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Biol 165 - Prokaryotes.pdf

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University of Waterloo
BIOL 165
Kirsten Muller

Biol 165: Diversity of Life   Prokaryotes Introduction • Non-nucleate organisms • Consists of Domain Bacteria and Archaea • They DO NOT have the following: o nucleus, nucleolus, ER, mitochondria, and chloroplasts • Their flagella are not homologous with that of eukaryotes o lack 9+2 composition • They are often MUCH smaller than eukaryotic organisms • The ribosomes of prokaryotes and eukaryotes are homologous, revealing a distant ancestor. • Classification • Traditional: used to be included in Kingdom of Monera • There are 100s of unknown and undescribed prokaryotes. • Their classification is based on 16S RNA sequences, and are MONOPHYLETIC. • Modern: Monera divided into 2 Domains o Domain Bacteria  many are disease causing  some are photosynthetic (autotroph)  others are heterotrophs  Divided into 16 Phyla, or 14 Kingdoms, depending on referred text. • o Domain Archaea  most are anaerobes (do not need oxygen).  NONE are known to cause diseases  They occupy extreme habitats (extremophiles) and are chemotrophs.  Divided into 2 Phyla or 3 Kingdoms: Crenarchaeota, Euryachaeota, and Korarchaeota. • • Scientists are still unsure if Archaea and Bacteria share a common ancestor, or Archaea and Eukarya do. Shapes of Bacteria Cell Division Biol 165: Diversity of Life   • occurs by simple Binary Fission • duplicated chromosomes attach to the cell membrane on opposite sides • new cell wall forms in middle and pinched apart to for two daughter cells. • some bacteria form a bud that is pinched off instead of division in the middle, dividing the cell equally. • • Chromosomes are coiled, and consist of Double-stranded DNA o 18-50% of a bacteria’s DNA is not indigenous. o bacteria exchange DNA through transfer of sequences from plamids – lateral gene transfer. o their 16S RNA sequence is not likely to be transferred – protected and necessary for cell to live. o Conjugation: the transfer of genes from one prokaryote cell to another. o Plasmids: extrachromosomal genetic material not essential for growth. Often act as vectors. These get passed between bacteria during conjugation. Flagella • not homologous with the undulipodia(flagella) of eukaryotes • do not have 9+2 microtubule configuration, and are composed of different proteins • are used for locomotion, and perform a propeller-like action. • Gram Staining of Bacteria • Gram+ bacteria have a cell wall consisting of mostly exposed peptitoglycan. o They stain PURPLE • Gram- bacteria have a protective outer membrane, and the peptitoglycan lies behind that wall. o They stain RED • As such, the Gram- bacteria are harder to treat with antibiotics because they have a more resilient outer membrane that does not permit easy access of the antibiotics. • This is often the first test performed in labs to determine the species of bacterial disease and the appropriate mode of treatment. • Biol 165: Diversity of Life   Kingdom: Bacteria Phylum: Proteobacteria/Myxobacteria Genus: Myxococcus • have a the most complex life cycle of all prokaryotes • known as “slime-molds”, and produce “fruiting-bodies”. • resemble fungi, but are not. • ALL LIFE STAGES ARE 1n! • are colonial, not multicellular. • Kingdom: Bacteria Phylum: Actinobacteria Genus: Streptiomyces and Actinomyces • Are a large group of filiamentous, and Gram+ bacteria. • They form fungal-like masses with elaborat
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