alpha-proteobacteria

Examples of alpha-proteobacteria in the following topics:

• The Evolution of Mitochondria

  • Alpha-proteobacteria are a large group of bacteria that includes species symbiotic with plants, disease organisms that can infect humans via ticks, and many free-living species that use light for energy.
  • Most mitochondria are shaped like alpha-proteobacteria and are surrounded by two membranes, which would result when one membrane-bound organism engulfs another into a vacuole.
  • The mitochondrial inner membrane involves substantial infoldings called cristae that resemble the textured, outer surface of alpha-proteobacteria .
  • Mitochondria have their own circular DNA chromosome that is stabilized by attachments to the inner membrane and carries genes similar to genes expressed by alpha-proteobacteria.
  • Mitochondria that carry out aerobic respiration have their own genomes, with genes similar to those in alpha-proteobacteria.

• Mitochondria

  • The mitochondrial inner membrane is extensive and involves substantial infoldings called cristae that resemble the textured, outer surface of alpha-proteobacteria.
  • Mitochondria have their own (usually) circular DNA chromosome that is stabilized by attachments to the inner membrane and carries genes similar to genes expressed by alpha-proteobacteria.

• The Evolution of Plastids

  • Like mitochondria, plastids appear to have a primary endosymbiotic origin, but differ in that they derive from cyanobacteria rather than alpha-proteobacteria.

• Pancreas

  • The pancreatic islets contain two primary cell types: alpha cells, which produce the hormone glucagon, and beta cells, which produce the hormone insulin.
  • As blood glucose levels decline, alpha cells release glucagon to raise the blood glucose levels by increasing rates of glycogen breakdown and glucose release by the liver.
  • The alpha and beta cells produce glucagon and insulin, respectively.

• Basic Structures of Prokaryotic Cells

  • Note that all gram-positive bacteria belong to one phylum; bacteria in the other phyla (Proteobacteria, Chlamydias, Spirochetes, Cyanobacteria, and others) are gram-negative.

• Endosymbiotic Theory and the Evolution of Eukaryotes

  • Other proteobacteria also have membrane-bound chromosomes.

• History of Bacterial Diseases

  • The causative agent, the (b) bacterium Yersinia pestis, is a gram-negative, rod-shaped bacterium from the class Gamma Proteobacteria.

• Stabilizing, Directional, and Diversifying Selection

  • Large, dominant alpha males obtain mates by brute force, while small males can sneak in for furtive copulations with the females in an alpha male's territory.
  • In this case, both the alpha males and the "sneaking" males will be selected for, but medium-sized males, which cannot overtake the alpha males and are too big to sneak copulations, are selected against.

• Transport of Oxygen in the Blood

  • Hemoglobin, or Hb, is a protein molecule found in red blood cells (erythrocytes) made of four subunits: two alpha subunits and two beta subunits .
  • Thalassemia is a rare genetic disease caused by a defect in either the alpha or the beta subunit of Hb.

• Lipid Molecules

  • Omega-3 fatty acid, or alpha-linoleic acid (ALA) , falls into this category and is one of only two fatty acids known to be essential for humans (the other being omega-6 fatty acid, or linoleic acid).
  • Alpha-linolenic acid is an example of an omega-3 fatty acid.