advance microbiology eukaryotic cell biology and microorganism

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.


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.


Diagram showing the overall structure of the mitochondrion. Note inner andoutermost membranes.


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.


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.


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



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.


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.


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



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.


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


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)


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.


Slime molds. Plasmodia of the acellular slime mold Physarumgrowing on an agar surface


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.


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.


Filamentous Fungi: Molds


• 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.


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.


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)


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.


(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.


a b c


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.


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.


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


(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


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.

advance microbiology eukaryotic cell biology and microorganism

Documents

eukaryotic cell structure

function slide

hydrogenosome slide

membraneenclosed nucleus

microorganism slide

permeable inner membrane

yeast cell

outer membranes