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Home , Peptidoglycan, Photoheterotroph, Prokaryote

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Prokaryotes (Domains & ) KEY POINTS 1. : recycle organic and inorganic molecules in environment; makes them available to other . 2. Essential components of symbioses. 3. Encompasses the origins of and metabolic diversity. 4. Origin of and formation of atmospheric Oxygen

Ceno- Meso- zoic zoic ANTIQUITY Humans Paleozoic Colonization of land

Animals Origin of solar system and • >3.5 BILLION years old.

• Alone for 2 1 4

billion years Proterozoic Archaean Billions of

2 years ago3 Multicellular

Single-celled eukaryotes Atmospheric oxygen

General characteristics

1. Small: compare to 10-100µm for 0.5-5µm eukaryotic ; single-celled; may form colonies. 2. Lack membrane- enclosed . 3. present, but different from cell wall.

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General characteristics

4. Occur everywhere, most numerous organisms. – More individuals in a handful of then there are people that have ever lived. – By far more individuals in our gut than eukaryotic cells that are actually us.

General characteristics

5. Metabolic diversity established nutritional modes of eukaryotes.

General characteristics

6. Important decomposers and recyclers

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General characteristics

6. Important decomposers and recyclers • Form the basis of global nutrient cycles.

General characteristics

7. Symbionts!!!!!!! • Parasites • Pathogenic organisms. • About 1/2 of all human diseases are caused by Bacteria

General characteristics

7. Symbionts!!!!!!! • Parasites • Pathogenic organisms. • Extremely important in agriculture as well. Pierce’s disease is caused by Xylella fastidiosa, a Gamma . It causes over $56 million in damage annually in California. That’s with $34 million spent to control it! = $90 million in California alone.

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General characteristics

7. Symbionts!!!!!!! • Commensalists • They are everywhere (really). • There can be 10 million cells per square centimeter of skin.

General characteristics

7. Symbionts!!!!!!! • Mutualists • Eukaryotic would be impossible without this.

General characteristics

7. Symbionts!!!!!!! • Mutualists • Allows herbivorous (plant-feeding) to digest cellulose and other low-quality plant tissues. • • Ungulates “chewing the cud” • Lagomorph coprophagy

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General characteristics

7. Symbionts!!!!!!! • Mutualists • Mealybug with endosymbionts.

General characteristics 7. Symbionts!!!!!!! • Mutualists • Komodo dragons and their “toxins”. • Hunt large prey and can inflict fairly minor wound. • Prey die fairly quickly from wound. • Infection by highly pathogenic Pasteurella multocida (Gamma Proteobacteria). • Prominent in saliva of dragons, but dragons have an anti- Pasteurella antibody.

TAXONOMY is problematic

• Relationships obscured by billions of years of • Also obscured by unique bacterial means of recombination (more later). • Grouped primarily by DNA sequence data. • Immense genetic/genomic diversity.

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Current is stabilizing • Note that “” is paraphyletic. Why? • Two Domains: • Archaea: (mostly), ancient, probable progenitors of eukaryotes. • Bacteria: most commonly-encountered prokaryotes.

Characteristics

• Cell Surface • Motility • • Reproduction & Growth • Metabolic Diversity • Nitrogen Metabolism • Oxygen Relationships

Cell Surface

• Archaea: plasma membrane of ether- (unique in life). • Bacteria: a -

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Cell Surface

• Cell wall is often modified with structures to adhere to substrate. • Many secrete a sticky capsule or adhere by fimbriae (ocasionally called pili).

Motility

• ~half the can move. 1. Flagella most common (different structure from ) 2. Spiral filaments: spirochetes corkscrew 3. Gliding over slimy secretions (via flagellar motors without filament) • Capable of (photo, chemo, geo, etc.)

Genome

• Small : ~1/1000th DNA content of eukaryotes. • No membrane enclosed nucleus. • DNA concentrated in ‘’ region.

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Genome

• One major , double stranded DNA molecule in ring. • Sometimes several small DNA rings of few : . – Replicate independently of main chromosome. – Permit recombination via conjugation (later). – Involved in resistance to antibodies/.

Genome

• Broadly, replication & of genetic info like that of eukaryotes; differ in details and simplicity. • Used in first DNA recombinant research. • : Not like eukaryotes (e.g. chiasma & crossing over)!! – Transformation – Conjugation –

Genome: Recombination via transformation • DNA taken up from the environment

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Genome: Recombination via conjugation • Direct transfer of DNA between cells. • Both plasmids and portions of bacterial chromosome.

Genome: Recombination via transduction • Transfer of DNA via phage .

Reproduction & Growth

• & NOT PRESENT. • Asexual binary . • DNA replication can be nearly continuous in ideal conditions (depends on pH, salinity, temperature, etc.) • Generation as fast as 20 minutes

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Metabolism Metabolic Diversity

• Nutrition: • Requires a source of carbon for synthesizing organic compounds: either or living . • Requires a source of to drive reactions: either light or chemical.

Metabolic Diversity: Metabolism Source of Carbon

• : Need only carbon

dioxide (CO2) as carbon source • : Need at least one organic nutrient as carbon source (e.g. ; petroleum)

• Both of these present in Eucarya as well.

Metabolic Diversity: Metabolism Source of Energy

• : Need only as energy source • : Derive energy from oxidation of organic molecules.

• Both of these present in domain Eucarya as well.

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Metabolism Metabolic Diversity: Combined

Energy Source:

Sun Environment

Photoautotroph Chemoautotroph CO2 Source: Source: Carbon Organic Photoheterotroph Chemoheterotroph molecules Which of these are present in multicellular Eucarya?

Metabolism Photoautotrophs

• Use sun for energy,

CO2 for carbon. • Photosynthetic bacteria (e.g. ). • Present in many and single- celled Eucarya

Metabolism Chemoautotrophs • Oxidize inorganics (H2S, NH3) for energy.

• Need only CO2 as carbon source. • Unique to Bacteria and Archaea. • E.g. Methanococcus jannaschii on hydrothermal vents at 2600m below sea level.

• Reduces H2 + CO2 to CH4 + 2H2O.

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Metabolism Photoheterotrophs

• Get enery from light but must obtain carbon in organic

form (NOT CO2). • Unique to Bacteria and Archaea. • E.g. salinarium.

Metabolism Chemoheterotrophs • Consume organic molecules for both energy and carbon. • Common among prokaryotes: – saprobes (decomposers) – parasites (rely on living hosts) • Also widespread in Protista, Animalia, Plantae.

Metabolism Nitrogen metabolism

• : • The only* mechanism that makes atmospheric Nitrogen available to other organisms.

• Convert N2 into ammonia (NH3) which is quickly protonated into + ammonium (NH4 ). • Essential for multicellular life!

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Oxygen Relationships

• Aerobic vs. Anaerobic • :

• Obligate aerobes: use O2 for – + O2 →CO2 cellular respiration. + H2O + energy • Facultative anaerobes: use • Fermentation: O2 if it is present by carry out – Carbohydrates →CO2 + or ethanol + energy fermentation in anaerobic • Anaerobic respiration: environment. – Carbohydrates + [X] → • Obligate anaerobes: bicarbonate + [X-] + energy poisoned by O2; use – Where [X] is a substance anaerobic respiration or other than O2 that accepts fermentation. electrons such as nitrates or sulfates

Oxygen Relationships

• Early life (during the Archaean) was primarily anaerobic. • Evolution of photosynthesis in Cyanobacteria changed all this.

Taxonomy of Prokaryotes

• Archaea or Archaebacteria – – – • Bacteria or Eubacteria – Protobacteria – Chlamyidias – Spirochetes – Cyanobacteria – Gram-positive bacteria

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Archaea or Archaebacteria

• Live in extreme environments (extremophiles): sulfur hot springs, deep sea vents, high salt environments. • Lack peptidoglycan, unique plasma membrane of liquids • Likely sister group of Eukaryotes

Archaea or Archaebacteria

• Methanogens

– Use H2 to reduce CO2 to methane (CH4). – Chemoautotrophs – Anaerobic – In swamps, marshes, deep sea vents, important decomposers.

Archaea or Archaebacteria

• Halophiles – Saline environments. – Salinity several times higher than sea water. – Photoheterotrophs

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Archaea or Archaebacteria

• Thermophiles – 60º-80ºCpH 2-4 optimal – Chemoautotrophs – Oxidize HS

Bacteria or Eubacteria

• Grouped by molecular systematics.

Bacteria or Eubacteria

Proteobacteria • VERY diverse, grouped into five taxa based on DNA sequence data. • Includes most types of metabolism that we’ve discussed. • Includes most of the types of symbioses we’ve discussed • Review the summary in Figure 27.16.

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Bacteria or Eubacteria Gram positive Bacteria: • Simple peptidoglycan cell wall. • Rival Proteobacteria in diversity. • Most are free-living decomposers. • Some pathogenic (e.g. strains of , , anthracis, botulinum). • Include the mycoplasms--the only bacteria that lack cell walls

Bacteria or Eubacteria Cyanobacteria: • Photoautotrophs • Only prokaryotes with plant-like, O2-generating photosynthesis. • Present in freshwater and marine environments. • Often colonial--first steps toward multicellularity?

Bacteria or Eubacteria

Spirochetes: • Helical • Recall motility: move by means of rotating, internal, -like filaments. • Free-living and parasitic. • Chemoheterotrophs (like us).

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Bacteria or Eubacteria

Chlamydias: • ALL are parasites of animals. • Intercellular. • Lack peptidoglycan in the cell wall (are they gram-positive or gram-negative?). • Most common form of STD in USA (urethritis).

Prokaryotes: Summary

• You should now have a good sense of prokaryote biology and diversity. • Including roles in metabolism, symbioses, global energy cycles. • Important distinguishing characteristics of cell wall, motility, genome, replication. • General aspects of their systematics.

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