Presentation on theme: "Ch. 24. BACTERIAL EVOLTUION AND CLASSIFICATION Microscopic prokaryotes Fossils from 3.5 billion years ago Bacteria have evolved into many different forms."— Presentation transcript:
BACTERIAL EVOLTUION AND CLASSIFICATION
Microscopic prokaryotes Fossils from 3.5 billion years ago Bacteria have evolved into many different forms Part of nearly every environment on Earth Hundreds of thousands of species of bacteria Adapted to places where no other organisms live
Unlike other organisms, have few morphological differences used to classify them Traditionally have been grouped based on: Structure Physiology Molecular composition Reaction to specific types of strains Bacteria generally called “germs” are members of kingdom Eubacteria
Treated as separate kingdom due to strong differences Have unusual lipids in membrane No peptidoglycan in cell wall: protein-carbohydrate compound found in cell wall of eubacteria Not only live in harsh environments, but all over Methanogens: broad phylogenetic group of archaebacteria, named for unique method of harvesting energy by converting H2 and CO2 into methane gas Ex. In intestinal tracks of humans, swamp Extreme halophiles: salt-loving archaebacteria, live in environments with very high salt concentration Ex. Salt lake, dead sea Thermoacidophiles: live in extremely acidic environments which have extremely high temperatures & pH less than 2 Ex. Volcanic vents, hydrothermal vents (crack on ocean floor)
Account for most bacteria Occur in many shapes and sizes Three basic shapes: Bacilli: rod-shaped Cocci: sphere-shaped Spirilla: spiral-shaped
Most species of eubacteria grouped into two categories based on response to laboratory technique: Gram stain Gram-positive: bacteria retain gram stain and appear purple under microscope Gram-negative: bacteria do not retain purple stain and take up second pink stain Gram-positive have thicker layer of peptidoglycan in cell wall than Gram-negative bacteria Both differ in susceptibilities to antibacterial drugs, production of toxic materials and reaction to disinfectants
Photosynthetic Early Earth filled with oxygen produced by cyanobacteria, allowing aerobic organisms to develop AKA blue-green algae Certain cyanobacteria grow in chains Some cells forms specialized cells called heterocysts: contain enzymes for fixing atmospheric nitrogen Thrive on phosphates and nitrates which have accumulated in bodies of water Eutrophication population bloom: sudden increase in number of cyanobacteria due to high availability of nutrients Following 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
Spirochetes: Gram-negative, spiral-shaped heterotrophic bacteria Some are aerobic, some anaerobic All move by means of a corkscrew-like rotation Live freely, symbiotically, or parasitically One example: Treponema pallidum Causes sexually transmitted disease syphilis
Not all members are Gram-positive Few Gram-negative grouped here because they share same molecular similarities with Gram-positive bacteria Gram-positive found: Oral cavity Intestinal tract Milk Teeth Actinomycetes: Gram-positive bacteria form branching filaments Grow in soil and produce many antibiotics: chemicals that inhibit growth of or kill microscopic organisms
Make one of largest & most diverse phylum of bacteria Divided into several sub-categories Enteric bacteria: Gram-negative heterotrophic bacteria that inhabit animal intestinal tracts & live in aerobic or anaerobic conditions E. coli Salmonella Chemoautotrophs: Gram-negative bacteria that extract energy from minerals by oxidizing chemicals in the minerals Iron-oxidizing bacteria Nitrogen-fixing bacteria Rhizobium: produces fixed nitrogen for plants in soil
Explain how the terms bacteria, eubacteria, and archaebacteria relate to one another List the characteristics that are used to classify bacteria List the habitats of three types of archaebacteria Distinguish btwn Gram-positive bacteria and Gram- negative bacteria Describe the significance of cyanobacteria in the formation of the Earth’s atmosphere Why are methanogens and cyanobacteria unable to live in the same environment?
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 reactions Archaebacteria 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 vents Gram-positive and Gram-negative bacteria differ with respect to the chemical components of their cell wall, their susceptibility to antibiotics, and the toxins they produce Cyanobacteria produced oxygen as a waste product of photosynthesis. This allowed for the development of oxygen-breathing organisms Methanogens are obligate anaerobes; thus, if cyanobacteria were present, the oxygen generated by cyanobacteria would be toxic to the methanogens
BIOLOGY OF BACTERIA
Composed of cell wall, cell membrane, cytoplasm Some have distinctive structures Endospores Capsules Outer membranes Variety among bacteria due to adaptations to indiviual nitches
Almost all eubacteria & archaebacteria have cell walls Eubacteria cell wall composed of peptidoglycan: composed of short chains of AA & carbohydrate Archaebacteria cell walls composed of different compound Gram-negative eubacteria: cell wall includes outer membrane composed of layer of lipids & sugars Outer membrane protects bacteria against some antibiotics by preventing entry into cell some antibiotics have no effect on Gram-negative bacteria
Composed of lipid-bilayer Contains enzymes that catalyze reactions of cellular respiration bacteria have no mitochondria & use membrane to set up proton gradient to carry out CR Photosynthetic bacteria: have thylakoids in cell membrane & harvest energy for photosynthesis Unlike eukaryotes, bacterial cells have no membrane- bound organelles Cytoplasm contains ribosomes and DNA single, closed loop (some bacteria also have plasmids)
Capsule: outer covering made of polysaccharides to protect against drying or harsh chemicals Protects from host body’s white blood cells Glycocalyx: capsule consisting of fuzzy coat of sticky sugars enables bacteria to attach to surface of host cells & tissues Pili: 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
Endospore: dormant structure produced by some Gram-positive bacterial species that are exposed to harsh environmental conditions Consist of thick outer covering that surrounds cell’s DNA Even when original cell destroyed by harsh conditions, endospore will survive Not reproductive cells, but help bacteria resist high temps, harsh chemicals, radiation, drying When conditions become favorable, endospore opens allowing living bacterium to emerge and begin multiplying Can be formed by species of genera Bacillus & Clostridium
Many bacteria use flagella Bacteria can have one or many flagella Bacteria that lack flagella have other ways of moving: Myxobacteria produce layer of slime and glide through it Some spiral-shaped bacteria move by corkscrew-like rotation have flexible cell walls
Depending on species can be heterotrophic or autotrophic Heterotrophic bacteria Saprophytes: feed on dead or decaying material Autotrophic bacteria Photoautotrophs: 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. requirements Thermophilic bacteria: grow best in temps. Btwn (40 o C-110 o C) Most bacteira grow best at pH
Non-reproductive methods bacteria can acquire/express new combinations of genetic material Transformation: occurs when bacteria takes in DNA from external environment Conjugation: process of two living bacteria binding together and one bacterium transfers genetic info to other Genetic donor must have plasmid pilus binds to recipient forming conjugation bridge: passageway for genetic info Transduction: 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
List the various structures of the bacterial cell, and describe their function Describe three types of movement among bacteria What 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 bacteria What eukaryotic structures are functionally similar to the bacterial cell membrane and its infoldings?
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—movement Motility found among bacteria include the propulsion provided by flagella, the gliding movement of myxobacteria, and the corkscrew-like rotation of spirochetes Bacteria that must have oxygen are obligate aerobes; obligate anaerobes cannot tolerate oxygen; and those that can tolerate both situations are facultative anaerobes A 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 bacterium Mitochondria and chloroplasts are homologous with the bacterial cell membrane and bacterial thylakoids
BACTERIA AND HUMANS
Pathology: scientific study of disease Pathogens: bacteria that cause disease Toxins: poisons produced by some bacteria Exotoxins: 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 bacteria Cause weakness, body aches, fever, damage vessels of circulatory system
Antibiotics: drugs that combat bacteria by interfering with various cellular function Penicillin: interferes with cell wall synthesis Tetracycline: interferes with bacterial protein synthesis Some antibiotics affect wide variety of organisms: Broad-spectrum antibiotics
When population bacteria exposed to antibiotic, most susceptible ones die A few mutants are resistant to antibiotic and continue to grow & reproduce new population of antibiotic resistant bacteria Antibiotics have been overused creating many diseases that were once easy to treat to become more difficult to treat
Bacteria affect our lives positively too: Sewage treatment: bacteria break down remains of organic matter in waste, recycling C & N Producing & 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)
Describe ways that bacteria cause human disease Describe the function of antibiotics in nature List three antibiotics used to treat disease and the mechanism of action of each List some of the positive uses of bacteria Explain how antibiotic resistance arises in bacteria and how bacteria resist antibiotics Why would a pickle processor carry out the preparation of pickles in anaerobic conditions?
Bacteria cause disease by producing toxins and digestive enzymes that destroy tissue Antibiotics are thought to function in nature as a mechanism of bacteria and fungi to protect themselves from microscopic invaders Bacteria 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 spills Antibiotic 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 cell Bacteria 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.