Eukaryotic microorganisms and viruses 2 1 Heribert Cypionka What is the main difference between the prokaryotic and the eukaryotic cell? Compartimentation >> Separation of reaction rooms >> More complex regulation >> Transport including fusion and separation of membrane vesicles 2 1
The eukaryotic cell and its structure Size + microscopy techniques Nucleus Mitochondria, hydrogenosomes Chloroplasts Endoplasmic reticulum and Golgi complex Lysosomes and peroxisomes Microfilaments and microtubules Flagella and cilia Life cycle Differences between prokaryotes and eukaryotes 3 Size Surface of a mouth mucosa cell of a healthy female student from the University of Oldenburg 4 2
Size "Microsomes" - many organells are bacterium-sized Structures smaller than bacteria are hardly resolved by light microscopy Cytoplasm of the same mouth mucosa cell 5 Principles of microscopy Bright field Staining TEM: Contrasting + short wavelength Phase contrast (differential interference contrast, DIC, needs polarisation and beam-splitting prismas) Dark field Epifluorescence Confocal laser scanning microscopy 6 3
bright field phase contrast dark field DIC 7 8 4
Come-back of light microscopy... 9 Pictures: Erhard Rhiel Electron microscopy Negative staining Contrasted Section TEM = Transmission electron microscopy Freeze etching + oblique sputtering 10 5
Scanning electron microscopy (SEM ) Object Detector screen Scanning beam Picture: Henrik Sass The image is not projected to the detector screen, but calculated from dark and bright pixels obtained from scanning! 11 Prokaryotes: Nucleoid Eukaryotes: Nucleus Nucleus The nucleus normally contains several linear chromosoms with telomers DNA is embedded in histons Large part of the DNA is non-coding introns, little is exons Nucleolus 12 6
A double membrane with pores encloses the nucleus The nucleolus (plural nucleoli) is a "sub-organelle" of the nucleus. A main function of the nucleolus is the production and assembly of ribosome components 13 Mitochondria membranebound! (Wikipedia) 14 7
Hydrogenosomes 15 Physiology of the hydrogenosome (Brock) (fully understood?) 16 8
Chloroplasts Same (homolog) structure as mitochondrion, ribosomes, DNA Different names (compare also with bacterial cell!) 17 Endoplasmic reticulum (ER) Rough ER -> production of (glyco-) proteins Smooth ER -> production of lipids, carbohydrates (Wikipedia) 18 9
Golgi complex Closely associated with ER (transitional vesicles) Asymmetric (cis-, trans-site) Modification of proteins (glycosilation, activation by limited proteolysis) Sorting of degradative enzymes (lysosomes), secretory enzymes (exoenzymes) Secretion Regeneration of the cell membrane 19 Phagocytosis and pinocytosis Incorporation (and release) of particular or liquid structures into membrane vesicles (food vacuoles) Uptake of compounds into the cytoplasm requires osmotrophic processes 20 10
Lysosomes and peroxisomes Lysosomes -> production of digestive enzymes (Don't mix with lysozyme) Peroxisomes -> production of reactive H 2 O 2 by incomplete O 2 reduction 21 Microfilaments and microtubules From Wikipedia, the free encyclopedia Microfilaments (fluorescence after staining with phalloidin) Microtubule structure Forming cytoskeleton Microfilaments 8 nm thick, protein: actin Microtubules 25 nm thick, protein: tubulin Homologs in prokaryotes: proteins MreB and FtsZ 22 11
Flagella and cilia 500 nm Prokaryotic flagellum (Brock) Eukaryotic flagella (Cross section, Wikipedia) Eukaryotic flagella long, cilia short Complex (9 + 2) structure, proteins: tubulin + dynein (= ATPase) Not rotating, ATP-consuming movement includes sliding of the central (axoneme) filaments against one another 23 Life cycle of yeast (Saccharomyces) Eukaryotes can have haploid and diploid cells, males and females, and sex Cell division normally occurs via mitosis, the transition from dipoloid to haploid involves meiosis 24 12
Differences between Bacteria, Archaea and Eukarya Bacteria Archaea Eukarya Compartments separated by membranes No (rare) No (rare) Nuclear membrane mitochondria, chloroplasts, endoplasmic reticulum, membrane vesicles, vacuoles Some: vacuoles or gas vacuoles (protein) Some: endospores Size 1 µm 1 µm 20 µm Chromosome 1 1 Several (often plasmids) Sexual reproduction No No Meiosis (Conjugation, partial transfer of DNA possible) Ribosomes 70 S 70 S 80 S Flagella Simple Simple Composed (9+2) structure Cell wall Murein Proteins, poly- Cellulose, carbonates, saccharides, silicate etc. pseudomurein etc. Membranes contain Hopanoids Ether lipids Steroids 25 Suggestions for homework Repeat the steps of mitosis, meiosis and the eukaryotic cell cycle Come to my office let's start a hay infusion 26 13