Microbiology With Diseases by Taxonomy Power Point Lecture

Metabolism Results in Reproduction § Result of microbial growth is discrete colony – an aggregation of cells arising from single parent cell § Reproduction results in growth Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Growth Requirements § Organisms use a variety of nutrients for their energy needs and to build organic molecules and cellular structures § Most common nutrients – those containing necessary elements such as carbon, oxygen, nitrogen, and hydrogen § Microbes obtain nutrients from variety of sources Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Nutrients: Chemical and Energy Requirements § Sources of carbon, energy, and electrons § Oxygen requirements § Nitrogen requirements § Other chemical requirements Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Sources of Carbon, Energy, and Electrons § Organisms are categorized into two groups based on source of carbon § Those using an inorganic source of carbon (carbon dioxide) are autotrophs § Those catabolizing reduced organic molecules (proteins, carbohydrates, amino acids, and fatty acids) are heterotrophs Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Sources of Carbon, Energy, and Electrons (continued) § Organisms categorized into two groups based on whether they use chemicals or light as source of energy § Those that acquire energy from redox reactions involving inorganic and organic chemicals are chemotrophs § Those that use light as their energy source are phototrophs Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Four Basic Groups of Organisms Copyright © 2007 Pearson Education, Inc. publishing as Benjamin

Oxygen Requirements § Oxygen is essential for obligate aerobes (final electron acceptor in ETC) § Oxygen is deadly for obligate anaerobes § How can this be true? § Neither gaseous O 2 nor oxygen covalently bound in compounds is poisonous § The forms of oxygen that are toxic are excellent oxidizing agents § Resulting chain of oxidations causes irreparable damage to cells by oxidizing compounds such as proteins and lipids Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Four Toxic Forms of Oxygen § Singlet oxygen – molecular oxygen with electrons boosted to higher energy state § Occurs during photosynthesis so phototropic organisms have carotenoids that remove the excess energy of singlet oxygen § Superoxide radicals – some form during incomplete reduction of oxygen in aerobic and anaerobic respiration § So reactive that aerobes produce superoxide dismutases to detoxify them § Anaerobes lack superoxide dismutase and die as a result of oxidizing reactions of superoxide radicals formed in presence of oxygen Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Four Toxic Forms of Oxygen (continued) § Peroxide anion – formed during reactions catalyzed by superoxide dismutase and other reactions § Aerobes contain either catalase or peroxidase to detoxify peroxide anion § Obligate anaerobes either lack both enzymes or have only a small amount of each Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Four Toxic Forms of Oxygen (continued) § Hydroxyl radical – results from ionizing radiation and from incomplete reduction of hydrogen peroxide § The most reactive of the four toxic forms of oxygen § Not a threat to aerobes due to action of catalase and peroxidase § Aerobes also use antioxidants such as vitamins C and E to protect against toxic oxygen products Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Classification of Organisms Based on Oxygen Requirements § Aerobes – undergo aerobic respiration § Anaerobes – do not use aerobic metabolism § Facultative anaerobes – can maintain life via fermentation or anaerobic respiration or by aerobic respiration § Aerotolerant anaerobes – do not use aerobic metabolism but have some enzymes that detoxify oxygen’s poisonous forms § Microaerophiles – aerobes that require oxygen levels from 2 -10% and have a limited ability to detoxify hydrogen peroxide and superoxide radicals Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Nitrogen Requirements § Anabolism often ceases due to insufficient nitrogen needed for proteins and nucleotides § Nitrogen acquired from organic and inorganic nutrients; also, all cells recycle nitrogen from amino acids and nucleotides § The reduction of nitrogen gas to ammonia (nitrogen fixation) by certain bacteria is essential to life on Earth because nitrogen is made available in a usable form Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Other Chemical Requirements § Phosphorus required for phospholipid membranes, DNA, RNA, ATP, and some proteins § Sulfur is a component of sulfur-containing amino acids, disulfide bonds critical to tertiary structure of proteins, and in vitamins (thiamin and biotin) § Trace elements – usually found in sufficient quantities in tap water § Growth factors – organic chemicals that cannot be synthesized by certain organisms (vitamins, certain amino acids, purines, pyrimidines, cholesterol, NADH, and heme) Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Physical Requirements for Growth § Temperature § p. H § Osmolarity § Pressure Copyright

Temperature § Effect of temperature on proteins § Effect of temperature on lipid-containing membranes of cells and organelles § If too low, membranes become rigid and fragile § If too high, membranes become too fluid and cannot contain the cell or organelle Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Effects of Temperature on Growth Copyright © 2007 Pearson Education, Inc. publishing as Benjamin

Catagories of Microbes Based on Temperature Range Copyright © 2007 Pearson Education, Inc. publishing

p. H § Organisms sensitive to changes in acidity because H+ and OH- interfere with H bonding in proteins and nucleic acids § Most bacteria and protozoa grow best in a narrow range around neutral p. H (6. 5 -7. 5) – these organisms are called neutrophiles § Other bacteria and fungi are acidophiles – grow best in acidic habitats § Acidic waste products can help preserve foods by preventing further microbial growth § Alkalinophiles live in alkaline soils and water up to p. H 11. 5 Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Physical Effects of Water § Microbes require water to dissolve enzymes and nutrients required in metabolism § Water is important reactant in many metabolic reactions § Most cells die in absence of water § Some have cell walls that retain water § Endospores and cysts cease most metabolic activity in a dry environment for years § Two physical effects of water § Osmotic pressure § Hydrostatic pressure Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Osmotic Pressure § Is the pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross membrane; related to concentration of dissolved molecules and ions in a solution § Hypotonic solutions have lower solute concentrations; cells placed in these solutions will swell and burst Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Osmotic Pressure § Hypertonic solutions have greater solute concentrations; cells placed in these solutions will undergo crenation (shriveling of cytoplasm) § This effect helps preserve some foods § Restricts organisms to certain environments § Obligate halophiles – grow in up to 30% salt § Facultative halophiles – can tolerate high salt concentrations Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Hydrostatic Pressure § Water exerts pressure in proportion to its depth § For every addition of depth, water pressure increases 1 atm § Organisms that live under extreme pressure are barophiles § Their membranes and enzymes depend on this pressure to maintain their three-dimensional, functional shape Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Ecological Associations § Organisms live in association with different species § Antagonistic relationships § Synergistic relationships § Symbiotic relationships § Biofilms § Complex relationships among numerous individuals § Form on surfaces often as a result of quorum sensing Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Culturing Microorganisms § Inoculum introduced into medium (broth or solid) § Environmental specimens § Clinical specimens § Stored specimens § Culture – refers to act of cultivating microorganisms or the microorganisms that are cultivated Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Clinical Sampling Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings Table 6.

Obtaining Pure Cultures § Cultures composed of cells arising from a single progenitor § Progenitor is termed a CFU § Aseptic technique is used to prevent contamination of sterile substances or objects § Two common isolation techniques § Streak plates § Pour plates Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Streak Plate Method Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings Figure

Pour Plate Method Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings Figure

Culture Media § Majority of prokaryotes have never been grown in culture medium § Six types of general culture media § Defined media § Complex media § Selective media § Differential media § Anaerobic media § Transport media Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Special Media Techniques § Techniques developed for culturing microorganisms § Animal and cell culture § Low-oxygen culture § Enrichment culture Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Preserving Cultures § Refrigeration § Deep-freezing § Lyophilization Copyright © 2007 Pearson Education, Inc.

Growth of Microbial Populations Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Arithmetic Versus Logarithmic Growth Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Phases of Microbial Growth Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Measuring Microbial Growth § Direct methods § Viable plate counts § Membrane filtration § Microscopic counts § Electronic counters § Most probable number Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Viable Plate Counts Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings Figure

Membrane Filtration Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.

Microscopic Counts Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings Figure 6.

Most Probable Number Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings Figure

Measuring Microbial Growth § Indirect Methods § Metabolic activity § Dry weight § Turbidity

Turbidity and Spectrophotometric Measurement Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Staining § Increases contrast and resolution by coloring specimens with stains/dyes § Smear of microorganisms (thin film) air dried to slide and then fixed to surface by heat or chemical fixation § Microbiological stains are usually salts composed of cation and anion and one is colored (chromophore) § Acidic dyes stain alkaline structures; basic dyes stain acidic structures and are used more commonly Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings

Staining § Simple stains § Differential stains § Gram stain § Acid-fast stain § Endospore stain § Special stains § Negative (capsule) stain § Flagellar stain § Fluorescent stains § Staining for electron microscopy Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings