* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Archaea
Cell encapsulation wikipedia , lookup
Cytoplasmic streaming wikipedia , lookup
Biochemical switches in the cell cycle wikipedia , lookup
Cell culture wikipedia , lookup
Cellular differentiation wikipedia , lookup
Extracellular matrix wikipedia , lookup
Signal transduction wikipedia , lookup
Organ-on-a-chip wikipedia , lookup
Cell growth wikipedia , lookup
Cell membrane wikipedia , lookup
Cytokinesis wikipedia , lookup
Cell nucleus wikipedia , lookup
Overview of lecture: •An introduc7on to Eukaryo7c microorganisms •General characteris7cs of Eukaryo7c cell structure and func7on Introduction to Microbiology •Highlight how eukaryo7c cells differ from prokaryo7c cells Eukaryotic microorganisms: Cell structure and function •Eukaryo7c cells are more complex than prokaryo7c cells Dr A. Fleming Eukaryotic cell morphology is diverse You are here • 3 domains •Arose from a common ancestor •Archaea and Eucaryota evolved independently, separate from bacteria Algae; Volvox Protozoa; Paramecium Fungi; Yeast Fungi; Aspergillus Eukaryotic microorganisms exhibit extreme diversity Diatoms Eukaryotic microorganisms can exist as multicellular macroscopic structures •Have a silicon‐based cell wall Mushroom Amoeba •Have no cell wall Eukaryo7c cells are complex •Have membrane bound nuclei •Have numerous organelles •Have more complex reproduc7on processes ‐ mitosis and meiosis Cell organelles •Defini7on: intracellular structures that perform specific func7ons •Analagous to the func7on of organs in the body •Organelles do not have to be membrane bound The cytoplasmic matrix is an organelle •Supports all other organelles and biochemical processes A major component of the cytoplasmic matrix is the cytoskeleton •Highly dynamic •Changes in the cytoplasmic matrix are essen7al for cell func7on •A network of 3 types of filaments •plays roles in cell shape and movement Cytoskeleton filaments: 1. Microfilaments 2. Microtubules •Ac7n protein filaments •4 – 7 nm in diameter •Can be scaRered or organised into networks •Role : •Involved in cell mo7on and cell shape change •a helix of α‐tubulin and β‐tubulin subunits •Thin cylinders ~ 25 nm in diameter •Role: 1.Maintain cell shape 2.Cooperate with microfilaments for cell movement 3.Par7cipate in intracellular transport Pathogens can hijack the eukaryo7c cytoskeleton 3. Intermediate filaments •Assembled from a mixed group of different proteins •10 nm in diameter Role: •Not well characterised •Can have a role in cell‐cell adhesion The nucleus •Listeria monocytogenes releases a ActA virulence factor •Ac7n polymerisa7on can propel Listeria monocytogenes through a host cell Eukaryo7c Genomes are large Organism Nucleus Prokaryote Eukaryote •Contains DNA •Bound by the double membrane nuclear envelope Genome size / bp No. of genes Phi‐X 174 5,386 10 Epstein‐Barr Virus 172,282 80 Bacillus sub*lis 4,214,814 4,779 E. coli K12 4,639,221 4,377 Saccharomyces cerevisiae 12,495,682 6000 Drosophila melanogaster 122,653,977 13,379 Anopheles gambiae 278,244,063 13,683 Human 3.3 x 109 ~20,500 Human mitochondria 16,569 37 DNA is packaged as chroma7n Gene transcrip7on in eukaryotes DNA double helix nucleosome Eukaryo7c RNA Polymerases folded nucleosomes Histones: H2A, H2B H3, H4 Pol II Pol I Pol III Transcrip7on chroma7n loop: Messenger RNA rRNA ~100,000 bp DNA Transla7on 50 – 70 % of total transcrip7on mito7c chromosome 5SrRNA and transfer RNA Proteins •Bacteria have one RNA polymerase Gene expression in prokaryotes RNA Polymerase σ ‐35 ‐10 Gene expression in eukaryotes RNA Polymerase gene1 gene2 gene3 DNA Operon TF TBP Gene TATA box Polycistronic mRNA Monocistronic mRNA Export Protein •RNA polymerase is directed by sigma factors •Transcrip7on and transla7on can occur simultaneously Protein •RNA polymerase is directed by TBP and transcrip7on factors •Genes may contain introns (non‐coding regions) Eukaryo7c ribosomes The nucleolus Prokaryo7c Eukaryo7c Nucleus Nucleolus Prokaryote Eukaryote •Very dense structure •not membrane bound •Site of ribosomal RNA synthesis and ribosome assembly •Immature ribosomes leave the nucleus via nuclear envelope pores Organelles of the secretory pathway •Eukaryo7c ribosomes are bigger protein factories The endoplasmic re7culum (ER) •A network of membranous tubes and flaRened sacks (cisternae) •Con7nuous with nuclear envelope Other organelles have roles in: •Movement of materials within the cell and out of the cell Smooth ER Rough ER •Involved in synthesis & export of proteins and lipids •Site of cell membrane synthesis The biosynthe7c‐secretory pathway The Golgi apparatus •Composed of flaRened membranous sacks (cisternae) A stack = dictyosome Maturing face 4‐8 cisternae / stack Dis7nct polarity E.g. Protein Secre7on •Movement of materials within or outside of cell 1.Protein synthesis 2.Glycosyla7on in ER 1. 3. Fusion with Cis face of Golgi Forming face 4.Packaging in Golgi Role: •Processing, packaging and secre7on of macromolecules Proteins are subject to quality control •Misfolded proteins are ubiquitylated •Modified proteins are degraded by the proteosome Proteosome 5.Transport Vesicle release 4. 5. 2. 3. The proteosome •A huge cylindrical protein complex •Proteolysis is ATP‐dependent Transport of materials into the cell •The Endocy7c pathway •Materials are enclosed within the plasma membrane •Delivery to a lysosome via three pathways 1.Phagocytosis (protrusions) Lysosomes •Single membrane bound spherical structures •Range from 50nm to several um in size •Contain hydroly7c enzymes 2.Endocytosis (invagina7ons) 3.Autophagy (recycling of cytosolic components) •Diges7on occurs in the lysosome •Small products leave the lysosome for use as nutrients Mitochondria Role: •Intracellular diges7on The proposed origin of the Eukaryo7c cell •The site of ATP synthesis •The endosymbio7c theory Size = 0.5 – 10um 1 ‐ 1000 / cell Prokaryo7c ancestor: ANAEROBIC 1.Lost the cell wall / phagocytosis of prokaryotes for nutrients 2.Formed symbio7c rela7onship with an engulfed aerobic bacteria 3.Photosynthe7c cyanobacteria promoted an oxic environment 4.Selected the above cell type 5.The endosymbio7c aerobic bacterium developed into mitochondria •They are double membrane structures: an inner membrane and outer membrane •The inner matrix is where ATP is formed Modern eukaryote: AEROBIC Eukaryo7c reproduc7on is more complex asexual reproduc7on: Mitosis Sexual reproduc7on: Meiosis •Chromosome number is reduced from diploid (2N) to haploid (1N) •Haploid cells may act as gametes to reform diploid organisms •A complex process involving several stages •Each new nucleus acquires a duplicate set of chromosomes Diversity of eukaryo7c external cell structures Other eukaryotes have a rigid cell wall Yeast Diatom (algae) Amoeba proteus •Some eukaryotes have no cell wall Rigid cell wall Glucose‐based Silica‐based cell wall (frustule) Cilia and Flagella Pro7sts have a pellicle underneath the membrane Cilia Flagella Euglena Paramecium Euglena spirogyra •Aid in mo7lity •the pellicle is striated, olen bearing rows of papillae Eukaryotic cilia and flagellar structure PaRerns of Flagellar and Ciliary movement wave •Membrane bound organelle, ~0.2m thick •Extensions of microtubule doublets arranged in a 9 + 2 structure •Originate from a basal body (centriole) beat The Archaea: a third form of life Comparison of Prokaryo7c and Eukaryo7c cells Prokaryote Eukaryote •Eukaryotes are more structurally and func7onally complex •Eukaryotes have a membrane –bound nucleus •Eukaryotes have a diverse collec7on of organelles •Replica7on is more complex –mitosis and meoisis •Eukaryotes carry out complex processes such as enodcytosis, amoeboid movement etc. •The Archaea: •Originally described as bacteria (archaebacteria) • are they are prokaryotes – have no nucleus ?? •Now proposed to form a dis7nct domain – a ‘third form’ of life Archaea have unique proper7es Archaea and eukaryotes share a common ancestry •All life arose from a common ancestor •Archaea and Eukaryotes evolved separately from the bacteria •Archaea and eukaryotes diverged and became separate domains •This common evolu7on is reflected in the way they process gene7c informa7on * * Archaea: General cell structure and morphology •Look similar to bacteria •Cell membrane is bound by a cell wall •Have a diverse morphology •Range in size from 0.1 – 200 μm •Commonly unicellular Methanococcus Janaschii ‐cocci with flagella Methanothermus fervidus ‐Short bacillus • Originally idenRfied in extreme environments Haloquadratum Walsbyi ‐square ? Methanosarcina Barkeri ‐lobed cocci Methanobacterium Thermoautotrophicum ‐filamentous How extreme is extreme ? Archaea • extremophiles – Hyperthermophiles – Methanogens – Extreme halophiles Thermophiles and hyperthermophiles Pyrolobus fumarii •Pyrolobus was found at a Hydrothermal vent (Black Smoker) The thermophile record holder (so far....) •Archaea Strain 121 •105 ºC is its op7mal growth temperature. • It cannot live below 90 ºC Psychrophiles: found in cold regions Strain 121 •Found at a hydrothermal vents Halophile habitat and structure Barophiles: • Found at the boRom of ocean trenches & gorges, such as the Mariana Trench •Resistant to extreme pressures Were the Archaea able to survive the violence of early earth? Did life on earth arrive from outer space ? Has life on earth spread to outer space ? •Via comets & Meteorites Could life originate on other planets ? Comets & Meteorites •Europa is a large moon of Jupiter •It is completely encased in water ice •Volcanoes could be ac7ve Alien life ? Alien life ? ? Could Archaea be the future of life on earth ? Summary • Eukaryotes have a more complex cell structure than prokaryotes – They have a nucleus and numerous organelles yeast • The Archaea form a third way of life • They have features of both prokaryotes and eukaryotes Extra Reading PrescoR, LM et. Al., Microbiology 7th edi7on McGraw‐Hill, Boston, 2008 Pages 70 ‐99