Lecture 12 - Bacteria, Archaea and Fungi PDF

Bacteria and Archaea Concepts: 27.1-27.3 Campbell. Biology. 3rd ed. Outline • 1. Structure and function of prokaryote • 2. Genetic diversity in prokaryotes • 3. Nutritional and metabolic adaptation of prokaryote • 4. Bacteria vs Archaea • 5. Role of bacteria to the environment and human health Ge...

Bacteria and Archaea Concepts: 27.1-27.3 Campbell. Biology. 3rd ed. Outline • 1. Structure and function of prokaryote • 2. Genetic diversity in prokaryotes • 3. Nutritional and metabolic adaptation of prokaryote • 4. Bacteria vs Archaea • 5. Role of bacteria to the environment and human health Getty Images. https://www.abc.net.au/radionational/program s/greatmomentsinscience/the-microscopic-high-tech-wizardryof-bacteria/7752152 1. Prokaryote Structure and Function Introduction to Prokaryotes • Fossils of bacteria (prokaryotic cells) - 3.5 billion years old • Fossils of first eukaryotic cells - 1.3 billion years old • Most bacteria 0.5- 5 micrometers in diameter (1 millimeter = 1000 micrometers). Compare to eukaryote cells 10-100 micrometer diameter. • Occur primarily in three forms or shapes: • Cocci = Spherical or elliptical • Bacilli = Rod shaped or cylindrical • Spirilla = Helix or spiral More on Prokaryotes • Capsule = sticky layer of polysaccharide or protein surrounding the cell wall of many prokaryotes • Endospores = a thick-coated resistant cell produced by some bacterial cells when they are exposed to harsh conditions (ie, can withstand boiling water) • Fimbriae = hair like appendages that allow the prokaryote to stick to its substrate or another prokaryote • Pili = hair like appendages that pull two prokaryotes together for conjugation (DNA transfer) • Mechanisms of movement ie, flagella aid in taxis ; chemotaxis is movement in response to chemicals • Reaction of cell walls to dye – Gram-negative – Gram-positive Cell Wall in Bacteria and Archaea Muramic acid (C9H17NO7) is a subunit of the peptidoglycan http://www.learner.org/courses/biology/archive/images/1965_d.html Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acid. It is found in outer side of the plasma membrane of the bacteria. Gram Positive and Gram Negative Gram(+) and Gram(-) Bacteria http://medicalsciences.wordpress.com/tag/gram-staining/ Importance of Gram Staining in Medicine Gram negative • Some lipids in the cell walls are toxic and can cause fever and shock • The outer membrane of these bacteria help protect it from the body's defences • More resistant to antibiotics due to outer membrane compared to gram positive Common features: 1. DNA 2. Plasma membrane 3. Cytoplasm 4. Ribosomes (smaller in Prokaryotes) Prokaryotic cells lack a nucleus and membrane bound organelles such as plastids, mitochondria, vacuole etc http://www.phschool.com/science/biology_place/biocoach/cells/common.html Prokaryote vs Eukaryote Internal Organization and DNA • Folds of plasma and other membranes (of bacteria) perform some of functions of organelles in eukaryotic cells. • Ribosomes present, but about half the size as those of eukaryotic cells. • Nucleoid - Single chromosome in form of ring • 30 or 40 plasmids may be present. • Plasmids - Small circular DNA molecules that replicate independently of chromosome • Entire complement of plasmids consists of multiple copies of one or few different DNA molecules. Section of Procloron celll Nucleoid - Single chromosome in form of ring Plasmids - Small circular DNA molecules that replicate independently of chromosome http://www.shmoop.com/biology-cells/prokaryotic-cells.html 2. Genetic Diversity: Reproduction and Recombination • Mitosis does not occur. Cellular division is binary fission. • Binary Fission: • The two copies of duplicated chromosomes migrate to opposite ends of cell. • Perpendicular walls and cell membranes formed in middle of cell. • The 2 new cells separate and enlarge to original size. Replication of nucleoid Cellular Detail and Reproduction of Bacteria Binary Fission: • May undergo fission every ~ 20 minutes under ideal conditions – Usually exhaust food supplies and accumulate toxic wastes (limitation of fission) New wall growing inward of dividing bacterial cell Cellular Detail and Reproduction of Bacteria Do not produce gametes (n) or zygotes (2n), and do not undergo meiosis Three Forms of Genetic Recombination: • Conjugation – DNA transferred from donor cell to recipient cell usually through pilus (pleural: pili). • Transformation – Living cell acquires DNA fragments released by dead cells. • Transduction – DNA fragments carried from one cell to another by viruses. Conjugation 3. Nutritional and Metabolic Adaptation of Prokaryotes 1) Heterotrophic - Obtain energy from organic or inorganic sources. Mainly saprobes (feed off dead/decaying organic material) 2) Autotrophic - obtain energy from photosynthesis or oxidation • eg. Cyanobacteria and some archaea • some evolve 02; some fix N2 • Nitrogen fixing prokaryotes • Some cyanobacteria and some archaea • Convert atmospheric nitrogen (N2) into ammonia (NH3) through biological fixation • Eg. Rhizobia form symbiotic relationship with some plant species (legumes) and provide nitrogen in exchange for carbohydrates (carbon) • Some prokaryotes have genes that code for both O2 and N2 fixation, however, a single cell can only carry out one or the other • O2 inhibits nitrogenase enzyme necessary for N2 fixation • Cyanobacteria Anabaena forms filamentous chains containing both photosynthetic and nitrogen fixing cells • Heterocyst = a specialized cell that performs nitrogen fixation in some filamentous cyanobacteria 4. Bacteria vs Archaea • Both Bacteria and Archaea are prokaryotic cells • No nuclear envelope, no membrane bound organelles, circular DNA • Bacteria has peptidoglycan in cell wall, Archaea does not • Bacterial growth is inhibited above 100C, Archaea not (in some species) • Some Archaea are Extremophiles (organisms that live in extreme conditions where few species survive) • Extreme Halophiles = highly saline environments (Dead Sea) • Extreme Thermophiles = high heat environments (Volcanic hot springs) 5. Role of Bacteria to the Environment and Human Health Bacteria are Decomposers • Bacteria decompose organic waste to form compost. True bacteria and disease: • Bacteria involved in diseases of plants, animals and humans, and in losses of food Harmful or Disease-Causing Bacteria • Modes of access of disease bacteria: – Access from the air o o – Coughs, sneezes - Saliva droplets contain bacteria. Diphtheria, whooping cough, some meningitis forms, pneumonia, strep throat, tuberculosis Access through contamination of food and drink o Food poisoning and diseases associated with natural disasters « Cholera, dysentery, Staphylococcus and Salmonella food poisoning o Legionnaire disease, Botulism, Escherichia coli Harmful or Disease-Causing Bacteria • Modes of access of disease bacteria: – Access through direct contact - Enter through skin or mucus membranes o Syphilis, Gonorrhea, anthrax, brucellosis – Access through wounds o Tetanus and gas gangrene – Access through bites of insects and other organisms o Bubonic plague, tularemia, rickettsias, mycoplasmas, Lyme disease Bacteria useful to humans • Biological control organisms – Bacillus thuringiensis - Effective against caterpillars and worms o – Multiplies in digestive tract and paralyzes gut Bacillus popilliae - Effective against Japanese beetle grubs • Bioremediation - Use of living organisms in cleanup of toxic waste and pollution Affect of Bacillus thuringiensis on tomato hornworm Bacteria useful to humans • Other useful bacteria – – Human health - Lactobacillus acidophilus o Aids in digestion o Used for elimination of yeast infections o Dairy - Buttermilk, sour cream, yogurt, cheese Industrial - Utilizes bacteria waste products o Solvents, explosives, ascorbic acid (vitamin C), citric acid Fungi Concepts: 31.1-31.5 Campbell. Biology. 3rd ed. Outline • 1. Fungal nutrition, structure and ecology • 2. Life cycles and reproduction • 3. Ancestry, lineage and diversity • 4. Lichens • 5. Human and ecological relevance https://www.sciencenewsforstudents.org/article/secret-forest-fungi-partn r-with-plants-and-help-the-climate 1. Fungal nutrition, structure and ecology • Fungi are eukaryotes (as are protists, plants and animals) • Fungi are heterotrophs (ie, not autotrophs and cannot make their own food) • Many fungi secrete enzymes into their environment which break down complex molecules into smaller organic compounds that can be absorbed • Some fungi are saprobes = feed on dead organic matter • Some fungi are parasites and pathogenic = acquire nutrients from a living host • Some fungi are mutualists = beneficial exchange between two living organisms • Arbuscular mycorrhizal fungi (associate with plant roots) https://www.easybiologyclass.com/kingdom-fungi-general-characteristicskey-points-with-ppt/nutrition-in-fungi-different-types/ Cell walls of fungi • Cell wall of fungi contain chitin, a nitrogen containing polysaccharide • Chitin is also present in the exoskeleton/cuticle of insects and other arthropods • Compare to cell walls of plants and some protists (oomycetes) which contain cellulose a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units FUNGAL BODY • Most common fungal body structures are multicellular filaments and single cells (yeast) • Fungi produce intertwined mass of delicate threads. • Hyphae (singular: hypha) Individual threads • Mycelium - Mass of hyphae • 1 cm3 of soil may contain 1km length of hyphae with a surface area of 300 cm3 Specialized Hyphae in Mycorrhizae • Mycorrhizal fungi have specialized branching hyphae known as arbuscules • Arbuscules are the site of nutrient exchange between the fungus and the plant (N, P, Cu, Zn in exchange for sugars) • Hyphae invade the cortical cells of the plants root (between the plant cell wall and the plasma membrane) and form a highly branched arbuscule • Two types of mycorrhizal fungi • Ectomycorrhizal = hyphae extend over root surface and grow into the intercellular spaces of the root cortex (ie, not inside the cortical cells) • Arbuscular = hyphae penetrate the cell wall and enter cell Mycorrhizae and plants • 70-90% of plants associate with Arbuscular Mycorrhizal Fungi (AMF) • photosynthate (carbon) transferred to fungus; fungus transfers nutrients (N, P, Cu, Zn) to plants • Indirect – AMF increase root surface area which facilitate nutrient compound uptake • Direct – form connections between plants and transfer nutrients across hyphal networks • Not subject to scavenging by soil microbes https://soilquality.org.au/factsheets/arbuscular-mycorrhizas-s-a https://www2.nau.edu/~gaud/bio300/mycorrhizae.htm Howplantswork.com https://www.nature.com/articles/41426/figures/1 • Most fungi reproduce both sexually and asexually • Fungi produce spores for asexual reproduction • 2. Life Cycles and Reproduction Spore is a reproductive cell capable of developing into a new individual • Fungi reproduce sexually through fusion of haploid nuclei • • • • dominant phase of life cycle = haploid mycelia of opposite mating types fuse = diploid zygote zygote produces spores through meiosis spores germinate and produce a new individual Figure 31.5 Generalized life cycle of fungi • Sexual reproduction begins with signaling via pheromones • Plasmogamy = union of the cytoplasm from two parent mycelia • Heterokaryotic stage = haploid nuclei from each parent remain separate despite fused mycelium cytoplasm • Karyogamy = haploid nuclei from both parents fuse to form diploid zygote • Other methods of asexual reproduction in fungi • Many asexual fungi grow as filamentous structures and produce spores by mitosis (ie, the moulds) • Some species reproduce asexually by growing as single celled yeasts • Do not produce spores but instead pinch off "bud cells" from a parent cell • Fungi evolved from a flagellated, single celled, aquatic protist ancestor • Clade Opisthokonts • Fungi, animals and their ancestral protistan relatives 3. Ancestry, lineage and diversity • Fungal-plant relationships developed quickly once plants and fungus both on land • Early land plants lacked root systems • 405 million year old fossils of hyphae within plants cells have structures similar to arbuscules • Molecular studies = "sym" genes in plant lineages for plant/fungal symbiotic relationships Nucleariids = unicellular protists Fungal Diversity • Chytrids = thought to include some of the earliest fungal groups to diverge from other fungi • Zygomycetes = includes decomposers such as the bread molds • Glomeromycetes = the arbuscular mycorrhizae fungi • Ascomycetes = sac fungi; cup shaped fruiting body • Basidiomycetes = includes the ectomycorrhizal fungi and the mushrooms • Scientists who study fungi are Mycologists Chytrids Chytrid zoospore with flagellum • Found in lakes and soil; ~1000 species • Some are decomposers, some parasites of protists, plants, animals and other fungi, some mutualists (live in digestive tracts of ruminants) Zygomycetes • ~1000 species; includes the fast growing molds such Rhizopus stolonifer (black bread mold) • Decomposers whose hyphae spread out over the food surface, penetrate, and absorb nutrients Sporangia Glomeromycetes • ~200 species identified to date • Mutualists with plants • Arbuscular mycorrhizae – tips of hyphae invade plant cells and exchange nutrients through specialized structures known as arbuscules • Mycorrhizae means "fungus roots" • Arbuscule, latin for "tree" owing to the treelike formation observed inside cortical root cells of plants An arbuscule (branched "tree-like hyphae" inside a plant cell Ascomycetes • ~65,000 species; common name is the "sac fungi" • Marine, freshwater and terrestrial habitats • Includes yeasts, morels, truffles, cup fungi • Decomposers • Plant pathogens including ergot and powdery mildew Basidiomycetes • ~30,000 species; common name is "club fungi". • Includes mushrooms, puffballs, shelf fungi • Decomposers, mutualists, plant parasites (rust and smuts) • Sexual: In response to unfavorable environmental conditions, the mycelium produces fruiting bodies called basidiocarps • Common mushroom found in supermarkets are examples of basidiocarps • Once mushroom forms, the cap becomes a protective structure for spores on the mushroom gills. Once mature, spores are released and carried on the wind 4. Lichens • Consist of a fungus and a green alga (or cyanobacterium) intimately associated in a spongy thallus (plant like body lacking distinct parts). • Photosynthetic component supplies food (carbon = algae and cyanobacterium) and/or (nitrogen depending on type of cyanobacterium). • Fungus protects the photosynthetic organism. It retains water and minerals, provides a suitable growing environment and secretes acids which aid in mineral uptake 4. Human and Ecological Relevance • Fungi are decomposers (as are bacteria) • Break down organic material, including plant cellulose and lignans • Breakdown of organic material release nutrients such as nitrogen making them available for plant uptake • Fungi are mutualists (symbiotic/beneficial relationship with host) • Mycorrhizae fungi = associate with plant roots only • Endophytes = live within plant tissues such as leaves, stems, flowers. NOT isolated to roots . • Fungi are parasites (not beneficial to host) • Absorb nutrients from living host but at a cost to the host • Dutch elm disease, ergot on rye, leaf rust on wheat • Practical Uses of Fungi • Food source (mushrooms, truffles, ripening cheeses) • Yeast for fermentation of alcoholic beverages and breads • Medicinal • Antibiotics = Penicillin = ascomycete • Blood pressure medicine = Ergot = ascomycetes Claviceps purpurea • https://www.youtube.com/watch?v=bxABOiay6oA The End • Thank you • Questions? • Have a wonderful day!