Gram staining procedure
The Gram staining method to differentiate bacteria was developed by Danish Physician Christian Gram in the year 1884. It is a differential staining procedure and it classifies bacteria into two classes - Gram positive and Gram negative. The steps involved in Gram staining procedure is given in Figure 1.10. The Gram positive bacteria retain crystal violet and appear dark violet whereas Gram negative type loose the crystal violet and when counterstained by safranin appear red under a microscope.
Most of the gram positive cell wall contain considerable amount of teichoic acid and teichuronic acid. In addition, they may contain polysaccharide molecules. The gram negative cell wall contains three components that lie outside the peptidoglycan layer. 1. Lipoprotein 2. Outer membrane 3.Lipopolysaccharide. Thus the different results in the gram stain are due to differences in the structure and composition of the cell wall (Figure 1.11). The difference between Gram Positive and Gram negative bacteria is given in Table 1.6.
What are Magnetosomes ?
Intracellular chains of 40-50 magnetite (Fe3O4) particles are found in bacterium Aquaspirillum magnetotacticum. and it help the bacterium to locate nutrient rich sediments.