Functional Anatomy of Prokaryotic Cells

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All living cells can be classified into two groups based on certain structural & functional characteristics

•Prokaryotes

•Eukaryotes•

They are chemically similar in the sense that they both contain

nucleic acids

proteins

lipids

carbohydrates

The distinguishing characteristic of prokaryotes & eukaryotes

•Proka. * 0.2-2.0 microm•

•* DNA is not enclosed within a membrane (singularly arranged chromosome)

•* DNA is not associated with histones=special chromosomal proteins found in euk

•

•* no membrane-enclosed organelles

•

•* cell wall almost always contain the complex polysaccharide peptidoglycan

•

•* divided by binary fission(DNA is copied & the cell splits into two cells

The distinguishing characteristic of prokaryotes & eukaryotes

•Euka. *10-100microm.•

• *DNA is found in cells nucleus which is separated from the cytoplasm by nuclear membrane (DNA is found in multiple chromosomes)

• • *DNA is associated with

histones

•* the have a number of membrane-enclosed organelles(mitochondria , endoplasmic reticulum Golgi complex lysosomes)

•

•* cell wall is chemically simple

•

• *cell division usually involves mitosis

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PROKARYOTES

BACTERIABACTERIA ARCHAEAARCHAEA E

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BACTERIABACTERIA

Naming and Classifying Microorganisms

•The system for nomenclature for microorganisms•The scientific name is binomial

The First is the genus name The Second is the species nameThe first letter of the genus name is always capitilizedStaphylococcus (genus) aureus (species)Both are underlined or italicizedStaphylococcus aureus Staphylococcus aureus

Identification of bacteria•Thousands of bacteria species are differentiated by many

factors including:

•**morphology (shape , size & arrangement)

**Chemical composition (staining)

**Nutritional requirements

**Biochemical activities

**Source of energy

MorphologySize -- Shape -- & Arrangement

Size = 0.2 – 2.0 micrometer in diameter 2.0 -- 8.0 micrometer in length Bacterial shapes are determined by heredity

Shapes & Arrangements of Bacteria

cocci

•Coccus=spherical =round or oval

•Diploccoci=pairs

•Streptococci=chainlike

•Staphylococci=groups (grapelike)

Bacilli•Bacilli= rode shape

mostly Single

•Diplobacilli=pairs

•Streptobacolli=chais

•Coccobacilli=oval

spiral

•Have one or more twists----never straight

•Vibrios=curved rods

•Spirilla=helical

•Spirochetes=helical & flexible

Structure of Bacteria

Particular structures capsuleflagella

pilispore

Essential structuresEssential structures cell wall cell wall

cell membrane cell membrane Cytoplasm & nuclear materialCytoplasm & nuclear material

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structures external to the cell wall

cell wall itself

structures internal to the cell wall

Structures

glycocalyx (capsule)

flagellaaxial filaments

fimbriaepili

structures external to the cell wall

•Glycocalyx=sugar coat=sub.that surround cells=sticky=external to cell wall

•Polysaccharide , polypeptide or both

•If attached to cell wall =capsule (well defined) or slim layer(not defined)

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Capsule or slime layer• Functions:

– Help adherence & attachment of bacterial cells to surfaces.– Provide nutrients– Protect bacterial cells against dehydration– Increase virulence of bacteriaProtect the pathogenic bacteria. From phagocytosis by hostWBC

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The degree of which bac. Cause disease

Streptococcus pneumoniaepneumoniarespiratory tract

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FLAGELLA•Some bacteria are motileSome bacteria are motile

•LocomotoryLocomotory organelles- organelles- flagellaflagella=long filamentous=long filamentous

•appendagesappendagesExternal to cell wallExternal to cell wall

Flagellar arrangements outside bacterial cell

Atrichous –lack flagella

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Monotrichous – single flagellum at one end

Lophotrichous-2 or more arising from one end of bacterial cell

Amphitrichous- flagella at both end of bacterial

Peritrichous – Flagella distributed over the entire

surface, low motility

Motility=is the ability of bac. to move itself

one directiondifferent directionswaves

toward a favorable environmentoraway from an adverse conditions chemotaxis=away from chemicalslight=phototaxis

Advantages of flagella•Identification of Bacteria

•H-antigen = flagellar protein is useful for distinguish variations within species

Motility of bacteria

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Axial filaments•similar to flagellum

•= bundles of fibrils that arise at the end of bacterial cell

•**Spiral motion

•**Snake-like movement

–spirochetes have unique structure & motility

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Pili (fimbriae)Pili (fimbriae)• hair-like projections of the cell

)shorter and thinner than flagella(

Occur at the poles or can evenly distributed on bacterial cell

Fibriae are involve in bacterial attachment to surfaces and resistance to phagocytosis === cause disease

Neisseria gonorrhoeaegonorrhea

Pili

Chemical nature is pilin

bacterial conjugation

Sex pili effect the transfer of conjugative plasmids

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SEX PILI

FIMBRIE FLAGELLA

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Composition & structure of cell wall

Bacterial cell wall•All prokaryotes have cell wall

•The cell wall of bacterial cell is •Complex

•Surround the fragile plasma membrane (cytoplasmic)

•Protect the interior of cell

The major functions of cell wallPrevent bacterial cells from rupturing,

when water pressure inside the cell is greater than that outside the cell , so it is essential for bacterial viability

Countering the effects of osmotic pressure

Providing a rigid platform for surface appendages- flagella, fimbriae, and pili all originate from the wall and extend beyond it

Cell wall major functionsSite of action of antibiotics, the most

important one

Resistance of Antibiotics

• Shape of bacteria

Functions of cell wall

The chemical composition of cell wall is used to differentiate major types of bacteria.

Be the sites of major antigenic determinants of the cell surface

Provide the immunological distinction among bacteria

•Bacterial cell wall is composed of macromolecular net work = peptidoglycan

Peptidoglycan = peptide + glycan

Peptidoglycan consists of repeating disaccharide attached by polypeptides , that surrounds & protects bacterial cell

Disaccharide portion is mad up of

Monosaccharides =

N-acetylglucosamine

(NAG)

&

N-acetylmuramic acid=

(NAM)

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Alternating (NAG) &( NAM) molecules are linked in rows to from a carbohydrate backbone (glycan portion )

Adjacent rows are linked by polypeptides

(peptide portion)

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Penicillin interferes with final linking of the peptidoglycan rows by peptide

=bac.cell wall is weakened & the cell undergoes lysis

= this destruction caused by rupture of the plasma membrane & the loss of cytoplasm

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Gram positive bacteriacell wall consists of many layers of peptidiglycan forming a thick , rigid structure

•Cell wall of Gram positive bac. Contain

•Teichoic acids= consist primarily of

•

• an alcohol (glycerol or ribitol)

•&

• phosphate

Teichoic acid classes

Lipoteichoic acid= spans the peptidoglycan layer & is linked to the plasma membrane

Wall teichoic acid = linked to the

peptidoglycan

Special components of Gram positive cell wall

Teichoic acid

SPA / M POTEIN

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•Teichoic acid=

•Regulate the movement of cations (+ve ions) into & out of the cell

•Assume in cell growth

•Provide wall s antigenic specificity = diagnosis

Gram negative bacteria cell wall•Consist of one layer of peptidoglycan

•&

• an outer membrane

•Do not contain teichoic acid

•the peptidoglycan is bonded to lipoproteins

• =)lipids linked to proteins (in the outer membrane

The outer membrane of Gm.-ve bac, consists of

•Lipopolysaccharides

• lipoproteins

•&

• phospholipids

Lipopolysaccharides

O polysaccharides

antigen

Lipid portionLipid Aendotoxin

Porin = is a proteins in the outer membrane which is important in the permeability of outer membrane

CELL WALL OF G+VE AND G-VE BACT.

GRAM STAIN TECHNIQUE

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1- No or very little cell wall material: Mycoplasma = are the smallest bacteria that can & reproduce outside living cell (sterols in the plasma membranes for protection)

2- Archaea: unusual wall-- No peptidoglycan, , proteins and polysaccharides.

3- Acid-fast cell walls: contain high constration (60%) of

Waxy material outside the peptidoglycan. = Mycolic acids prevent uptake of stains.

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Damage to the cell wall

Chemicals that damage bact. Cell wall often do not harm the cells of an animal host .Why??

When bacteria are treated with 1) enzymes that are lytic for the cell wall e.g. lysozyme

(tears,mucus, saliva)Active on major cell wall components of most Gram +ve bact.**back bone disaccharide wall-less cell (protoplast)When Gram –ve bact. Treated with lysozyme cell wall is not

destroyed to the same extant as in Gram +ve bact. Why ?? (outer membrane) (spheroplast)

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•Effect of "lysozyme", which is found naturally in tears, mucus, and saliva.

-Gram positives are most susceptible and typically they burst (lyse) or, in favorable environments, they may form "protoplasts", which have no cell wall.

-Gram negatives are less susceptible and some of the cell wall material remains (spheroplasts)--> Can only survive in

favorable conditions as they are weak.

Damage to the cell wall

2) antibiotics that interfere with biosynthesis of peptidoglycan, wall-less bacteria are often produced.

antibiotics that damage bact. Cell wall often do not harm the cells of an animal host .Why??

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Structures internal to the cell wall

•**Is a thin structure lying inside the cell wall & enclosing the cytoplasm

•**consist primarily of phospholipids & proteins

Structures internal to the cell wall

Plasma or cytoplasmic membrane

Functions of Plasma membrane

• Selective permeability = certain molecules & ions pass through the membrane , but others prevented from passing through it

•Breakdown of nutrients and the production of energy ( contain enzymes catalyzing the chemical reaction)

•Some antibiotics and antibacterial agents kill bacteria by attacking the plasma membrane

Damage of plasma membrane

•Many antibiotics have effect on plasma membrane

•Polymyxins = disrupting phospholipids of the plasma membrane

•Alcohols & ammonium compounds = used as disinfectants

Structures within the bacterial cell

• Cytoplasm: thick aqueous (80% water) semitransparent.

• Contains organic molecules and inorganic ions. Proteins(enzymes) , carbohydrates , & lipids

• The major structures in the cytoplasm are:

• Nucleoid, ribosomes, inclusions

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The major structures in the cytoplasm are:

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Single, long, double stranded circular DNA=bacterial chromosome.

Carry all the genetic information required for cell structure & function

Plasmids :

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•extra-chromosomal DNA

•Small,circular,doubl-stranded DNA .not connected to bact. Chromosome, replicate

independently

•May be gained or lost. Without harming bact.

•Can be transfer from one bact. To other (biotechnology)

•5-100 genes))Cary genes for :

•antibiotic resistance,

• tolerance to toxic metals,

• production of toxins and synthesis of enzymes

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Plasmids :

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Nuclear material

• No nuclear membrane,

absence of nucleoli, hence known as nucleic

material or nucleoid,

one to few per bacterium.

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Ribosomes

Sites of protein synthesisComposed of two subunits made of protein and

ribosomal RNA.

Prokaryotic ribosomes are 70S while Eukaryotic ribosomes are 80S.

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Erythromycin and chloramphenicol attach to 50 S subunit Streptomycin and gentamicin attach to 30 S subunit and inhibit protein

synthesis.

•Bacterial cell can be killed by antibiotic while eukaryotic cell remains unaffected. Why???

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Inclusions

•Several kinds of reserve deposits within the cytoplasm

•Cells may accumulate certain nutrients when they are plentiful & use them when the environment is deficient

•Their number depend on bact. Species == identification

Inclusions• Reserve deposits• Metachromatic granules.

• Polysaccharide granules = carbohydrate

• Lipid inclusions = lipid storage material

• Sulphur granules = energy server

• Carboxyzomes = enzymes ** photosynthesis

• Gas Vacuoles

• Magnetosomes72

Inclusions

• =Metachromatic granules =large inclusions

• some time stain red with blue dye

have diagnostic significance

=stores inorganic phosphate

Corynebacterium diphtheriae

Endospores (spores)

•Resting structures

•Clostridium= tetanus – gas gangrene – food poisoning

•Bacillus = anthrax

•Highly durable dehydrated cells with thick walls & additional layers which formed internal to the bact. cell membrane

•Endospores when released into environment they survive

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• --extreme heat

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•-- lack of water

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•-- exposure to many toxic chemicals & radiation

•Sporulation = sporogenesis•formation of endospore •)endospre forming bact(.

•This occur when nutrient (carbon , nitrogen source ) becomes unavailable or scarce

•Germination = formation of vegetative form

Endospores (spores)

Identification of Bacteria

Pathogenesis

Resistance

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•One vegetative cell single endospore

•Single endospore one vegetative cell

•Not a means of reproduction

•protection•

Sporulation

germination

•Endospores are clinically important

•Food industry

•Resist heating

•Freezing

•Desiccation

•Use of chemicals & radiation

•Some bact. Produce toxins

BACILLUS ANTHRAX

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First Term Exam.Good Luck