Review for Final Exam - Ch 1, 3-15 PDF

Review for Final Exam Part of the Exam will cover Ch. 1, 3-15; study only the slides in this PowerPoint for these chapters (you may also want to refer back to your notes on these topics for illustrations and examples) The remainder of the Exam will cover Ch. 16-20 (from lecture notes)...

Review for Final Exam Part of the Exam will cover Ch. 1, 3-15; study only the slides in this PowerPoint for these chapters (you may also want to refer back to your notes on these topics for illustrations and examples) The remainder of the Exam will cover Ch. 16-20 (from lecture notes) Good luck!  Bacteria Occur in 3 major basic shapes: – Bacillus (rods) – Coccus (circular) – Spirillum (spiral)  The Germ Theory of Disease 1876: Robert Koch proved that a bacterium causes anthrax and provided the experimental steps, Koch’s postulates, to prove that a specific microbe causes a specific disease. – Discovered a bacterium in the blood of a cow that had died from Bacillus anthracis (anthrax). – Inoculated healthy cows with the diseased blood, and the healthy cows got sick and died. – Examined all the dead cows’ blood, and found the same bacteria in it.  Biofilms Microbes attach to solid surfaces and grow into masses They will grow on rocks, pipes, teeth, and medical implants Bacterial communities that form slimy layers on surfaces, such as your teeth, are called biofilms. Protect your mucous membranes from harmful microbes Can cause infections from forming on catheters and other medical implants Often form a protective barrier against antibiotics  Gram Stain Color of Color of Gram-Positive Cells Gram-Negative Cells Primary Stain: Purple Purple Crystal Violet Mordant: Purple Purple Iodine Decolorizing Agent: Purple Colorless Alcohol-Acetone Counterstain: Purple Red Safranin  Identification Identification – may use several methods including: - macroscopic and microscopic appearance - biochemical tests (pH indicator giving color change) - genetic characteristics - immunological testing (testing isolates against known antibodies) 6  Staining Simple stains – one dye is used; reveals shape, size, and arrangement Differential stains – use a primary stain and a counterstain to distinguish cell types or parts. Examples: 1) Gram stain -- some species hold dye in cell wall (Gram +) while others do not (Gram -). 2) Acid-fast stain -- cell wall holds dye tightly/ “fast” even when washed with acid. 3) Endospore stain-- distinguish between endospores which hold the stain and vegetative cells. Structural stains – reveal certain cell parts not revealed by conventional methods: capsule stains and flagellar stains 7  Prokaryote Eukaryote Usually one circular Multiple paired chromosomes, chromosome, not in a in nuclear membrane (nucleus) membrane Histones No histones (chromosomal Organelles (membrane proteins) enclosed structures) No organelles Polysaccharide cell walls (if Bacteria: peptidoglycan cell present) walls Mitotic spindle (an assembly of Archaea: pseudomurein cell microtubules; involves forming walls of two nuclei) Binary fission (cell division, DNA copied, but no mitotic spindle forms)  Glycocalyx Outside cell wall Usually sticky (means “sugar coat”) Extracellular polysaccharide and/or polypeptide – Allows cell to attach to surfaces teeth, small intestinal wall, medical implants, etc. – Very important component of biofilms – May help prevent dessication 2 possible forms: – Capsule: neatly organized and firmly attached to cell wall (increases virulence by preventing phagocytosis, which is the ingestion/digestion of microbes) – Slime layer: unorganized and loosely attached  Gram-Positive Gram-Negative Cell Wall Cell Wall ▪ Thin peptidoglycan layer Thick peptidoglycan bonded to lipoproteins (lipids + layer proteins) ▪ Outer membrane, containing Contain teichoic acids lipopolysaccharides, (an alcohol/phosphate lipoproteins, and phospholipids molecule) ▪ Periplasmic space with periplasm, which is a gel-like fluid between the outer membrane and the plasma membrane  Plasmid Separate piece of DNA – Circular, smaller than chromosome – Contains 5-100 genes – Replicate independently – Not crucial for survival – Give advantages such as antibiotic resistance, beneficial enzymes, tolerance to toxic metals, toxin production – Can be transferred from one bacteria to another through a pilus  Endospores Resting cells Resistant to desiccation, heat, chemicals Resistant to normal processes that kill vegetative cells (ex., can survive in boiling water for several hours) Bacillus, Clostridium Sporulation: endospore formation Germination: return to vegetative state when conditions in environment become favorable  The Plasma Membrane Selective permeability allows passage of some molecules Know the definitions of each of the following types of transport: Simple diffusion Facilitative diffusion Osmosis Active transport Endocytosis – Phagocytosis: pseudopods extend and engulf particles – Pinocytosis: membrane folds inward, bringing in fluid and dissolved substances – Receptor-mediated: substances bind to receptors in the membrane, membrane folds inward  Organelles, membrane enclosed structures with specific functions Nucleus: contains chromosomes (DNA); DNA is combined to proteins called histones; when appear as a threadlike mass, called chromatin – Surrounded by double membrane = nuclear envelope; has nuclear pores, openings that allows substances into and out of nucleus – Contains spherical body called nucleolus, where rRNA is synthesized Endoplasmic reticulum (ER): transport network Golgi complex: membrane formation and secretion Lysosome: digestive enzymes Vacuole: brings food into cells and provides support  Organelles Mitochondrion: cellular respiration – 2 membranes: outer and inner – Inner membrane arranged in folds called cristae, where enzymes for ATP production reside – Center is called matrix – Have own DNA and replication – Divide/reproduce independently within cell – Have 70s ribosomes Chloroplast: photosynthesis Peroxisome: oxidation of fatty acids; destroys H2O2 Centrosome: consists of protein fibers and centrioles  Enzymes Most metabolic reactions would not occur fast enough to sustain life without the help of enzymes. Enzymes are specific proteins that serve as biological catalysts, which are molecules that increase the rate of a chemical reaction by lowering the energy of activation. The energy of activation is the resistance to a reaction, which must be overcome for a reaction to proceed. The enzyme is not permanently altered in the reaction and is re-used for more reactions. Enzyme promotes a reaction by serving as a physical site for specific substrate molecules to position for a reaction to take place. – A substrate is a reactant molecule that participates in the reaction – Substrates (Reactants) Enzyme Products 16 E. Anaerobic Respiration, the 1st part of C.R. 1. The first part of cellular respiration may involve the splitting of 6-C glucose that occurs through a series of enzyme-catalyzed steps called glycolysis. 2. The result is two 3-C molecules of pyruvate (pyruvic acid). 3. Glycolysis occurs in the "cytosol" (cytoplasm) and does not require oxygen (anaerobic), but only generates a net of 2 ATP molecules. 4. Energy from ATP is used to start the process but there is a net gain of energy as a result. 17 F. Aerobic Respiration in C.R. 1. Oxygen is needed for aerobic respiration - occurs within the mitochondria of eukaryotes, but in the cell membrane and cytoplasm of prokaryotes - occurs in two series of reactions called: 1) the "citric acid cycle" (also called tricarboxylic acid cycle (TCA cycle), or the Krebs cycle) 2) the "electron transport chain" (ETC) - includes oxygen accepting the hydrogens from glucose, making water; hence oxygen is required as the "electron acceptor") - each of these two series of reactions generate more ATP and release water and CO2 as end products. 18 F. Aerobic Respiration in C.R. (cont.) 2. There is a much greater net gain of ATP molecules from the processes of aerobic respiration (up to 36 new ATP). - Most of the ATP is produced in the ETC 3. The final products of aerobic respiration are carbon dioxide (waste product), water, and energy (ATP). 19  Metabolic Strategies Nutrient processing is varied among the many species of bacteria, yet in many cases is based on three catabolic pathways that convert glucose to CO2 and gives off energy Aerobic respiration – glycolysis, the Kreb’s cycle, respiratory chain Anaerobic respiration – glycolysis, the TCA cycle, respiratory chain; molecular oxygen is not final electron acceptor, but rather inorganic ions such as nitrates or sulfates Fermentation – glycolysis, organic compound (pyruvate or a derivative) are the final electron acceptors; produces ethyl alcohol or lactic acid 20  Fermentation Incomplete oxidation of glucose or other carbohydrates in the absence of oxygen Uses organic compounds as terminal electron acceptors; yields a small amount of ATP Alcoholic fermentation includes conversion of pyruvic acid to ethyl alcohol by yeasts acting on glucose. – Carbon dioxide is another product of alcoholic fermentation of various bacteria (ex: the bubbles in beer and champagne = CO2 from alcoholic fermentation; also, the CO2 gas is what causes bread rolls to rise). Pyruvic acid may be converted to other types of acids: "acid fermentation" (ex: lactic acid bacterial producers largely responsible for souring of milk; human muscles can also revert to lactic acid fermentation in the absence of oxygen to produce energy). 21  8.5 Photosynthesis: The Earth’s Lifeline The ultimate source of all the chemical energy in cells comes from the sun light 6CO2 + 6H2O C6H12O6 + 6O2 22 Growth Factors: Essential Organic Nutrients Organic compounds that cannot be synthesized by an organism because they lack the genetic and metabolic mechanisms to synthesize them – Note the difference between “growth factors” (which only includes organic) and “essential nutrients” (includes all nutrients, both organic and inorganic) Growth factors must be provided as a nutrient – Examples: Essential amino acids, vitamins 23  3 Temperature Adaptation Groups 1. Psychrophiles – optimum temperature below 15oC (59oF) ▪ capable of growth at 0oC (32oF) = freezing temp for water ▪ can grow between -5oC to 20oC ▪ storage in refrigerator incubates them ▪ rarely pathogenic ▪ Ex: Staphylococcus aureus; often causes food-borne illness 2. Mesophiles – optimum temperature 20o-40oC (68o-104oF) ▪ can grow between 10oC to 50oC ▪ most human pathogens 3. Thermophiles – optimum temperature greater than 45oC (113oF) ▪ can grow at 35oC and above ▪ a heat-sterilizing device can be used to incubate these, rather than sterilize ▪ most don’t grow above 60oC, however a few do 24  Heterotrophs and Their Energy Sources Majority are chemoheterotrophs – Aerobic respiration -- uses oxygen to break down organic compounds (the carbon source) to produce energy. Two categories of chemoheterotrophic microbes: – Saprobes: some are free-living microorganisms that feed on organic detritus from dead organisms; fungi and certain bacteria Opportunistic pathogen (normally nonpathogenic; cause disease in an immunologically compromised host) Facultative parasite (not obligate; not restricted to a host) – Parasites: derive nutrients from host All are pathogens Some are obligate parasites (cannot live outside host) 25  Categories of Oxygen Requirement Aerobe – utilizes oxygen and can detoxify it Obligate aerobe – cannot grow without oxygen Facultative anaerobe – utilizes oxygen when present, but can also grow in its absence Microaerophilic – requires only a small amount of oxygen 26  Effects of pH Majority of microorganisms grow at a pH between 6 and 8 Acidophiles – grow at extreme acid pH Alkalinophiles – grow at extreme alkaline pH 27  The Population Growth Curve In laboratory studies, populations typically display a predictable pattern over time – growth curve Stages in the normal growth curve: 1. Lag phase – “flat” period of adjustment, enlargement; little growth 2. Exponential growth phase – a period of maximum growth will continue as long as cells have adequate nutrients and a favorable environment 3. Stationary phase – rate of cell growth equals rate of cell death caused by depleted nutrients and/or O2, excretion of organic acids and pollutants 4. Death phase – as limiting factors intensify, cells die exponentially 28  Culturing Microbes 1. Inoculation – introduction of a sample into a container of media to produce a culture of observable growth. medium = a nutrient used to grow microbes outside of their natural habitats. culture = the visible accummulation of microbes in or on a nutrient medium; or, to propogate microbes. 29  Isolation techniques are based on the concept that if an individual bacterial cell is separated from other cells and has space on a nutrient surface, it will grow into a mound of cells-- a colony. A colony consists of one species. 30  Isolation techniques include streak plate method, pour plate method (or loop dilution), and spread plate method. – Streak plate technique: uses an inoculating loop to spread a sample thinly over the surface of a medium in an agar plate; each streak quadrant further dilutes the original sample, allowing for isolated growth. 31 Most commonly used media: – Nutrient broth – liquid medium containing beef extract and peptone. (peptone = a complex water-soluble product that is obtained by digesting protein (as meat) with an enzyme (as pepsin or trypsin). – Nutrient agar – solid media containing beef extract, peptone, and agar 32 Most commonly used solidifying agent is agar A complex polysaccharide isolated from red algae – Solid at room temperature, liquefies at boiling (100oC), does not re-solidify until it cools to 42oC (107.6oF) – Provides framework to hold moisture and nutrients – Not digestible for most microbes 33  Terminology and Methods of Control Sterilization – a process that destroys all viable microbes, including viruses and endospores. – Note: But not prions, which are extraordinarily resistant; see pg. 319 if you want more info. INANIMATE: Disinfectant – physical or chemical agents usually used on inanimate objects to destroy vegetative pathogens, not endospores. ANIMATE: Antiseptic – chemical agents applied directly to exposed body surfaces to destroy or inhibit vegetative cells (practice called antisepsis). 34  Antimicrobial Agents’ Modes of Action Cellular targets of physical and chemical agents: 1. The cell wall – cell wall becomes fragile and cell lyses; some antimicrobial drugs, detergents, and alcohol 2. The cell membrane – loses integrity; detergent surfactants (a surface-active agent that forms a water soluble interface; ex: dishwashing deter.) 3. Protein and nucleic acid synthesis – prevention of replication, transcription, translation, peptide bond formation, protein synthesis; the antibiotic chloramphenicol, ultraviolet radiation, formaldehyde 4. Proteins – disrupt or denature proteins, block binding sites; alcohols, phenols, acids, heat 35  Methods of Physical Control Know that the following are methods of physical control, and the general purpose and effectiveness of each: I. Heat – moist and dry II. Cold temperatures III. Desiccation IV. Radiation V. Filtration 36  Levels of Chemical Decontaminants/Germicides High-level – kill endospores; may be sterilants – Used on devices such as catheters, heart-lung equipment, and implants that are not heat sterilizable and are intended to enter body tissues Intermediate-level – kill fungal spores (not endospores), resistant pathogens such as tubercle bacillus, and viruses; (tubercle = swellings that form such as in TB) – Used to disinfect devices that will come in contact with mucous membranes but are not invasive (respiratory equipment, thermometers) Low-level – eliminate only vegetative bacteria, vegetative fungal cells, and some viruses – Clean surfaces that touch skin but not mucous membranes (electrodes, furniture) 37 Chromosome is subdivided into genes. A gene is: – The fundamental unit of heredity responsible for a given trait – Site on the chromosome that provides information for a certain cell function – Segment of DNA (a specific sequence of nucleotides) that contains the necessary code to make a protein or RNA molecule Three basic categories of genes: 1. Genes that code for proteins – structural genes 2. Genes that code for RNA 3. Genes that control gene expression – regulatory genes 38  DNA Two strands twisted into a double helix Basic unit of DNA structure is a nucleotide Each nucleotide consists of 3 parts: – A 5 carbon sugar – deoxyribose – A phosphate group – One of 4 nitrogenous bases – adenine, guanine, thymine, or cytosine Nucleotides covalently bond (share electrons) in an arrangement that forms a sugar-phosphate linkage = the backbone – Each sugar attaches to two phosphates 39  RNAs Single-stranded molecule made of nucleotides – 5 carbon sugar is ribose – One of 4 nitrogenous bases – adenine, uracil (instead of thymine), guanine, or cytosine – Phosphate 40  DNA Replication Making an exact duplicate of the DNA involves 30 different enzymes Begins at an origin of replication Helicase (enzyme) unwinds and unzips the DNA double helix An RNA primer is synthesized at the origin of replication – short strand of RNA that serves as a starting point for adding nucleotides DNA polymerase adds nucleotides – Both strands are copied (synthesized) 41  Applications of the DNA code TRANSCRIPTION Information stored on the DNA molecule is conveyed to "messenger RNA" molecules (mRNA) through the process of transcription (occurs at the chromosome) – mRNA’s are relatively short single-stranded segments of nucleotides that code for proteins. – An mRNA is transcribed from only one strand of DNA, the template strand, which contains the gene. The other complementary DNA strand is called the nontemplate strand. Which strand becomes the “template” varies from one gene to another. 42  Gene-Protein Connection TRANSLATION - Each "triplet" of nucleotides on the mRNA, called a codon, specifies a particular amino acid. The information contained in the mRNA molecule is used to produce proteins in a process called translation, which occurs in the ribosome (which is in the cytoplasm). – Molecules called tRNA ("transfer RNA") bring the proper amino acids to the ribosomes, in the sequence encoded in the mRNA. – There exist a specific tRNA molecule for each kind of amino acid. – Each tRNA carries an anticodon, which is a triplet of nucleotides that binds to a complementary codon in the mRNA. Hence the amino acids are brought to the ribosomes in the proper order, and then bonded together in the proper sequence. 43  Conjugation Conjugation – transfer of a plasmid or chromosomal fragment (DNA) from a donor cell to a recipient cell via a direct connection (pilus) Example: – Gram-negative cells have a fertility factor, which is a plasmid that contains genes that code for the synthesis of a conjugative pilus – Recipient cell is a related species or genus without a fertility factor – Donor replicates its plasmid and then transfers fertility factor to recipient through its pilus; now recipient can synthesize pili, thus acquiring a new ability to initiate "sex" (to conjugate) 44  Some other traits acquired by conjugating bacteria Drug or antibiotic resistance (acquired first by random mutation in the DNA that gives bacteria a selective advantage in its environment) – plasmids contain the genes that give the bacteria this type of resistance New enzymes Toxin production Metal resistance 45  Biotechnology and Recombinant DNA Biotechnology: the use of microorganisms, cells, or cell components to make a product – Foods, antibiotics, vitamins, enzymes, vaccines Recombinant DNA (rDNA) technology (genetic engineering): – insertion or modification of genes to produce desired proteins – Example: a gene can be taken from human DNA and be inserted into a bacterium’s DNA – bacteria and yeasts can be used to: produce mass amounts of product, as the inserted gene is expressed by the microbes (e.g., insulin) produce thousands of copies of a gene  Biotechnology and Recombinant DNA Vector: self-replicating DNA used to carry the desired gene to a new cell; can be a plasmid. – gene is inserted into the vector – vector is taken up by a bacterium Clones: populations of cells arising from one cell; all cells are genetically identical and carry the new gene (vector) E. coli is used to mass produce the human growth hormone, which is administered to humans who do not produce enough and would otherwise have stunted growth.  Therapeutic Applications Antigen = a foreign substance that elicits an immune response in the form of antibodies; surface proteins that uniquely identify a pathogenic microbe, and is recognized by the host as foreign. Human enzymes and other proteins (such as the hormone insulin) are produced by recombinant DNA techniques Subunit vaccines consists of only a portion of a pathogen (the antigenic determinant), enough to build an immune response – protein portion is produced by, and harvested from, genetically modified cells – used for hepatitis B vaccinations – advantage is that there is no chance of actually getting infected  Scientific Nomenclature Common names – Vary with languages – Vary with geography Binomial nomenclature (genus + specific epithet, species) – Used worldwide – First term capitalized, can be abbreviated with just capital letter and a period – Second term lower case – Both terms italicized when in print, underlined if handwritten – Examples: Escherichia coli or E. coli Homo sapiens  Classification of Eukaryotes Animalia: multicellular; no cell walls; chemoheterotrophic, ingest food; include parasitic worms (helminths) Plantae: multicellular; cellulose cell walls; usually photoautotrophic Fungi: chemoheterotrophic; unicellular or multicellular; cell walls of chitin; develop from spores or hyphal fragments; absorb pre-digested food Protista: a catchall kingdom for eukaryotic organisms that do not fit other kingdoms – include algae, protozoans  Identification Methods Morphological characteristics: shape, arrangement, flagella?, endospores? Differential staining: Gram staining, acid-fast staining Biochemical tests: determines presence of bacterial enzymes – Ex: metabolize lactose?, produce acid or gas during metabolism? – Selective and/or differential media Proteobacteria: Neisseria gonorrhoeae 820,000 new gonorrheal infections occur in the U.S. each year Also called a “gonococcus”. Causes gonorrhea, a common STD Spread through vaginal, oral, or anal sexual contact. Infections in the throat cause few symptoms. © 2013 Pearson Education, Inc. 2. Cyanobacteria – Gram-negative, the only group of prokaryotes with plantlike, oxygen-generating photosynthesis. – Some species, such as Anabaena, have specialized cells that fix nitrogen. © 2012 Pearson Education, Inc.  3. Chlamydias ▪ Gram-negative, live inside eukaryotic host cells. – Chlamydia trachomatis – is a common cause of trachoma, an infection of the eye that causes blindness in developing countries and – A different strain causes nongonococcal urethritis, the most common sexually transmitted disease in the United States. – often symptomless; 40% of infected women develop pelvic inflammatory disease, which can cause infertility – frequent testing essential to detecting early before complications occur; easily cured by antibiotics © 2012 Pearson Education, Inc. 4. Spirochetes – Gram-negative, helical bacteria with axial filaments used for movement, and – are notorious pathogens, causing – Syphilis, caused by Treponema pallidum – characterized in its primary stage by genital sores. If untreated, can develop much more serious and fatal symptoms. – Lyme disease, caused by Borrelia spcs. – transmitted by ticks and characterized initially by a rash followed by flu-like symptoms including fever, joint pain, and headache – http://content.lib.utah.edu/utils/getfile/collection/EHSL-NOVEL/id/210/filename/785.pdf © 2012 Pearson Education, Inc. 5. Gram-positive bacteria – rival proteobacteria in diversity and – include the “actinomycetes” common in soil as organic matter decomposers. – Streptomyces is often cultured by pharmaceutical companies as a source of many antibiotics including streptomycin. – includes pathogenic bacteria such as Staphylococcus and Streptococcus, and Bacillus anthracis © 2012 Pearson Education, Inc.  Microscopic Fungi Exist in one of two morphologies: – Yeast cell – round ovoid shape; many only reproduce by “budding” = an asexual method in which swellings grow and become separate cells. – Hyphae cells – long, filamentous, thread-like fungi = molds Some alternate between forms depending on growth conditions (i.e., change in temp) – dimorphic – particularly characteristic of some pathogenic molds 57  Roles of Fungi Adverse impact – Mycoses, allergies (airborne spores), toxin production (poisonous mushrooms) – Destruction of crops and food storages Beneficial impact – Decomposers of dead plants and animals – Sources of antibiotics, alcohol, foods, flavors, vitamins 58  Protozoa Diverse group of 65,000 species Vary in shape, lack a cell wall Most are unicellular; colonies are rare Most are harmless, free-living in a moist habitat Some are animal parasites and can be spread by insect vectors (Ex: Plasmodium, causes malaria) All are heterotrophic – lack chloroplasts Feed by engulfing other microbes and organic matter 59  Important Protozoan Pathogens Pathogenic flagellates – Trypanosomes – Trypanosoma (infect blood, transmitted by blood-sucking vectors, causes fever, inflammation, heart/brain damage, and sometimes death) T. brucei – African sleeping sickness (vector: tsetse fly) T. cruzi – Chaga’s disease; South America (vector: kissing bug) Infective amoebas – Entamoeba histolytica – amebic dysentery (nausea, vomiting, diarrhea); worldwide 60  Parasitic Helminths Multicellular animals; possess organs for reproduction, digestion, movement, protection Parasitize host tissues Have mouthparts for attachment to or digestion of host tissues Most have well-developed sex organs that produce eggs and sperm Fertilized eggs go through larval period in or out of host body 61 KNOW THIS CHART 62  6.5 Modes of Viral Multiplication General phases in animal virus multiplication cycle: (APUSAR) 1. Adsorption – binding of virus to specific molecule on host cell. 2. Penetration – genome enters host cell by endocytosis or fusion. 3. Uncoating – the viral nucleic acid is released from the capsid/envelope. 4. Synthesis – viral components are produced. 5. Assembly – the new viral particles are put together. 6. Release – assembled viruses are released by budding (exocytosis) or host cell lysis. 64  Multiplication Cycle in Bacteriophages Bacteriophages [-fayj] – viruses that infect bacteria (phages) Most widely studied are those that infect Escherichia coli Multiplication goes through similar stages as animal viruses Only the nucleic acid is inserted by the phage and enters the cytoplasm - uncoating is not necessary Release is a result of cell lysis induced by viral enzymes and by the bacteria becoming over-packed with viruses - lytic cycle 65  Lysogeny: The Silent Virus Infection Not all phages complete the lytic cycle initially. Some DNA phages, called temperate phages, undergo adsorption and penetration but don’t replicate. The viral genome inserts into bacterial genome and becomes an inactive prophage – the cell is not lysed. Prophage is retained and copied during normal cell division resulting in the transfer of temperate phage genome to all host cell progeny; lysogeny = potential ability of bacteria to produce phage; allows spread of the virus without killing the host initially. Induction = activation of prophage resulting in viral replication and the lytic cycle 66  Pathology, Infection, and Disease Pathogen: disease-causing microorganism Pathology: the scientific study of disease Etiology: the cause of a disease (for example, the name of the species that causes the disease) – Ex: Clostridium botulinum causes botulism (food poisoning) Pathogenesis: the manner in which a disease develops – how is infection acquired – what areas of the body does the microbe infect  Contact, Colonization, Infection, Disease Microbes that engage in mutual or commensal associations, but do not penetrate into the host's sterile tissues, are called normal (resident) flora, indigenous flora [in-dij'-uh-nuhs], or microbiota. Human body = 1 ×1013 body cells – harbors 1 ×1014 bacterial cells (10 times more) 68  Resident Flora Bacterial flora benefit host by preventing overgrowth of harmful microbes as a result of limited number of attachment sites to host– called microbial antagonism. – competition among microbes for nutrients, space – producing substances harmful to pathogens – affecting pH and oxygen conditions 69  Major Factors in the Development of an Infection True pathogens – capable of causing disease in healthy persons with normal immune defenses – Examples: Influenza virus, plague bacillus, malarial protozoan Opportunistic pathogens – cause disease when the host’s defenses are compromised or when they grow in part of the body that is not natural to them – Ex: Candida albicans is a normal resident of mouth, throat, intestine, vagina; can proliferate and cause infections, such as vaginal yeast infections; women taking antibiotics are particularly susceptible to this opportunistic infection due to the resulting change/imbalance of normal flora that normally keep this yeast in check. 70  Major Factors in the Development of an Infection Severity of the disease depends on the virulence of the pathogen. Characteristic or structure that contributes to the ability of a microbe to cause disease, and that determine the degree of tissue damage and severity of the disease, is called a virulence factor. – Example: certain toxins that some infectious agents secrete, antiphagocytic factors 71  Causing Disease Toxigenicity – capacity to produce toxins at the site of multiplication – Endotoxin – toxin that is not secreted but is released after the cell is damaged – Exotoxin – toxin molecule secreted by a living bacterial cell into the infected tissue Antiphagocytic factors – Some bacteria kill phagocytes in our immune system – Slimes or capsules can make it physically difficult for the phagocyte to engulf the pathogen 72  Patterns of Infection Primary infection – initial infection Secondary infection – another infection by a different microbe – caused by an opportunistic pathogen after primary infection has weakened the body’s defenses Acute infection – comes on rapidly, with severe but short-lived effects – Ex: influenza Chronic infections – progresses more slowly, may be less severe, but persist over a long period of time – tuberculosis, hepatitis B 73  Acquisition and Transmission of Infectious Agents Communicable disease – when an infected host can transmit the infectious agent to another host and establish infection in that host Highly communicable disease is contagious Non-communicable infectious disease does not arise through transmission from host to host – Occurs primarily when a compromised person is invaded by his or her own normal microflora – Contact with organism in natural, non-living reservoir 74  Classifying Infectious Diseases Symptom: a change in body function that is felt by a patient as a result of disease Sign: a change in a body that can be measured or observed as a result of disease Syndrome: a specific group of signs and symptoms that accompany a disease  Patterns of Transmission Direct contact – physical contact or fine aerosol droplets Indirect contact – passes from infected host to intermediate conveyor and then to another host – Vehicle – inanimate material, food, water, biological products, fomites (which are any nonliving objects involved in the spread of an infection) – Airborne – droplet nuclei, aerosols 76  Nosocomial Infections Diseases that are acquired or developed during a hospital stay From surgical procedures, equipment, personnel, and exposure to drug-resistant microorganisms 2 to 4 million cases/year in U.S. with approximately 90,000 deaths Most commonly involve urinary tract, respiratory tract, and surgical incisions Most common organisms involved: Gram-negative intestinal flora – E. coli, Pseudomonas, Staphylococcus 77 Portals of Entry – gaining entrance into the host Mucous membranes – lining respiratory tract, gastrointestinal tract, genitourinary tract, and conjunctiva inhaled on drops of moisture or airborne dust particles contaminated food, water, or fingers sexually transmitted Skin – If unbroken, mostly impenetrable – access through hair follicles, sweat gland ducts – some fungi grow on the keratin  Adherence – attachment to host very important for most pathogens Adhesins/ligands are surface molecules (glycoproteins or lipoproteins) that bind to complementary surface receptors on cells of certain host tissues Adhesins located on flagella, pili, or: – Glycocalyx: Streptococcus mutans – Fimbriae: Escherichia coli – M protein: Streptococcus pyogenes Form biofilms – masses of microbes and their extracellular products that attach to living and nonliving surfaces – Ex: dental plaque on teeth, algae on pool walls, scum in showers.  How Pathogens Damage Host Cells 1) Using host cell’s nutrients (such as iron) 2) Direct Damage: – Disrupt host cell function – Produce waste products – Cause host cell to rupture 3) Toxins (toxigenicity—capacity to produce toxins) – exotoxins and endotoxins – can produce fever, cardiovascular disturbances, diarrhea, shock, destroy tissues – can be fatal  Portals of Exit Pathogens depart by a specific avenue; greatly influences the dissemination of infection – Respiratory – mucus, sputum, nasal drainage, saliva – Skin scales – Fecal exit – Urogenital tract – Removal of blood 81  Portals of Exit Respiratory tract – Coughing and sneezing Gastrointestinal tract – Feces and saliva Genitourinary tract – Urine and vaginal secretions Skin Blood – Arthropods that bite; needles or syringes