Microbiology Lecture 1: Morphology and Structure of Microorganisms PDF

LEC 1 Microbiology Morphology and -Structure of Microorganism Dr Ausama Ahmed  Morphology and -Structure of Microorganism Microbiology: is of biological sciences deal with microorganisms, it study organisms that is too small to be seen without magnification....

LEC 1 Microbiology Morphology and -Structure of Microorganism Dr Ausama Ahmed  Morphology and -Structure of Microorganism Microbiology: is of biological sciences deal with microorganisms, it study organisms that is too small to be seen without magnification. Micro - too small to be seen with the naked eye Bio – life logy - study of Microorganisms include bacteria /viruses /fungi /Parasite {protozoa and helminthes (worms) } /algae  Cell Theory The cell theory states that: All living things are made of one or more cells. and are the basic unit of structure and function in living things. All cells come from other cells. Cell Types There are several classes of living organisms Living organisms can be classified into two main types of cells based on their cellular structures: 1. Cell that have membrane-bound organelles Called Eukaryotic Cells 2. Cells that do not have membrane-bound organelles called prokaryotic cells 1. 1. Eukaryotic Cells: Structure: Eukaryotic cells are generally larger and more complex in structure than prokaryotic cells. Membrane-Bound Organelles: Eukaryotic cells have various membrane-bound organelles, including a well-defined nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and more. Nucleus: Eukaryotic cells have a true nucleus enclosed by a double membrane. (nuclear membrane) This nucleus contains chromosomes with DNA. Cytosol: Eukaryotic cells have a semi-fluid substance called cytosol that surrounds the organelles within the cell. Plasma Membrane: Like prokaryotic cells, eukaryotic cells have a plasma membrane that controls the movement of substances in and out of the cell. Ribosomes: Eukaryotic cells contain ribosomes involved in protein synthesis, which are larger and structurally more complex than prokaryotic ribosomes. Organisms: Eukaryotic organisms include a wide range of life forms, including animals, plants, fungi, protozoa, and algae. They can be unicellular or multicellular  Prokaryotic Cells: Structure: Prokaryotic cells are relatively small and simple in structure. Membrane-Bound Organelles: Prokaryotic cells lack membrane-bound organelles such as a nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus. Nucleoid: Prokaryotic cells have a nucleoid region where the DNA is concentrated, but it is not enclosed by a nuclear membrane. Plasma Membrane: All prokaryotic cells are surrounded by a plasma membrane that regulates the passage of substances in and out of the cell. Ribosomes: Ribosomes in prokaryotic cells are smaller and structurally different from those in eukaryotic cells. They are involved in protein synthesis. Organisms: Prokaryotes are predominantly unicellular organisms and include bacteria and blue-green algae  Similarities between Prokaryotic and Eukaryotic Cells: Plasma Membrane: Both types of cells have a plasma membrane that encloses the cell and regulates the passage of materials. Chromosomes: Both prokaryotic and eukaryotic cells contain chromosomes made of DNA that carry genetic information. Ribosomes: Ribosomes, responsible for protein synthesis, are found in both prokaryotic and eukaryotic cells.  On other hand the main difference between prokaryotic and eukaryotic cells is that, Prokaryotic cells are smaller, simpler, lack membrane-bound organelles, and have their DNA concentrated in the nucleoid. While Eukaryotic cells are larger, more complex, possess various membrane-bound organelles, and have a well- defined nucleus  Bacteria Are a type of prokaryotic microorganisms, Bacteria can be classified based on their shape into six basic groups: Cocci: Cocci are round or oval-shaped bacteria. They can exist as single cells, in pairs (diplococci), in chains (streptococci), or in clusters (staphylococci). Bacilli: Bacilli are rod-shaped bacteria. Spirochetes: Spirochetes are spiral-shaped bacteria with a flexible spiral structure. Spirilla – rigid spiral forms vibrios, which are comma-shaped bacteria,  It is important to note that the shape of a bacterium is determined by its rigid cell wall, which provides structural support. In bacteriology, the unit of measurement is the micron (µm), also known as a micrometer. Bacteria of medical importance typically range from 0.2 to 1.5 µm in diameter and 3 to 5 µm in length, though some may differ from these averages. the smallest bacteria, such as Mycoplasma, can be even smaller, while the longest bacteria rods can have sizes similar to some yeasts and human red blood cell Anatomy of Bacterial Cell: 1. Outer layer - two components: A. Rigid cell wall B. Cell membrane or Plasma membrane present beneath cell wall A. Rigid Cell Wall: The outermost layer surrounding the bacterial cell that provides shape and rigidity. It is composed of Mucopeptide (peptidoglycan/ murein) which is responsible for the cell wall's rigidity and shape determination. Peptidoglycan is formed by chains of N- acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) held together by peptide bonds. The cell wall carries bacterial antigens important for virulence and immunity. The chemical nature of the cell wall helps classify bacteria into two broad groups - Gram-positive and Gram-negative. Several antibiotics may interfere with cell wall synthesis e.g. Penicillin, Cephalosporins  Gram-positive Cell Wall: Composed of a thick, multilayered peptidoglycan sheath outside the cytoplasmic membrane. Teichoic acids are linked to and embedded in the peptidoglycan, and lipoteichoic acids extend into the cytoplasmic membrane  Gram-negative Cell Wall: Composed of an outer membrane linked to thin single-layered peptidoglycan by lipoproteins. The peptidoglycan is located within the periplasmic space between the outer and inner membranes. The outer membrane includes porins that allow the passage of small hydrophilic molecules and lipopolysaccharide (LPS) molecules that extend into the extracellular space B. Cell Membrane or Plasma Membrane: A thin layer (5-10 nm) present beneath the cell wall that acts as a semi-permeable membrane, controlling the inflow and outflow of metabolites. It is composed of lipoproteins with small amounts of carbohydrates. 2. Cytoplasm: is semi-fluid substance inside the cell membrane where various cellular processes occur. It contains the bacterial chromosome, ribosomes, and other molecules. A Ribosomes: Cellular structures made up of RNA and protein, serving as the site of protein synthesis. B Mesosomes: play a role as principal sites of respiratory enzymes and coordinate nuclear and cytoplasmic division during binary fission. More prominent in Gram-positive bacteria. C Intra-cytoplasmic Inclusions: Some bacterial species produce cytoplasmic inclusion bodies appearing as round granules, such as metachromatic granules in diphtheria bacilli. These inclusions serve as reserves of energy and phosphate for cell metabolism and are composed of either glycogen or starch. They appear reddish when stained with certain dyes. D Nucleus: Bacterial cells lack a true nucleus. The genome consists of a single, circular double- stranded DNA chromosome located in the nucleoid region. The chromosome divides by binary fission during cell division. 3 Additional structures - plasmid, slime layer, capsule, flagella, fimbriae (pili) and spores A plasmid is a small, circular piece of DNA in a bacterial cell that is separate from the main chromosomal DNA. It can carry specific genes that provide advantages to the bacterium, such as antibiotic resistance, and can be transferred between bacterial cells during processes like conjugation. Plasmids are not essential for the basic life functions of the cell but contribute to its adaptability and survival in various environments..  B Capsule /Slime Layer: Viscous layers secreted around the cell wall. The capsule is a well defined, antigenic structure that protects bacteria from lytic enzymes and inhibits phagocytosis. Capsules can be demonstrated using the Quellung reaction The slime layer is loosely associated with the bacterium and can be easily washed off.. whereas a capsule is attached tightly to the bacterium and has definite boundaries C Flagella: Long filamentous surface appendages serving as organs of locomotion. They are composed of proteins called flagellins and are useful in identifying and classifying bacteria Flagella may serve as antigenic determinants (e.g. the H antigens of flagella in Gram-negative enteric bacteria) D Fimbriae/ Pili: Thin, hair-like appendages on the surface of many Gram-negative bacteria. They act as organs of adhesion, allowing bacteria to colonize surfaces or cells and resist flushing. Pili can be of two types: common pili (short and abundant) and sex pili (long and few), which are involved in the process of DNA transfer during conjugation. Pili made up of proteins called pilins. E spores: Highly resistant resting stages formed by certain bacteria during adverse conditions, such as nutrient depletion. Endospores are formed inside the parent cell and are very resistant to heat, radiation, and drying, enabling them to remain dormant for extended periods. They are formed by bacteria like Clostridium and Bacillus