the bacteria cell

8/3/2019 The Bacteria Cell

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THE BACTERIA CELL

GROUP MEMBERS :ØRosnitah Bt Yacob D20091035118ØNur Eliana Bt Mohmad Noor D20091035093ØNurushuhada Bt Yahya D20091035102ØPhua Wan Jien D20091035



Traditionally, allprokaryote werecalled bacteria

Later, prokaryote dividedinto bacteria and archaedue to the genetic

evidence

How prokaryote differ fromeukaryote??

•

lack of intracellular organelles(mitochondria, chloroplast,

Bacteria as a Prokaryote



Much of the knowledgeabout bacteria comefrom the studies of diseases-causingbacteria

Three basic shape of bacteria :

• Spherical ( coccus)• Rodlike ( bacillus )• Curved (vibrio, spirillum, spirochete)

Bacteria diverse groupof organisms that differin size, shape, habitat,

and metabolism

DIVERSITY OF STRUCTURE OF BACTERIA



Smaller bacteria :•Mycoplasma pneumoniae

•Bordetella pertussis•Treponema pallidum

Relatively large

bacteria :• Azotobacter • Synechococcus• Achromatium

Average-size

bacterium :• Escherichia coli•Staphylococcus aureus

Giant bacteria :• Titanospirillumnamibiensis•Epulopsiciumfishelsoni



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• Gram staining -method of differentiating bacterial species(Gram-positive and Gram-negative).

• based on the chemical and physical properties of their cell walls.

• Detects peptidoglycan, which is present in a thicklayer in Gram positive bacteria.

• Gram positive purple/blue color• Gram negative pink/red color.

The Gram stain

MORPHOLOGICAL FEATURESOF BACTERIA




• A bacteriological laboratory technique

-used to differentiate bacterial speciesinto two large groups (Gram-positive and Gram-negative) based on thephysical properties of their cell walls.• Gram staining is not used to classify

archaea, formally archaeabacteria, sincethese microorganisms yield widely varying

responses that do not follow theirphylogenetic groups.




• Gram-positive bacteria thick mesh-like cell wall made of peptidoglycan (50-90% of cell wall),

which are stained purple by crystal violet• Gram-negative bacteria thinner layer (10% of

cell wall), which are stained pink by the counter-stain.

• There are four basic steps of the Gram stain:Ø applying a primary stain (crystal violet) to a

heat-fixed (death by heat) smear of a bacterialculture

Ø the addition of a trapping agent (Gram's iodine)Ø rapid decolorization with alcohol or acetone,

andØ counterstaining with safranin.




•

Cell membrane and cell wall plus an outermembrane if one is present.

• The cell wall consists of the peptidoglycan layerand attached structures. Most bacterial cellenvelopes fall into two major categories

–

Gram positive and Gram negative.• The peptidoglycan

– a single bag-shaped, highly cross-linkedmacromolecule that surrounds the bacterialcell membrane and provides rigidity.

–

Peptidoglycan consists of a glycan(polysaccharide) backbone consisting of N-acetyl muramic acid and N-acetyl glucosaminewith peptide side chains containing D- and L-amino acids and in some instances

diaminopimelic acid.

The Cell Envelope



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GLYCOCALYX

CAPSULES

SLIME LAYERS

• The glycocalyx is considered a capsulewhen the polysaccharides are morefirmly attached to the cell wall.

• Capsules have a gummy, sticky

consistency and provide protection as wellas adhesion to solid surfaces and tonutrients in the environment.

• A glycocalyx is

considered a slime layer when the glycoproteinmolecules are looselyassociated with the cellwall.

• Bacteria that arecovered with this looseshield are protected fromdehydration and loss of nutrients.



CAPSULES



FUNCTIONS

CAPSULES

• A layer that lies outside the cell wall• Well organized layer, not easily

washed off • Attached tightly to the bacterium

and has definite boundaries•Usually polymers of simple sugars(polysaccharides)

• Considered a virulencefactor - enhances the abilityof bacteria to cause disease(prevents by phagocytosis).

• Capsules make bacterialsurface components moreslippery, helping thebacterium to escapeengulfment by phagocyticcells

• Hydrophilic and help thebacterium avoid desiccation(dehydration)



ØThe capsule is found most commonlyamong Gram-negative bacteria:• Escherichia coli• Klebsiella pneumoniae• Haemophilus influenzae

ØSome Gram-positive bacteria may alsohave a capsule:• Bacillus megaterium for example,synthesizes a capsule composed of

polypeptide and polysaccharides.•Streptococcus pyogenes synthesizesa hyaluronic acid capsule.

WHICH BACTERIA DOESHAVE A CAPSULE…??



FLAGELLA

PILI / FIMBRIAE

•Purpose : motility•Structures : longspecialized appendageswhich rotate by meansof a ‘motor’•Located : under cytoplasmic membrane•May have one, a few or many flagella in differentposition on the cell

PILI• An elongate and hollow appendage-allows the transfer of plasmid DNA from

one bacterial cell to another (called sex pili)

FIMBRIAE• Fine, hairlike made of protein(pilin) – allowbacteria to attach to other cell

•

Found mostly in male cells•Most in Gram negative bacteriaEx : Neisseria gonorrhoeae and N.menigitidis



BACTERIALCONJUGATION

PILUS



CYTOPLASM

The cytoplasm is where theorganelles carry out the

processes necessary for the lifeof the bacterium. The

components of the cytoplasmare responsible for cell growth,

metabolism, elimination of

waste and replication(reproduction) of the cell.



CytoplasmGenetic Content

•The DNA appear as long coil distributed through the cytoplasm.•Mostly DNA present as a single, circular chromosome.•But, some consist 2 chromosomes, some linear form.•Consist plasmid. (carry auxiliary information)•Sequence of bases in the DNA determined bacteria.Exp:

§ Mycoplasma gallinarum (580,000 base pairs)§ E. coli (4,700,000 base pairs)§ Myxococcus xanthus (9,140,000)

Bacterial DNA contains 4 nitrogenous bases:Ø Adenine (A)Ø Cytosine (C)Ø Guanine (G)Ø Thymine (T)



• High concentrations of enzymes, metabolites, and salts.• Ribosomes scattered throughout the cytoplasm• But smaller, have fewer constituents compare to ribosomes of eukaryoticcells• Can be inhibited by antibiotics• Consists numerous inclusion bodies, or granules in the bacterial cytoplasm.• Not enclosed by membrane and served as storage vessels.• Possess lipid droplets that contain polymeric esters of poly-β-hydroxybutyric acid.• Storage granules produced under favourable growth conditions.• Consumed after nutrients have been depleted from the medium.• Aquatic bacteria produces gas vacoule.• Consist internal membranous.

Cytoplasmicstructures



Biotypes of bacteria

• Distinguishable by serological tests.• Identify bacteria by the presence of specific molecules on their surfaces, detected by antibodies.• Antibodies are serum protein that bind very tightly to foreign molecules(antigens).• Antibodies have remarkable specificity.• Bacteria able to respond effectively to the intense defensive actions of the immunesystem.

the bacteria cell

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