6. Cell wall - Peptidoglycan layer Gram –Negative bacteria

7. H ö ltje 1998 Peptidoglycan: PBP activities endopeptidase DD-carboxypeptidase D-Ala

8. Peptidoglycan -Gram Positive bacteria

9. Lipopolysaccharide (endotoxin) in Gram–negative bacteria Lane 1 marker Lane 2 O-antigen positive E. coli strain Lane 3 O-antigen negative E. coli strain Backbone composed of alternating pyrophosphate units (POP), linked to glucosamine (G) and it is flanked outward by repeating units of polysaccharides (O-antigen) and inward by long chain fatty acids (Lipid A)

15. Nuclear region or nucleoid: Nucleoid is centrally located, contains DNA, RNA and proteins associated with it. Most of the bacterium contains one circular chromosome (except V. cholerae , which has two). Manipulation of the microbial genome/ chromosomes is the most important tool in any biotechnology industry. Internal membrane systems: Photosynthetic and cyanobacteria contain internal membrane system (chromometaphore), which has membranes derived from cell membrane (CM) and pigments (helps to capture lights). Nitrifying bacteria, soil organisms those convert nitrogen compounds into forms usable by green plants, also have internal membranes. They house enzymes and those are used in deriving energy from oxidation of nitrogen compounds.

16. Inclusion bodies: Bacteria can have within their cytoplasm a variety of small bodies collectively referred to as inclusion bodies. Some are called granules and other are called vesicles. Granules: Densely compacted substances without a membrane covering. Each granule contains specific substances, such as glycogen (glucose polymer) and polyphosphate (phosphate polymer, supplies energy to metabolic processes). Sulfur bacteria contains reserve granules of sulfur. Polyphosphate granules are called volutin or metachromic granules, because they display metachromasia (metachromic granules exhibit different intensities of color). These granules are depleted in starvation. Vesicles: Certain bacteria have specialized membrane enclosed structures called vesicles (or vacuoles). Some aquatic photosynthetic bacteria and cyanobacteria have rigid gas-filled vacuoles and it helps in floating at a certain level. Some magnetotactic bacterium, eg. Aquaspirillium magnetotacticum , stores Magnetitite (Ferric oxide). The presence of such magnetic inclusions enables these bacteria to responds to magnetic fields.

18. Polar monotrichous Pseudomonas Polar amphitrichous Spirillium Lophotrichous Spirillum Peritrichous Salmonella Flagella: SEM of peritrichous strain Proteous Note: bacteria without flagella are called atrichous.

19. In Gram-negative Bacteria

21. In Gram-positive Bacteria