Chapter 23 Bacteria http://topnews.in/health/files/Rain-bacteria.jpg
Section 1 Vocabulary Pretest • Prokaryote • Peptidoglycan • Methanogen • Halophile • Thermoacidophile • Bacillus • Coccus • Spirillum • Streptococcus • Staphylococcus • Gram-negative bacteria • Gram-positive bacteria • Rod-shaped bacteria • Spiral-shaped bacteria • Sphere-shaped bacteria • Clusters of sphere-shaped bacteria • Chains of sphere-shaped bacteria • “Salt-loving” archaea • “Heat-living” archaea • Anaerobic archaea • Protein-carbohydrate found in bacterial cell walls • Appear reddish-pink when dyed • Appear purple when dyed • Cells w/ no nucleus
Answer Key • Prokaryote L • Peptidoglycan I • Methanogen H • Halophile F • Thermoacidophile G • Bacillus A • Coccus C • Spirillum B • Streptococcus E • Staphylococcus D • Gram-negative bacteria J • Gram-positive bacteriaK
pROKARYOTES • Most numerous organisms on Earth • Found almost everywhere • Fossils date back 3.5 bya(first forms of life) • Single cells with no nucleus • Major source of food for many organisms • Important decomposersin the environment • Divided into two domains: • Domain Archaea • Domain Bacteria Notice that Archaea are more closely related to Eukarya than to Bacteria and thus share a more recent common ancestor.
Domain Archaea • Archaea = archaic(ancient) • Differ from other prokaryotes in the following ways: • Cell walls do not contain peptidoglycan • Have introns(portions of DNA that do not code for proteins) • Live in extreme environments • Different lipidsin cell membranes • rRNA resembles rRNA of eukaryotes • Genes resemble genes of eukaryotes
Archaeal Groups • Methanogens: • Convert hydrogen gas and carbon dioxide into methane gas. • Anaerobic • Live in muddy swamps, sewers, intestines of cows and termites http://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Arkea.jpg/220px-Arkea.jpg
Halophiles: • “Salt-loving” archaea • Live in very high salt concentrations (Great Salt Lake and the Dead Sea) Owens Lake in CA. The lake became extremely salty when the Owens river was diverted to supply water to LA. PPG operated a soda ash plant (seen in the background) for making glass. The color is due to the millions of halophiles that now live in the lake
Thermoacidophiles: • Live in acid environments (pH <2) with very high temperatures (>230 degrees F). • Ex: Hot sulfur springs of Yellowstone National Park; deep water thermal vents (black smokers)
Domain Bacteria • Unlike archaea, members of the domain bacteria: • Have cell walls with peptidoglycan • Have no introns • Live in a wide variety of environments • Have lipid membranes • rRNA is unlikerRNA of eukaryotes • Genes are unlikeeukaryotes genes
Basic Shapes • Bacteria come in a few basic shapes: • Bacilli(rod-shaped): streptobacilli (chains) • Cocci(sphere-shaped):streptococci (chains): staphylococci (clusters) • Spirilla(spiral-shaped) • Spirochaete(corkscrew) • Vibrio(comma-shaped)
Gram Stain • A staining technique called the gram stain illustrates a fundamental difference between two categories of bacteria: the gram positive and the gram negative bacteria. • Gram negative have complex cells walls with little peptidoglycan. They stain a reddish color. • Gram positive have simpler cell walls with a lot of peptidoglycan. They stain a purple color.
Bacterial Groups • Classifying bacteria based on evolutionary relationships has been difficult because bacteria can pick up genes from their environment through transformation. • Most scientists recognize the following groups:
Proteobacteria • Proteobacteria: • Very largeand diversegroup • Include: nitrogen-fixing bacteria that live in nodules inside the roots of legumes (peas, beans, alfalfa, and clover). These bacteria convert atmospheric nitrogen to ammonia, which plants can use. • Also includes some disease-causing bacteria such as rickettsia bacteria (causes Rocky Mountain Spotted Fever) and helicobacter pylori (causes stomach ulcers) • Also includes enteric bacteria (symbiotic bacteria that live in intestinal tracts of humans and animals)Ex: E. colilives in our intestines and secretes vitamin K as well as assisting in the digestive breakdown of foods. • Other strands of E.coli and Salmonellacause food poisoning. E.coli bacteria
Gram-Positive Bacteria • Gram-positive bacteria: will stain purple when gram stain is applied. • Examples include: • Streptococcus: causes strep throat • Clostridium botulinum: causes botulism also used in botox injections • Lactobacilli: sours milk; used in yogurt • Bacillus anthracis: causes anthrax • Actinomycetes: soil bacteria used to make many antibiotics
Cyanobacteria • Cyanobacteria: photosynthetic bacteria • Earth’s first oxygen-producing organisms and are believed to be responsible for transforming Earth’s early atmosphere • Some grow in long filaments • Some form specialized cells called heterocystswhich can fix nitrogen
spirochetes • Spirochetesare gram-negative spiral-shaped bacteria. • Move with a corkscrew rotation • Can be free living or pathogenic • Ex: Treponemapallidum: causes syphilis Borreliaburgdorferi: causes Lyme disease
Chlamydia • Chlamydia are gram-negative bacteria that live only inside animal cells. • There cell walls lack peptidoglycan • Ex: Chlamydia trachomatis: causes chlamydia (sexually transmitted disease) and trachoma eye disease, a leading cause of blindness. Bacteria are the purple dots inside a cell (pinkish brown)
Section 2 Vocabulary Pretest • Plasmid • Capsule • Glycocalyx • Pilus • Endospore • Heterotroph • Autotroph • Phototroph • Chemotroph • Obligate anaerobe • Facultative anaerobe • Obligate aerobe • Transformation • Conjugation • Tranduction • Sticky sugars found in bacterial capsules • Structure formed to survive harsh environmental conditions • Short, hair-like projection • One bacteria transfers DNA to another • Bacteria takes in DNA from its outside environment • Virus introduces DNA from one bacteria to another • Small, circular loop of DNA • Outer polysaccharide covering • Obtain carbon from CO2 • Obtain carbon from other organisms • Get energy from light • Get energy from chemicals • Can live with or without oxygen • Must have oxygen • Must live without oxygen
Answer Key • Plasmid G • Capsule H • Glycocalyx A • Pilus C • Endospore B • Heterotroph J • Autotroph I • Phototroph K • Chemotroph L • Obligate anaerobe O • Facultative anaerobe M • Obligate aerobe N • Transformation E • Conjugation D • TranductionF
Structure and Function • General prokaryotic structure includes: • Capsule • Cell wall • Cell membrane • Cytoplasm • Ribosomes • DNA (nucleoid region) • Pili • Flagella
Cell Wall • Cell wall • Provides shape and protection • Made of peptidoglycanand lipopolysaccharides (only on gram negative) • Many antibioticsare designed to kill bacteria by breaking down the peptidoglycans of their cell walls. They are most effective on gram positive bacteria.
Cell Membrane • Also called the plasma membrane, the cell membrane controls what gets in or out of the bacteria cell. • Consists of a lipid bilayer and proteins • Contains catalytic enzymes for respiration and photosynthesis
DNA • DNA of prokaryotes consists of a single closed loop of double-stranded DNA • Located in a central area called the nucleoid region • Most bacteria also have small rings of DNA called plasmids • Self-replicate • Not necessary for cell survival • Often carry genes that allow bacteria to cause disease • Often carry genes that provide bacteria to become resistant to antibiotics
Capsules • Many bacteria have an outer covering of polysaccharidescalled a capsule • Their function: • Protectionfrom drying out • Protection from phagocytic white blood cells • Fuzzy glycocalyx capsules allow bacteria to connect to host cells and tissues (often appears as a “halo” around stained bacteria cells
Pili • Piliare short, hairlike projections that help bacteria connect to each other and to host cells and other surfaces. • Can serve as a bridge to pass genetic material
endospores • Endosporesform in gram-positive bacteria when environmental conditions become harsh. • They can resist high temps, strong chemicals, radiation, and drying out. • Cell copies its DNA and then forms a thick, protective covering around this copy. Most of the water is removed and the endospore becomes metabolically inactive. The rest of the cell will die, but the endospore, with its DNA cargo can remain viable for centuries. • It will reactivatewhen environmental conditions become favorable. • Can only be killed if heated to very high temperatures under pressure.
Prokaryotic Movement • Some move by flagella • Movement toward or away from a stimulus is called taxis • Chemotaxis=response to chemical stimuli such as food or toxins. • Phototaxis=response to light http://www.youtube.com/watch?v=6p9e0oolbmE
Nutrition and Metabolism • Two basic needs exist for prokaryotes: • Source of carbon • Source of energy • Two ways to obtain the carbon source: • Heterotrophs: obtain carbon from other organisms • Autotrophs: obtain carbon from CO2 • Two ways to obtain the energy source: • Phototrophs: obtain energy from light • Chemotrophs: obtain energy from chemicals
Major Bacterial nutritional Modes • These needs can be used to divide prokaryotes into four nutritional groups:
Prokaryotic Habitats • Habitats occupied are based on biochemical abilities of different types of bacteria. • Oxygen requirements: • Obligate anaerobes cannot live in the presence of oxygen. Ex: Clostridium tetani • Facultative anaerobes can live with or without oxygen. Ex: E.coli • Obligate aerobes require oxygen to live. Ex: Mycobacteriaum tuberculosis
Temperature requirements: • Psychrophilic prokaryotes: “cold-loving” grow well in 32-68oF. Can survive Antarctic temps by growing under the surface of rocks. • Mesophilic prokaryotes: grow well in moderate temperatures between 68-104oF. • Thermophilic prokaryotes: grow well in very hot temperatures between 113-230oF.
pH requirements: • Most bacteria thrive in pHs between 6.5 and 7.5 • Acidophilesare bacteria that thrive in low pHs (below 6)
Reproduction • Usually reproduce by binary fission • Asexual reproduction • DNA duplicates • DNA molecules move to poles • Cell divides • Two identical daughter cells are formed
Recombination • Recombination occurs when prokaryotes exchange pieces of DNA without reproduction. • Three ways recombination can occur: • Transformation—a prokaryote takes DNA from its outside environment. • Conjugation—two prokaryotes bind together and one cell transfers DNA to the other through a sex pilus. • Transduction—viruses transfer pieces of one prokaryotes DNA to another
Conjugation involves something called the F factorto be present in the donor cell.
Transduction involves defective bacteriophages that carry host DNA instead of viral DNA.
Section 3 Vocabulary Pretest • Pathology • Exotoxin • Endotoxin • Antibiotic resistance • Zoonosis • Bioremediation • Toxic substances made from lipids and carbs that are released after the cell dies. • Toxic substances secreted by bacteria into their environment • Evolution of pathogenic bacteria that antibiotics cannot kill • Study of diseases • A disease that can pass from animal to humans • Using bacteria to recycle compounds in nature
Answer Key • Pathology D • Exotoxin B • Endotoxin A • Antibiotic resistance C • Zoonosis E • Bioremediation F
Bacteria and Humans • Roles of bacteria: • Cause disease • Food production • Nitrogen fixation • Decomposers • Bioremediation
Bacteria and Health • Pathology—study of diseases • Pathogens: disease causing agents • Some bacteria cause disease by destroying body tissues. Ex: Streptococcus • Some bacteria cause disease by secreting toxins: • Exotoxins—toxins secreted by bacteria into their environment. Ex: Clostridium tetani secretes toxins that cause tetanus • Endotoxins—toxins released after the bacteria cell dies. They can cause fever, body aches, diarrhea, hemorrhage and weakness. Ex: E. coli
Antibiotics • Antibioticsare substances used to kill bacteria. • Made naturally by some fungi and bacteria • Kill neighboring bacteria or fungi that compete for resources • Some (Penicillin) interfere with the formation of cell walls by breaking down peptidoglycans • Some (Tetracycline) interfere with protein synthesis
Antibiotic Resistance • Antibiotic resistance is the evolution of populations of pathogenic bacteria that antibiotics are unable to kill. • Because of over-prescription of antibiotics, many resistant genes are now on R-plasmids which can easily pass from one bacteria to the next by transformation. • This leads to multiple resistances to many antibiotics… Superbugs!
Emerging and Infectious Bacterial diseases • Most emerging diseases develop when infectious agents, such as bacteria, pass from wild animals to humans • Zoonosis—a disease that can pass from animal to human • Zoonotic disease are on the rise due to: • Human population growth • Global travel and trade
Food and Hygiene and bacteria • Foodborne illnesses result from the improper preparation, handling or storage of food. • To avoid: • Wash all raw fruits and vegetables • Wash hands and all utensils during food preparation • Refrigerate raw foods (eggs and lunchmeats) • Cook meat thoroughly • Refrigerate leftovers promptly
Methods of food preparation • Several methods can be used to prevent food spoilage by bacteria: • Foods can be dried and salted: Sausages and hams • Refrigeration: Milk and eggs • Adding large amounts of sugar: Jellies and jams • Picklingadds acids which slow bacterial growth: Pickles and relishes • Cooking at high temps: Meat products • Sealing and canning: canned foods • Adding preservatives: bread, juice and fruits
Bacteria and Industry • Used in food production: • Buttermilk, sour cream, yogurt, cheeses, sauerkraut, pickles, coffee, and soy sauce • Used in chemical production: • Acetone, acetic acid, enzymes, antibiotics and insulin • Used to help break down sewageand added to laundry detergent to dissolve stains • Used in some pesticides • Used in bioremediation to breakdown pollutants • Used in recombinant DNA technology