2.2 Prokaryotes

From study guide

Define each type of extremophile

Acidophiles - pH 3 & below

Alkaliphile - pH 9 & higher

Tempophile - 60-80 C

Hypertemphile - 80-122 C

Psychrophile - 5-10 C

Halophile - Salt concentration 0.2M

Osmosphile - High Sugar concentration

Hypolith - Low humidity / Water

Describe basic structure of prokaryotic cell

• Unicellular, but can form communities

• Single circular, double-stranded DNA chromosome (No nucleus- no membrane)

• Nuclieoid: Region (no envelope) of the cell that contains the genome

• Cell wall & plasma membrane

• Ribosomes

Differences in structures between Archaea & Bacteria

1. Plasma Membrane: Archea: Branched with ether bonds Bacteria: Unbranded with ester bonds

2. Cell Wall Archaea: Composed of polysaccharides (Long chains of sugar) Bacteria: Composed of peptidoglycan

3. Gene expression Archaea: Transcription and translation are more similar to those of eukaryotes; enzymes are also similar

4. Pathogenetic Archaea: none are pathogenic to humans (infect humans) Bacteria: Are infectious

Evolutionary relationship between archaea & bacteria

Share a common ancestor LUCA

Explain the reproduction in prokayotes

• Asexually only, by binary fission, do not undergo mitosis

  • Chromosomes are replicated

  • Cell pinches inward

  • Two clone cells are created

Describe Horizontal gene transfer

• Horizontal gene transfer: transfer of genetic material from an organism to another organism, not its offspring

  • can occur between different species

  • Responsible for most genetic variation rather than mutation

  • Can cause large-scale changes in bacterial genome

  • If transferred genes do not provide a selective advantage they are always lost by deletion

Explain Macro and Micro nutrients needed by prokaryotes

Terms for which prokaryotes get energy

1. Energy source used to generate ATP

   • Phototrophs: Sunlight

     • Photoorganotrophs (organic)

     • Photolithotrophs (inorganic)

   • Chemotrophs: Chemical compound

     • Chemoorgoniotroph (organic)

     • Chemolithotroph (inorganic)

   2. Carbon source

   • Autotrophs: Inorganic compounds such as CO2

   • Heterotrophs: organic compounds

Define obligate aerobes

Need Oxygen

Define obligate anaerobes

Oxygen is toxic

Define facultative anaerobes

Can survive with or without oxygen (used in fermentation)

Compare gram-positive & gram-negative

Positive = Thic cell wall

Negative = Thin cell wall

What is the role of prokaryotes in the carbon cycle

Produce: photosynthesis

Consume: use organic compounds from producers and release CO2 to the atmosphere

Decomposers: release organic molecules by breaking down dead organisms

What is the role of prokaryotes in the nitrogen cycle

• Nitrogen in the atmosphere (N2) is not usable by plants

• Nitrogen fixation: N2 to NH3 (ammonia)

• Ammonification: released during decomposition

• Nitrification: ammonia converted to nitrate

Plants can’t use nitrogen directly from the air, bacteria pull it from the air convert it to nitrate, and put it into the soil for plants to use

Explain why natural reservoirs make disease eradication difficult

• The population of organisms that harbor a pathogen and transmits it to the target population.

  • Reservoir species typically do not experience symptoms of the diseases (Bats, rats, cows, etc.)

Explain how the over use of antibiotics may be creating “super bugs”

Antibiotic resistance is caused by overuse and misuse of antibiotics it allows bacteria to develop resistance to the antibiotic, meaning that the drug becomes ineffective against them

Explain the importance of MRSA with respect to the problem of antibiotic resistance

it is a strain of bacteria that has developed resistance to a wide range of commonly used antibiotics, particularly those in the penicillin class, making infections caused by MRSA difficult to treat and potentially life-threatening

Describe the beneficial effects of bacteria that colonize our skin and digestive track.

• Food digestion

• Protection from pathogens

• Produce vitamins

• Gut microbes can influence our mood, energy level, weight control

• Allergies & autoimmune diseases