3Evolution Microscopic prokaryotes Fossils from 3.5 billion years ago Bacteria have evolved into many different formsPart of nearly every environment on EarthHundreds of thousands of species of bacteriaAdapted to places where no other organisms live
4ClassificationUnlike other organisms, have few morphological differences used to classify themTraditionally have been grouped based on:StructurePhysiologyMolecular compositionReaction to specific types of strainsBacteria generally called “germs” are members of kingdom Eubacteria
5Kingdom Archaebacteria Treated as separate kingdom due to strong differencesHave unusual lipids in membraneNo peptidoglycan in cell wall: protein-carbohydrate compound found in cell wall of eubacteriaNot only live in harsh environments, but all overMethanogens: broad phylogenetic group of archaebacteria, named for unique method of harvesting energy by converting H2 and CO2 into methane gasEx. In intestinal tracks of humans, swampExtreme halophiles: salt-loving archaebacteria, live in environments with very high salt concentrationEx. Salt lake, dead seaThermoacidophiles: live in extremely acidic environments which have extremely high temperatures & pH less than 2Ex. Volcanic vents, hydrothermal vents (crack on ocean floor)
6Kingdom Eubacteria Account for most bacteria Occur in many shapes and sizesThree basic shapes:Bacilli: rod-shapedCocci: sphere-shapedSpirilla: spiral-shaped
7Gram StainMost species of eubacteria grouped into two categories based on response to laboratory technique: Gram stainGram-positive: bacteria retain gram stain and appear purple under microscopeGram-negative: bacteria do not retain purple stain and take up second pink stainGram-positive have thicker layer of peptidoglycan in cell wall than Gram-negative bacteriaBoth differ in susceptibilities to antibacterial drugs, production of toxic materials and reaction to disinfectants
9Phylum Cyanobacteria Photosynthetic Early Earth filled with oxygen produced by cyanobacteria, allowing aerobic organisms to developAKA blue-green algaeCertain cyanobacteria grow in chainsSome cells forms specialized cells called heterocysts: contain enzymes for fixing atmospheric nitrogenThrive on phosphates and nitrates which have accumulated in bodies of waterEutrophication population bloom: sudden increase in number of cyanobacteria due to high availability of nutrientsFollowing the above, many cyanobacteria die and are decomposed by heterotrophic bacteria population increases and consume available oxygen in water, causing other organisms (fish) to die
10Phylum SpirochetesSpirochetes: Gram-negative, spiral-shaped heterotrophic bacteriaSome are aerobic, some anaerobicAll move by means of a corkscrew-like rotationLive freely, symbiotically, or parasiticallyOne example: Treponema pallidumCauses sexually transmitted disease syphilis
11Phylum Gram-Positive Bacteria Not all members are Gram-positiveFew Gram-negative grouped here because they share same molecular similarities with Gram-positive bacteriaGram-positive found:Oral cavityIntestinal tractMilkTeethActinomycetes: Gram-positive bacteria form branching filamentsGrow in soil and produce many antibiotics: chemicals that inhibit growth of or kill microscopic organisms
12Phylum Proteobacteria Make one of largest & most diverse phylum of bacteriaDivided into several sub-categoriesEnteric bacteria: Gram-negative heterotrophic bacteria that inhabit animal intestinal tracts & live in aerobic or anaerobic conditionsE. coliSalmonellaChemoautotrophs: Gram-negative bacteria that extract energy from minerals by oxidizing chemicals in the mineralsIron-oxidizing bacteriaNitrogen-fixing bacteriaRhizobium: produces fixed nitrogen for plants in soil
13Review QuestionsExplain how the terms bacteria, eubacteria, and archaebacteria relate to one anotherList the characteristics that are used to classify bacteriaList the habitats of three types of archaebacteriaDistinguish btwn Gram-positive bacteria and Gram- negative bacteriaDescribe the significance of cyanobacteria in the formation of the Earth’s atmosphereWhy are methanogens and cyanobacteria unable to live in the same environment?
14Review Questions: Answers Bacteria are microscopic prokaryotes. Eubacteria are prokaryotes that have a peptidoglycan cell wall and lack introns. Archaebacteria are prokaryotes that lack peptidoglycan and have introns. They can be found in extreme environments.Bacteria are classified according to their structure, physiology, molecular composition, and staining reactionsArchaebacteria inhabit anaerobic environments, such as the bottoms of swamps and sewage; high salt environments, such as the Great Salt Lake and Dead Sea; and very hot environments, such as hot springs and volcanic ventsGram-positive and Gram-negative bacteria differ with respect to the chemical components of their cell wall, their susceptibility to antibiotics, and the toxins they produceCyanobacteria produced oxygen as a waste product of photosynthesis. This allowed for the development of oxygen-breathing organismsMethanogens are obligate anaerobes; thus, if cyanobacteria were present, the oxygen generated by cyanobacteria would be toxic to the methanogens
16Structure Composed of cell wall, cell membrane, cytoplasm Some have distinctive structuresEndosporesCapsulesOuter membranesVariety among bacteria due to adaptations to indiviual nitches
17Cell Wall Almost all eubacteria & archaebacteria have cell walls Eubacteria cell wall composed of peptidoglycan: composed of short chains of AA & carbohydrateArchaebacteria cell walls composed of different compoundGram-negative eubacteria: cell wall includes outer membrane composed of layer of lipids & sugarsOuter membrane protects bacteria against some antibiotics by preventing entry into cell some antibiotics have no effect on Gram-negative bacteria
18Cell Membrane and Cytoplasm Composed of lipid-bilayerContains enzymes that catalyze reactions of cellular respiration bacteria have no mitochondria & use membrane to set up proton gradient to carry out CRPhotosynthetic bacteria: have thylakoids in cell membrane & harvest energy for photosynthesisUnlike eukaryotes, bacterial cells have no membrane- bound organellesCytoplasm contains ribosomes and DNA single, closed loop (some bacteria also have plasmids)
19Capsules and Pili Capsule: outer covering made of polysaccharides to protect against drying or harsh chemicalsProtects from host body’s white blood cellsGlycocalyx: capsule consisting of fuzzy coat of sticky sugars enables bacteria to attach to surface of host cells & tissuesPili: short, hairlike protein structures found on surface of some species bacteria help adhere to host cells OR to transfer genetic material from one bacterium to another
20EndosporesEndospore: dormant structure produced by some Gram-positive bacterial species that are exposed to harsh environmental conditionsConsist of thick outer covering that surrounds cell’s DNAEven when original cell destroyed by harsh conditions, endospore will surviveNot reproductive cells, but help bacteria resist high temps, harsh chemicals, radiation, dryingWhen conditions become favorable, endospore opens allowing living bacterium to emerge and begin multiplyingCan be formed by species of genera Bacillus & Clostridium
21Movement Structures Many bacteria use flagella Bacteria can have one or many flagellaBacteria that lack flagella have other ways of moving:Myxobacteria produce layer of slime and glide through itSome spiral-shaped bacteria move by corkscrew-like rotation have flexible cell walls
22Nutrition and GrowthDepending on species can be heterotrophic or autotrophicHeterotrophic bacteriaSaprophytes: feed on dead or decaying materialAutotrophic bacteriaPhotoautotrophs: use sunlight as energy source (i.e. cyanobacteria)Obligate anaerobes: cannot survive in presence of oxygen (Clostridium tetani)Facultative anaerobes: can live with or without oxygen (ex. Escherichia coli)Obligate aerobes: cannot survive without oxygen (ex. Mycobacterium tuberculosis)Bacteria have varying temp. requirementsThermophilic bacteria: grow best in temps. Btwn (40oC-110oC)Most bacteira grow best at pH
23Genetic Recombination Non-reproductive methods bacteria can acquire/express new combinations of genetic materialTransformation: occurs when bacteria takes in DNA from external environmentConjugation: process of two living bacteria binding together and one bacterium transfers genetic info to otherGenetic donor must have plasmid pilus binds to recipient forming conjugation bridge: passageway for genetic infoTransduction: virus obtains fragment of DNA from host bacterium as virus replicates inside bacterium, new copies of bacterial DNA produced virus goes to different bacteria carrying initial bacterial DNA with it
25Review QuestionsList the various structures of the bacterial cell, and describe their functionDescribe three types of movement among bacteriaWhat specific terms are used to describe the oxygen requirements of bacteria?In what key way do photoautotrophs and chemoautotrophs differ?List and summarize three methods of genetic recombination in bacteriaWhat eukaryotic structures are functionally similar to the bacterial cell membrane and its infoldings?
26Review Questions: Answers Cell wall—protects bacteria; outer membrane—protects cell from some antibiotics; cell membrane—regulates movements into and out of cell, contains respiratory enzymes; chromosome—carries genetic information; plasmid—contains genetic information from genetic recombination; capsules/slime layer—protects cell and assists in attaching cell to surfaces; endospores—protects cell from harsh environments; pili—assists in attaching to surfaces and used in genetic recombinations; flagella—movementMotility found among bacteria include the propulsion provided by flagella, the gliding movement of myxobacteria, and the corkscrew-like rotation of spirochetesBacteria that must have oxygen are obligate aerobes; obligate anaerobes cannot tolerate oxygen; and those that can tolerate both situations are facultative anaerobesA photoautotroph is an autotroph that synthesizes nutrients using light energy from the sun; a chemoautotroph synthesizes nutrients using the energy of inorganic substances.In transformation, bacteria acquire DNA fragments from the environment and incorporate them into their genome. In conjugation, a fragment of DNA passes from the donor bacterium to the recipient bacterium through a conjugation bridge. In transduction, a virus picks up a fragment of DNA from a donor and transports it into the cytoplasm of a recipient bacteriumMitochondria and chloroplasts are homologous with the bacterial cell membrane and bacterial thylakoids
28Bacteria and Disease Pathology: scientific study of disease Pathogens: bacteria that cause diseaseToxins: poisons produced by some bacteriaExotoxins: toxins made of protein; produced by living Gram-positive bacteria and secreted into surrounding environment (ex. Tetanus caused by exotoxin)Endotoxins: toxins made of lipids & carbohydrates; associated with outer membrane of Gram-negative bacteria; secreted by dead bacteriaCause weakness, body aches, fever, damage vessels of circulatory system
29AntibioticsAntibiotics: drugs that combat bacteria by interfering with various cellular functionPenicillin: interferes with cell wall synthesisTetracycline: interferes with bacterial protein synthesisSome antibiotics affect wide variety of organisms: Broad-spectrum antibiotics
30Antibiotic Resistance When population bacteria exposed to antibiotic, most susceptible ones dieA few mutants are resistant to antibiotic and continue to grow & reproduce new population of antibiotic resistant bacteriaAntibiotics have been overused creating many diseases that were once easy to treat to become more difficult to treat
31Useful Bacteria Bacteria affect our lives positively too: Sewage treatment: bacteria break down remains of organic matter in waste, recycling C & NProducing & Processing food: bacteria ferment lactose in milk producing sour-milk products (yogurt, sour cream)Other s digest protein in milk and produce unripened cheeses (ricotta and cottage cheese)
32Review Questions Describe ways that bacteria cause human disease Describe the function of antibiotics in natureList three antibiotics used to treat disease and the mechanism of action of eachList some of the positive uses of bacteriaExplain how antibiotic resistance arises in bacteria and how bacteria resist antibioticsWhy would a pickle processor carry out the preparation of pickles in anaerobic conditions?
33Review Questions: Answers Bacteria cause disease by producing toxins and digestive enzymes that destroy tissueAntibiotics are thought to function in nature as a mechanism of bacteria and fungi to protect themselves from microscopic invadersBacteria transform sewage into simpler organic compounds, produce and process food, produce industrial chemicals, and recycle nutrients in the environment. Bacteria can also be used to leach minerals from ore, as insecticides, and to clean chemical and oil spillsAntibiotic resistance in bacteria occurs when mutant bacteria survive an antibiotic treatment and give rise to a resistant population. Bacteria resist antibiotics by producing antibiotic-destroying enzymes or by having a cell wall that prevents entry of antibiotics into the bacterial cellBacteria make pickles from cucumbers by fermentation, which is an anaerobic process. Oxygen would allow the bacteria to utilize aerobic respiration, which would not yield fermentation products.