BacteriaChapter 24

Two Kingdoms ofProkaryotes

Comparing EubacteriaWith Archaebacteria

Three Bacterial Cell Shapes

Gram Staining

Tour of a Bacterium

Bacterial Diseases and Modes of Transmission

Gram-positive bacteria (Gram +) • Thick layer of peptidoglycan

(protein-sugar) complex in cell walls & single layer of lipids

• Stain purple

• Lactobacilli are used to make yogurt, buttermilk ….

• Actinomycetes make antibiotics like tetracycline & streptomycin

Gram-negative bacteria (Gram -)• Cell walls have a thin layer of

peptidoglycan & an extra layer of lipids on the outside

• Stain pink or reddish  • Lipid layer prevents the purple stain &

antibiotics from entering (antibiotic resistant)

• Some are photosynthetic but make sulfur, not oxygen

Mixture of gram positive and gram negative bacteria, G+ purplish, G-

Pinkish

Bacteria

Kingdom Archaebacteria• Found in harsh environments (undersea

volcanic vents, acidic hot springs, salty water)

• Cell walls without peptidoglycan • Subdivided into 3 groups based on their

habitat --- methanogens, thermoacidophiles, & extreme halophiles

Methanogens• Live in anaerobic environments (no oxygen) • Obtain energy by changing H2 and CO2 gas into

methane gas • Found in swamps, marshes, sewage treatment

plants, digestive tracts of animals • Break down cellulose for herbivores (cows) • Produce marsh gas or intestinal gas (methane)

Extreme Halophiles• Live in very salty

water.• Found in the dead sea,

great salt lake, etc.• Use salt to help

generate ATP (energy).

Thermoacidophiles (Thermophiles)

• Live in extremely hot (1100C) and acidic (ph 2) water

• Found in hot springs in Yellowstone national park, in volcanic vents on land, & in cracks on the ocean floor that leak scalding acidic water

Kingdom Eubacteria (true bacteria)• Most bacteria in this kingdom • Come in 3 basic shapes --- cocci (spheres), bacilli

(rod shaped), spirilla (corkscrew shape)

• Bacteria can occur in pairs ( diplo- bacilli or cocci)

• Bacteria occurring in chains are called strepto- bacilli or cocci

• Bacteria in grapelike clusters are called staphylococci

• Most are heterotrophic (can’t make their own food)

• Can be aerobic (require oxygen) or anaerobic (don’t need oxygen)

• Subdivided into 4 phyla --- Cyanobacteria (blue-green bacteria), spirochetes, gram-positive, & Proteobacteria

• Can be identified by gram staining (gram positive or gram negative)

• Disease-causing gram + bacteria produce poisons called toxins

• Clostridium causes tetanus or lockjaw • Streptococcus cause infections such as

“strep” throat • Staphylococci cause “staph” infections • Also cause toxic shock, bacterial

pneumonia, botulism (food poisoning), & scarlet fever

• Can be treated with penicillin (antibiotics) & sulfa drugs

Nutrient pollution often causes explosive algal growth which depletes waters of oxygen when the algae die. Toxic and foul smelling compounds may also be produced through this process. Nutrient pollution is the single largest pollution problem effecting coastal waters of the United States (Howarth et al., 2000). Most excess nutrients come from discharges of sewage treatment plants and septic tanks, storm-water runoff from overfertilized lawns, golf courses and agricultural fields. Over 60 percent of the coastal rivers and bays in the United States are moderately to severely affected by nutrient pollution (Howarth et al., 2000). (Photo: Weeks Bay NERRS site)