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Microbiology • Antonie van Leeuwenhoek (1632-1723) improved early microscope – Dutch lens maker and scientist – First to view microscopic organisms in drop of water • Spontaneous generation: the idea that living organisms can come from non-living things • Microbiology: the study of microorganisms like viruses, bacteria, archaea, protists, & some fungi • Disease causing microbes are called pathogens. Louis Pasteur • In 1859, Pasteur devised experiment to refute spontaneous generation • In 1884, he proposed the idea of viruses causing disease • Developed some of the first vaccines for rabies • Responsible for pasteurization process Chapter 16: Microbiology • Bacteria and fungi are decomposers – Break down organic & inorganic materials – Some can be used to clean environment (oil spills) • Both bacteria & archaea are prokaryotes • Bacteria have three shapes: rod (bacillus), spherical (coccus), & spiral (spirilli) Anatomy of a Prokaryotic Cell Biology of Bacteria • All have plasma membrane (lipid bilayer) • Most have a cell wall – Contains carbohydrate peptidoglycan • Gram stain is a common test used to identify bacteria – Gram-positive bacteria have cell walls with thick peptidoglycan layer & stain purple – Gram-negative bacteria have thin or lacking peptidoglycan layer & stain pink • Gram-negative bacteria have an outer membrane that contains lipopolysaccharides (LPS) – Released when bacterium is killed by immune system – Triggers inflammation & fever • Some bacteria have a slimy polysaccharide layer called capsule – Protect cell from dehydration & immune system Biology of Bacteria • Motile bacteria have flagella (NEVER cilia) • Fimbriae that bind to specific surface receptors of cells • Most have single circular chromosome located in nucleoid region • Some bacteria form endospores – Thick-walled, dehydrated structures – Capable of surviving extremely harsh conditions – Not for reproduction Bacterial Reproduction • Bacteria can reproduce asexually via binary fission • Each daughter cell is a clone of parent cell • Cell divides with each cell getting a copy of DNA & about half of cytoplasm Bacterial Reproduction • 1. 2. Sexual reproduction does not occur, but there are three forms of genetic recombination: Conjugation= male cell passes DNA to female cell via a sex pilus Transformation= occurs when bacterium takes up DNA released into environment by dead bacteria 3. Transduction= viruses carrying portions of bacterial DNA from one bacterium to another Bacterial Metabolism • Most bacteria are heterotrophic and must gain nutrients from consuming other organisms • Some are chemoautotrophs – Reduce carbon dioxide to organic compound • Cyanobacteria are capable of photosynthesis Bacterial Diseases in Humans • Streptococcus infections – Cause more disease than any other type of bacterium – Streptococcus pneumoniae causes pneumonia, meningitic, & middle ear infections – Streptococcus mutans cause teeth decay – Streptococcus pyogenes cause mild to severe skin diseases • Tuberculosis – One of leading worldwide causes of death due to infectious disease – Caused by Mycobacterium tuberculosis – Usually infects lungs, but can be found in other areas – Lesions produce tubercles that cause lung tissue to harden – Infects many people who are also infected with HIV Bacterial Diseases in Humans • Food Poisoning – – – – – Can cause infection once they enter intestine Or can produce toxins while they are growing in food Salmonella causes gastroenteritis after introduced in intestines Staphylococcus produce toxins in food Clostridium botulinum produce endospores that survive canning process (possibly most toxic substance on Earth) • Chlamydia Infections – Can cause blindness – Also one of most common sexually transmitted diseases in US – Can cause life-threatening pelvic inflammatory disease (PID) • Antibiotics kill or reduce bacteria by inhibiting protein synthesis or bacterial cell wall biosynthesis Biology of Archaea • More closely related to eukarya than to bacteria • Survive in harsh conditions that are similar to early Earth – Thermoacidophiles= high temperature, low pH like hot springs – Methanogens= anaerobic environments like swamps & animal guts – Halophiles= salty environments such as great salt lakes • Plasma membrane is made up of a monolayer of lipids which helps them resist acid & heat • Cows have large populations of methanogens in digestive tract – Release large amounts of methane gas into environment – Methane gas is a greenhouse gas which contributes to global warming Protists • • • • • • • • • Domain Eukarya, kingdom Protista All are eukaryotic, mostly unicellular, microscopic Capable of sexual or asexual reproduction Algae can be unicellular, colonial, filamentous or multicellular Phytoplankton are small, aquatic algae that are photosynthetic Algae may aquatic (marine or freshwater) or terrestrial (soil, rocks, on trees) Algae have chloroplasts that contain chlorophyll & sometimes other pigments Have rigid cell walls made of cellulose Pyrenoids are organelles that store starch in algae Types of Algae • Green algae • Characteristics that support close relation to plants 1. Both have cellulose in cell wall 2. Chlorophylls a & b 3. Storage of reserve food as starch in chloroplast • Volvox Examples: Volvox, Chlamydomonas, Spirogyra Spirogyra Types of Algae cont. • Diatoms – – – – Marine & freshwater Contain brown pigment Have shells made of silica Fossilized remains form diatomaceous earth • Dinoflagellates – Cause red tide & may produce potent toxin – Members of phytoplankton in marine & freshwater – Have protective cellulose plates encrusted with silica – Have 2 flagella that provide whirling motion – Symbiont with coral – May be bioluminescent Types of Algae cont. • Red algae – Mostly multicellular – Contain chlorophyll, red & blue pigments – Some have calcium carbonate in cell wall & help form coral – Produce useful gelling agents • Agar • Carageenan • Porphyra is used as a sushi wrap in Japan Porphyra Types of Algae cont. • Brown algae – Multicellular seaweeds – Contain accessory pigments that range from pale beige to yellow-brown to almost black – Allow absorption of sunlight at deeper depths of ocean – Produces slimy matrix that retains water when tide is out – Algin is used in ice cream, cream cheese, cosmetics – Kelps have blades, stipes, holdfasts similar to leaves, stems, roots of plants Euglena • Freshwater, unicellular organisms • Many have chloroplasts, but some do not • Autotrophic or heterotrophic • Have 2 flagella • Have an eyespot that is photoreceptor for detecting light The Animal-like Protists • Protozoans – Motile, eukaryotic, unicellular – Heterotrophic by ingestion – Grouped according to mode of locomotion • Some are nonmotile • Some move by flagella, cilia, pseudopodia – – – – Distributed in a variety of habitats May have more than one nucleus Contractile vacuoles control osmoregulation Produce cysts that protect them from harsh environements • Promote dispersal to better areas • Have thick cell walls & low metabolic rates • Zooplankton – Found in aquatic environments – Microscopic, suspended organisms that feed on other organisms Ciliates • Largest group of protozoans • All have cilia – Help capture prey – Used to sweep food to mouthparts • Most are freely motile, but some are anchored • Paramecium Paramecium – Macronucleus= produces mRNA & directs metabolic functions – Micronucleus= involved in sexual reproduction called conjugation • Most protozoans reproduce asexually Vorticella Amoeboids • Move by pseudopodia (cytoplasmic streaming) • Aquatic environments • Eat by phagocytosis • Digestion occurs in food vacuole • Entamoeba – Cause amoebic dysentery – Invades intestinal lining & reproduces there • Foraminiferans – A skeleton called a test that covers plasma membrane – Pseudopods push out of test – Can be used to date sedimentary rock • Radiolarians have internal test Radiolarian tests Zooflagellates • Heterotrophic protozoans that use 1 or more flagella • May be parasitic or symbiotic • Trypanosoma brucei – Cause African sleeping sickness – Transmitted by tsetse fly – Attacks blood & causes inflammation decreases blood flow to brain Trypanosoma • Trypanosoma cruzi causes Chagas disease – Transmitted by kissing bug • Giardia can cause diarrhea Giardia Sporozoans • Produce spores • All phases of life cycle are nonmotile except male gametes & zygotes • Either intercellular or extracellular parasites • Plasmodium vivax – Causes malaria – Transmitted by mosquitos • Toxoplasma – Transmitted by cat feces – Can be harmful to fetus Molds as Protists • Water molds & slime molds are protists because both have flagellated cells. • Water molds – – – – – Saprotrophic: feed on dead organic matter Responsible for potato famine in Ireland in 1840s Filamentous body like fungi, but cell walls composed of cellulose Flagellated spores produced during asexual reproduction In sexual reproduction, eggs & sperm are produced • Slime molds – Plasmodial (acellular) slime molds: diploid, multinucleated, cytoplasmic mass enveloped by slime sheath – Creeps along phagocytizing decaying plant material in forest • Cellular slime molds – Exist as individual amoeboid cells – Common in soil where they feed on bacteria & yeasts Fungi • Found in domain Eukarya, kingdom Fungi • Only heterotropic – Release digestive enzymes into external environment – Digest food outside of body • Saprotrophic: decomposes corpses of plants, animals, & microbes • Break down organic nutrients & return inorganic nutrients to producers • Body is composed of a mass of individual filaments called hyphae • The hypha form an interwoven mass called mycelium • Some have septa (cross walls) that separate nuclei • Lack chloroplasts & cell walls are composed of chitin • Are nonmotile & lack flagella Fungi cont. • Use spores to reproduce sexually & asexually • Spores are haploid reproductive cells • Asexual reproduction involves spore developing into new organism without fusing with another cell • Sexual reproduction involves joining of hyphae from two different mating types (+) & (-) to form zygote Zygospore Fungi • Phylum Zygomycota • Mostly saprotrophic, may be parasitic • Ex. Rhizopus stolonifer (black bread mold) • Hypha are specialized – Sporangium: specialized hypha with capsule that produces spores Sac Fungi • Phylum Ascomycota • Named for cuplike reproductive structure called ascocarp • Produce sexual spores called conidia • Ex. Truffles, chestnut blight, Dutch elm disease, Ergot, Penicillium, yeast Club Fungi • Phylum Basidiomycota • Named for their clubshaped sexual reproductive structures called basidia • Most reproduce sexually, but can make asexual spores • Basidia are enclosed in basidiocarp that is formed from (+) & (-) hyphae fusing • Ex. Bracket fungi, puffballs, bird’s nest fungi, stinkhorns Viruses, Viroids, Prions • Viruses are not composed of cells • They are obligate parasites – They can only reproduce inside a living cell – Have no metabolic activity when outside of a cell – Contain nucleic material that directs reproduction once inside host – Contain either RNA or DNA – Have a protein capsid that covers nucleic material – May have a lipid membrane called an envelope that surrounds capsid • Viroids are strands of RNA that can reproduce inside of a cell. • Prions are protein molecules that cause other proteins to become prions. Life Cycle of Typical Animal Virus