Microbial Physiology Lec1 PDF

Microbial Physiology Microbial Physiology Giving a brief introduction to the microbial physiology: Cell Structure and Function Growth Nutrition Metabolism Regulation of gene experision Cell Structure and Function I-Structure and Function of Procaryotic Cell A: Prokary...

Microbial Physiology Microbial Physiology Giving a brief introduction to the microbial physiology: Cell Structure and Function Growth Nutrition Metabolism Regulation of gene experision Cell Structure and Function I-Structure and Function of Procaryotic Cell A: Prokaryotic Cell Surfaces II-Structure and Function of Eucaryotic Cells A-Eukaryotic Cell Surfaces  1-Cilia and flagella They are the most prominent organelles associated with motility. They move the microorganism along. They differ from one another in two ways: - First, cilia are typically only 5 to 20 µm in length, whereas flagella are 100 to 200 µm long. - Second, their patterns of movement are usually distinctive.  2- Cell wall Both eukaryotic and prokaryotic microorganisms are often enclosed within a rigid cell wall. Many algae, as well as oomycetes, contain cellulose (cellulose, a β-1,4-linked polymer) as a major cell wall constituent. The cell walls of many fungi contain chitin, a linear polymer of N-acetyl glucosamine. Most fungi, algae, and higher plants contain microfibrils of either cellulose or chitin as a prominent skeletal component of their cell walls. Production of these microfibrils occurs at or near the surface of the cell. Chemical analysis of yeast walls reveals the presence of 29% β- glycans (both 1,6-β-glycan and 1,3-β-glycan are found), 31% mannan, and 13% protein. Yeast cell walls also contain small percentages of lipids and other materials.  1. Flagella It is a long filament structure made up of a protein of a special type called flagelin. Function: motility and swarming.  2. Fimbriae and pili: Fimbriae and pili are hair-like appendages present on the bacterial cell wall. Fimbriae: are shorter than flagella and consist of the protein fimbrilin. It helps the cell to adhere to surfaces Pili: are found in abundance in the negative bacteria and consist of the protein pilin. Forms the place where bacteriophage is fixed, It also fixes the bacteria themselves in hemagglutination reactions. It involved in the process of bacterial conjugation  3-Slime layer or capsule Capsule: a sticky gelatinous layer surround the bacterial cell mostly composed of complex polysaccharide and in some species amino acids are included in its composition. Importance of the capsule protects bacteria from adverse environmental conditions, especially drought provides resistance against cellular phagocytosis. help the cell adhere to surfaces  4. Cell Wall: The cell wall consists of several layers of polysaccharides, lipids, and some amino acids that together form what is called peptidoglycan. The carbohydrates that enter into its composition are two compounds: the amino sugar N-acetyl glucose amine and the other is N-acetyl muramic acid linked together by beta 1-4 glycosidic bonds. Importance of the cell wall: Cell wall gives cells their external shape and protects them from osmotic pressure. forms the substrate on which bacteriophages can attach. B: Protoplast  1- Cytoplasmic membrane The plasma membrane or bacterial cytoplasmic membrane is composed of a phospholipid bilayer. The phospholipids of bacteria contain ester-linked phospholipids whereas the archaea contain fatty alcohols linked to glycerol via either diether or tetraether bonds. Unlike eukaryotes, bacterial membranes generally do not contain sterols. Function: as a permeability barrier for most molecules as the location for the transport of molecules into the cell as the location for energy conservation  2- Cytoplasm The cytoplasm consists of all of the contents of the cell inside the plasma membrane, which mainly contains: 70S ribosomes and chromatophores in green bacteria, in addition to various inclusions.  3-Ribosomes Ribosomes may be filled the cytoplasmic or loosely attached to the plasma membrane. Ribosomes are made of both protein and ribonucleic acid (RNA). Procaryotic ribosomes are smaller than the cytoplasmic or endoplasmic reticulum-associated ribosomes of eukaryotic cells. Function: They are the site of protein synthesis.  4- Inclusion Bodies Inclusion bodies, granules of organic or inorganic substances, are present in the cytoplasmic matrix. Some inclusion bodies may be: -free in the cytoplasme -enclosed by a shell Many inclusion bodies are used -for storage and also - reduce osmotic pressure.  Stored organic materials a- Glycogen and poly-β-hydroxybutyrate (PHB) inclusion bodies are carbon storage reservoirs providing material for energy and biosynthesis. Many bacteria also store carbon as lipid droplets. b- Cyanobacteria have two distinctive organic inclusion bodies: Cyanophycin granules are composed of large polypeptides. The granules store extra nitrogen for the bacteria. Carboxysomes are polyhedral protein and contain ribulose-1, 5- bisphosphate carboxylase, called Rubisco. Rubisco is the critical enzyme for CO2 fixation. Carboxysomes also may be a site of CO2 fixation. c- Gas vacuoles are present in many photosynthetic bacteria and a few other aquatic prokaryotes. Gas vacuole, provides buoyancy to some aquatic prokaryotes.  Stored inorganic materials: a- Polyphosphate granules Many bacteria store phosphate as polyphosphate granules or volutin granules. Thus volutin granules function as storage reservoirs for phosphate, an important component of cell constituents (e.g. nucleic acids). b- Sulfur granules Photosynthetic bacteria can use hydrogen sulfide and store the resulting sulfur in either the periplasmic space or in special cytoplasmic globules.  5 - Nucleoid The cell's DNA content is occurred in the nuclear region as coiled fine filaments that contains all or most of the genetic material. The nuclear material: *is not surrounded by basic proteins, *is not defined by a nuclear membrane, * does not contain nuclei. Function: carrying genetic material (DNA)  6 - Plasmids: Plasmids are found in gram-positive or gram- negative bacteria. They are double-stranded circular DNA molecules outside the chromosomes, and can replicate independently of the bacterial chromosomes. Different types of plasmids may exist in a single cell. i-Transmissible plasmids ii- Non-transmissible plasmids i-Transmissible plasmids: These plasmids can be transferred from one cell to another. They are large and contain about 12 genes responsible for the formation of sexual cilia and the enzymes necessary for transport. They are found in the cell in small numbers (1-3 units). ii- Non-transmissible plasmids They are small and do not contain transfer genes, They are often found in large numbers 1-60 units in the cell. Plasmids carry genes that code for the following functions and structures: -resistance to antibiotic by many enzymes. -resistance to heavy metals with the help of the enzyme reductase -resistance to ultraviolet light with the presence of modification enzymes (DNA repair -including many enterotoxins (Exogenous Toxins). II-Structure and Function of Eucaryotic Cells A-Eukaryotic Cell Surfaces  1-Cilia and flagella They are the most prominent organelles associated with motility. They move the microorganism along. They differ from one another in two ways: First, cilia are typically only 5 to 20 µm in length, whereas flagella are 100 to 200 µm long. Second, their patterns of movement are usually distinctive.  2- Cell wall Both eukaryotic and prokaryotic microorganisms are often enclosed within a rigid cell wall. Many algae, as well as oomycetes, contain cellulose (cellulose, a β-1,4-linked polymer) as a major cell wall constituent. The cell walls of many fungi contain chitin, a linear polymer of N-acetyl glucosamine. Most fungi, algae, and higher plants contain microfibrils of either cellulose or chitin as a prominent skeletal component of their cell walls. Chemical analysis of yeast walls reveals the presence of 29% β- glycans (both 1,6-β-glycan and 1,3-β-glycan are found), 31% mannan, and 13% protein. Yeast cell walls also contain small percentages of lipids and other materials. B: Protoplast  1- Cytoplasmic membrane (Plasma Membrane) The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols. The membrane also contains membrane proteins, including: -integral proteins that serve as membrane transporters, -peripheral proteins that acting as enzymes to facilitate interaction with the cell's environment. Glycolipids embedded in the outer lipid layer serve a similar purpose (recognition sites for cell–cell interactions). Selectively permeable barrier with transport systems, mediates cell-cell interactions.  2-The cytoplasmic matrix The many organelles of eucaryotic cells lie in the cytoplasmic matrix. It is the “environment” of the organelles and the location of many important biochemical processes. The Eucaryotic Cytoplasmic Matrix and Cytoskeleton  3-The Endoplasmic Reticulum The endoplasmic reticulum (ER) is an irregular network of branching and membranous tubules. The nature of the ER varies with the functional and physiological status of the cell. In cells synthesizing a great deal of protein for purposes such as secretion, a large part of the ER is scattered on its outer surface with ribosomes and is called rough endoplasmic reticulum (RER). Other cells, such as those producing large quantities of lipids, have ER that lacks ribosomes. This is smooth ER (SER). The endoplasmic reticulum has many important functions. it transport proteins, lipids, and other materials  4-The Golgi apparatus The Golgi apparatus is composed of flattened, saclike cisternae stacked on each other. There are usually around 4 to 8 cisternae in a stack. These stacks of cisternae, often called dictyosomes, can be clustered in one region or scattered about the cell. These membranes, like the smooth ER, lack bound ribosomes. There are usually around 4 to 8 cisternae in a stack. A complex network of tubules and vesicles is located at the edges of the cisternae. Function: packages materials and prepares them for secretion. Often participates in the development of cell membranes. The Golgi apparatus  5-Lysosomes They are found in most eukaryotic organisms, including protists, fungi, plants, and animals. Lysosomes are roughly spherical and enclosed in a single membrane. Function: They are involved in intracellular digestion contain the enzymes needed to digest all types of macromolecules.  6- Eucaryotic ribosomes The eucaryotic ribosome is larger than the procaryotic ribosome. Eucaryotic ribosomes can be either associated with the endoplasmic reticulum or free in the cytoplasmic matrix. Function: Both free and ER-bound ribosomes synthesize proteins.  7-Mitochondria Mitochondria usually are cylindrical structures and bounded by two membranes, an outer membrane separated from an inner membrane by intermembrane space. The inner membrane has special enfolding's called cristae (s., crista), which greatly increase its surface area. Enzymes and electron carriers involved in electron transport and oxidative phosphorylation that yield energy in the form of ATP are located only in the inner membrane. The enzymes of the tricarboxylic acid cycle and catabolism of fatty acids are located in the matrix. Mitochondrial Structure  8- Nucleus The nucleus is the most prominent organelle in eukaryotic cells. The nucleus is the storehouse for the cell’s genetic information and is its control center. Nuclear Structure Nuclei are membrane-defined spherical bodies. Chromatin (DNA-containing part of the nucleus) can be seen within the nucleoplasm of the nucleus. In nondividing cells, chromatin is dispersed, but it condenses during cell division to become visible as chromosomes. The nucleus is bounded by the nuclear envelope, a complex structure consisting of inner and outer membranes. Many nuclear pores penetrate the envelope and serve as a transport track between the nucleus and surrounding cytoplasm. Cilia and flagella Cell movement Cell wall Strengthen and give shape to the cell Plasma membrane Mechanical cell boundary, selectively permeable barrier with transport systems, mediates cell-cell interactions and adhesion to surfaces, secretion Cytoplasmic matrix Environment for other organelles, location of many metabolic processes Microfilaments, and microtubules Cell structure and movements, form the cytoskeleton Endoplasmic reticulum Transport of materials, protein and lipid synthesis Ribosomes Protein synthesis Golgi apparatus Packaging and secretion of materials for various purposes, lysosome formation Lysosomes Intracellular digestion Mitochondria Energy production through use of the tricarboxylic acid cycle, electron transport, oxidative phosphorylation, and other pathways vacuole Temporary storage and transport, digestion (food vacuoles), water balance (contractile vacuole) Nucleoid Repository for genetic information, control center for cell Nucleolus Ribosomal RNA synthesis, ribosome construction