Chapters 23 and

The most numerous organisms on earth Earliest fossils 3.5 Billion years old Lived before other life evolved. Two major domains: Archaea and Bacteria

1. 2. Living organisms have been categorized into three main groups based on ribosomal RNA analysis.

Different from bacteria Makeup of cell walls different– no peptidoglycan Different lipids in cell membranes DNA has introns Three groups Methanogens: convert hydrogen gas and carbon dioxide to methane. Anaerobic, many live in intestinal tract of cows and termites.

Halophiles: salt loving Thermoacidophiles: acidic environments that are high in temperature.

Most prokaryotes are bacteria Three common shapes Bacilli Cocci Spirilla They may occur in chains (streptococci) or clusters (staphylococci) Work with your shoulder partner to complete the “Classifying Bacteria : Shapes of Bacteria” worksheet.

Proteobacteria: live symbiotically with other organisms Example: nitrogen-fixing Rhizobium Gram-Positive Bacteria: many cause disease such as streptocaccus, others are helpful such as Lactobacilli which makes yogurt Cyanobacteria: use photosynthesis but lack membrane-bound nucleus and chloroplasts. Spirochetes: move by a corkscrew-like motion. Chlamydia: gram-negative, coccoid pathogens live only inside animal cells.

Cell Wall: protective, different composition in Bacteria compared to Archaea Cell Membrane and Cytoplasm: lipid bilayer but different between Archaea and Bacteria Important metabolic functions occur on the membrane such as respiration. In photosynthetic bacteria, the membrane folds like a thylakoid DNA: a single closed loop of double-stranded DNA. Additional DNA maybe found in plasmids which are small, circular and self-replicating.

Capsules and Pili Capsule is made of polysaccharides and protects the cell against drying or harsh chemicals, or in the case of pathogens, the hosts white blood cells. Pili: short, hair-like protein structures on the surface. Help bacteria connect to each other and to surfaces such as the host cell.

Endospores: a thick-coated, resistant structure formed by some bacteria when environmental conditions aren’t favorable. Can resist high temp., chemicals, radiation, drying and other environmental extremes. This allows the bacteria’s DNA to survive for a long time.

Prokaryotes obtain nutrients either from nonliving environment or by utilizing the products or bodies of living organisms. Heterotrophs obtain carbon from other organisms Autotrophs obtain their carbon from CO 2

Live in habitats based on their biochemical abilities Obligate anaerobes: ? Facultative anaerobes:? Obligate aerobes:? Prokaryotes have various temperature requirements for growth Most bacterial species grow best at a pH of 6.5 to 7.5

Prokaryotes usually reproduce by binary fission which is a form of asexual reproduction.

Three ways: Transformation: takes in NDA from its outside environment. Conjugation: two prokaryotes bind together and one transfers DNA to the other. Transduction: a virus obtains a small part of DNA from a host prokaryote which gets copied with the viral DNA

How can bacteria cause disease in humans? Exotoxins: toxic substances that bacteria secrete into their environment. Clostridium tetani = tetanus Endotoxins: not released until the bacteria dies. E. coli = fever, body aches, diarrhea, hemorrhage and weakness By destroying body tissues by releasing enzymes.

Complete the activity with both the helpful and harmful bacteria and the microviewers.