Microbiology notes chapters 1, 2, 4, 5, 6, & 7
Microbiology notes chapters 1, 2, 4, 5, 6, & 7 BIO 2600
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This 28 page Study Guide was uploaded by Katelyn Farris on Monday August 29, 2016. The Study Guide belongs to BIO 2600 at William Carey University taught by Dr. Cunningham in Fall 2015. Since its upload, it has received 36 views. For similar materials see Microbiology in Biology at William Carey University.
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Chapter 1 notes Microbiology -The study of organisms too small to be seen without magnification -Microorganisms include: -Bacteria -Viruses -Fungi -Protozoa -Helminths (worms) -Algae Microbiology Endeavors Table -Immunology -Public health microbiology and epidemiology -Food, dairy, and aquatic microbiology -Agricultural microbiology -Biotechnology -Genetic engineering and recombinant DNA technology Microbial Involvement in Energy and Nutrient Flow -The flow of energy and food through the earth’s ecosystems -Photosynthesis: Light fueled conversion of carbon dioxide to organic material -Decomposition: Breakdown of dead matter and wastes into simple compounds Infectious Diseases -Pathogens: Microorganisms that do harm -Nearly 2000 different microbes cause disease -10 Billion infections a year worldwide -12 Million deaths from infections a year worldwide Characteristics of Microbes -Two cell lines -Prokaryote – microscopic, unicellular organisms, lack nuclei and membrane-bound organelles Eukaryote – unicellular (microscopic) and multicellular, nucleus and membrane-bound organelles -Viruses -Acellular, parasitic particles composed of a nucleic acid and protein Basic Structure of Cells and Viruses: The six types of Microorganisms 1. Bacteria 2. Fungus 3. Algae 4. Virus 5. Vorticella 6. Helmith Lifestyles of Microorganisms -Majority live a free existence, are relatively harmless and often beneficial -Many Microorganisms have close associations with other organisms -Parasites -Hosts Historical Foundations of Microbiology -300 years old -Prominent discoveries include: -Microscopy -Scientific method -Development of medical microbiology -Microbiology techniques Spontaneous Generation -Early belief that some forms of life could arise from vital forces present in nonliving or decomposing matter (flies from manure, etc.) Antoni Van Leeuwenhoek -Dutch linen merchant -First to observe living microorganisms -Single-lens magnified up to 300x The Development of Medical Microbiology -Early experiments led to the realization that microbes are everywhere -This discovery led to immediate applications in medicine -Germ theory of Disease: resulted in the use of sterile, aseptic, and pure culture techniques Discovery of Spores and Sterilization -John Tyndall and Ferdinand Cohn each demonstrated the presence of heat resistant forms of some microbes -Cohn determined these forms to be heat-resistant bacterial endospores -Sterility requires the elimination of all life forms including endospores and viruses Development of Aseptic Technique -The human body is a source of infection -Dr. Oliver Wendel Holmes - observed that mothers of home births had fewer infections than those who gave birth in hospitals -Dr. Ignaz Semmelweis – correlated infection with physicians coming directly from the autopsy room to the maternity ward -Joseph Lister – introduced aseptic techniques reducing microbes in medical settings and prevention wound infections -washing hands for surgery -heat sterilization Pathogens and Germ Theory for Disease -Many diseases are caused by the growth of microbes in the body and not by sins, bad character, or poverty, etc. -Two major contributors: -Louis Pasteur and Robert Koch Louis Pasteur -Showed microbes caused fermentation and spoilage -Disproved spontaneous generation -Developed pasteurization -Demonstrated Germ Theory of Disease Robert Koch -Established Koch’s postulates – a sequence of experimental steps that verified the germ theory -Identified cause of anthrax, TB, and cholera -Developed pure culture method Taxonomy -Taxonomy: organizing, classifying, and naming living things -Formal system originated by Carl von Lime’ -Concerned with: -Classification – orderly arrangement of organisms into groups -Nomenclature – assigning names -Identification Levels of Classification Domain – Archaen, Bacteria, and Eukarya Kingdom Phylum or Division Class Order Family Genus Species Assigning Specific Names -Binomial nomenclature -Gives each microbe two names -Genus – capitalized -Species – lowercase -Both italicized or underlined -Inspiration for names is extremely varied 3 Domains -Bacteria – true bacteria -Archaea – odd bacteria that live in extreme environments -Eukarya – have nucleus and organelles Chapter 2 notes Chemistry of Carbon and Organic Compounds -Organic chemicals – compounds containing carbon bonded to hydrogen -Carbon is the basic element of life -Contains 4 atoms in its outer orbital -Can form single, double, or triple covalent bonds -Can form linear, branched, or ringed bonds Functional Groups of Organic Compounds -Accessory molecules that bind to organic compounds -Confer unique reactive properties on the whole molecule Macromolecules -Biochemicals are organic compounds produced by living things -Macromolecules are large compounds assembled from smaller subunits -Monomer: a repeating subunit -Polymer: a chain of monomers Macromolecules 1. Carbohydrates – monosaccharides, disaccharides, polysaccharides 2. Lipids – triglycerides (fats and oils), phospholipids, steroids 3. Proteins 4. Nucleic Acid – DNA, RNA Carbohydrates -Sugars and polysaccharides -General formula (CH2O)n -Aldehydes and Ketones -Saccharide: simple carb -Monosaccharide: 3-7 carbons -Disaccharide: two monosaccharides -Polysaccharide: five or more monosaccarides *Look at figure 2.15b* Carbs -Subunits linked by glycosidic bonds -Dehydration synthesis: loss of water in a polymerization reaction -Functions – cell structure, adhesion, and metabolism Chapter 2 notes Lipids -Long or complex, hydrophobic, C-H chains -Triglycerides, phospholipids in membranes, steroids like cholesterol -Functions -triglycerides – energy storage -phospholipids – major cell membrane component -steroids – cell membrane component Proteins -Predominant molecules in cells -Monomer – amino acids -Polymer – peptide, polypeptide, protein -Subunits linked by peptide bonds -Fold into very specific 3-D shapes -Functions – support, enzymes, transport *Table 41* *Table 2.5* know essential ? *Figure 2.21* Nucleic Acid -DNA and RNA -Monomer – nucleotide -DNA – deoxyribonucleic acid -A,T,C,G – nitrogen bases -Double Helix -Function – hereditary material -RNA – ribonucleic acid -A,U,C,G – nitrogen bases -Function: organize protein synthesis *Figure 2.24* Look at something on page 51 Double Helix of DNA -DNA is formed by two very long polynucleotide strands linked along their length by hydrogen bonds Passing on the Genetic Message -Each strand is copied -Replication is guided by base pairing -Each result is two separate double strands ATP: The Energy Molecule of Cells -Adenosine triophosphate -Nucleotide – adenine, ribose, three phosphates -Function – transfer and storage of energy Chapter 4 notes *4.3 Prokaryotic Profiles pg. 91 *Figure 4.1 Structure of a Bacterial Cell External Structures -Appendages -Two major groups 1. Motility – flagella and axial filaments 2. Attachment or channels – fimbrial and pili -Glycocalyx – surface coating Flagella -3 parts: 1. Filament – long, thin, helical structure composed of protein flagellin 2. Curved sheath 3. Basal Body – stack of rings firmly anchored in cell wall -Rotates 360 degrees -Number and arrangement of flagella varies -Monotrichous, lophotrichous, amphitrichous -Functions in motility through cell environment Flagellar Arrangements 1. Monotrichous – single flagellum at one end 2. Lophotrichous – small bunches emerging from the same site 3. Amphitrichous – flagella at both ends of cell 4. Peritrichous – flagella are dispersed randomly Flagellar Responses -Guide bacteria in a direction in response to external stimulus -Chemical stimuli – chemotaxis; positive and negative -Light stimuli -Signal sets flagella into rotary motion clockwise or counterclockwise Periplasmic Flagella -Internal flagella, enclosed in the space between the outer sheath and the cell wall peptidoglycan -Produce cellular motility by contracting and imparting twisting or flexing motion Fimbriae -Fine, proteinaceous, hair-like bristles emerging from the cell surface -Function in adhesion to other cells and surfaces Pili -Rigid tubular structure made of pilin protein -Found only in gram-negative cells -Function to join bacterial cells for partial DNA transfer called conjugation -Important in transfer of antibiotic resistance Glycocalyx -Coating of molecules external to the cell wall, made of sugars and/or proteins -Two types: 1. Slime layer – loosely organized and attached 2. Capsule – highly organized, tightly attached -Functions: - Protect cells from dehydration and nutrient loss - Inhibit killing by white blood cells by phagocytosis contributing to pathogenicity - Attachment – formation of biofilms - Related to quorum sensing *Pay attention to inside 4.1 in the book The Cell Envelope -External covering outside the cytoplasm -Composed of two basic layers: -Cell wall and cell membrane -Maintains cell integrity -Two different groups of bacteria demonstrated by Gram stain: -Gram-positive bacteria: thick cell wall composed primarily of peptidoglycan and cell membrane -Gram-negative bacteria: outer membrane, thin peptidoglycan layer, and cell membrane *Pay attention to pg. 73 inside 3.2 Structure of Cell Walls -Determines cell shape, prevents lysis (bursting) or collapsing due to changing osmotic pressure -Peptidoglycan is primary component: -Unique macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments Gram-Positive Cell Wall -Thick, homogeneous sheath of peptidoglycan -20-80 nm thick -Includes teihoic acid and lipoteichoic acid: function in cell wall maintenance and enlargement during cell division; move cations across the cell envelope; stimulate a specific immune response -Some cells have a periplasmic space, between the cell membrane and cell wall Gram-Negative Cell Wall -Composed of an outer membrane and a thin peptidoglycan layer -Outer membrane is similar to cell membrane bilayer structure -Outermost layer contains lipopolysaccharides and lipoproteins (LPS) -Lipid portion (endotoxin) may become toxic when released during infections -May function as receptors and blocking immune response -Contain porin proteins in upper layer – regulate molecules entering and leaving cell -Bottom layer is a thin layer of *Table 4.1 The Gram Stain -Differential stain that distinguishes cells with a gram-positive cell wall those with a gram-negative cell wall -Gram-positive – retain crystal violet and stain purple -Gram-negative – lose crystal violet and stain red from safranin counterstain -Important basis of bacterial classification and identification -Practical aid in diagnosing infection and guiding drug treatment Nontypical Cell Walls -Some bacterial groups lack typical cell wall structure, Ex. Mycobacterium and Nocardia -Gram-positive cell wall structure with lipid mycolic acid (cord factor) -Pathogenicity and high degree of resistance to certain chemicals and dyes -Basis for acid-fast stain used for diagnosis of infections caused by these microorganisms -Some have no cell wall, Ex. Mycoplasma -Cell wall is stabilized by sterols -Pleomorphic Cell Membrane Structure -Phospholipid bilayer with embedded proteins – fluid mosaic model -Functions in: -Providing site for energy reactions, nutrient processing, and synthesis -Passage of nutrients into the cell and the discharge of wastes -cell membrane is selectively permeable Bacterial Internal Structures -Cell cytoplasm: -Dense gelatinous solution of sugars, amino acids, and salts -70-80% water -serves as solvent for materials used in all cell functions Bacterial Internal Structures -Chromosomes -Single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell -Aggregated in a dense area called the nucleoid -DNA is tightly coiled -Plasmids -Small circular, double-stranded DNA -Free or integrated into the chromosome -Duplicated and passed on to offspring -Not essential to bacterial growth and metabolism -May encode antibiotic resistance, tolerance to toxic metals, enzymes, and toxins -Used in genetic engineering – readily manipulated and transferred from cell to cell -Ribosomes -Made of 60% ribosomal RNA and 40% protein -Consist of two subunits: large and small -Prokaryotic differ from eukaryotic ribosomes in size and number of proteins -Site of protein synthesis -Present in all cells -Inclusions and granules -Intracellular storage bodies -Vary in size, number, and content -Bacterial cell can use them when environmental sources are depleted -Examples: glycogen, particles of iron oxide, etc -Cytoskeleton -Many bacteria possess an internal network of protein polymers that is closely associated with the cell wall Bacterial Internal Structures cont.. -Endospores -Inert, resting, cells produced by some G+ genera: Clostridium, Bacillus, and Sporosarcina -Have a 2-phase life cycle: -Vegatative cell – metabolically active and growing -Endospore – when exposed to adverse environmental conditions; capable of high resistance and very long-term survival -Sporulation – formation of endospores -Hardiest of all life forms -Withstands extremes in heat, drying, freezing, radiation, and chemicals -Not a means of reproduction -Germination – return to vegetative growth Endospores -Resistance linked to high levels of calcium and dipicolinic acid -Dehydrated, metabolically inactive -Thick coat -Longevity verges on immortality, 250 million years Bacterial Shapes, Arrangements, and Sizes -Vary in shape, size, and arrangement but typically described by one of three basic shapes: -Coccus – spherical -Bacillus – rod -Coccobacillus – very short and plump - Vibrio – gently curved Spirillum – helical, comma -Arrangement of cells is dependent on pattern of division and how cell remains attached after division Classification Systems in Prokaryotae 1. Microscopic morphology 2. Macroscopic morphology – colony appearance 3. Bacterial physiology 4. Serological analysis 5. Genetic and molecular analysis Bacterial Taxonomy Based on Bergey’s Manual -Bergey’s Manual of Determinative Bacteriology – Five-volume resource covering all known prokaryotes -Classification based on genetic information – phylogenetic -Two domains: Archaea and Bacteria -Five major subgroups with 25 different phyla Chapter 5 notes The History of Eukaryotes -Evidence suggests evolution from prokaryotic organisms by symbiosis -Organelles originated from prokaryotic cells trapped inside them-the endosymbiotic hypothesis *Insight 5.1 *Profile of Eukaryotic Cell pg. 126 *Figure 5.6 Mitosis Kingdom Fungi -100,000 species divided into two groups -Macroscopic fungi (mushrooms, puffballs, gill fungi) -Microscopic fungi (molds, yeasts) -Majority are unicellular or colonial; a few have cellular specialization Microscopic Fungi -Exist in two morphologies: -Yeast – round ovoid shape, asexual reproduction -Hyphae – long filamentous fungi or molds -Some exist in either form – dimorphic – characteristic of some pathogenic molds Fungal Nutrition -All are heterotrophic -Majority are harmless saprobes living off dead plants and animals -Some are parasites, living on the tissues of other organisms, but none are obligate - Mycoses – Fungal infections -Growth temperature 20-40 degrees C -Extremely widespread distribution in many habitats Fungal Organization -Most grow in loose associations or colonies -Yeast – soft, uniform texture and appearance -Filamentous fungi – mass of hyphae called mycelium; cottony, hairy, or velvety texture -Hyphae may be divided by cross walls – septate -Vegetative hyphae – digest and absorb nutrients -Reproductive hyphae – produce spores for reproduction *Pictures on pg. 137 Chapter 5 notes Fungal Reproduction -Primarily through spores formed on reproductive hyphae -Asexual reproduction – spores are formed through budding or mitosis; conidia or sporangiospores *Figure 5.18 *Figure 5.19 Fungal Reproduction -Sexual reproduction – spores are formed following fusion of two different strains and formation of sexual structure -Zygospores, ascospores, and basidiospores -Sexual spores and spore-forming structures are one basis for classification Fungal Classification -Kingdom Eumycota is subdivided into several phyla based upon the type of sexual reproduction: 1. Zygomycota – Zygospores; sporangiospores and some conidia 2. Ascomycota – Ascospores; conidia 3. Basidiomycota – Basidiospores; conidia 4. Fungi that produce only Asexual Spores (Imperfect) *Figure 5.20 *Figure 5.21 Saccharomyces cerevisiae – baker’s yeast, ale production Saccharomyces bayanus – wine production Pneumocystis pneumonia: The most frequent opportunistic infection seen in AIDS patients Candida albicans – yeast infection Stachybotrys: “Black mold” *Figure 5.22 Cryptococcus neoformans Roles of Fungi -Adverse impact -Mycoses, allergies, toxin production (aflatoxins) -Destruction of crops and food storages -Beneficial impact -Decomposers of dead plants and animals Chapter 5 notes -Sources of antibiotics, alcohol, organic acids, vitamins -Used in making foods and in genetic studies *Pg. 143 and Table 5.3 Kingdom Protista -Algae – eukaryotic organisms, usually unicellular and colonial, that photosynthesize with chlorophyll a -Protozoa – unicellular eukaryotes that lack tissues and share similarities in cell structure, nutrition, life cycle, and biochemistry Algae -Photosynthetic organisms (Produce large proportion of atmospheric O2) -Contain chloroplasts with chlorophyll and other pigments -Microscopic forms are unicellular, colonial, and filamentous -Macroscopic forms are colonial and multicellular -Cell wall -May or may not have flagella -Most are free-living in fresh and marine water – plankton -Provide basis of food web in most aquatic habitats Pathogenic Algae -Dinoflagellates can cause red tides and give off toxins that cause food poisoning with neurological symptoms 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 -All are heterotrophic – lack chloroplasts -Cytoplasm divided into ectoplasm and endoplasm -Feed by engulfing other microbes and organic matter Protozoa -Most have locomoter structures -Flagella -Cilia -Psuedopodia Protozoa -Exist as trophozoite – motile feeding stage -Many can enter into a dormant resting stage when conditions are unfavorable for growth and feeding – cyst Chapter 5 notes -All reproduce asexually, mitosis or multiple fission; many also reproduce sexually – conjugation *Figure 5.27 Mastigophora -Primarily flagellar motility, some flagellar and amoeboid; sexual reproduction -Trypanosoma: sleeping sickness and Chagas disease -Giardia: giardiasis (“beaver fever”) -Trichomonas: STD Sarcodina -Primarily amoeba; asexual by fission; most are free-living -Entamoeba histolytica: amebic dysentery Ciliophora -Possess cilia; trophozoites and cysts; most are free-living, harmless -Paramecium Apicomplexans -Motility is absent except male gametes; sexual and asexual reproduction; complex life cycle – all parasitic -Unusual life cycle normally involving 2 hosts: 1. Intermediate host (asexual stage) 2. Definitive host (sexual stage) – typically humans -Plasmodium: malaria *Figure 5.33 Chapter 6 notes The Search for the Elusive Virus -Louis Pasteur postulated that rabies was caused by a virus (1884) -Ivanovski and Beijerinck showed a disease in tobacco was caused by a virus (1890s) -1950s virology was a multifaceted discipline -Viruses: noncellular particles with a definite size, shape, and chemical composition General Structure of Viruses -Electron microscope is required Viral Components: Capsids, Nucleic Acids, and Envelopes -Viruses bear no resemblance to cells -Lack protein-synthesizing machinery -Viruses contain only the parts needed to invade and control a host cell *Virus profile pg. 162 General Structures of Viruses -Capsids -All viruses have capsids – protein coats that enclose and protect their nucleic acid - The capsids together with the nucleic acid are nucleocapsid -Some viruses have an external covering call envelope; those lacking an envelope are naked -Each capsid is constructed from identical subunits called capsomers made of protein -Two structural types: -Helical – continuous helix of capsomers forming a cylindrical nucleocapsid -Icosachedral – 20-sided with 12 corners -Vary in the number of capsomers -Each capsomer may be made of 1 or several proteins -Some are enveloped -Viral Envelope -Mostly animal viruses -Acquired when the virus leaves the host cell -Exposed proteins on the outside of the envelope, called spikes, essential for attachment of the virus to the host cell Functions of Capsid/Envelope -Protects the nucleic acid when the virus is outside the host cell -Helps the virus to bind to a cell surface and assists the penetration of the viral DNA or RNA into a suitable host cell Chapter 6 notes General Structure of Viruses -Complex viruses: atypical viruses -Poxviruses lack a typical capsid and are covered by a dense layer of lipoproteins -Some bacteriophages have a polyhedral nucleocapsid along with a helical tail and attachment fibers* deceptacon* *Figure 6.9 *Figure 6.10 Nucleic Acids -Viral genome – either DNA or RNA but never both -Carries genes necessary to invade host cell and redirect cell’s activity to make new viruses -Number of genes varies for each type of virus – few to hundreds -DNA viruses -Usually double stranded (ds) but may be single stranded (ss) -Circular or linear -RNA viruses -Usually single stranded, may be double stranded may be segmented into separate RNA pieces -ssRNA genomes ready for immediate translation are positive- sense RNA -ssRNA genomes that must be converted into proper form are negative-sense RNA General Structure -Pre-formed enzymes may be present -Polymerases – DNA or RNA -Replicases – copy RNA -Reverse transcriptase – synthesis of DNA from RNA (AIDS virus) Modes of Viral Multiplication -General phases in animal virus multiplication cycle: 1. Adsorption – binding of virus to specific molecule on host cell 2. Penetration – genome enters host cell 3. Uncoating – the viral nucleic acid is released from the capsid 4. Synthesis – viral components are produced 5. Assembly – new viral particles are constructed 6. Release – assembled viruses are released by budding (exocytosis) or cell lysis *Figure 6.11 pg. 170 Chapter 6 notes Adsorption and Host Range -Virus coincidentally collides with a susceptible host cell and adsorbs specifically to receptor sites on the cell membrane -Spectrum of cells a virus can infect – host range -Hepatitis B – human liver cells -Poliovirus – primate intestinal and nerve cells -Rabies – various cells of many mammals Penetration/Uncoating -Flexible cell membrane is penetrated by the whole virus or its nucleic acid by: -Endocytosis – entire virus is engulfed and enclosed in a vacuole or vesicle -Fusion – envelope merges directly with membrane resulting in nucleocapsid’s entry into cytoplasm *Figure 6.13 Replication and Protein Production -Varies depending on whether the virus is a DNA or RNA virus -DNA viruses generally are replicated and assembled in the nucleus -RNA viruses generally are replicated and assembled in the cytoplasm -Positive-sense RNA contain the message for translation -Negative-sense RNA must be converted into positive-sense message Release -Assembled viruses leave host cell in one of two ways: -Budding – exocytosis; nucleocapsid binds to membrane which pinches off and sheds the viruses gradually; cell is not immediately destroyed -Lysis – nonenveloped and complex viruses released when cell dies and ruptures -Number of viruses released is variable -3,000 – 4,000 released by poxvirus - >100,000 released by poliovirus Damage to Host Cell -Cytopathic effects – virus-induced damage to cells 1. Changes in size and shape 2. Cytoplasmic inclusion bodies 3. Inclusion bodies 4. Cells fuse to form multinucleated cells (syncytia) 5. Cell lysis Chapter 6 notes 6. Alter DNA 7. Transform cells into cancerous cells -Some animal viruses enter host cell and permanently alter is genetic material resulting in cancer – transformation of the cell -Transformed cells have increased rate of growth, alterations in chromosomes, and capacity to divide for indefinite time periods resulting in tumors -Mammalian viruses capable of initiating tumors are called oncoviruses -Papillomavirus – cervical cancer -Epstein-Barr virus – Burkitt’s lymphoma Lysogeny: The Silent Virus Infection -Not all phages complete the lytic cycle -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 -Induction can occur resulting in activation of lysogenic prophage followed by viral replication and cell lysis *Figure 6.17 *Pg. 174-176 Lysogeny -Results in the spread of the virus without killing the host cell -Phage genes in the bacterial chromosome can cause the production of toxins or enzymes that cause pathology – lysogenic conversion -Corynebacterium diphtheria -Vibrio cholera -Clostridium botulinum Persistent Infections -Persistent infections – cell harbors the virus and is not immediately lysed -Can last weeks or host’s lifetime; several can periodically reactive – chronic latent state -Measles virus – may remain hidden in brain cells for many years -Herpes simplex virus – cold sores and genital herpes Chapter 6 notes -Herpes zoster virus – chickenpox and shingles Prions and Other Infectious Particles -Prions – misfolded proteins, contain no nucleic acid -Cause transmissible spongiform encephalopathies – fatal neurodegenerative diseases -Common in animals: -Scrapie in sheep and goats -Bovine spongiform encephalopathies (BSE), aka mad cow disease -Wasting disease in elk - Humans – Creutzfeldt-Jakob Syndrome (CJS) -Extremely resistant to usual sterilization techniques Kuru: a prion disease transmitted by ritual cannibalism Prions are not viruses Chapter 7 notes Microbial Nutrition -Nutrition – process by which chemical substances (nutrients) are acquired from the environment and used in cellular activities -Essential nutrients – must be provided to an organism -Two categories of essential nutrients: -Macronutrients – required in large quantities; play principal roles in cell structure and metabolism -Proteins, carbohydrates -Micronutrients or trace elements – required in small amounts; involved in enzyme function and maintenance of protein structure -Manganese, zinc, nickel Nutrients -Organic nutrients – contain carbon and hydrogen atoms and are usually the products of living things -Methane, carbohydrates, lipids, proteins, and nucleic acids -Inorganic nutrients – atom or molecule that contains a combination of atoms other than carbon and hydrogen -Metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water Chemical Analysis of Microbial Cytoplasm -70% water -Proteins -96% of cell is composed of 6 elements -Carbon -Hydrogen -Oxygen -Phosphorous -Sulfur -Nitrogen Sources of Essential Nutrients -Carbon sources -Heterotroph – must obtain carbon in an organic form made by other living organisms such as proteins, carbohydrates, lipids, and nucleic acids -Autotroph – an organism that uses carbon dioxide, and inorganic gas as its carbon source -Not nutritionally dependent on other living things 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 Chapter 7 notes -Growth factors must be provided as a nutrient -Essential amino acids, vitamins Nutritional Types -Main determinants of nutritional type are: -Carbon source -Heterotroph – uses organic sources of carbon -Autotroph – uses inorganic sources of carbon -Energy source -Chemotroph – gain energy from chemical compounds -Phototrophs – gain energy through photosynthesis Combinations of Nutritional Types -Chemoheterotrophs -Photoautotrophs -Chemoautotrophs (nitrifying bacteria, sulfur bacteria, most of which are members of the Archea) -Photoheterotrophs (purple and green bacteria) Heterotrophs and Their Energy Sources -Two categories -Saprobes: Free-living microorganisms that feed on organic detritus from dead organisms -Parasites: derive nutrients from host -Many pathogens can alternate between these two approaches: opportunistic Transport: Movement of Chemicals Across the Cell Membrane -Passive transport – does not require energy; substances exist in a gradient and move from areas of higher concentration toward areas of lower concentration -Diffusion -Osmosis – diffusion of water -Facilitated diffusion – requires a carrier *Figure 7.6 !!!!!!!!!!!!!!!!! *Figure 7.7 Transport: Movement of Chemicals Across the Cell Membrane -Active transport – requires energy and carrier proteins; gradient independent -Group translocation – transported molecule chemically altered -Bulk transport – endocytosis, exocytosis, and pinocytosis Environmental Factors That Influence Microbes -Factors include: Chapter 7 notes -Temperature -Oxygen requirements -pH -Osmotic pressure -Barometric pressure -Environmental factors usually affect the function of metabolic enzymes Effects of Temperature on Microbial Growth -Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism -Maximum temperature – highest temperature that permits a microbe’s growth and metabolism -Optimum temperature – promotes the fastest rate of growth and metabolism 3 Temperature Adaptation Groups 1. Psychrophiles – optimum temperature below 15 degrees Celsius; capable of growth at 0 degrees Celsius 2. Mesophiles – optimum temperature 20-40 degrees Celsius; most human pathogens 3. Thermophiles – optimum temperature greater than 45 degrees Celsius Gas Requirements Oxygen -As oxygen is utilized it is transformed into several toxic products: -Singlet oxygen ( O2), superoxide ion (O2), peroxide (H2O2), and hydroxyl radicals(OH) -Most cells have developed enzymes that neutralize these chemicals: -Superoxide dismutase, catalase -If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats Categories of Oxygen Requirements -Aerobe – utilizes oxygen and can detoxify it -Obligate aerobe – cannot grow without oxygen -Facultative anaerobe – utilizes oxygen but can also grow in its absence -Microaerophilic – requires only a small amount of oxygen Categories of Oxygen Requirements -Anaerobe – does not utilize oxygen -Obligate anaerobe – lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment Chapter 7 notes -Aerotolerant anaerobes – do not utilize oxygen but can survive and grow in its presence Carbon Dioxide Requirement -All microbes require some carbon dioxide in their metabolism -Capnophile – grows best at higher CO t2nsions than normally present in the atmosphere Effects of pH -Majority of microorganisms grow at a pH between 6 and 8 -Obligate acidophiles – grow at extreme acid pH -Alkalinophiles – grow at extreme alkaline pH Osmotic Pressure -Most microbes exist under hypotonic or isotonic conditions -Halophiles – require a high concentration of salt -Osmotolerant – do not require high concentration of solute but can tolerate it when it occurs Other Environmental Factors Barophiles – can survive under extreme pressure and will rupture if exposed to normal atmospheric pressure *Ecological Associations Among Microorganisms pg. 201 Ecological Associations Among Microorganisms -Symbiotic – two organisms live together in a close partnership -Mutualism – obligatory, dependent; both members benefit -Commensalism – commensal member benefits, other member neither harmed nor benefited -Parasitism – parasite is dependent and benefits; host is harmed -Non-symbiotic – organisms are free-living; relationships not required for survival -Synergism – members cooperate to produce a result that none of them could do alone -Antagonism – actions of one organism affect the success or survival of others in the same community (competition) -Antibiosis Interrelationships Between Microbes and Humans -Human body is a rich habitat for symbiotic bacteria, fungi, and a few protozoa – normal microbial flora -Commensal, parasitic, and synergistic relationships Microbial Biofilms Chapter 7 notes -Biofilms result when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers -Dominate the structure of most natural environments on earth -Communicate and cooperate in the formation and function of biofilms – quorum sensing *Figure 7.13 The Study of Microbial Growth -Microbial growth occurs at two levels: growth at a cellular level with increases in size, and increase in population -Division of bacterial cells occur mainly through binary fission (transverse) -Parent cell enlarges, duplicates its chromosome, and forms a central transverse septum dividing the cell into two daughter cells *Figure 7.14 Rate of Population Growth -Time required for a complete fission cycle is called the generation, or doubling time -Each new fission cycle increases the population by a factor of 2 – exponential growth -Generation times vary from minutes to days 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 O 2 ,excretion of organic acids and pollutants 4. Death phase – as limiting factors intensify, cells die exponentially
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