Question

The main difference between Gram +ve and Gram –ve resides in the composition of
A) Cilia
B) Cell wall
C) Cell membrane
D) Cytoplasm

Answer 1

Anton Van Leuwenhoek discovered bacteria in the pond water and tartar scraped from the teeth. They are the microscopic, unicellular, prokaryotic organisms. They lack a true nucleus.

Complete answer:
Bacteria are classified as gram positive and gram negative based on their staining. The gram positive and gram negative bacteria respond differently to the staining because of the differences in their cell wall composition. Gram positive bacteria retain the original purple or blue color of the stain while gram negative loose the stain after the treatment with alcohol.The cell wall of gram positive bacteria consists of multilayers of peptidoglycan and is around 20-30 nm thick. The outer membrane of lipids is absent in this case but the cell wall also has teichoic acid and lipoteichoic acid.The cell wall of gram negative bacteria has an outer lipid membrane and a very thin peptidoglycan layer. There is lipopolysaccharide on the outer side but a typical lipid layer on the inner side of the upper lipid membrane.Membrane porins are found in the outer membrane of gram negative bacteria which are absent in the gram positive bacteria. As the cell wall of gram positive bacteria has very little lipid content so very little stain leaks out of their walls in organic solvent while the gram negative bacteria has high lipid content which dissolves with the organic solvent and the stain comes out along with it.

Note: Danish bacteriologist Hans Christian Gram developed the gram staining technique in 1884. The procedure involves staining of bacterial smear first with weakly alkaline solution of crystal violet. The blue stained cells are then treated with 5% iodine- KI solution and washed with 95% alcohol or acetone.