User:Anwar29

There is a definite thin cell wall, consisting of a single layer. It is made of a nitrogenous substance chitin resembling carbohydrates. The cell wall becomes gelatinous in some cases and appears-like a sheath or capsule. The sheath holds the cells together to form colonies. On stagnant water surface these colonies appear like scum and this scum-like resting stage in the life cycle of bacteria is known as zooglea stage. The slimy capsule composed largely of polysaccharides outside the cell wall serves as an additional protective layer. The cell wall accounts for 20% of the dry weight of the cell. It gives shape and firmness to the cell. It can resist mechanical and chemical injuries and also the attack by other micro¬organisms. The chemical composition of cell wall is known as 'muco- complex' which consists of proteins, polysaccharides and lipids. However, the cell wall can be dissolved in an enzyme called Iysozyme. The cell wall of certain bacteria shows a characteristic reaction to the stain devised by C. Gram. Those bacteria which retain the stain are known as Gram-positive and those which do not retain the stain are termed Gram- negative. Generally the flagellated bacteria remain covered by a slimy layer whereas; the unflagellated bacteria under certain conditions of growth remain covered by a distinct capsule which is composed of polysaccharides or polypeptides. Just beneath the cell wall there occurs a thin delicate, permeable cell membrane. This membrane surrounds the protoplast which consists of cytoplasm and the nucleus in the form of chromatin body. There is no cytoplasmic streaming in the bacterial cells as it is found in the cells of other higher plants.