Bacterial Morphology, Growth & Physiology Lecture 1 PDF

General Microbiology & Immunology SMS233z BACTERIAL MORPHOLOGY, GROWTH AND PHYSIOLOGY Prof. Zeinab Abd Elkhalek Ibraheim Prof. of Microbiology & Immunology MSA University LECTURE OUTLINE INTRODUCTION TO MICROORGANISM...

General Microbiology & Immunology SMS233z BACTERIAL MORPHOLOGY, GROWTH AND PHYSIOLOGY Prof. Zeinab Abd Elkhalek Ibraheim Prof. of Microbiology & Immunology MSA University LECTURE OUTLINE INTRODUCTION TO MICROORGANISMS BACTERIA STRUCTURE AND ORGANIZATION BACTERIAL ULTRA-STRUCTURES AND FUNCTIONS BACTERIAL GROWTH AND PHYSIOLOGY LECTURE ILOs Describe bacterial morphology and physiology Understand bacterial morphology. INTRODUCTION TO MICROORGANISMS Microorganisms are generally unicellular i. e. the whole organism is one cell. A single microbial cell performs all the functions required to maintain itself and propagate. Microorganisms may be classified in the following large biological groups: 1.Algae 2. Protozoa..Slime molds.3 4. Fungi..Bacteria.5 BACTERIA STRUCTURE AND ORGANIZATION Bacteria are differentiated into major categories, based on their morphological features such as shape, size, arrangement and staining characteristics. G+ve cocci & G-ve bacilli Gram-stained Gram-stained BACTERIAL ULTRA-STRUCTURES AND FUNCTIONS Functions of the cell wall: 1.It maintains the characteristic shape of the bacterium. 2.It supports the weak cytoplasmic membrane against the high internal osmotic pressure of the protoplasm. 3.It plays an important role in cell division. 4.It is responsible for the staining affinity of the organism.  Wall deficient variants 1- Mycoplasma: It is group of bacteria that exists naturally without cell wall. Accordingly, Mycoplasmas; Do not assume a defined shape Do not stained by Gram stain Naturally resistant to cell wall inhibitors ,e. g. penicillins 2- L. Forms: They are wall deficient bacteria. “L” forms may develop from cells that normally possess cell wall, when they are exposed to hydrolysis by lysozyme or by blocking peptidoglycan biosynthesis with antibiotics, such as penicillin. Some L. forms resynthesize their walls once the inducing stimulus is removed. their reversion to the walled state can produce relapses of the overt infection.  Cytoplasmic Membrane It is a phospholipid protein bilayer similar to that of eukaryotic cells except that, in bacteria, it lacks sterols. Functions: 1. Selective transport: molecules move across the CM by simple diffusion, facilitated diffusion and active transport. 2. Excretion of extracellular enzymes: Hydrolytic enzymes; which digest large food molecules Enzymes used to destroy harmful chemicals, such as antibiotics. 3. Respiration: The respiratory enzymes are located in the CM 4. Reproduction: Specific protein in the CM attaches to the DNA and separates the duplicated chromosomes from each other. In addition, a septum is formed by the CM to separate the cytoplasm of the two daughter cells. 5. Chemotactic system: Attractants and repellants bind to specific receptors in the cytoplasmic membrane and send signals to the cell’s interior.  CYTOPLASM The CYTOPLASM is the TOTAL OF EVERYTHING INSIDE of the cytoplasmic membrane. It has a gel-like consistency, but small molecules can move through it rapidly;. The following components are in the cytoplasm. Proteins, mostly #enzymes.. Proteins vary in size from 8,000 molecular weight to >1,000,000 #RIBOSOMES are composed of RNA and protein and are the FACTORIES upon which the proteins are made. Several STORAGE GRANULES may be present in a cell e. g. STARCH, FAT, SULFUR, or PHOSPHATE. Bacteria exist in a very competitive environment where nutrients are usually in Short supply, so they tend to store up extra nutrients when possible PLASMIDS are small circular, self replicable DNA molecules that can be thought of as carrying EXTRA GENES that can be used for special situations. Each cell contains a large CIRCULAR GENOME composed of f #DNA. This is referred to as the CHROMOSOME of a cell. This chromosome contains the basic genetic information needed by the cell to survive and produce daughter cells. Each cell contains NUTRIENTS it has imported in from the outside, or made inside, and all the chemical intermediates the cell required to make new structures. In addition, cells contain waste materials that are subsequently excreted.  FLAGELLA Flagella are long, rigid protein rods that provide movement to many motile bacteria. They are made of protein called Flagelline, which is highly antigenic. The number and arrangement of flagella on a cell is part of its genetic Monotrichous Lophotrichous Peritrichous  Axial filaments These structures are composed of two groups of fibers. Spirochaetes move by means of these axial filaments. When the cell moves, it rotates around its longitudinal axis and flexes and bends along its length.  PILI Pili are relatively short, HOLLOW PROTEIN RODS that are important in binding the cell to solid surfaces. Because of this characteristic pili are very important in pathogens. Pili are important in producing biofilms, which are the slimy layers covering your teeth “dental plaque” SEX PILI are longer (than the adhesion-pili), hollow protein rods that are involved in the TRANSFER OF GENETIC MATERIAL from one cell to another. Cells which carry the genes for having sex pili are said to be MALE or F+ cells. The process of DNA transfer is called conjugation  Capsule and related structures The most exterior components of bacterial cells are the CAPSULE and SLIME layers. They are usually composed of sugar polymers that are excreted by the cell. The term capsule usually applies to a DEFINED layer with a distinct outer edge, whereas a slime layer describes an ILL DEFINED concentration of polymeric material. Capsule production is usually occur in vivo. Functions of capsule: It protects the cell from DRYIN It serves as an extra source of NUTRITION. in times of need It helps the cells STICK or attach to things because of its sticky (adhesive) nature e.g. S. mutans It PROTECTS the cell from phagocytosis. It may be TOXIC or inhibitory to a host's defense system and so aid in the disease process. Bacterial capsule  Bacterial Spores Spores are much more resistant to disinfectants, drying and heating. Moist heat at 121°C for 10-20 minutes is needed to kill spores. The marked resistance of the spores has been attributed to: 1.Thermal resistance is provided by their high content of Ca2+ and dipicolinic acid (unique to endospores). 2.The impermeability of their cortex and outer coat. 3.Their low content of water. 4.Their very low metabolic and enzymatic activity Bacterial spores BACTERIAL GROWTH AND PHYSIOLOGY Definitions: Bacterial growth: increase in the size and number of organisms. It is indicated by: - Colonies on solid media. - Turbidity of the fluid media. Generation time (doubling time): is the time between two successive divisions. It may be as short as 13min. in V. cholerae and may reach 24 h. in M. tuberculosis.  Growth Requirements: these are essential factors needed for bacterial growth; they are: 1. Nutrients. 2. Oxygen (O2). 3. Respiration and energy production. 4. Carbon dioxide (CO2). 5. Hydrogen ion concentration (pH). 6. Temperature.  1. Nutrients: bacteria can be classified according to the way by which they can obtain energy and raw material into: Bacteria Autotrophs Heterotrphs Can’t use simple inorganic Can use simple inorganic material as a source of Carbon material as a source of Carbon but need complex organic and form their own organic compounds from it materials to form their own organic compounds from it. Phototrophs Chemotrophs Chemical compounds is the Light is the source of energy source of energy 2. Oxygen (O2): According to O2 requirements, bacteria are classified into: 3. Respiration and energy production: N.B.: - Aerobic respiration results in the production of energy in the form of 38 ATP molecules. - In aerobic respiration superoxide (O2‑) radicals and hydrogen peroxide (H2O2) are formed (highly toxic molecules and detoxified by two superoxide dismutase and catalase enzymes in aerobes). - Anaerobic respiration results in the production of energy in the form of 17 ATP molecules. - Obligate anaerobes lack superoxide dismutase and catalase and so they can not grow in presence of O2. - Fermentation results in the production of energy in the form of 2 ATP molecules. Fermentation is used by facultative anaerobes in presence of unsuitable inorganic final electron acceptor. -Aerotolerant organisms contain only superoxide dismutase enzyme. - Microaerophilic organisms contain superoxide dismutase and catalase enzymes but in low concentration so they can use O2 in a low concentration. 4. Carbon dioxide (CO2): -The minute amount of CO2 present in air is sufficient for most bacteria. - Certain species require higher concentrations (5 ‑10%) Of CO2 for growth (capnophilic) e.g. Neisseria. 5. Hydrogen ion concentration (pH): - Most microorganisms of clinical significance grow best pH close to that of human body. - Alkaliphilic microorganisms: grow better at an alkaline pH (8‑9), e.g. V. cholerae. - Acidophilic microorganisms: grow better at an acidic pH (4 or less), e.g. Lactobacilli. 6. Temperature: - Mesophiles: are organisms able to grow within a temperature range of 20 – 40 ˚C with an optimum temperature of 37 ˚C, e.g. most of human pathogens. - Psychrophiles: (cold‑loving) are capable of growth at refrigeration temperature (0 ‑ 8 ˚C), e.g. Flavobacterium. - Thermophiles: (heat‑loving) grow best at high temperature (>60 ˚C),e.g. B. stearothermophilus. WTH‑PHASES (BACTERIAL GROWTH CURVE):  Bacterial growth phases No. of viable Causes of events of the phase organisms Lag Constant at initial - Adaptation to new environment number - Formation of new enzymes and phase intermediates Exponential Markedly increase -High replication rate (Rr) in a Phase short time Stationary Constant at a high - Replication rate (Rr) = Death rate phase level (Dr) due to beginning of: * exhaustion of nutrients and O2 * accumulation of Metabolites Decline Markedly reduced - Dr markedly > Rr due to massive: phase * exhaustion of nutrients and O2 * accumulation of Metabolites * Release of lytic enzymes from dead organisms