Microbial Diversity & Taxonomy PDF

Microbial Diversity & Bacterial Morphology Dr. Asmaa M. El-Nasser Ass. Prof./ Medical Microbiology & Immunology Faculty of Medicine for Girls Al Azhar University 1 Learning outcomes 1- Intro...

Microbial Diversity & Bacterial Morphology Dr. Asmaa M. El-Nasser Ass. Prof./ Medical Microbiology & Immunology Faculty of Medicine for Girls Al Azhar University 1 Learning outcomes 1- Introduction to Microbiology 2- Eukaryotic &Prokaryotic cells 3-Classification &Nomenclature of bacteria 4- Morphology of Bacteria 5- Bacterial structure 2 What is the scope of Microbiology????? 3  Introduction to Microbiology Science dealing with micro-organisms (so small that they cannot be seen without a microscope) Significance of microorganisms in our life: Play fundamental roles in ecosystems everywhere on earth (an ecological balance) Maintain animal & human health Involved in production of food & chemicals, biofuels, medicines, and even foods. Produce disease (pathogenic) 4 Microbes are every where 5  Taxonomy  Taxonomy is the science of classification, description, identification, and naming of living organisms.  A method for classifying microorganisms into groups based on similar morphologic, physiologic, and genetic similarities.  The classification system consists of : Kingdom Family (contains similar genera) Genus (contains similar species) Species 6  Living organisms Classification of Micro-organisms 7 Biological division of cells 8 Biological division of Microorganism Eukaryotic cell Prokaryotic cell There is a nuclear membrane There is NO nuclear membrane There are NO mesosomes There are mesosomes There is MORE than one There is a single chromosome chromosome 80 S ribosome, there are 70S ribosome, there are NO -mitochondria mitochondria They reproduce sexually & They reproduce asexually by asexually simple binary fission. e.g. protozoa – fungi- human e.g. bacteria & Rickettsia cell – animal cell 9  Fungi Are eukaryotes.Have rigid complex carbohydrate cell walls containing Mannan, glucans and chitin Incapable of producing their ownfood ( Heterotrophs) Ergosterol in cytoplasmic membrane Have mitochondria Reproduce by spore formation Flourish in damp environment The majority is saprophytic 10  Fungi Some multicellular fungi, (called molds) made up of long filaments. Molds play a critical role in the decomposition of dead plants and animals. Some molds can cause allergies, and others produce disease-causing metabolites called mycotoxins. Molds have been used to make pharmaceuticals, e.g. penicillin and cyclosporine. Mold has cottony fluffy colonies. Unicellular fungi—yeasts, some have beneficial uses, others can cause diseases. Yeast has creamy colonies 11  virus Viruses are acellular microorganisms (not a true cells) Viruses are small size Viruses are smaller than all infectious agents Viruses have size vary from 10- 300 nm Are inert outside of a host organism. However, by incorporating themselves into a host cell, viruses are able to command the host’s cellular machinery for survival, multiplication and infection of other hosts. 12  virus Consists of proteins and genetic material—either DNA or RNA, but never both— Viruses have no metabolic activity outside susceptible host cells They do not posses any ribosomes or protein synthesis apparatus It can only replicate inside living cells(obligatory intracellular parasite) Viruses are only seen by electron microscope 13  Bacteria Classification &Nomenclature of bacteria: 1- Classification :Arrangement of bacteria into taxonomic groups on basis of similarities or relationships(order-family- genera- species) 2- Nomenclature : Scientific naming of bacteria. Bacteria named binomially By incorporating the genus and the species names. e.g Staphylococcus aureus The genus name The species name 14  Morphology of bacteria Morphological characters includes : - Size.------------µm (1/1000 mm) - Shape. - Staining properties. - Arrangement. - Motility. - Sporulation. - Capsule. - flagellae 15 The relative sizes of various micro-organisms 16 17 18 Bacterial Structure  Bacterial Structure The bacterial cell is composed of the following structures: I. Bacterial cell wall: Peptidoglycan: Gram-positives have a thick layer (50-60 %), while Gram-negatives have a very thin layer (5-10 %); Net- like structure  Gram-positive bacteria : Have teichoic acid or lipoteichoic acid for attachment & highly immunogenic.  Gram-negative bacteria: have an outer membrane covering the peptidoglycan contains the endotoxin lipopolysaccharide (LPS). LPS is highly immunogenic and binds specifically to receptors (LPS receptor, or TLR-4).  Function of the bacterial cell wall 1. Maintains the characteristic shape of bacteria. 2.Supports the cytoplasmic membrane against the high effects of osmotic pressure. 3. Responsible for gram reaction. 4.Play an essential role in cell division 5.Providing attachment sites for bacteriophages 6.Antigenic determinants may be found in cell wall. 7.It is responsible for endotoxin activity of Gram-negative bacteria. 8.They are one of the most important sites for attack by antibiotics. 10/5/2023 Dr.Haneya Anani 21 22  Staining properties of bacteria Gram-staining character of bacteria is dependent on the structure of the cell wall. -Gram positive -Gram negative Gram stain procedure 23  Bacteria with deficient cell wall - Mycoplasma: Pleomorphic penicillin resistant - L form :Environmental conditions - Protoplast - Spheroplast G+ve G-ve Hypertonic medium Antibiotics  Bacterial II. Cytoplasmic membranes: Structure Phospholipid bilayer with embedded proteins. Functions of cytoplasmic membrane : 1.Selective permeability to different molecules 2.Active transport of ions (H+,Na+,K+etc...) and nutrients to achieve osmotic balance and a pool of nutrients. 3.Supplies the cell with energy through electron transport and oxidative phosphorylation ,i.e. site of respiration. 4.Excretion of hydrolytic enzymes which degrade the different nutrients into subunits small enough to penetrate cytoplasmic membrane. 5.Provides enzymes and lipid carriers for cell wall synthesis. 6.Play a role in DNA replication. Cytoplasmic membranes 26  III. Intracytoplasmic Structures 1- The nuclear body: double stranded DNA (Bacterial chromosome) 2- Ribosomes: protein + RNA Bacteria ribosomes: 70S 30S + 50S subunits : protein synthesis. 3- Plasmids : Circular extrachromosomal DNA. 4- Intracytoplasmic inclusions : food reserves. Bacterial Structure IV. Surface structures of the bacterial cell: A-Capsule: -Polysaccharide layer (except poly-d-glutamate on B. anthracis). - Function : Protects against phagocytosis. -By Gram stain : unstained hallow. Stained by special stain. B- Glycocalyx: Polysaccharide lying outside the cell. - Function : Adherence on surfaces. - e.g : S. mutans ( dental caries ) C-Flagellum: - Organ of motility. - Formed of protein flagellin. - Consists of a filament , a hook , basel body. - Anchored to Cytoplasmic membranes. D-Pili ( fimbriae ) - Hair-like projection: shorter + thinner - Formed of Protein pilin. Mainly in Gram-ve. a- Ordinary pili : Adherence of bacteria to cell surface. b- Sex pili : with F + plasmid – transfer of DNA from F+ to F- bacteria ( conjugation ) V. Special structures: Bacterial spores: - Keratin-like coat containing peptidoglycan, DNA. - In Gram positive. - Survival: Resist dehydration, heat, chemicals and freezing. - In response to starvation or unfavorable growth conditions - Killed by autoclave. - Don’t take ordinary stain. - Organisms: Bacillus and Clostridium spp. - Function: survival not reproduction (1 bacterium → 1 spore)- Test your self 1-Which of the following components are found in the cell wall of Gram negative and not found in Gram positive bacteria: A-Cytoplasmic membrane B-Lipopolysaccharide (LPS) C-Peptidoglycan D-Ribosomes 2-As regard flagellum, which of the following is true: A-Help in adherence B-Lipopolysaccharide in nature C-organ of motility D-Found in all bacteria 3-Name: Bacterial surface structure, protects bacteria against phagocytosis (..) 32 References: 1. Bailey & Scott’s: Diagnostic Microbiology, 15 th edition. 2022 2. Warren L. : Review of Medical Microbiology & Immunology, 14th edition 2016, McGraw Hill Education, P 4. 3. Richard A. , Cynthia N. and Bruce D. : Lippincott’s Illustrated Reviews Microbiology, 3rd edition, 2018, Wolters Kluwer, P 49.