Prokaryotic Cell Division: Binary Fission

• Prokaryotes are single-celled organisms classified as either prokaryotic or eukaryotic.
• Prokaryotes lack a well-defined nucleus due to the absence of a nuclear membrane.
• Prokaryotes do not have membrane-bound organelles like the endoplasmic reticulum, golgi apparatus, mitochondria, or chloroplasts.
• Prokaryotes divide by binary fission instead of mitosis, which is a form of asexual reproduction.
• During cell division, DNA replicates, the two rings are pulled to opposite sides of the cell, the cell membrane pinches in, and new cell wall material is deposited.

Cell Division

• Initiation: Cell division starts with a signal, such as abundant food supplies.
• DNA Replication: Genetic material duplicates, giving each cell a complete, identical set of genes.
  • Typically have 1 chromosome, with 1 circular DNA molecule.
• DNA Segregation: Daughter DNAs are equally separated to each new cell, guided by ori regions.
  • The chromosome has two regions: ori, where replication starts, and ter, where replication ends.
• Cytokinesis: A new cell wall separates the two new cells.
• Mutations are the main source of genetic variation in prokaryotes.

Three Domains of Life

• All living organisms are organized into three domains, two of which are prokaryotes.
• Bacteria, archaea, and eukarya are all descended from a single, common ancestor.
• Archaea are more closely related to eukaryotes than they are to bacteria.
• All three domains of life have plasma membranes, ribosomes, glycolysis, DNA as genetic material, protein production via transcription and translation, and DNA that replicates semi conservatively.
• Eukaryotic genes contain introns, which are DNA sequences transcribed into mRNA but spliced out before translation.
• Bacteria and archaea commonly have plasmids, which are small circular DNA distinct from the main chromosome that contains genes not critical to the cell's life.

Prokaryote Success

• Prokaryotes can be found everywhere and are the most numerous living group.
• Prokaryotes form diverse communities called biofilms.
• Species in biofilms change in response to environmental conditions.
• Prokaryote biofilms can form on living and non-living things.
• Some prokaryotes are pathogens, while others are in beneficial relationships with other organisms.
• Aliivibrio fischeri is a bacterium found in marine environments and demonstrates bioluminescence.

Other key prokaryote information

• Prokaryotes communicate with signals like bioluminescence.
• Prokaryotes have diverse metabolic pathways.
  • Obligate anaerobes: Oxygen is poisonous for them.
  • Facultative anaerobes: Can shift from fermentation to cellular respiration.
  • Aerotolerant anaerobes: Have anaerobic.
• The two prokaryote domains are archaea and bacteria.

Domain Bacteria

• Bacteria can be described according to 3 characteristic forms: coccus (spherical), bacillus (rod-shaped) and spirillum (spiral).
• Bacteria may live singly or in chains or clusters.
• Bacteria are grouped as gram-negative or gram-positive based on cell wall characteristics.
• Peptidoglycan, found only in bacterial cell walls, is a distinctive structural component.
• A thick peptidoglycan layer in gram-positive bacteria, and thin in gram-negative cells.
• Gram staining uses violet dye, then alcohol, and then red dye to stain cell walls.
• Gram-positive cells retain violet stain, while gram-negative cells are only stained by red dye.
• Penicillin and ampicillin interfere with the formation of peptidolgycan cell walls, therefore they only harm bacteria cells.
• Other antibiotics interfere with the smaller, 70s bacterial ribosome but do not affect the larger 80s eukaryotic ribosome.
• Most bacteria are harmless or useful to humans, but some cause diseases.

Groups of Bacteria

• Spirochetes: Cell body is like helix, live as parasites in humans, some are pathogens (syphilis, Lyme disease).
  • Syphilis: Sexually transmitted, caused by Treponema pallidum, causes paralysis, dementia, blindness and even death
• Chlamydias: Very small parasites that take up ATP from a host cell and cause sexually transmitted diseases.
• High GC Gram-Positives: Have a high ratio of guanine and cytosine to A-T nucleotide pairs and a branched system to access water and nutrients.
  • Actinobacteria
• Low GC Gram-Positives: Have low ratio of guanine and cytosine to A-T nucleotide pairs and some produce endospores when conditions are bad for survival
• Proteobacteria- Purple Bacteria: Include E.coli, Vibrio Cholerae, and nitrogen fixing bacteria

Bacterial diseases

• Cholera: The disease is caused by Vibrio cholera which kills over 150,000 people a year. The bacteria releases a sever toxin, causing loss of body salts.
• Bubonic Plague: Caused by Yersinia pestis, killing 25-45% of Europe's population in the 14th century. Transmitted to humans via flea bites from rats.
• Cyanobacteria: The phorotrophs have chlorophyll a used for photosynthesis that release oxygen They form the following cells filamentous colonies:

1. Vegetative cells
2. Spores - Resting Stages
3. Heterocysts - Nitrogen Fixation

Nitrogen Cycle

• Bacteria play a key role in balancing the environment through the cycling of nutrients.
• Bacteria play a key role in the essential cycling of nitrogen so they will benefit proteins, nucleic acids and ATP.
• There are 5 main steps in the nitrogen cycle:

1. Fixation
2. Assimilation
3. Ammonification
4. Nitrification
5. Denitrification

• The bacteria can synthesize and produce vitamin K, vitamin Biotin, and produce initial immune system in babies
• Probiotics can outcompete harmful bacteria

Domain Archaea

• This is used to create and find other types of foods and the waste is deposited through water
• The bacteria are used in sewarage and waste treatment with the use of aerobic bacteria
• Bacteria aids in consuming the hydrocarbons in oil spills and turning the waste into carbon dioxide and water
• Archaea (or Archeobacteria) live in hot springs, salt lakes, swamps, and oceans (also in extreme environments).
• Archaea cell membranes are distinctive, with branched chains and monolayer membranes for more rigid resistance.

Archaea groupings

• They lack petidoglycan walls and are split into two main groups:

1. Euryarchaeota - Including Halophiles, the "salt lover"
2. Crenarchaeota - "Acid-loving" also include Thermophiles.

Crenarchaeota grouping

• Ex) Sulfolobus lives in hot sulfur springs with a PH of 2 to 3.