Structure of Bacteria PDF

Sub: BP303T Pharmaceutical Microbiology Unit I Dr. Biswatrish Sarkar Assistant Professor Department of Pharmaceutical Sciences & Technology Prokaryotic & Eukaryotic cell: Overview  Prokaryotic & Eukaryotic cell: Overv...

Sub: BP303T Pharmaceutical Microbiology Unit I Dr. Biswatrish Sarkar Assistant Professor Department of Pharmaceutical Sciences & Technology Prokaryotic & Eukaryotic cell: Overview  Prokaryotic & Eukaryotic cell: Overview……..continued Prokaryotic cells Eukaryotic Cells 1. DNA not enclosed in membrane, DNA found in nucleus, which is separated from cytoplasm by nuclear membrane, 2. DNA is not associated with histone, other proteins DNA consistently associated with chromosomal are associated with the DNA proteins called histones and with nonhistones 3. Lack membrane enclosed organelles Numerous membrane enclosed organelles e.g 4. Cell wall always contain Cell wall when present are chemically simple 5. Divide by i.e., DNA is copied and Cell division involves , in which chromosomes cells split into 2 cells replicate and an identical set is distributed into each of two nuclei. Size, Shape & Arrangement of Bacterial cells  Size Average bacteria 0.2 - 2.0 µm in diam. and 2-8 µm in length RBC is 7.5 µm in diam. Surface Area (SA) ~12 µm Volume is ~4 µm Surface Area to Volume is 3:1 Typical Eukaryotic Cell SA/Vol is 0.3:1 Food enters through SA, quickly reaches all parts of bacteria Eukaroytes need structures & organelles Fig. Sizes of Bacteria and Viruses. The sizes of selected bacteria relative to the red blood cell and viruses (Source: Microbiology by L. M. Prescott, 5th Edition)  Shape Coccus Chain = Streptococcus Cluster = Staphylococcus Bacillus Chain = Streptobacillus Coccobacillus Vibrio = curved Spirillum Spirochete Square Star Different Coccus Neisseria gonorrhoeae Faecal Streptococci Tetrad: Divide in two planes and remain in groups of four Deinococcus radiodurans Staphylococci: divide in multiple planes and form grapelike clusters or broad sheets Sarcina: Those divide in three planes and remain attached in cube like groups of eight  BACILLI ✓ Bacilli divide across their short axis ✓ Most bacilli appear as single rods ✓ Diplobacilli appear in pairs after division ✓ Streptobacilli appear in chains ✓ Some are oval, a cocci lookalike, hence called as coccobacilli ✓ “Bacillus” has two meanings ▪ bacterial shape ▪ when capitalized and italicized it refers genus Bacillus e.g. Bacillus anthracis ▪ Vibrio ▪ Curved rod like bacteria called as Vibrios. e.g. Vibrio cholerae ▪ Spirillas ▪ Spirillas are Helical shaped, cork screw like bacteria Mostly have a rigid body. ▪ Uses flagella for movement ▪ Spirochetes ▪ Spiral bacteria with a flexible body called as spirochetes ▪ Uses axial filaments for movements  Special Structures Star shaped bacteria Square shaped bacteria e.g genus Stella of genus Haloarcula  STRUCTURE OF BACTERIAL CELL 1. STRUCTURES EXTERNAL TO CELL WALL: ▪ Glycocalyx ▪ Flagella ▪ Axial flaments ▪ Fimbriae & Pili 2. CELL WALL 3. STRUCTURES INTERNAL TO CELL WALL: ▪ Cytoplasm ▪ Nuclear area or ▪ Nucleoid  FLAGELLA Motility - movement Swarming occurs with some bacteria Spread across Petri Dish Proteus species most evident Monotrichous : 1 flagella Lophotrichous : tuft at one end Amphitrichous : both ends Peritrichous : all around Monotrichous Amphitrichous Lopotrichous Peritrichous Movement of Bacteria Ultra structure of Flagella  Pili/ Fimbrae Short protein appendages smaller than flagella Adhere bacteria to surfaces E. coli has numerous types K88, K99, F41, etc. Antibodies will block adherance F-pilus; used in conjugation Exchange of genetic information Fimbriae- occur at the poles of bacterial cell Pili- longer, one or two per cells F-Pilus for Conjugation  Capsule or Slime Layer Thick layer outside cell wall When the layer is well organized and not easily washed off, it is called a capsule. A slime layer is a zone of diffuse, unorganized material that is removed easily Glycocalyx - Polysaccharide on external surface Adhere bacteria to surface S. mutans and enamel of teeth Prevents Phagocytosis Complement can’t penetrate sugars  Cell Wall Rigid structure outside cell membrane Protects from osmotic lysis Peptido-glycan Polymer (amino acids + sugars) Unique to bacteria Sugars: NAG & NAM – N-acetylglucosamine – N-acetymuramic acid D form of Amino acids used not L form – Hard to break down D form Amino acids cross link NAG & NAM Peptidoglycans GRAM POSITIVE & GRAM NEGATIVE CELL WALL Gram’s Staining Method and comparison of cell walls in bacteria  Cell Membrane/ Plasma Membrane Made up of both lipids and proteins Contains high proportion of proteins than eukaryotes Bilayer Phospholipid: lipids are structurally asymmetric with polar and nonpolar ends (amphiphatic) The polar ends interact with water and are hydrophilic the nonpolar hydrophobic ends are insoluble in water and tend to associate with one another (Source: Microbiology by L. M. Prescott, 5th Edition) ▪ Water can penetrate ▪ Flexible ▪ Not strong, ruptures easily ▪ Osmotic Pressure created by cytoplasm  Cytoplasm 80% Water {20% Salts-Proteins} – Osmotic Shock important Thick, aqueous, semi-transparent , elastic Nuclear area contains DNA, ribosomes, mesosomes etc. Plasmids; extra circular DNA – Antibiotic Resistance No organelles (Mitochondria, Golgi, etc.)  NUCLEAR AREA/ NUCLEOID Single. Long, continuous, and circualrly arranged thread of double stranded DNA (Bacterial chromosome) Not surrounded by Nuclear envelope and do not contain Histone Chromosome is attached to plasma membrane Proteins in plasma membrane responsible for DNA replication PLASMIDS: ✓Extrachromosomal genetic elements ✓Not connected to bacterial chromosome ✓ Replicate independently ✓ Contains 5 to 100 genes ✓Responsible for Antibiotic resistance, Tolerance to toxic metals, productions of toxins, synthesis of enzymes  Ribosomes ❑ Protein synthesis takes place within ribosomes ❑ It gives a granular appearance to the cytoplasm ❑ Composed of two subunits, each of which consists of protein and a type of RNA called ribosomal RNA (rRNA) ❑ Prokaryotic ribosomes are called as 70S ribosomes ❑ The letter S refers to Svedberg units (relative rate of sedimentation during ultra-high-speed centrifugation) ❑ The sub-units of a 70S ribosome are a small 30S subunit containing one molecule of rRNA and a larger 50S subunit containing two molecules of rRNA ❑ Ribosomes could be the target of various drugs like Antibiotics  Inclusions Bodies ▪ Metachromatic Granules ▪ Polysaccharide Granules ▪ Lipid Inclusions ▪ Sulfur Granules