Transcript Prokaryotes
Prokaryotes Chapter 27 Where Are We Going? Adaptations of prokaryotes Diversity of prokaryotes Ecological Impact of prokaryotes Importance to humans Organismal Domains Prokaryotes 1-5 um in size (10 fold diff.) 10X’s more biomass Wider range of environments Greater diversity Single, circular chromosome Best known as bacteria Disease causing agents are pathogens Can live without the other Eukaryotes 10-100 um in size Membrane bound nucleus and organelles DNA arranged on multiple chromosomes Can’t live without prokaryotes Gram Staining Medicinally used to determine type of bacteria causing infection Bacteria can be gram (+) or gram (-) (+) simple walls with thicker peptidoglycan, sugar polymer joined by polypeptides (-) more complex walls with less peptidoglycan and lipopolysaccharide outer layer Make them more threatening, toxic, and resistant to antibiotics which prevent synthesis of peptidoglycan which inhibits cell wall growth External Prokaryotic Adaptations Cell wall (previously discussed) Come in a variety of shapes Multiple methods for adhesion Capsule: polysaccharide or protein Fimbriae: hair-like protein structures Sex pili: pull cells together before DNA transfer Prokaryote Adaptations Motility Internal organization Directional movement often made possible by flagella Exhibit taxis, movement to or from a stimuli Simpler than eukaryotes = no organelles 1/1000 as much DNA in the nucleoid region Accessory rings of DNA or plasmids Reproduction and adaptation Reproduce asexually by binary fission Can form endospores when conditions unfavorable Water removed and metabolism halts Genetic Diversity in Prokaryotes Exhibit wide range of adaptations and variation 3 factors determine Rapid reproduction Reproduce by binary fission, not sexually Mutation Rare for a particular gene Genetic recombination Most offspring identical, some changes likely Transformation, transduction, and conjugation Combine 1st two and get genetic diversity and rapid evolution Fit individuals survive and reproduce more prolifically than less fit Transformation Genotype (some phenotype) altered by uptake of foreign DNA Harmless strains transformed to virulent when placed in dead virulent cell medium Forms a recombinant cell Frederick Griffith experiment from 2107 Transduction Bacteriophages carry bacterial genes from one host to another Lack machinery to be able to reproduce Infect bacteria (1) and incorporate their DNA into new bacteriophages Bacteriophages that result then repeat with new mixed DNA Conjugation Genetic material transferred between 2 connected cells Sex pili form bridge One way process Often is beneficial Antibiotic resistance or other tolerance Nutritional Adaptations Prokaryotes categorized based on how energy and carbon are obtained Gr: plants and algae Ylw: certain prokaryotes Pur: marine prokaryotes and halophiles Bl: most prokaryotes, protists, fungi, animals, and some plants Prokaryotic Metabolism Oxygen Obligate aerobes use O2 for cellular respiration Obligate anaerobes are poisoned by O2 Use fermentation or anaerobic respiration Facultative anaerobes use O2 if present, but can use alternate methods Nitrogen Eukaryotes limited in available nitrogen Prokaryotes use nitrogen fixation to convert N2 (nitrogen gas) to NH3 (ammonia) Necessary to produce AA’s Increases nitrogen for plant usage Biofilms Secrete signaling molecules to recruit nearby cells and grow Produce proteins to stick to self and substrates Nutrients in and wastes out via channels Dental plaque below is an example Prokaryotic Diversity Archaea Live where other organisms can’t survive Extreme halophiles Extreme thermophiles Salt environments E.g Great Salt Lake, Dead Sea, or seawater evaporating ponds Very hot water E.g ocean vents, or acidic conditions Methanogens Anaerobic environments with methane as a waste product E.g. swamps and GI tracts of animals Proteobacteria Gram-negative Both aerobic and anaerobic species 5 subgroups Alpha: Live in root nodules to fix atmospheric nitrogen Beta: Nitrogen cycling Gamma: Photosynthetic and inhabit animal intestines Delta: Can form fruiting bodies for selves when food is scarce and attack other bacteria E.g Salmonella, Vibrio cholerae, and Escheria coliDelta: E.g myxobacteria and Bdellovibrios Epsilon: pathogenic to humans or other animals E.g Campylobacter and Helicobacter pylori Other Prokaryotes Chlamydias Spirochetes Only survive within animal cells Gram (-), but lack peptidoglycan Spiral through environments by rotating internal filaments E.g Treponema pallidum (syphilis) and Borrelia burgdorferi (Lyme disease) Cyanobacteria Oxygen-generating photosynthesis (only bacteria) Food for freshwater and marine ecosystems Gram-Positive Bacteria Actinomycetes Streptomyces Cultured as sources of antibiotics Bacillus anthracis 2 species responsible for tuberculosis and leprosy Most are free-living decomposers, leave ‘earthy’ odor of soil Forms endospores Clostridium botulinum Staphylococcus Streptococcus Mycoplasmas Lack cell walls and are tiniest cells Free-living soil bacteria, but some are pathogens Ecological Interactions Central role in symbiosis, where 2 species live close Formed between larger host organism and themselves (symbiont) Types of interactions can vary Mutualism Commensalism both species benefit one species benefits while other is unchanged Parasitism parasite eats cellular components Usually harm, but not kill Pathogens are the parsites that cause disease Bacterial Poisons Exotoxins are proteins secreted by bacteria Can exist in the bacteria or without Vibrio cholerae releases Cl- to gut and water follows Clostridium tetani produces muscle spasms (lockjaw) Staphylococcus aureus common on skin and in nasal passages Produces several types causing varying problems Acquired from genetic transfer between species E. coli benign resident of intestines Acquires genes that produce harmful effects Endotoxins are components of gram (-) outer membranes Released when cell dies or digested by defensive cell Cause same general symptoms Neisseria meningitidis (bacterial meningitis) and Salmonella (typhoid fever) Research and Technology Convert milk into cheese and yogurt Principle agents in bioremediation Use organisms to remove pollutants Oil clean up Sewage treatment Solid sludge from filters added to anaerobe colonies Transformed into use for fertilizer or landfill Liquid waste over biofilms remove organic material