BIOS1073 Microbial Cell Structure and Function_LSS PDF

BIOS1073 Microbial Cell structure and Function Dr Loo Shu San Intended Learning Outcomes ILO1 Introduction to Microbiology ILO2 Key facts about Microbes ILO3 Bacterial Cell Structure & Function  What is Microbiology? The Scientific study of microorganisms Study of microbial...

BIOS1073 Microbial Cell structure and Function Dr Loo Shu San Intended Learning Outcomes ILO1 Introduction to Microbiology ILO2 Key facts about Microbes ILO3 Bacterial Cell Structure & Function  What is Microbiology? The Scientific study of microorganisms Study of microbial cells in single culture, in complex environments and their interactions with host organisms Physiology (structure and function) Biochemistry (chemical processes and pathways) Genetics (gene regulation and inheritance)  How is microbe used in the real world? Microbes in Food Microorganisms are used in the production of fermented food and beverages Saccharomyces cerevisiae (bread, beer, wine) Aspergillus oryzae (soy sauce) Lactobacillus sp. (yogurt, cheese) Microbes are an essential part of the food industry Extend the shelf life of food, Improve the flavor, texture, and nutrition of food.  How is microbe used in the real world? Microbes in Medical Microorganisms helps in: Research on diseases Development of treatments, prevention and diagnostics. Microorganisms used in the production of: Antibiotics (Penicilium notatum) Vaccines (Covid-19 virus, Polio virus, Hepatitis virus) Insulin  How is microbe used in the real world? Microbes in Agriculture Microorganisms are used as Biofertilizers and Biopesticides Rhizobium, Bacillus, Azotobacter Rhizobium fixes atmospheric nitrogen (N2) and increases fertility to soil. Bacillus thuringiensis (also known as Bt) produces a toxin that is effective at killing the target insects as an insecticide.  How is microbe used in the real world? Microbes in Industry Microorganisms e.g. Aspergillus niger, Bacillus subtilis Produce important acids, enzymes, pigments Microorganisms e.g. Alcaligenes latus, Cuprivadus necator Produce biodegradable plastics, polyhydroxyalkanoates (PHAs), Microorganisms e.g. Clostridium thermocellum, Nannochloropsis oculata Produce biofuels like biodiesel and bioethanol  How is microbe used in the real world? Microbes in Environment Conservation Microorganisms (e.g. Pseudomonas, Alcanivorax) are able to degrade toxic waste materials like oil, petroleum, plastic, etc and clean up a polluted site - BIOREMEDIATION Microorganisms are used in Water Treatment/Sewage Treatment. Prokaryotes vs Eukaryotes  Prokaryotes vs Eukaryotes Prokaryotes: Eukaryotes: Structurally simple Structurally more complex Found only in single-celled Single celled eukaryotic organisms organisms such as amoeba and Possess nuclear material in fungi nucleoid Multicellular forms such as No membrane bound plants and animals intracellular compartments Possess nuclei (Most) possess rigid cell walls Have membrane bound Placed in the domains of organelles & compartments Archaea and Eubacteria Plant cells have additional vacuoles, chloroplasts and rigid cell walls Prokaryote cells Eukaryote cells (Single celled) Fungi Protozoa Amoeba Yeast Eukaryote cells (Multicellular) Major groups of microbes Week 8  Protozoa Eukaryotic, animal-like protists Greek words “protos” & “zoon” → 1st animal No cell wall or chlorophyll, ingest particulate food Unicellular (e.g. fission, budding) Haploid or diploid Asexual and sexual reproduction (different hosts) Motile (flagella, cilia, amoeboid) Mostly, exist as parasites e.g. Paramecium, Amoeba, Trypanosoma Paramecium Amoeba 1. Nucleus 2. Contractile vacuole 3. Food vacuole 4. Pseudopodium Size: 15 - 750 m Amoeba Engulfs Prey  Trypanosoma Trypanosome Causes fatal African sleeping cell sickness Membrane flap Vector: Tsetse fly Size: About 20 m  Algae Eukaryotic, plant-like protists; contain rigid cell wall (most), chlorophyll; can be multicellular e.g. Euglena, Chlamydomonas, Gonyaulax Chlamydomonas Euglena Green algae Unicellular Unicellular No cell wall Cellulose cell wall Fresh water, a few marine Mainly marine About 15 m 5 - 100 m  Algae Gonyaulax Karenia brevis Have cell wall No cell wall Fresh water, more Marine common in marine Size 20-45 m Size 25-140 m Produce Brevetoxin Produce Saxitoxin Kills large number of fish and other “Red tide” caused by massive sea life growth of saxitoxin-producing Makes shellfish poisonous to Gonyaulax humans and can cause neurotoxic Red tide phenomenon in Malaysia  Fungi Eukaryotic organisms that includes microorganisms such as yeasts, molds, as well mushrooms Range in size from unicellular microscopic forms to large mushrooms & tree bracket fungi  Microscopic Fungi Yeast: Unicellular fungi, a single nucleus Spherical / oval / cylindrical cell shapes Reproduces asexually by budding, or sexually by spore formation Mould: Filamentous fungi, can have multiple nuclei – Hypha (long, branched, threadlike filament of cells); Hyphae (plural) – Mycelium (tangled mass of hyphae) Yeast Saccharomyces  Yeast Candida Cause of human diseases candidiasis or thrush Commonly in skin or mucosal membranes like mouth, gut and genitalia of humans  Mould Aspergillus Penicillium  Difference between Yeast and Mould Characteristics Yeast Mould 1 Habitat Very common, many places Typically found in damp, dark or – e.g. fruits and animals. steam-filled areas. 2 Cell Unicellular (one cell) Multicellular (multiple cells) 3 Shape Round or oval in shape Filamentous fungi, Threadlike 4 Appearance White and thread (mainly Fuzzy appearance; can be orange, colourless) green, black, brown, pink or purple (very colourful) 5 Hyphae No true hyphae but form Have microscopic filaments called multicellular structures hyphae called pseudo-hyphae 6 Types There are 1,500 types of There are 400,000 types of moulds yeasts 7 Reproduction Reproduce mostly asexually Sexually and asexually: reproduce (budding) into multi-cellular form 8 Asexual Spores Blastospore Sporangiospores and Conidia 9 Sexual Spores No Sexual Spores Zygospores, Ascospores and Basidiospores 10 Examples Saccharomyces cerevisiae, Alternaria, Aspergillus, Fusarium, Cryptococcus neoformans Mucor, Penicillium, Rhizopus  Archaea found in extreme environments Thermoacidophiles: Sulphur-rich hot springs; 90°C, pH 1-5 Sulphobus acidocaldarius Irregular cell shape, often lobed Cells attach to sulphur crystals Can be used in microbial mining  Archaea found in extreme environments Extreme thermophiles: Hydrothermal vents; high temperature and pressure Methanococcus jannaschii Isolated from depth of 2,600 m Growth range of 50-86°C Produce methane Biotechnology uses enzymes for high temperature reactions  Archaea found in extreme environments Halophiles: Salt-lakes, salt-mines; require 20-25% NaCl to grow Halobacterium salinarium Grows at 4-5 M NaCl (not below 3 M) Has specialised membrane patches (purple membrane [arrows]) required for generating ATP  Archaea found in extreme environments Methanogens: Strict anaerobes (killed by O2) & produce methane; found in rumen, sewage and human gut Methanobacterium hermoautotrophicum Isolated from deep sediments in lakes Can grow in mineral medium containing only H2 and CO2 as sources of energy  Archaea vs Bacteria Previously known as Archaebacteria Previously known as Eubacteria Archaea Bacteria BASIC SHAPES OF BACTERIA e.g. Staphylococcus sp. e.g. Bacillus sp. e.g. Vibrio sp. e.g. Myxococcus sp. e.g. Streptomyces sp.  e.g. Mycoplasma sp. e.g. Treponema pallidum variable in shape (syphilis) lack a single characteristic form No rigid cell wall  CELL ARRANGEMENT Can be used to aid identification Streptobacillus Form Rod in chain Grow in clumps chain STRUCTURES OF BACTERIAL CELL  Bacterial Cell Wall Peptidoglycan (aka murein) is synthesized inside the cells as dimers and assembled OUTSIDE CM Peptido = amino acids; Glycan- = polysaccharides. PG = polymer of sugar and amino acids Polysaccharide is made up of repeating sugar units linked by glycosidic bonds Polysaccharide chains cross-linked via peptide bridges Cell wall helps maintain cell shape  Bacterial Cell Wall: Peptidoglycan Basic building block is peptidoglycan [NAG] [NAM] (murein) Peptidoglycan is consisting of: 2 sugar dimers: N-acetylglucosamine, NAG N-acetylmuramic acid, NAM Amino acids: L-Alanine and D-Alanine D-Glutamic acid either Lysine or Diaminopimelic acid (DAP) Glycan-Tetra-peptide  GRAM-POSITIVE CELL Teichoic acids (fatty acid polymers) are not found in Gram -ve bacteria – attached to PG, or anchored to CM with a lipid chain and is called Lipoteichoic acids Teichoic acids are highly antigenic and can be used to identify cells by serotype  GRAM-NEGATIVE CELL Peptidoglycan surrounded by second membrane – outer membrane – anchored to PG by lipoproteins – outer leaflet composed of lipopolysaccharide (LPS) LPS highly antigenic; acts as endotoxin Space between two membranes = periplasmic space GRAM STAIN  Examples of Bacteria Gram-negative bacteria Escherichia coli Salmonella typhimurium Agrobacterium tumefaciens Campylobacter jejuni Gram-positive bacteria Bacillus anthracis Spore-formers Clostridium botulinum Staphylococcus aureus Listeria monocytogenes Streptococcus pneumoniae  VEGETATIVE CELL STRUCTURE Vegetative cell =active form for bacterial cells (growing, metabolizing, etc) BACTERIAL ENDOSPORES CYTOPLASMIC MEMBRANE  LIPID BILAYERS Lipids are amphipathic: a hydrophilic region (polar or charged) that interact with aqueous solvent a hydrophobic region that segregate away from aqueous solvent Spontaneously associate to form a lipid bilayer  CYTOPLASMIC MEMBRANE Separates the cytoplasm of unicellular organism from the environment: prevents release of cell components allows uptake of nutrients allows excretion of by-products acts as a “sensor” of the environment  CYTOPLASMIC MEMBRANE Gases enter cell by simple diffusion CO2, & O2 Water tends to move into cell by osmosis i.e. towards the highest solute concentration Cells are usually in a hypotonic environment turgor pressure helps maintain cell shape Pili Short hair-like appendage covering the surface of bacteria For motility Conjugation Colonization and attachment to surfaces/host cells Antigenic – stimulates immune response