Bacteria Section 18.2

Diversity of Prokaryotes Belong to the kingdoms Archaebacteria and Eubacteria Because they are so different, many scientists propose that archaebacteria and eubacteria arose from a common ancestor several billion years ago.

Archaebacteria: The extremists There are three types of archaebacteria that live mainly in extreme habitats where there is usually no free oxygen available. –Methane gas producers Lake sediments Cow intestines Sewage treatment plants

Archaebacteria: The extremists –water with high concentrations of salt. Dead Sea

Archaebacteria: The extremists –hot, acidic waters of sulfur springs. –These bacteria are chemautotrophic (make energy from chemicals)

Eubacteria: true bacteria Some are autotrophic –Photosynthetic Cyanobacteria –Some are chemautotrophic

Eubacteria: true bacteria Some are heterotrophic = “eaters” –Decomposers: break down dead plants or animals –Symbiotic: have close association with another organism (parasitic or mutualistic)Symbiotic

Symbiotic relationships Mutualism: both benefit –E. coli in digestive tract –In termite’s guts –In grazer’s guts –In flashlight fishIn flashlight fish Parasitism: one benefits (parasite), one hurt (host) –Pathogenic bacteria, (make you sick)

Bacterial Cells Smallest single-celled organisms (2μm) Prokaryotic (lack a nucleus) Have a cell wall –Made of peptidoglycan (unique) –Cytoplasm is hypertonic, protects cell from exploding –Antibiotics may disrupt cell wall

Bacteria on a pin

Bacterial Cells May be surrounded by a capsule –Sticky –Protects May have flagellaflagella May form endospore under harsh conditionsendospore –Withstands boiling, drying up –Cell emerges when conditions improve

Anthrax endospore

Bacterial Cells Different shapes –Coccoid = spherical –Baccilus = rod-shaped –Spirillus = spiral shaped

Bacterial Reproduction Binary fission (bacterial cell division)

Nitrogen Fixation Ability to convert nitrogen gas to ammonia that a plant can use Legumes (clover, beans, alfalfa) have these bacteria near roots –Rotated crop

Bacterial Importance Major Decomposers Can cause disease Can cure disease (many antibiotics come from bacteria) Can spoil food Can make food –Yogurt, cheese, vinegar, sauerkraut

Section 18.2 Summary – pages Bacteria cause disease Diseases Caused by Bacteria Disease TransmissionSymptoms Treatment Strep throat (Streptococcus) Inhale or ingest through mouth Fever, sore throat, swollen neck glands Antibiotic Tuberculosis InhaleFatigue, fever, night sweats, cough, weight loss, chest pain Antibiotic Tetanus Puncture wound Stiff jaw, muscle spasms, paralysis Open and clean wound, antibiotic; give antitoxin Lyme disease Bite of infected tick Rash at site of bite, chills, body aches, joint swelling Antibiotic Dental cavities (caries) Bacteria in mouth Destruction of tooth enamel, toothache Remove and fill the destroyed area of tooth Diptheria Inhale or close contact Sore throat, fever, heart or breathing failure Vaccination to prevent, antibiotics