , Cladothrix , Nocardia and Beggiatoa.

15. 7. ROSETTE Bacillus arranged in a rosette attached by stalks to a substrate. Caulobacter

16. 8. Star-shaped bacteria e.g. Stella 9. Square-shaped e.g. Haloarcula , a salt-loving member of the Archaea.

17. 10. Pleomorphic Many bacteria change their shape and structure with the change in environmental conditions. These bacteria which are found in various forms are known as pleomorphic bacteria e.g. Acetobacter.