BFI Microbiology Notes

• Biologists use microscopes and tools of biochemistry to study cells.
• Eukaryotic cells have internal membranes that compartmentalize their functions.
• Mitochondria and chloroplasts change energy from one form to another, and have an interesting prokaryotic evolutionary origin.
• In a light microscope (LM), visible light is passed through a specimen and then through glass lenses, which refract (bend) the light, so that the image is magnified.
• The size range of cells is from 10^-12 to 10^-6 m.
• Three important parameters of microscopy are magnification, resolution, and contrast.
• Magnification is the ratio of an object’s image size to its real size, making something appear bigger.
• Resolution is the measure of clarity of the image, determining if two separate points on the image can be distinguished.
• Contrast is the visibility of differences in parts of the sample, determining if a feature can be distinguished from the background.
• Light Microscopy (LM) magnifies effectively to about 1,000 times the size of the actual specimen.
• The Phanerozoic includes the last half billion years, and encompasses multicellular eukaryotic life.
• Prokaryotes were Earth’s sole inhabitants from 3.5 to about 2.1 billion years ago.
• The endosymbiotic theory suggests that an early ancestor of eukaryotes engulfed an aerobic (oxygen-using) nonphotosynthetic prokaryote.
• The oldest known fossils are stromatolites, rocks formed by the accumulation of sedimentary layers on bacterial mats.
• A second endosymbiotic event involved a photosynthetic prokaryote being engulfed by a eukaryote containing mitochondria.
• Stromatolites date back 3.5 billion years ago.
• The engulfed prokaryote was maintained within the host cell and became an endosymbiont, eventually evolving into a mitochondrion.
• Peroxisomes are oxidative organelles, using oxygen for some molecular breakdown, forming peroxides but also converting those peroxides into water, protecting other cellular components.
• Mitochondria are the site of cellular respiration, a metabolic process that uses oxygen to generate ATP.
• Chloroplasts, found in plants and algae, are the site of photosynthesis, a metabolic process that uses the energy from sunlight to fix carbon (from CO2) and uses it to generate energy-rich organic molecules such as glucose.
• This endosymbiont evolved into a chloroplast.
• Energy-transducing mitochondria and chloroplasts are not part of the endomembrane system, and are derived from prokaryotes.
• The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic.
• Mitochondria and chloroplasts change energy from one form to another.
• Various techniques enhance contrast and enable cell components to be stained or labelled in Light Microscopy.
• Most subcellular structures, like organelles, are too small to be resolved by standard Light Microscopy.
• Some groups survived and adapted using cellular respiration to harvest energy.
• Serial endosymbiosis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events.
• The initial rise in O2 was likely caused by ancient cyanobacteria.
• O2 produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations.
• The "oxygen revolution" caused extinction of many prokaryotic groups.
• In the process of becoming more interdependent, the host and endosymbionts became a single organism.
• The oldest fossils of eukaryotic cells date back approximately 1.8 billion years.
• Eukaryotic cells have a nuclear envelope, mitochondria, endoplasmic reticulum, and a cytoskeleton.
• An endosymbiont is a cell that lives within a host cell.
• The endosymbiont theory states that mitochondria and plastids were formerly prokaryotes living within larger host cells.
• Prokaryotic ancestors of mitochondria and plastids probably gained entry into host cell as undigested prey or internal parasites.
• Most atmospheric oxygen (O2) is of biological origin.
• By about 2.7 billion years ago, O2 began accumulating in the atmosphere and rusting iron-rich terrestrial rocks, a process known as the "oxygen revolution".
• Later increases in atmospheric O2 might have been caused by the evolution of eukaryotic cells containing chloroplasts.