Microbiology 1

• The hidden world includes organisms that are only visible using a microscope, which are divided into cellular (living) and acellular (non-living) microbes.
• Cellular microbes include bacteria, archaea, protists, fungi.
• Acellular microbes include viruses, viroids, satellites and prions.
• Reading Chapter 1 and 2 of Prescott’s Microbiology is a good start for this lecture.
• Independent study involves spending time writing notes after each lecture to help with revision throughout term.
• Many steps in the OOC relate to this lecture: particularly the timelines and animations.
• The three domains of life are Prokaryotes, Eukaryotes, and Archaea.
• A eukaryotic cell consists of a membrane, cytoplasm, membrane-enclosed organelles, nucleus, and DNA (throughout nucleus).
• A prokaryotic cell consists of a membrane, cytoplasm, and DNA (no nucleus).
• The RNA world hypothesis suggests that the original replicating molecule must have fulfilled both enzymatic and hereditary function.
• Ribozymes are RNA molecules that form peptide bonds, perform cellular work and replication.
• The earliest cells may have been RNA surrounded by liposomes.
• Stromatolites are rock-like structures in shallow water formed by microbes, including cyanobacteria.
• The Great Oxygenation Event was the evolution of photosynthetic bacteria (cyanobacteria) which led to an increase in O2 in Earth’s atmosphere.
• Banded iron formations are due to the formation of insoluble iron oxides, free iron is much harder for organisms to obtain.
• The extinction of many ancient anaerobic microbes may have occurred during the Great Oxygenation Event.
• The first fossil evidence of microbial fossils includes Archaeon apex chert of Australia – granular silica, and Stromatolites.
• The first human-like species, Genus Homo, appeared 2-3 Mya.
• LUCA, the Last Universal Common Ancestor, is likely an anaerobe, probably an extremophile, with a lipid membrane surrounding a nucleic acid genome.
• All living organisms on Earth share the same genetic code.
• Bacteria and archaea diverged as separate lineages.
• An endosymbiotic event between an archaeal cell and a bacterium led to the evolution of eukaryotes.
• Viruses also use the same genetic code but have evolved many times.
• At least one species of virus infects every species of living organism, probably many more than this.
• Microbes today exhibit an amazing diversity, with more species being discovered every day, and live in every environment on Earth in microbial communities.
• Extremophiles inhabit hostile environments.
• Syntrophy is a phenomenon where some species of microbes rely on the metabolic activity of other organisms to grow.
• Basic dyes have positive charges.
• Transmission Electron microscopy (TEM) uses electrons excited from the surface of a specimen to create a detailed image, produces a realistic 3D image of specimen’s surface features, and can determine the actual in situ location of microorganisms in ecological niches.
• Confocal Microscope, also known as Confocal scanning laser microscopy (CLSM), creates a sharp, composite 3D image of specimens by using a laser beam, an aperture to eliminate stray light, and a computer interface.
• Mycobacterium tuberculosis causes tuberculosis and Mycobacterium leprae causes leprosy.
• Acid dyes have negative charges.
• Gram-positive bacteria can be stained with Acid-Fast Stain, which is particularly useful for staining members of the genus Mycobacterium, including Mycobacterium tuberculosis and Mycobacterium leprae.
• Phase-contrast microscopy converts differences in refractive index/cell density into detected variations in light intensity.
• Scanning electron microscopy (SEM) uses electrons excited from the surface of a specimen to create a detailed image, produces a realistic 3D image of specimen’s surface features, and can determine the actual in situ location of microorganisms in ecological niches.
• Microbial warfare includes the use of antimicrobials and antimicrobial resistance.
• High lipid content in cell walls (mycolic acid) is responsible for the staining characteristics of Mycobacterium.
• Electron Microscopy replaces light as the ‘illuminating’ beam, has a much shorter wavelength than light, resulting in much higher resolution, and allows for study of microbial morphology in great detail.
• Dyes increase the visibility of internal and external structures of cells by increasing contrast with the background.
• Fluorescence microscopy excites fluorochrome or fluorescent protein with light of specific wavelength, causing it to emit longer wavelength light, resulting in a bright image.