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Advance Microbiology
EUKARYOTIC CELLBIOLOGY AND
MICROORGANISM
Eukaryotic Cell Structure
In contrast to prokaryotes, eukaryotes contain amembrane-enclosed nucleus and several other organells.
Nucleus• The nucleus contains the genome of the
eukaryotic cell.
• In eukaryotic, DNA within the nucleus iswound around histones to formnucleosomes, and from themchromosomes.
• The nucleus is enclosed by pairof membranes, the innermembrane is a simple sac, whilethe outer membrane is in manyplaces continuous with theendoplasmic reticulum.
• The inner and outer nuclear membranes specialize ininteractions with the nucleoplasm and the cytoplasm,respectively.
• The nuclear membrane also contains pores, formed fromholes where the inner and outer membranes are joined. Thepores allow a complex of proteins to import and export otherproteins and nucleic acids into and out of the nucleus, aprocess called nuclear transport.
• Within the nucleus, the nucleolus is the site of ribosomal RNAsynthesis.
Eukaryotic Cell Structure And Function
The nucleus. Electronmicrograph of a yeastcell by freez-etching,showing a surface viewof the nucleus.
Mitochondria
• For respiration and oxidative phosphorylation (a mechanismof ATP formation).
• Can be rod-shaped or nearly spherical.
• A typical animal cell can contain over 1000 mitochondria.
• Surronded by two membranes. The outer membrane,composed of an equal mixture of protein and lipid, relativelypermeable and contains numerous minute channels thatallow passage of ions and small organic molecules. The innermembrane is more protein rich and is also less permeable.
Eukaryotic Cell Structure And Function
Respiratory and Fermentative Organells:the Mithocondrion and the Hydrogenosome
• Mitochondria also possess a series of folded internalmembranes called cristae, the sites o enzymes involved inrespiration and ATP production.
• The matrix contains a number of enzymes involved in theoxidation of organic compounds-in particular, enzymes of thecitric acid cycle.
Eukaryotic Cell Structure And Function
Diagram showing the overall structure of the mitochondrion. Note inner andoutermost membranes.
Eukaryotic Cell Structure And Function
Tranmission electron micrographs of mitochondria from rattissue, showing the variability in morphology. Note the cristae.
The Hydrogenosome• Some anaerobic eukaryotic microorganisms lack mitochondria
and contain instead a hydrogenosome.• The hydrogenosome lacks cristae and citric acid cycle.
Eukaryotic Cell Structure And Function
Electron micrograph of a thin section through a cell of theanaerobic flagellate, Trichomonas vaginalis.
Biochemistry of the hydrogenosome
• Chloroplasts are choropyll-containing organelles found inphototrophic eukaryotes-algae.
• Chloroplasts have permebleoutermost membrane, a muchless permeable innermembrane, and anintermembrane space.
• The inner membranesurrounds the lumen of thechloroplast, called the Stroma.
Photosynthetic Organells:The Chloroplast
a
b
Photomicrographs of algal cellsshowing chloroplasts. (a)Stephanodiscus, (b) Spirogyra,spiral-shaped chloroplasts
• Instead, chlorophyll and all other components needed forphotosynthesis are located in a series of flattened membranediscs called thylakoids. In green algae and green plants,thylakoids are typically stacked into discrete structural unitscalled grana.
• The chloroplats stroma contains large amounts of the enzymeribulose bisphosphate carboxylase (RubisCo), a key catalist ofthe calvin cycle, the series of biosynthetic reactions by which
most photosynthetic organism convert CO2 into organiccompound.
Chloroplast
Thylakoid
Chloroplast of the goldenbrown alga Ochromonasdanica. Note thylakoids.
1.2.3.
4.
5.
Endosymbiosis: Relationships of Mithocondria andChloroplasts to Bacteria
Mithochondria and chloroplasts contain DNAThe eukaryotic nucleus contains bacterially derived genesMitochondria and chloroplasts contain their own ribosomes70S-same as prokaryotes ribosomes.Antibiotic specifitySeveral antibiotics (ex. Streptomycin) kill or inhibit bacteria. These sameantbiotics also inhibit protein synthase in mitocondria and chloroplast.Molecular phylogenyUsing comparative ribosomal RNA sequencing methods and oranellargenome studies have shown convincingly that the chlorolpast andmitochondrion originated from the Bacteria.
Eukaryotic Cell Structure And Function
Endoplasmic Reticulum (ER)• Is a network of membranes continuous with the nuclear
membrane.• Two types: rough, which contains attached ribosomes, and
smooth, which does not.• Smooth ER participates in the synthesis of lipids and in some
aspects of carbohydrate metabolism.• Rough ER, through the activity of its ribosomes, is a major
producer of glycoproteins and also produces new membranematerial.
Other Organelles and Eukaryotic Cell Structure
Eukaryotic Cell Structure And Function
Eukaryotic Cell Structure And Function
Golgi Complex• Consists of a stack of membranes distinct from the ER, but
which functions in concert with the ER.• In the golgi complex products of the ER are chemically
modified and sorted into those destinied to secreted, forexample hormones or digestive enzymes.
Cell of the protozoan Toxoplasma gondii. The golgi is colored in red.
Eukaryotic Cell Structure And Function
LysosomesAre membrane-enclosed structures that contain variousdigestive enzymes that the cell uses to digest macromoleculessuch as proteins, fats, and polysacharides.
Peroxisomeis a membrane-enclosed structures whose function is toproduce hydrogen peroxide (H2O2) from the reduction of O2by various hydrogen donors, including alcohols and long chainfatty acids. The H2O2 produced in the peroxisome is degradedto H2O and O2 by enzyme catalase.
Eukaryotic Cell Structure And Function
Microfilaments and Mirotubules
• These structures form the cell cytoskeleton.• Microfilaments are about 8 nm in diameter and are polymers
of the protein actin. These fibers form scaffolds throughoutthe cell, defining, and maintaining the shape of the cell.
• Mirotubules are larger filaments, about 25 nm in diameter,and are composed of the protein tubulin. Microtubules assistmicrofilaments in maintaining cell structure.
• They also play an important role in cell motility.
Microfilaments and eukaryotic cell architecture
Eukaryotic Cell Structure And Function
Eukaryotic Cell Structure And Function
Flagella and Cilia• Are organelles of motility, allowing cells to move by swimming
motility.• Cilia are essentially short flagella that beat in synchrony to
propel the cell – usually quite rapidly – through the medium.• Flagella are long appendages present singly or in groups that
push the cell along – typically more slowly than by cilia –through a whip-like motion.
• Eukaryotic cells divided by mitosis and then undergo sexualreproduction.
• From a genetic standpoint, eukaryotic cells can exist in twoforms: haploid or diploid.
• Mitosis is the process following DNA replication in a cell inwhich chromosomes condense, divide, and are separated intotwo sets, one for each doughter cell.
• Meiosis is the process by which the conversion from thediploid to the haploid stage occurs.
Overview of Eukaryotic Genetic
Eukaryotic Genetics
Mitosis, as seen in the light microscope
Eukaryotic Genetics
Metaphase,chromosome arepaired in the centerof the cell.
Anaphase,Chromosome are
separating
The Mating Process in Yeast: Mating Types
Eukaryotic Genetics
Life cycle of a typical yeast, Sacharomyces cerevisiae. A haploid cellof S. Cerevisiae contain 16 chromosome.
Eukaryotic Microbial Diversity
Phylogenetic tree based on comparative 18S ribosomal RNAsequences. Note how endosymbionts (mitochondria and chloroplasts)are shown to originate in the domain Bacteria.
Eukaryotic Microbial Diversity
A phylogenetic tree based on other eukaryotic genes and proteins
ProtozoaCharacteristics of the major groups of protozoa
Group
Mastigophora
Euglenoids
Sarcodina
Ciliophora
Common Name
Flagellates
Photorophicflagellates
Amebas
Ciliates
Typicalrepresentatives
Trypanosoma,Giardia,
Leishmania,Trichomonas
Euglena
Amoeba,Entamoeba
Balantidium,Paramaecium
Habitats
Freshwater;parasites of
animals
Freshwater;freshmarine
Freshwater andmarine; animal
parasites
Freshwater andmarine; animal
parasites; rumen
Common deases
African sleepingsickness,giardiasis,
leishmaniasis
None known
Amebic dysentery(amebiasis)
Dysentery
Apiconplexa SporozoansPlasmodium,Toxoplasma
Primarily animalparasites; insects
(vector for parasiticdeseases)
Malaria,toxoplasmosis
Eukaryotic Microbial Diversity
Typical protozoa. (a) Amoeba. (b) A typical ciliate, Paramaecium. (c) Aflagellate, Dunaliella (this flagellate contains chlooroplasts and thus canalso be consider an alga). (d) Plasmpdium vivax, an apicomplexansporozoan, growing in a human red blood cell.
Red blood cellMembrane flap
Trypanosomes.Photomicrograph of theflagellated protozoanTrypanosoma brucei, thecausative agent of Africansleeping sickness, from a bloodsmear.
Trypanosoma cell
Shelled amoebae:foraminifera. Note the
ornate and multilobed test.
Eukaryotic Genetics
Side view of a moving amoeba, Amoeba proteus, taken from a film. Thetime interval from top to bottom is about 6 second. The arrows point to a
fixed spot on the surface. A single cell is about 80 μm in diameter.
Yeast cell (for scale)Cilia
Mouth (gullet)
Eukaryotic Microbial Diversity
Paramaecium, a ciliated protozoan
Slime Molds• Slime molds are microbial eukaryotes that have
phenotipic similarity to both fungi and protozoa. Likefungi, slime molds undergo a life cycle and canproduce spores. However, like protozoa slime moldsare motile and can move across a solid surface ratherrapidly.
• Divided into two groups, cellular slime molds, whosevegetative forms are composed of single amoebae,and the acellular slime molds, whose vegetativeforms are masses of protoplasm of indefinitife sizeand shape called plasmodia.
Eukaryotic Microbial Diversity
Slime molds. Plasmodia of the acellular slime mold Physarumgrowing on an agar surface
Eukaryotic Microbial Diversity
Photomicrograph of various stages in the life cycle of the celullar slimemold Dictyostellium discoideum.(a) Amoebae in preaggregation stage. (b)Aggregating amoebae. (c) Low-power view of aggregating amoebae. (d)Migrating pseudoplasmodia (slugs) moving on an agar surface and leaving trailsof slime in their wake. (e,f) Early stage of fruiting body, (g) Mature fruiting body.
Eukaryotic Microbial Diversity
Stages in fruiting-body formation in the cellular slime moldDictyostellium discoideum. (A-C) Aggregation of amoebae;aggregtaion is triggered by cAMP. (D-G) Migration of the slug formedfrom aggregated ampebae. (H-L) Culmination and formation of thefruit-ing body. (M) Mature fruiting body composed of stalk and head.
Fungi
Fungi include the molds and yeast. Fungi differfrom protozoa by virtue of their rigid cell wall,production of spores, lack of motility, andphylogenetic position. Mushrooms are large,often edible fungi that produce fruiting bodiescontaining basidiospores.
Eukaryotic Microbial Diversity
Filamentous Fungi: Molds
Eukaryotic Microbial Diversity
• They are widespread in nature and are commonly seen onstale bread, cheese, or fruit.
• Each filament grows mainly at the tip, by extension of theterminal cell.
• A single filament is called hypha, a collectively called amycelium.
• Has aerial branches spores called conidia. Conidia are asexualspores.
• Some molds also produce sexual spores (different typedepending on the group). Sexual spores of fungi are typicallyresistant to drying, heating, freezing, and some chemicalagents.
Eukaryotic Microbial Diversity
Mold Structure and Growth
Photomicrograph of a typical mold.Conidia are seen as the sphericalstructure and the ends of aerial hyphae.
Diagram of a mold life cycle. Conidia canbe either wind-blown or be trasported byanimals.
on an agar plate.
Eukaryotic Microbial Diversity
a
b
(a) Conidiophore and conidia ofAspergillus fumigatus. (b) Coloniesof an Aspergillus species growing
FungiCharacteristics and major properties of fungi
Group
Ascomycetes
CommonName
Sac fungi
Hyphae
Septate
Typicalrepresentati
ves
Neurospora,Saccharomyces, morchella
(morales)
Type ofSexualspore
Ascospore
Habitats
Soil,decaying
plant material
Commondeases
Dutch elm,chesnut
blight, ergot,rots
Basidiomycetes
Club fungi,mushrooms
Septate
Amanita(poisonousmushroom),
Agaricus(edible
BasidiosporeSoil,
decayingplant material
Blact stem,wheat rust,corn smut
ZygomycetesBreadmolds
Coenocytic
Mucor,Rhizopus(common
bread mold)
ZygosporeSoil,
decayingplant material
mushroom)
Foodspoilage;
rarelyinvolved in
parasiticdeseases
Characteristics and major properties of fungi
GroupCommon
NameHyphae
Typicalrepresentati
ves
Type ofSexualspore
Habitats Commondeases
OomycetesWatermolds
Coenocytic
Allomyces Oospore Aquatic
Potatoblight,
certain fish
Deuteromycetes
Fungiimperfecti
SeptatePenicillium,Aspergillus,
CandidaNone known
Soil,decaying
plantmaterial,
surfaces ofanimalbodies
deseases
Plant wilt,infections of
animalssuch as
ringworm,athlete’s
foot, surfaceof systemicinfections(Candida)
Eukaryotic Microbial Diversity
Macroscopic Fungi: Mushrooms
• Mushrooms are filamentous basidiomycetes thatform large fruiting bodies.
• During most of its existence, the mushroom funguslives as a simple mycelium, growing in soil, leaf litter,or decaying logs. However, when environmentalcondition are favorable, usually following periods ofwet and cool weather, the fruiting body develops.
• Sexual spores, called basidiospores are formed,borne on the underside of the fruiting body on flatplates called gills.
Eukaryotic Microbial Diversity
(a) Amanita, a highly poisonous mushroom. (b) Gills on the undersideof the mushroom fruiting bodycontain the spore-bearing basidia. (c )Scanning electron micrograph of basidiospores released frommushroom basidia.
Eukaryotic Microbial Diversity
a b c
Eukaryotic Microbial Diversity
Life cycle of a typical mushroom
Unicellular Fungi: Yeasts
• The yeasts are unicellular fungi, and most ofthem belong to Ascomycetes.
• Yeast cells are typically spherical, oval, orcylindrical, and cell division typically takes placeby budding.
• In the budding process, a new cell forms as asmall outgrowth of the old cell; the bud graduallyenlarges and then separates.
• Yeast flourish in habitats where sugars arepresent, such as fruits, flowers, and the bark oftrees.
• The most important commercial yeast are thebaker’s and brewer’s yeasts, which are membersof the genus Sacharomyces.
Eukaryotic Microbial Diversity
Sacharomycescerevisiae
Algae
• Alga are phototrophic Eukarya that containchlorophyll and caretenoid pigments within astructure called chloroplast. The chloroplasts itselfhas its roots in the domain bacteria.
• Most algae are either unicellular or colonial, the laterexisting as aggregates of cells. When the cells arearranged end-to-end, the algae is said to befilamentous.
Eukaryotic Microbial Diversity
Properties of major group of algae
Algal Group
Chlorophyta
Euglenophyta
Dinoflagellata
Chrysophyta
CommonName
Greenalgae
Euglenoids
Dinoflagellates
Golden-brownalgae,
diatoms
Morphology
Unicellular toleafy
Unicellular,flagellated
Unicellular,flagellated
Unicellular
Typicalrepresenta
tives
Chlamydomonas
Euglena
Gonyaulax
Nitzschia
Carbonreserve
materials
Starch
Paramylon
Strach
Lipids
Cell wall
cellulose
No wallpresent
Cellulose
Twooverlappingcomponents
made ofsilica
Majorhabitats
Fresh water,soils, a few
marine
Fresh water,a few marine
Mainlymarine
Fresh water,marine, soil
Properties of major group of algae
Algal GroupCommon
NameMorphology
Typicalrepresentati
ves
Carbonreserve
materials
Cell wall Majorhabitats
PhaeophytaBorwnalgae
Filamentousto leafy,
occasionallymassive and
plantlike
Laminaria Lammarin Cellulose Marine
Rhodophyta Red algaeUnicellular,
Filamentousto leafy
PolysiphoniaFloridean
starchCellulose Marine
Eukaryotic Microbial Diversity
(a) Micrasterias, a single cell. (b) Volvox colony, containing a largenumber of cells. (c) Scenedesmus. A packet of four cells. (d) Sirogyra. Afilamentous algae.
a
c
b
d
Euglena
Polysiphonia, amarine red alga
Frustule of themarine diatomNitschia
Frustule of themarine diatomThalassiosira
Frustule of themarine diatomAsteriolampra
Cell of the marinedinoflagellate,Ornithocercus
magnificus
and also accumulates in shelfih that feed on thedinoflagellates. (b) A toxic spores of P. piscicida.(c) Fish killed by P. piscicida
Eukaryotic Microbial Diversity
b
a
Toxic dinoflagellates. (a) “a red tide” caused bymassive growth of toxin-producing dinoflagellates,such as Gonyaulax. Toxin excreted into the water
c
Endholitic (grow inside ofrocks) Cyanobacteria.
Photograph of a limestone rockfrom Makhtesh Gadol, NegevDesert, Israel, showing a layerof cells of the cyanobacteriumChroococcidiopsis
Photomicrograph of cells ofChroococcidiopsis isolated
from a sandstonerock inthe Negev Desert.
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