Introduction to Microorganisms Lecture 3 PDF

Introduction to microorganisms Lecture 3  Eucaryotic cell structure  A eucaryotic cell has a true nucleus (DNA is enclosed by a nuclear membrane)  It has 10 to 30μm in diameter  It has cell membrane, nucleus, cytoplasm, endoplamic reticulum,...

Introduction to microorganisms Lecture 3  Eucaryotic cell structure  A eucaryotic cell has a true nucleus (DNA is enclosed by a nuclear membrane)  It has 10 to 30μm in diameter  It has cell membrane, nucleus, cytoplasm, endoplamic reticulum, ribosomes, golgi complex, lysosomes and peroxisomes, mitochondria, plastids, cytoskeleton, cell wall. Flagella and cilia.  Cell wall Glycocalyx layer of material containing substantial amounts of sticky carbohydrates  It is an external structures that provide rigidity, shape, and protection  Cell wall is absent In animals, protozoa and Mycoplasma species and in present in plants, algae, fungi and most bacteria.  Algae: Cellulose  Fungi: Polysaccharide (glucan and mannan) and Chitin (a polymer of N- acetylglucosamine (NAG) units  Protozoa : flexible protein: pellicle  The fungal cell wall The overlapping mannan, glucan, chitin, and protein elements are shown. Proteins complexed with the mannan (mannoproteins) extend beyond the cell wall.  Cell Membrane  It is a mosaic composed of large molecules of proteins and phospholipids (sterols that resist lysis from osmotic pressure)  The cell membrane regulates the passage of nutrients, waste products, and secretions into and out of the cell (simple diffusion, facilitated diffusion, osmosis, or active transport. Plasma membrane is responsable for endocytosis (phagocytosis, pinocytosis)  Eukaryotic membranes contain carbohydrates, which serve as attachment sites for bacteria and as receptor sites (cell-cell recognition)  Cytoplasm  Cytoplasm is a semifluid, gelatinous, nutrient matrix (also referred to as the cytosol).  Insoluble granules and a variety of cytoplasmic organelles including the endoplasmic reticulum, ribosomes, Golgi complexes, mitochondria, centrioles, microtubules, lysosomes, and other membrane-bound vacuoles.  The cytoplasm is where most of the cell’s metabolic reactions occur.  Cytoskeleton  The three types of cytoskeletal fibers are 1. Microtubules: are slender, hollow tubules composed of spherical protein subunits called tubulins 2. Microfilaments (actin filaments) 3. Intermediate filaments.  Microtubules and microfilaments are essential for a variety of activities, such as  cell division  contraction  motility  movement of chromosomes within the cell.  Ribosomes  Eucaryotic ribosomes are 18 to 22 nm in diameter.  They consist mainly of ribosomal RNA (rRNA) and protein.  Each eucaryotic ribosome (80S) is composed of two subunits: a large subunit (the 60S subunit) and a small subunit (the 40S subunit) that are produced in the nucleolus  Nucleus The nucleus has three components: nucleoplasm, chromosomes, and a nuclear membrane.  Nuclear envelope: membrane that serves as a “skin” around the nucleus  Nuclear pores allow the nucleus to communicate with the cytoplasm  Nucleoplasm is the gelatinous matrix or base material of the nucleus.  Nucleolus: area near the nucleus where rRNA molecules are manufactured  Eucaryotic chromosomes consist of linear DNA molecules and proteins (histones and non-histone proteins).  The DNA and its associated proteins appear as a threadlike mass called chromatin.  During nuclear division, the chromatin coils into shorter and thicker rodlike bodies called chromosomes  Genes are located along the DNA molecules  The number and composition of chromosomes and the number of genes on each chromosome are characteristic of the particular species of organism.  Endoplasmic Reticulum  The endoplasmic reticulum (ER) are arranged to form a transport network of tubules and flattened sacs within the cytoplasm.  ER has a rough, granular appearance.This rough appearance is due to the many ribosomes attached to the outer surface of the membranes (factory for synthesizing secretory proteins and membrane molecules)  Endoplasmic reticulum to which ribosomes are not attached is called smooth endoplasmic reticulum (SER) (phospholipids synthesis)  Golgi Complex  A Golgi complex, also known as a Golgi apparatus or Golgi body, connects or communicates with the ER.  This stack of flattened, membranous sacs completes the transformation of newly synthesized proteins into mature functional ones and packages them into small, membrane-enclosed vesicles for storage within the cell or export outside the cell (exocytosis or secretion).  Mitochondria and Chloroplast Mitochondria  Mitochondria are about 0.5 to 1 μm in diameter and up to 7 μm in length  Is the energy (ATP) producing organelle  The ATP molecules are the major energy carrying or energy storing molecules within cells  The number of mitochondria in a cell varies greatly depending on the activities required of that cell Chloroplasts: Energy-producing organelle  membrane-bound structures containing various photosynthetic pigments; they are the sites of photosynthesis  Lysosomes and Peroxisomes Lysosomes  They are small (about 1 μm diameter) vesicles that originate at the Golgi complex.  They contain lysozyme and other digestive enzymes that break down foreign material taken into the cell by phagocytosis and may destroy the entire cell by a process called autolysis. Peroxisomes  They are membrane-bound vesicles where hydrogen peroxide is both generated and broken down.  Peroxisomes contain the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide into water and oxygen  Flagella and Cilia Flagella  Thin, motile  Some organism have two more flagella Cilia  Thin, short, coordinated, rhythmic movement  Prokaryotes Eukaryotes Their DNA is found in the cell's nucleus, DNA is not enclosed within a membrane which is separated from the cytoplasm by a nuclear membrane linear chromosome DNA is found in multiple chromosomes DNA is consistently associated with DNA is not associated with histones chromosomal proteins called histones and with nonhistones They have a number of membrane-enclosed They lack membrane-enclosed organelles,including mitochondria, endoplasmic organelles reticulum, Golgi complex, lysosomes, and sometimes chloroplasts Their cell walls almost always contain Their cell walls, when present, are chemically the complex polysaccharide simple peptidoglycan They usually divide by binary fission Cell division usually involves mitosis  REPRODUCTION OF MICRORGANISMS AND THEIR CELLS There are two types of reproduction: Asexual and sexual Asexual:  In asexual reproduction, a single organism is the sole parent: mitotic division. The genomes of the offspring are identical to the parent’s genome  Procaryotic organisms reproduce asexually by a process known as binary fission. Sexual:  In sexual reproduction, two parents give rise to offspring that have unique combinations of genes inherited from both parents (meiosis).  In meiosis, a zygote (fertilized egg) is formed by the fusion of gametes  Prokaryotic cell reproduction  Procaryotic cells reproduce by a process known as binary fission, where one cell (the parent cell) splits in half to become two daughter cells  Generation time: The time it takes for binary fission to occur  Eukaryotic cell reproduction Mitosis  mitosis refers to nuclear division  In mitosis, there is equal division of one nucleus into two genetically identical nuclei.  After mitosis occurs, the cytoplasm divides resulting in two daughter cells. Meiosis  Only diploid cells can undergo meiosis  Meiosis involves two divisions (called meiosis I and meiosis II). The end result is four daughter cells, each of which contains only half as many chromosomes as the parent cell Mitosis Meiosis Diversity and physiology of microorganisms  Acellular Microbes Virions:  range in size from 10 to 300 nm in diameter  They possess either DNA or RNA  They are unable to replicate (multiply) on their own  Unlike cells, they do not divide by binary fission, mitosis, or meiosis  They lack the genes and enzymes necessary for energy production  They depend on the ribosomes, enzymes, and metabolites of the host cell for protein and nucleic acid production The virus encloses: DNA or RNA Capsid Envelop (In some) Viruses are characteristics by: 1. type of genetic material 2. shape of the capsid 3. number of capsomeres 4. size of capsid 5. presence or absence of an envelope 6. type of host 7. type of disease produced 8. target cell 9. immunologic properties Virus replication  Bacteriophages Bacteriophages: viruses that infect bacteria There are three categories of bacteriophages:  Icosahedron bacteriophages  Filamentous bacteriophages  Complex bacteriophages  Oncogenic Viruses  Latent viruses usually does not cause any noticeable symptoms and can last a long period of time before becoming active and causing symptoms.  Animal viruses  Plant Viruses  Viroids consist of short, naked fragments of single-stranded RNA (about 300 to 400 nucleotides in length)  Prions are small infectious proteins that cause fatal neurologic diseases in animals, such as scrapie in sheep and goats; bovine spongiform encephalopathy (mad cow disease).  Unique bacteria Rickettsias and chlamydias  They are bacteria with a Gram-negative-type cell wall.  They are obligate intracellular pathogens that cause diseases in humans and other animals.  To grow such organisms in the laboratory, they must be inoculated into embryonated chicken eggs, laboratory animals, or cell cultures. Mycoplasma  It is the smallest of the cellular microbes  They lack cell walls  They assume many shapes, from coccoid to filamentous Eucaryotic Microbes 2- Protozoa: Protozoan parasites consist of a single "cell-like unit" which is morphologically and functionally complete and can perform all functions of life Protozoa typically lack cell walls.  They have Pellicle, membrane covering that protects the inner part (serves as an osmotic shield). Plasma membrane: has a sticky carbohydrate called glycocalyx on its surface. Glycocalyx is made up of covalently bonded lipids and proteins which anchor the glycocalyx to the cell, giving the cell strength and helping the cell to adhere to other cells Cytoplasm Cytosome (cell mouth) Nucleus Contractile vacuoles Golgi apparatus, microtubules. mitochondria, lysosomes, food vacuoles  Locomotion Protozoa employ a variety of mechanisms of locomotion and may be classified according to these mechanisms of locomotion:  flagellates  ciliates  amoebas  sporozoans  Flagellates The flagellates are protozoa which move by means of flagellar action. Some flagellates have their flagella attached in a structure called an undulating membrane.  Ciliates: Cilia moving  Amoabe Many amoebas employ their pseudopodia to engulf food. Amoebas live in moist terrestrial or aquatic environments.  Sporozoans The sporozoans are parasitic spore formers which do not locomote under their own power. Plasmodium spp., the cause of malaria, are sporozoans.  Reproduction of protozoa and nutrition 1. Asexual multiplication: All protozoa employ asexual methods of replication. (mitotic cell division) (a) Simple binary fission (b) Multiple fission or schizogony 2. Sexual reproduction: Most protozoa also reproduce via a sexual cycle. (a) Conjugation (b) Syngamy  Nutrition: Protozoa require organic materials and require moisture. Holozoic: (engulf their nutrient): they engulf animal debris, plant debris, bacteria, or other protozoa) Holophytic : Photosynthesizers Saprozoic: (or saprophytic):Saprozoic (or saprophytic) protozoa absorb nutrients from the extracellular environment. Obtaining nourishment by absorption of dissolved organic and inorganic materials Amebas engulf particulate food (phagocyte) or droplets through a “mouth” (cytosome), perform digestion and absorption in a food vacuole, and eject the waste substances (cytosome). Pinocytosis is a method of ingesting nutrient materials whereby fluid is drawn through small, temporary openings in the body wall. 3. Fungus  Saprophytic fungi and parasitic fungi  Fungi are a diverse group of eucaryotic organisms that include yeasts, molds, and mushrooms  Their main source of food is dead and decaying organic matter  Fungal cell walls do contain a polysaccharide called chitin  Fungal are unicellular, and others grow as filaments called hyphae  Mycellum (thallus) is a mass of hyphae Fungi can be present as septate and aseptate hyphae  fungal cells can reproduce by budding,hyphal extension, or the formation of spores (sexual and asexual)  Sexual spores are produced by the fusion of two gametes  Some species of fungi produce both asexual and sexual spores.  Classification of fungi into these phyla is based on their mode of sexual reproduction 1. Zygomycotina (bread mold) 2. Chytridiomycotina (water and soil mold) 3. Ascomycotina (Trufffles) 4. Basidiomycotina (terrestial, trees…) 5. Deuteromycotina contains fungi having no mode of sexual reproduction. Yeast:  Yeast are microscopic, eucaryotic, single-celled organisms that lack mycelia  They usually reproduce by budding  Some yeasts produce thick-walled, spore-like structures called chlamydospores  Yeasts are found in soil and water and on the skins of many fruits and vegetables  Yeasts are also a good source of nutrients for humans because they produce many vitamins and proteins  Some yeasts (e.g., Candida albicans and Cryptococcus neoformans) are human pathogens. Budding yeast of Candida albicans Molds:  Mold have commercial importance: Within the Ascomycotina and the Basidiomycotina classes are found many antibiotic- producing molds, such as Penicillium and Cephalosporium  Some molds are used to produce large quantities of enzymes, citric acid, and other organic acids that are used commercially Fleshy Fungi  Mushrooms are a class of true fungi that consist of a network of filaments or strands (the mycelium) that grow in the soil and a fruiting body (the mushroom that rises above the ground) that forms and releases spores  Each spore, much like the seed of a plant, germinates into a new organism Dimorphic Fungi:  A few fungi, including some human pathogens, can live either as yeasts or as molds, depending on growth conditions 4- Heminthes  Helminths are eucaryotic, multicellular animals  They range from 1mm to 1m  They have an external surface which is a protective layer, known as cuticle  They live in a large variety of tissues  Eucaryotic Microbes 1. Algae  All algae cells consist of cytoplasm, a cell wall, cell membrane, a nucleus, plastids, ribosomes, mitochondria, and Golgi bodies  Most algal cell walls contain cellulose, a polysaccharide not found in the cell walls of any other microorganisms  Some have  a pellicle and/or flagella  a stigma (photoreceptive organelle) found in the flagellate  Algae range in size from tiny, unicellular, microscopic organisms, large, multicellular, plant-like seaweeds.  Algae may be arranged in colonies or strands and are found in fresh and salt water, in wet soil, and on wet rocks  Type of Algae  Diatoms are tiny, usually unicellular algae that live in both fresh and sea water. They have silicon dioxide in their cell walls; thus, they have cell walls made of glass  Dinoflagellates are microscopic, unicellular, flagellated, often photosynthetic algae. Like diatoms, they are important members of the phytoplankton, producing much of the oxygen that is in our atmosphere and serving as important links in food chain  Green algae include desmids, Spirogyra, Chlamydomonas,Volvox, and Euglena, all of which can be found in pond water  Type of Algae (Cont’d)  Spirogyra is an example of a filamentous alga, often producing long green strands in pond water.  Chlamydomonas is a unicellular, bi-flagellated alga, containing one chloroplast and a stigma.  Volvox is a multicellular consisting of as many as 60,000 interconnected, bi- flagellated cells, arranged to form a hollow sphere  Euglena contains chloroplasts, is photosynthetic, and stores energy in the form of starch.  Algae are an important source of food, iodine and other minerals, fertilizers, emulsifiers for pudding, and stabilizers for ice cream and salad dressings; they are also used as a gelling agent for jams and nutrient media for bacterial growth. (A) Vaucheria. (B) Diatom. (C) Navicula. (D) Oocystis. (E) Scenedesmus.(F) Spirogyra. (G) Nostoc. (H) Oscillatoria. Prototheca is a genus of algae that cause human infections knows as protothecosis.  Prototheca lives in soil and can enter wounds, especially those located on the feet.  Itproduces a small subcutaneous lesion that can progress to a crusty, warty-looking lesion.  Itcan enter the lymphatic system and causes fatal infection in immunosuppressed individual Algae in several other genera secrete substances (phycotoxins) that are poisonous to humans, fish, and other animals