eChapter Name: Morphology of Bacteria
9789389992359
eBook Name: FOOD MICROBIOLOGY: BASIC AND APPLIED WITH LABORATORY EXERCISES
by Dr. Rita Narayanan, Dr. B.Dhanalakshmi, B.Dhanalakshmi, Rita Narayanan
Bacteria are morphologically different. This characteristic is helpful in the identification of bacteria. Routine study of bacterial morphology should include examination of stained preparations. Motility should be examined by hanging drop preparation. According to the requirement, certain cell structures may be stained. Stained preparations should be made preferably from fresh agar slant cultures. Smears of Streptococcus should be made from a liquid culture. Morphology of bacteria may be described under the following terms:
1.Shape: Spherical, coccobacillary, short or long rods, filamentous, comma- shaped, curved or spiral forms.
2.Size: Spherical are measured in diameter and rod-shaped in length and breadth. Measurement is expressed in microns (µ).
3.Sides: Straight, concave, bulging, parallel or irregular.
4.Ends: Round, pointed, truncate or concave.
5.Axis: Straight or curved.
6.Arrangement: Singly, in twos, in groups of four or eight, in grape-like bunches, in long chains, or scattered irregularly, may be in bundles, angular arrangements or in Chinese letters.
7.Pleomorphism: Bacteria may differ from their typical shape. Some of the older cultures may depart greatly from their typical forms, and may show spindles, clubs, and filaments, swollen and branching forms. Variation may be both in shape and size.
8.Capsule: May or may not be present. When present, size should be noted. This requires special staining.