Prokaryotes and Viruses

Chapters 23 and 242013

Prokaryotes

The most numerous organisms on earthEarliest fossils 3.5 Billion years oldLived before other life evolved.Two major domains: Archaea and Bacteria

What are the traits of prokaryotes?1. 2.Living organisms have been categorized into three main groups based on ribosomal RNA analysis.

Archaea

Different from bacteriaMakeup of cell walls different– no peptidoglycanDifferent lipids in cell membranesDNA has introns

Three groupsMethanogens: convert hydrogen gas and carbon dioxide to methane. Anaerobic, many live in intestinal tract of cows and termites.

Halophiles: salt lovingThermoacidophiles: acidic environments that are high in temperature.

Domain Bacteria

Most prokaryotes are bacteriaThree common shapes

BacilliCocciSpirilla

They may occur in chains (streptococci) or clusters (staphylococci)

Work with your shoulder partner to complete the “Classifying Bacteria : Shapes of Bacteria” worksheet.

Important Bacterial Groups

Proteobacteria: live symbiotically with other organisms Example: nitrogen-fixing RhizobiumGram-Positive Bacteria: many cause disease such as streptocaccus, others are helpful such as Lactobacilli which makes yogurtCyanobacteria: 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.

Biology of Prokaryotes

Cell Wall: protective, different composition in Bacteria compared to ArchaeaCell 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 PiliCapsule 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.

Nutrition and Metabolism

Prokaryotes obtain nutrients either from nonliving environment or by utilizing the products or bodies of living organisms.Heterotrophs obtain carbon from other organismsAutotrophs obtain their carbon from CO2

Prokaryotic Habitats

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

Reproduction and Recombination

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

Prokaryotes can exchange pieces of DNA through recombination

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

Bacteria and Humans

How can bacteria cause disease in humans?Exotoxins: toxic substances that bacteria secrete into their environment.

Clostridium tetani = tetanusEndotoxins: not released until the bacteria dies.

E. coli = fever, body aches, diarrhea, hemorrhage and weakness

By destroying body tissues by releasing enzymes.

Bacteria Microviewers

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