Microbiology Reviewer

C O M P R E H E N S I V E S T U D Y R E V I E W E R Microbiology History of Microbiology · Cell Structure and Function Compiled from: 1 · History of Microbiology (Lesson deck) 2 · Microbiology with Diseases by Body System, 2nd ed. Chapter 3 — Cell Structure and Function HOW TO USE THIS REVIEWER Yellow highlight = Key point — the fact most likely to be tested. Green highlight = Terminology — defined in the Glossary at the end. Part I — History | Part II — Cell Structure | Part III — Glossary.

The Early Years of Microbiology 1.1 Learning Objectives Describe the world-changing scientific contributions of Leeuwenhoek. Define microbes in the words of Leeuwenhoek and as we know them today. List the six groups of microorganisms. Differentiate prokaryotic from eukaryotic organisms. 1.2 Pioneers of the Early Years SCIENTIST GUIDING QUESTION / FOCUS CONTRIBUTION Anton van Leeuwenhoek "What does life really look like?" Examined water and visualized tiny animals, fungi, algae, and single-celled protozoa , which he called animalcules . Made the first observations of microbial life. Robert Hooke Structure of living matter Associated with the cell theory — the foundation for describing living things as being made of cells. Carolus Linnaeus "How can microbes be classified?" Developed the taxonomic system for naming plants and animals and grouping similar organisms together — the initial effort to organize microbes into a logical classification. Key point: By the end of the 19th century, these organisms were called microorganisms — the term that replaced Leeuwenhoek's "animalcules." 1.3 The Six Groups of Microorganisms Leeuwenhoek's microorganisms are now grouped into six categories : GROUP CELL TYPE DEFINING CHARACTERISTICS Bacteria Prokaryotic Unicellular and lack nuclei ; much smaller than eukaryotes; found everywhere there is sufficient moisture; reproduce asexually . Cell walls contain peptidoglycan ; some lack cell walls. Archaea Prokaryotic Unicellular and lack nuclei; some isolated from extreme environments ; reproduce asexually. Cell walls composed of polymers other than peptidoglycan . Fungi Eukaryotic Have a membrane-bound nucleus ; obtain food from other organisms ; possess cell walls. Include molds (multicellular, long filaments, reproduce by sexual and asexual spores ) and yeasts (unicellular, reproduce asexually by budding ; some produce sexual spores). Protozoa Eukaryotic Single-celled eukaryotes similar to animals in nutrient needs and cellular structure; live freely in water, some live in animal hosts; asexual (most) and sexual reproduction. Most are capable of locomotion . Algae Eukaryotic Unicellular or multicellular; photosynthetic ; simple reproductive structures; categorized on the basis of pigmentation and composition of cell wall . P A R T I · H I S T O R Y.

GROUP CELL TYPE DEFINING CHARACTERISTICS Small multicellular animals Eukaryotic The sixth group of organisms originally observed among Leeuwenhoek's "animalcules." Structures of protozoan locomotion STRUCTURE DESCRIPTION Pseudopods Pseudopods — cell extensions that flow in the direction of travel. Cilia Cilia — numerous short protrusions that propel organisms through the environment. Flagella Flagella — extensions of a cell that are fewer, longer, and more whiplike than cilia . Also studied by microbiologists: Parasites and viruses — organisms and agents outside the six groups above..

The Golden Age of Microbiology 2.1 The Four Driving Questions Scientists of the Golden Age searched for answers to four questions : # QUESTION FIELD / OUTCOME IT PRODUCED 1 Is spontaneous generation of microbial life possible? Rejection of spontaneous generation; the scientific method 2 What causes fermentation ? Pasteurization ; industrial microbiology ; biochemistry 3 What causes disease? Germ theory of disease ; etiology ; Koch's postulates ; Gram staining 4 How can we prevent infection and disease? Epidemiology , immunology , chemotherapy 2.2 Does Microbial Life Spontaneously Generate? Some philosophers and scientists of the past thought living things arose from three processes : asexual reproduction, sexual reproduction, and nonliving matter . SCIENTIST EXPERIMENT CONCLUSION / EFFECT Aristotle Philosophical proposal Proposed spontaneous generation — living things can arise from nonliving matter. He is the scientist who argued in favor of spontaneous generation. Francesco Redi Decaying meat kept isolated from flies vs. meat exposed to flies. When meat was kept isolated from flies, maggots never developed ; exposed meat was soon infested. As a result, scientists began to doubt Aristotle's theory . John Needham Beef gravy and infusions of plant material. Scientists did not believe animals could arise spontaneously, but believed microbes could — Needham's results reinforced that idea. Lazzaro Spallanzani Repeated Needham's work with better heating and sealing of vials. Concluded Needham failed to heat vials sufficiently to kill all microbes or had not sealed them tightly enough; microorganisms exist in air and can contaminate experiments; spontaneous generation of microorganisms does not occur . Critics: sealed vials did not allow enough air for organisms to survive, and prolonged heating destroyed the "life force." Louis Pasteur Swan-necked flask experiment. When flasks remained upright, no microbial growth appeared . When a flask was tilted, dust from the bend in the neck seeped back in and made the infusion cloudy with microbes within a day — settling the debate while still admitting air. P A R T I · H I S T O R Y.

The scientific method — the four steps of investigation used by Pasteur: (1) observation, (2) hypothesis, (3) experiment, (4) conclusion (accept, reject, or modify the hypothesis). 2.3 What Causes Fermentation? Spoiled wine threatened the livelihood of vintners ; they funded research on methods to promote alcohol production and prevent spoilage during fermentation. Some believed air caused fermentation; others insisted living organisms caused it — a debate also linked to the spontaneous-generation debate. SCIENTIST FINDINGS AND SIGNIFICANCE Louis Pasteur Applied the scientific method to fermentation. Led to the development of pasteurization — the process of heating liquids just enough to kill most bacteria . Began the field of industrial microbiology — the intentional use of microbes for manufacturing products . Eduard Buchner Demonstrated fermentation does not require living cells ; showed enzymes promote chemical reactions. Began the field of biochemistry and the study of metabolism . Exam cue: Pasteur may be considered the Father of Microbiology ; Buchner is the scientist whose experiments led to the field of biochemistry . 2.4 What Causes Disease? Pasteur developed the germ theory of disease . Robert Koch studied the causative agents of disease ( etiology ), including anthrax , and examined colonies of microorganisms. Koch's contributions to microbiology (at least seven) # CONTRIBUTION 1 Simple staining techniques 2 First photomicrograph of bacteria 3 First photomicrograph of bacteria in diseased tissue 4 Techniques for estimating CFU/ml 5 Use of steam to sterilize media 6 Use of Petri dishes 7 Techniques to transfer bacteria 8 Established bacteria as distinct species Koch's postulates — the four steps to prove the cause of an infectious disease STEP REQUIREMENT 1 Suspected causative agent must be found in every case of the disease and be absent from healthy hosts..

STEP REQUIREMENT 2 Agent must be isolated and grown outside the host. 3 When the agent is introduced into a healthy, susceptible host, the host must get the disease. 4 The same agent must be found in the diseased experimental host. Gram's contribution Hans Christian Gram developed the Gram staining procedure, which separates bacteria into Gram-positive (purple) and Gram-negative (pink) — still the most widely used differential stain in microbiology. 2.5 How Can We Prevent Infection and Disease? PRACTITIONER INNOVATION FIELD FOUNDED / IMPACT Ignaz Semmelweis Handwashing Pioneering research in public health microbiology; reduced transmission in hospitals. Joseph Lister Antiseptic technique Antiseptic surgery — preventing infection of wounds. Florence Nightingale Nursing Established sanitary nursing practice and infection control. John Snow Infection control Founded the field of epidemiology . Edward Jenner Vaccine Began the field of immunology . Paul Ehrlich The quest for a "magic bullet" Began the field of chemotherapy — a chemical that kills the pathogen without harming the host. Naming the four: Semmelweis, Lister, Nightingale, and Snow are the health care practitioners who did pioneering research in public health microbiology and epidemiology. Jenner and Von Behring/Kitasato-era vaccine work began immunology..

The Modern Age of Microbiology 3.1 The Four Questions That Drive Microbiology Today # QUESTION FIELDS / KEY DEVELOPMENTS 1 What are the basic chemical reactions of life? Biochemistry 2 How do genes work? Microbial genetics , molecular biology , recombinant DNA technology , gene therapy 3 What role do microorganisms play in the environment? Environmental microbiology — bioremediation and chemical recycling 4 How do we defend against disease? Serology , immunology , chemotherapy Exam cues: Environmental microbiology is the field that studies the role of microorganisms in the environment. Molecular biology / microbial genetics is the fastest-growing scientific discipline in microbiology today. 3.2 Biochemistry Began with Pasteur's work on fermentation and Buchner's discovery of enzymes in yeast extract . Kluyver and van Niel — microbes used as model systems for biochemical reactions. Practical applications: design of herbicides and pesticides; diagnosis of illnesses and monitoring of patients' responses to treatment; treatment of metabolic diseases; drug design. 3.3 How Do Genes Work? FIELD KEY DISCOVERIES AND APPLICATIONS Microbial genetics Avery, MacLeod, and McCarty determined genes are contained in molecules of DNA. Beadle and Tatum established that a gene's activity is related to protein function. Translation of genetic information into protein explained; rates and mechanisms of genetic mutation investigated; control of genetic expression by cells described. Molecular biology Explanation of cell function at the molecular level. Pauling proposed gene sequences could provide understanding of evolutionary relationships, establish taxonomic categories reflecting those relationships, and identify microbes that have never been cultured . Woese determined cells belong to bacteria, archaea, or eukaryotes. Example: cat scratch disease is caused by an unculturable organism. Recombinant DNA technology Genes in microbes, plants, and animals manipulated for practical applications — e.g. production of human blood-clotting factor by E. coli to aid hemophiliacs . Gene therapy Inserting a missing gene or repairing a defective one in humans by inserting the desired gene into host cells. 3.4 Microorganisms in the Environment Bioremediation uses living bacteria, fungi, and algae to detoxify polluted environments . Recycling of chemicals such as carbon, nitrogen, and sulfur . P A R T I · H I S T O R Y.

3.5 How Do We Defend Against Disease? FIELD DEFINITION / LANDMARK Serology The study of blood serum. Von Behring and Kitasato — existence in the blood of chemicals and cells that fight infection. Immunology The study of the body's defenses against specific pathogens. Chemotherapy Fleming discovered penicillin ; Domagk discovered sulfa drugs . Penicillin produces a zone of inhibition in a bacterial "lawn." What will the future hold? Microbiology is built on asking and answering questions — the more questions we answer, the more questions we have..

Cell Structure and Function — Overview 4.1 Processes of Life PROCESS WHAT IT MEANS FOR A CELL Growth Increase in size of the individual cell or population. Reproduction Production of new individuals — asexual in prokaryotes ; asexual and/or sexual in eukaryotes. Responsiveness Reaction to stimuli in the environment. Metabolism The sum of all chemical reactions in the cell. 4.2 Prokaryotic vs. Eukaryotic Cells FEATURE PROKARYOTES EUKARYOTES Nucleus Do not have a membrane surrounding their DNA; lack a nucleus Have a membrane surrounding their DNA; have a nucleus Internal structures Lack various internal structures bound with phospholipid membranes Have internal membrane-bound organelles Size Small, ~1.0 µm in diameter Larger, 10–100 µm in diameter Complexity Simple structure More complex structure Composed of Bacteria and archaea Algae, protozoa, fungi, animals, and plants Ribosomes 70S 80S (60S + 40S subunits) 4.3 Comparative Cell Wall and Cell Membrane Chemistry GROUP CELL TYPE CELL WALL CELL MEMBRANE Archaea Prokaryotic Polysaccharides and proteins; pseudomurein The lipid membrane is ether -linked , with the branching of aliphatic acids (R–O–R) Bacteria Prokaryotic Made up of peptidoglycan with muramic acid Lipid membrane of ester bonds with fatty acids (R–CO–OR) Fungi Eukaryotic Chitin Lipid bilayer, with sterol ( ergosterol ) Algae Eukaryotic Cellulose Lipid bilayer, with sterols ( phytosterols ) Protozoa Eukaryotic None Lipid bilayer, with sterols (ergosterol) Animalia Eukaryotic None Lipid bilayer, with sterols ( cholesterol ) High-yield contrast: Archaeal membrane lipids are ether-linked and branched; bacterial (and eukaryotic) membrane lipids are ester-linked with straight fatty acids. P A R T I I · C H A P T E R 3.

Prokaryotic Cell Structures 5.1 External Structures — Glycocalyces Glycocalyces are a gelatinous, sticky substance surrounding the outside of the cell , composed of polysaccharides, polypeptides, or both . There are two types: TYPE STRUCTURE FUNCTION Capsule Composed of organized repeating units of organic chemicals; firmly attached to cell surface. Protects cells from drying out; may prevent bacteria from being recognized and destroyed by the host . Slime layer Loosely attached to cell surface; water soluble . Protects cells from drying out; sticky layer that allows prokaryotes to attach to surfaces . 5.2 External Structures — Fimbriae and Pili Both are rod-like proteinaceous extensions . STRUCTURE CHARACTERISTICS FUNCTION Fimbriae Sticky, bristlelike projections ; shorter than flagella; may be hundreds per cell . Used by bacteria to adhere to one another, to hosts, and to substances in the environment ; serve an important function in biofilms . Pili Tubules composed of pilin ; also known as conjugation pili ; longer than fimbriae but shorter than flagella ; typically only one or two per cell . Mediate the transfer of DNA from one cell to another (conjugation) . 5.3 Prokaryotic Cell Walls General functions Provide structure and shape and protect the cell from osmotic forces . Assist some cells in attaching to other cells or in eluding antimicrobial drugs. Not present in animal cells — so the cell wall of bacteria can be targeted with antibiotics. Bacteria and archaea have different cell wall chemistry. Bacterial cell walls Most have a cell wall composed of peptidoglycan . Peptidoglycan is composed of sugars, NAG , and NAM . Chains of NAG and NAM are attached to other chains by tetrapeptide crossbridges . Bridges may be covalently bonded to one another, or held together by short connecting chains of amino acids. Scientists describe two basic types of bacterial cell walls: Gram-positive and Gram-negative. FEATURE GRAM-POSITIVE GRAM-NEGATIVE Peptidoglycan Relatively thick layer Only a thin layer P A R T I I · C H A P T E R 3.

FEATURE GRAM-POSITIVE GRAM-NEGATIVE Unique components Contain unique polyalcohols called teichoic acids ; some covalently linked to lipids, forming lipoteichoic acids that anchor peptidoglycan to the cell membrane . Bilayer membrane outside the peptidoglycan containing phospholipids, proteins, and lipopolysaccharide (LPS) . Gram stain result Retain crystal violet dye — appear purple Appear pink following the Gram staining procedure Clinical note Up to 60% mycolic acid in acid-fast bacteria helps cells survive desiccation . May be an impediment to the treatment of disease. Archaeal cell walls Do not have peptidoglycan. Contain a variety of specialized polysaccharides and proteins. Gram-positive archaea stain purple; Gram-negative archaea stain pink..

Prokaryotic Membranes and Cytoplasm 6.1 Prokaryotic Cytoplasmic Membranes — Structure Referred to as a phospholipid bilayer ; composed of lipids and associated proteins. Approximately half is composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels — integral proteins , peripheral proteins , and glycoproteins . The fluid mosaic model describes the current understanding of membrane structure. 6.2 Prokaryotic Cytoplasmic Membranes — Function FUNCTION DETAILS Energy storage Harvest light energy in photosynthetic prokaryotes . Selectively permeable Naturally impermeable to most substances ; proteins allow substances to cross the membrane; occurs by passive or active transport processes . Maintain gradients Maintain concentration and electrical gradients — chemicals concentrated on one side of the membrane or the other; a voltage exists across the membrane . 6.3 Cytoplasm of Prokaryotes COMPONENT DESCRIPTION Cytosol The liquid portion of the cytoplasm. Inclusions May include reserve deposits of chemicals. Endospores Unique structures produced by some bacteria that are a defensive strategy against unfavorable conditions. Ribosomes Nonmembranous organelles — sites of protein synthesis (70S in prokaryotes). Cytoskeleton Nonmembranous; plays a role in forming the cell's basic shape . P A R T I I · C H A P T E R 3.

Eukaryotic Cell Structures 7.1 External Structures — Glycocalyces Never as organized as prokaryotic capsules. Help anchor animal cells to each other ; strengthen the cell surface; provide protection against dehydration. Function in cell-to-cell recognition and communication . 7.2 Eukaryotic Cell Walls Fungi, algae, plants, and some protozoa have cell walls but no glycocalyx. Composed of various polysaccharides . ORGANISM CELL WALL COMPOSITION Plants Cellulose Fungi Cellulose, chitin, and/or glucomannan Algae Cellulose, proteins, agar , carrageenan , silicates, algin , calcium carbonate, or a combination of these 7.3 Eukaryotic Cytoplasmic Membranes All eukaryotic cells have a cytoplasmic membrane — a fluid mosaic of phospholipids and proteins . Contain steroid lipids to help maintain fluidity , and regions of lipids and proteins called membrane rafts . Control movement into and out of the cell using diffusion , facilitated diffusion , osmosis , and active transport. Perform endocytosis — phagocytosis if a solid substance, pinocytosis if a liquid substance . Exocytosis enables substances to be exported from the cell. 7.4 Eukaryotic Flagella and Cilia STRUCTURE STRUCTURE AND ARRANGEMENT FUNCTION Flagella Shaft composed of tubulin arranged to form microtubules . "9 + 2" arrangement of microtubules in all flagellated eukaryotes. Filaments anchored to the cell by a basal body ; no hook . Basal body has a "9 + 0" arrangement. May be single or multiple; generally found at one pole of the cell. Do not rotate, but undulate rhythmically. Cilia Shorter and more numerous than flagella. Composed of tubulin in "9 + 2" and "9 + 0" arrangements. Coordinated beating propels cells through their environment ; also used to move substances past the surface of the cell. 7.5 Other Nonmembranous Organelles ORGANELLE DETAILS Ribosomes Larger than prokaryotic ribosomes — 80S versus 70S ; composed of 60S and 40S subunits . P A R T I I · C H A P T E R 3.

ORGANELLE DETAILS Cytoskeleton Extensive. Functions: anchors organelles; cytoplasmic streaming and movement of organelles; movement during endocytosis and amoeboid action ; produces the basic shape of the cell. Made up of tubulin microtubules, actin microfilaments, and intermediate filaments . Centrioles & centrosome Centrioles play a role in mitosis , cytokinesis , and in the formation of flagella and cilia ; composed of a "9 + 0" arrangement of microtubules. The centrosome is the region of cytoplasm where centrioles are found..

Eukaryotic Membranous Organelles ORGANELLE STRUCTURE FUNCTION Nucleus Often the largest organelle in the cell. Semi-liquid portion called nucleoplasm ; one or more nucleoli present in the nucleoplasm. Nucleoplasm contains chromatin — masses of DNA associated with histones . Surrounded by the nuclear envelope — a double membrane composed of two phospholipid bilayers , which contains nuclear pores . Contains most of the cell's DNA. RNA is synthesized in the nucleoli. Endoplasmic reticulum Netlike arrangement of flattened, hollow tubules continuous with the nuclear envelope. Two forms — SER and RER . Functions as a transport system. SER plays a role in lipid synthesis . RER has ribosomes attached to its outer surface and transports proteins produced by ribosomes. Golgi body Composed of flattened hollow sacs surrounded by a phospholipid bilayer . Not in all eukaryotic cells. Receives, processes, and packages large molecules for export from the cell ; packages molecules in secretory vesicles that fuse with the cytoplasmic membrane. Lysosomes, peroxisomes, vacuoles, vesicles Membrane-bound sacs within the cytoplasm. Store and transfer chemicals within cells ; may store nutrients. Lysosomes contain catabolic enzymes ; peroxisomes contain enzymes that degrade poisonous wastes . Mitochondria Have two membranes composed of phospholipid bilayer. Interior matrix contains 70S ribosomes and a circular molecule of DNA . Produce most of the cell's ATP . Chloroplasts Have two phospholipid bilayer membranes and DNA ; have 70S ribosomes . Light-harvesting structures found in photosynthetic eukaryotes. 8.1 Endosymbiotic Theory STEP PROPOSITION 1 Eukaryotes formed from the union of small aerobic prokaryotes with larger anaerobic prokaryotes. 2 The smaller prokaryotes became internal parasites . 3 Parasites lost the ability to exist independently; retained a portion of DNA, ribosomes, and cytoplasmic membranes. 4 The larger cell became dependent on the parasites for aerobic ATP production . 5 Aerobic prokaryotes evolved into mitochondria ; a similar scenario explains the origin of chloroplasts. Caution: The endosymbiotic theory is not universally accepted. Supporting evidence: mitochondria and chloroplasts both have two membranes, their own circular DNA, and 70S (prokaryote-sized) ribosomes. P A R T I I · C H A P T E R 3.

Glossary of Terminologies Every term highlighted in green throughout this reviewer is defined below, in order of first appearance by topic. A. History of Microbiology TERM DEFINITION Animalcules Leeuwenhoek's original name for the tiny living things — animals, fungi, algae, and single- celled protozoa — he visualized in water with his microscope. Microorganisms The modern term, adopted by the end of the 19th century, for the microscopic organisms Leeuwenhoek called animalcules. Cell theory The principle, associated with Robert Hooke's work, that living things are composed of cells. Taxonomic / Taxonomy The system, developed by Carolus Linnaeus, for naming organisms and grouping similar organisms together; modern taxonomy also reflects evolutionary relationships. Prokaryotic Describing a cell that does not have a membrane surrounding its DNA (lacks a nucleus), lacks membrane-bound internal structures, is small (~1.0 µm), and is simple in structure. Includes bacteria and archaea. Eukaryotic Describing a cell that has a membrane surrounding its DNA (has a nucleus) and internal membrane-bound organelles, is larger (10–100 µm), and is more complex. Includes algae, protozoa, fungi, animals, and plants. Asexual reproduction Reproduction producing offspring from a single parent without the fusion of gametes; the mode of reproduction of bacteria and archaea. Peptidoglycan The polymer of sugars (NAG and NAM) linked by tetrapeptide crossbridges that forms bacterial cell walls. Archaeal walls are made of other polymers. Membrane-bound nucleus A nucleus enclosed by a nuclear envelope; the defining feature of eukaryotic cells, including fungi. Molds Multicellular fungi that grow as long filaments and reproduce by sexual and asexual spores. Yeasts Unicellular fungi that reproduce asexually by budding; some also produce sexual spores. Spores Reproductive cells produced by fungi (sexually or asexually) that can develop into a new organism. Budding A form of asexual reproduction in which a new cell grows out of the parent cell as an outgrowth; the way yeasts reproduce asexually. Locomotion Self-powered movement of an organism from place to place; in protozoa achieved by pseudopods, cilia, or flagella. Pseudopods Cell extensions that flow in the direction of travel, used by some protozoa for locomotion. Cilia Numerous short protrusions that propel organisms through the environment; shorter and more numerous than flagella. Flagella Extensions of a cell used for movement that are fewer, longer, and more whiplike than cilia. P A R T I I I · D E F I N I T I O N S.

TERM DEFINITION Photosynthetic Capable of converting light energy into chemical energy; a defining feature of algae. Parasites Organisms that live on or in a host and derive benefit at the host's expense; studied by microbiologists although outside the six microbial groups. Viruses Acellular infectious agents studied by microbiologists that require a host cell to replicate. Spontaneous generation The idea, proposed by Aristotle, that living things can arise from nonliving matter. Disproved through the experiments of Redi, Spallanzani, and finally Pasteur. Scientific method The four-step process of investigation — observation, hypothesis, experiment, and conclusion — that Pasteur applied to the questions of spontaneous generation and fermentation. Swan-necked flask Pasteur's flask with a curved neck that admitted air but trapped dust; no microbes grew while upright, but tilting it let trapped dust re-enter and clouded the infusion within a day. Fermentation The chemical process, investigated by Pasteur and Buchner, by which microbes (or their enzymes) convert sugars into products such as alcohol; shown by Buchner not to require living cells. Vintners Wine makers, whose losses to spoiled wine funded Pasteur's research into fermentation. Pasteurization The process of heating liquids just enough to kill most bacteria, developed from Pasteur's fermentation work. Industrial microbiology The intentional use of microbes for manufacturing products; a field begun by Pasteur's work. Enzymes Biological catalysts that promote chemical reactions; Buchner showed they, not living cells, carry out fermentation. Biochemistry The study of the basic chemical reactions of life; the field begun by Buchner's discovery of enzymes in yeast extract. Metabolism The sum of all chemical reactions within a cell; one of the four processes of life. Germ theory of disease Pasteur's theory that microorganisms are the cause of many diseases. Etiology The study of the causative agents of disease; Koch's field of study. Anthrax The disease Koch investigated when establishing the link between a specific microorganism and a specific disease. Colonies Visible masses of microorganisms grown from a single cell on solid media; examined by Koch. Staining The application of dyes to make microbes visible under the microscope; Koch developed simple staining techniques. Photomicrograph A photograph taken through a microscope; Koch produced the first photomicrographs of bacteria and of bacteria in diseased tissue. CFU/ml Colony-forming units per milliliter — a measure of the number of viable microorganisms in a sample; Koch developed techniques for estimating it. Sterilize To destroy all microbial life in or on a material; Koch used steam to sterilize media. Petri dishes Shallow covered dishes used to hold solid culture media; introduced in Koch's laboratory..

TERM DEFINITION Koch's postulates The four steps that must be taken to prove that a specific agent causes a specific infectious disease (see Section 2.4). Gram staining Gram's differential staining procedure that separates bacteria into Gram-positive (purple) and Gram-negative (pink) based on cell wall structure. Gram-positive Bacteria with a thick peptidoglycan layer containing teichoic acids that retain crystal violet and appear purple. Gram-negative Bacteria with a thin peptidoglycan layer and an outer bilayer membrane containing LPS; they appear pink after Gram staining. Antiseptic A chemical applied to living tissue to prevent infection; Lister introduced antiseptic technique in surgery. Epidemiology The study of the occurrence, distribution, and control of disease in populations; founded through John Snow's work on infection control. Vaccine A preparation that stimulates protective immunity against a specific pathogen; Jenner's vaccine began the field of immunology. Immunology The study of the body's defenses against specific pathogens. "Magic bullet" Ehrlich's concept of a chemical that would kill a pathogen without harming the host; the quest for it began the field of chemotherapy. Chemotherapy The use of chemicals to treat disease, especially to kill or inhibit pathogens within a host. B. Modern Microbiology TERM DEFINITION Microbial genetics The study of how genes work in microorganisms; produced the discoveries of Avery, MacLeod, and McCarty (genes are DNA) and Beadle and Tatum (gene activity relates to protein function). Molecular biology The explanation of cell function at the molecular level; includes Pauling's use of gene sequences for evolutionary relationships and Woese's division of cells into bacteria, archaea, and eukaryotes. Mutation A change in the genetic sequence of an organism; its rates and mechanisms were investigated by microbial geneticists. Recombinant DNA technology The manipulation of genes in microbes, plants, and animals for practical applications — e.g. producing human blood-clotting factor in E. coli. Gene therapy Inserting a missing gene, or repairing a defective one, in humans by inserting the desired gene into host cells. Environmental microbiology The field of microbiology that studies the role of microorganisms in the environment, including bioremediation and the recycling of carbon, nitrogen, and sulfur. Bioremediation The use of living bacteria, fungi, and algae to detoxify polluted environments..

TERM DEFINITION Serology The study of blood serum; Von Behring and Kitasato showed the blood contains chemicals and cells that fight infection. Penicillin The antibiotic discovered by Fleming, produced by the fungus Penicillium, which creates a zone of inhibition in a bacterial lawn. Sulfa drugs Antimicrobial chemicals discovered by Domagk, an early success of chemotherapy. Zone of inhibition The clear area around an antimicrobial agent in a bacterial "lawn" where growth has been prevented. C. Cell Structure and Function TERM DEFINITION Phospholipid The lipid molecule, with a phosphate head and fatty acid tails, that forms the bilayer of cell membranes. Membrane-bound organelles Internal cell structures enclosed by phospholipid membranes; present in eukaryotes, absent in prokaryotes. Pseudomurein The polysaccharide-and-protein cell wall polymer found in archaea, taking the place of bacterial peptidoglycan. Ether (linkage) The R–O–R bond joining branched aliphatic chains to glycerol in archaeal membrane lipids. Ester (linkage) The R–CO–OR bond joining straight-chain fatty acids to glycerol in bacterial and eukaryotic membrane lipids. Muramic acid The sugar component characteristic of bacterial peptidoglycan (NAM). Chitin The polysaccharide that makes up fungal cell walls. Cellulose The polysaccharide found in the cell walls of plants and algae, and also in fungal cell walls. Sterol / Steroid lipid A lipid embedded in eukaryotic membranes that helps maintain fluidity — ergosterol in fungi and protozoa, phytosterols in algae, cholesterol in animals. Glycocalyces A gelatinous, sticky substance surrounding the outside of a cell, composed of polysaccharides, polypeptides, or both. In prokaryotes it occurs as a capsule or slime layer. Capsule A glycocalyx of organized repeating units firmly attached to the cell surface; protects cells from drying out and may prevent recognition and destruction by the host. Slime layer A loosely attached, water-soluble glycocalyx that protects cells from drying out and allows prokaryotes to stick to surfaces. Biofilms Communities of microorganisms attached to a surface; fimbriae serve an important function in forming them. Pilin The protein subunit that makes up the tubules of pili. Conjugation The transfer of DNA from one bacterial cell to another, mediated by conjugation pili..

TERM DEFINITION Osmotic forces Pressures created by water movement across a membrane; the cell wall protects the cell against them. NAG N-acetylglucosamine — one of the two alternating sugars in peptidoglycan. NAM N-acetylmuramic acid — the other sugar in peptidoglycan, unique to bacterial cell walls. Tetrapeptide crossbridges Four-amino-acid links that attach chains of NAG and NAM to other chains, giving peptidoglycan its strength. Teichoic acids Unique polyalcohols found in Gram-positive cell walls. Lipoteichoic acids Teichoic acids covalently linked to lipids, anchoring peptidoglycan to the cell membrane in Gram-positive bacteria. Crystal violet The primary dye of the Gram stain, retained by Gram-positive cells so they appear purple. Lipopolysaccharide (LPS) A molecule of lipid and sugar in the outer bilayer membrane of Gram-negative cell walls; may be an impediment to the treatment of disease. Mycolic acid A waxy lipid making up as much as 60% of the wall of acid-fast bacteria, helping cells survive desiccation. Acid-fast Describing bacteria whose mycolic-acid-rich walls resist decolorization by acid-alcohol during staining. Desiccation Drying out; acid-fast cells survive it because of their mycolic acid content. Phospholipid bilayer The two-layer sheet of phospholipids, with associated proteins, forming the cytoplasmic membrane. Integral proteins Membrane proteins embedded within the phospholipid bilayer. Peripheral proteins Membrane proteins attached to the surface of the bilayer rather than embedded in it. Glycoproteins Membrane proteins with attached carbohydrate groups. Fluid mosaic model The current model of membrane structure — a fluid bilayer in which proteins are distributed like tiles in a mosaic. Passive transport Movement of substances across the membrane without expenditure of cellular energy (e.g. diffusion, osmosis). Active transport Movement of substances across the membrane that requires cellular energy, often against a gradient. Cytosol The liquid portion of the cytoplasm. Inclusions Cytoplasmic bodies that may include reserve deposits of chemicals. Endospores Unique dormant structures produced by some bacteria as a defensive strategy against unfavorable conditions. Polysaccharides Long chains of sugar molecules; the main structural component of eukaryotic cell walls. Glucomannan A polysaccharide that, with cellulose and/or chitin, may compose fungal cell walls..

TERM DEFINITION Agar A polysaccharide from algal cell walls, widely used to solidify microbiological culture media. Carrageenan A polysaccharide found in the cell walls of certain algae. Algin A polysaccharide component of some algal cell walls. Membrane rafts Regions of lipids and proteins within the eukaryotic cytoplasmic membrane. Diffusion Passive movement of a substance from an area of higher to lower concentration. Facilitated diffusion Passive movement of a substance across a membrane with the help of a carrier or channel protein. Osmosis The diffusion of water across a selectively permeable membrane. Endocytosis The process by which a eukaryotic cell brings substances into the cell by engulfing them in a portion of its membrane. Phagocytosis Endocytosis of a solid substance. Pinocytosis Endocytosis of a liquid substance. Exocytosis The process that enables substances to be exported from the cell. Tubulin The protein that forms microtubules in eukaryotic flagella, cilia, centrioles, and the cytoskeleton. Microtubules Hollow tubes of tubulin; arranged "9 + 2" in eukaryotic flagella and cilia and "9 + 0" in basal bodies and centrioles. Basal body The structure that anchors a eukaryotic flagellum to the cell; has a "9 + 0" arrangement of microtubules and no hook. Cytoplasmic streaming The cytoskeleton-driven flow of cytoplasm that moves organelles within a eukaryotic cell. Amoeboid action Cytoskeleton-driven crawling movement of a cell by extension of the cytoplasm. Actin The protein that forms the microfilaments of the eukaryotic cytoskeleton. Intermediate filaments Cytoskeletal fibers, intermediate in size between microtubules and microfilaments, that help produce the cell's basic shape. Centrioles "9 + 0" microtubule structures that play a role in mitosis, cytokinesis, and the formation of flagella and cilia. Centrosome The region of cytoplasm where centrioles are found. Mitosis Division of the eukaryotic nucleus, producing two genetically identical nuclei. Cytokinesis Division of the cytoplasm following nuclear division. Nucleoplasm The semi-liquid portion of the nucleus. Nucleoli One or more bodies within the nucleoplasm where RNA is synthesized. Chromatin Masses of DNA associated with histones, found in the nucleoplasm..

TERM DEFINITION Histones Proteins with which nuclear DNA is associated to form chromatin. Nuclear envelope The double membrane, composed of two phospholipid bilayers, that surrounds the nucleus. Nuclear pores Openings in the nuclear envelope that allow exchange between nucleus and cytoplasm. SER (smooth endoplasmic reticulum) The form of ER without attached ribosomes; plays a role in lipid synthesis. RER (rough endoplasmic reticulum) The form of ER with ribosomes attached to its outer surface; transports proteins produced by those ribosomes. Secretory vesicles Membrane sacs in which the Golgi body packages molecules; they fuse with the cytoplasmic membrane for export. Lysosomes Membranous organelles containing catabolic enzymes. Catabolic Describing enzymes or reactions that break larger molecules down into smaller ones. Peroxisomes Membranous organelles containing enzymes that degrade poisonous wastes. Matrix (mitochondrial) The interior compartment of a mitochondrion, containing 70S ribosomes and a circular molecule of DNA. ATP Adenosine triphosphate — the cell's main energy currency, most of which is produced by mitochondria..