the bacteria cell
TRANSCRIPT
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 1/21
THE BACTERIA CELL
GROUP MEMBERS :ØRosnitah Bt Yacob D20091035118ØNur Eliana Bt Mohmad Noor D20091035093ØNurushuhada Bt Yahya D20091035102ØPhua Wan Jien D20091035
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 2/21
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
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 3/21
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
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 4/21
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
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 5/21
Click icon to add clip art
• 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
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 6/21
Click icon to add clip art
• 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.
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 7/21
Click icon to add clip art
• 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.
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 8/21
Click icon to add clip art
•
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
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 9/21
Click icon to add clip art
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 10/21
Click icon to add clip art
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 11/21
Click to edit Master subtitle style
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.
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 12/21
CAPSULES
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 13/21
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)
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 14/21
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…??
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 15/21
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 16/21
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
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 17/21
BACTERIALCONJUGATION
PILUS
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 18/21
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.
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 19/21
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)
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 20/21
• 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
8/3/2019 The Bacteria Cell
http://slidepdf.com/reader/full/the-bacteria-cell 21/21
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.