LESSON 3

• Glycocalyx


  Also referred as the “sugar coat”. It is a thick layer of slimy, gelatinous material produced by the plasma membrane and secreted outside the cell wall.
• capsule


  is a highly organized layer. it protects the bacteria from phagocytosis.
• slime layer


  unorganized and loose.
• Cell Wall


  Is chemically composed of peptidoglycan (also known as murein) and muramic acid. It primarily provides the overall strength and shape to the cell.
• When the bacterial cell moves from one environment to another or transports in nutrients from its surroundings, water can freely move across both the cell membrane and the cell wall. Because of this, the cell is at risk for an osmotic imbalance, which could put pressure on the relatively weak plasma membrane. In this case, the cell wall also serves as protection from osmotic lysis.
• The two different cell wall types can be identified in the lab by a differential stain known as the Gram stain. Developed in 1884, it’s been in use ever since. Originally, it was not known why the Gram stain allowed for such reliable separation of bacterial into two groups. Once the electron microscope was invented in the 1940s, it was found that the staining difference correlated with differences in the cell walls.
• GRAM POSITIVE CELL WALL


  Composed predominantly of peptidoglycan. has an additional component called teichoic acid, a glycopolymer embedded within the peptidoglycan layers. Teichoic acid contributes to the maintenance of the cell’s shape, particularly in rod-shaped organisms.
• GRAM NEGATIVE CELL WALL


  Contains a smaller percentage of peptidoglycan layer. is made up of two layers: the outer membrane and the periplasmic space.
• Outer membrane


  located outside of the peptidoglycan layers which is composed of a lipid bilayer, very similar in composition to the cell membrane and lipopolysaccharide (LPS), which are anchored into the outer membrane and project from the cell into the environment. It serves as selective permeability barrier and forms the periplasm. It serves to protect bacteria from phagocytes, complement, and antibiotics
• Periplasmic space


  the space located between cell membrane and outer membrane containing substances known as periplasm. It contains enzymes that are utilized by gram negative bacteria. Periplasmic space is also found in gram positive bacteria between the cell membrane and cell wall.
• Plasma/Cell Membrane


  Thin semi-permeable membrane that separates the rigid cell wall from cytoplasm. Being selectively permeable, it controls which substances may enter or leave the cell. It is a phospholipid bilayer embedded with peripheral and integral proteins. It is the site of cellular respiration in bacteria.
• Cytoplasm

  Sticky fluid rich in RNA and bacterial enzymes. It has a complex mixture for all the materials required for metabolic function.
• Ribosome


  Small cytoplasmic particles. It is composed of RNA and proteins. It is the site of protein synthesis.
• Chromosome

  The control center of the bacterial cell.

  It consists of singular strand of DNA molecule which is not surrounded by a nuclear membrane, lacks definite shape and contains little to no protein material. A plasmid is a separate piece of DNA that can be the existence of chromosome. Plasmid can render bacteria drug-resistant.
• Nucleoid


  Nuclear region of bacteria since bacteria has no nucleus. It is made up of strands of DNA molecule.
• Mesosome


  Large invagination of the plasma membrane which is usually seen as cytoplasmic sacs. It provides an increase in membrane surface for enzyme activity involved in respiration and transport.
• Cytoplasmic Inclusions


  Represent accumulated food reserves. Inclusions may appear as volutin granules (from inorganic phosphates), granulose (from polymers of glucose) and sulfur granules. The number of cytoplasmic inclusions depends on the nature of the medium and functional state of the cell.
• Pili


  are used for conjugation (the transfer of DNA from one bacterial cell)
• Fimbriae


  short bristle-like appendages which are made of protein that may cover the cell surface. They allow attachment
• Flagella


  Are thread like protein appendages with a whip-like motion that enables bacteria to move through self-propelling. They originate from the basal body of the cell membrane and project out of the cell wall and capsule. bacteria can also be classified whether flagellated (motile) and non-flagellated (nonmotile) bacteria.
• Flagella arrangements

  Monotrichous, Amphitrichous, Lophotrichous, Peritrichous
• Axial Filaments


  Flagella-like fibrils in the periplasmic space (endoflagella) and are anchored at one end of a cell. These structures are found only in one type of bacteria: SPIROCHETES. enable the bacterial cell to rotate, like a corkscrew.
• Spirochetes


  are groups of motile, slender, helically coiled and flexible gram negative bacteria. They are the only bacteria that contains axial filament, enabling them to swim by flexing and spinning movement.
• Leptospira


  aerobic bacteria with tight regular coils, bent or hooked end. There are two (2) axial fibrils present among these bacteria.
• Treponema


  microaerophilic bacteria with tight regular coils. There are three (3) to eight (8) axial fibrils present among these bacteria.
• Borrelia


  anaerobic bacteria with coarse, irregular coils. There are 15-20 axial fibrils present among these bacteria.
• Endospores


  These are complex multilayered structures usually ovoid and smooth walled. The two genera of bacteria that can form endospores are Bacillus and Clostridium. Bacteria containing this are often referred as “resting cells”. The presence of endospores makes these bacteria resistant to desiccation, heat, chemicals, etc.