Prokaryotes Chapter 27

Where Are We Going?  Adaptations of prokaryotes  Diversity of prokaryotes  Ecological Impact of prokaryotes  Importance to humans

Organismal Domains Prokaryotes Eukaryotes  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  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  Directional movement often made possible by flagella  Exhibit taxis, movement to or from a stimuli  Internal organization  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  Most offspring identical, some changes likely  Mutation  Rare for a particular gene  Genetic recombination  Transformation, transduction, and conjugation  Combine 1 st 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 O 2 for cellular respiration  Obligate anaerobes are poisoned by O 2  Use fermentation or anaerobic respiration  Facultative anaerobes use O 2 if present, but can use alternate methods  Nitrogen  Eukaryotes limited in available nitrogen  Prokaryotes use nitrogen fixation to convert N 2 (nitrogen gas) to NH 3 (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 Salt environments E.g Great Salt Lake, Dead Sea, or seawater evaporating ponds Extreme thermophiles 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  E.g Salmonella, Vibrio cholerae, and Escheria coliDelta:  Delta: Can form fruiting bodies for selves when food is scarce and attack other bacteria  E.g myxobacteria and Bdellovibrios  Epsilon: pathogenic to humans or other animals  E.g Campylobacter and Helicobacter pylori

Other Prokaryotes  Chlamydias  Only survive within animal cells  Gram (-), but lack peptidoglycan  Spirochetes  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  2 species responsible for tuberculosis and leprosy  Most are free-living decomposers, leave ‘earthy’ odor of soil  Streptomyces  Cultured as sources of antibiotics  Bacillus anthracis  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  both species benefit  Commensalism  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