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BACTERIBACTERIOLOGIOLOGI BACTERIBACTERIOLOGIOLOGI
5/03/2012 1Masdiana Padaga
Bacteria on Earth
Bacteria are in every environment imaginable!
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Size
Fig. 2-5 Six Comparisons Among Various Living Things and Molecules5/03/2012 3Masdiana Padaga
Rod-Shaped Bacteria
Spherical Bacteria
Spiral-Shaped Bacteria
Spi
roch
ete:
Bor
relia
bur
gdor
feri
Bacterial Morphology
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Bac
teria
l Ana
tom
y (O
verv
iew
)
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Prokaryotic Cells• Means “before a nucleus”
• Domains Bacteria and Archaea• Can live in environmental extremes
• Live off diverse energy sources
http://micro.magnet.fsu.edu/cells/bacteriacell.html http://www.daviddarling.info/encyclopedia/P/prokaryoticcell.html
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Prokaryotic Structures• Cytoplasm
– A liquid material that particles are suspended in
• Ribosomes– Site of protein synthesis– Located in cytoplasm
• Nucleoid– Contains hereditary
material (DNA) of the cell
– Located in cytoplasm5/03/2012 10Masdiana Padaga
Prokaryotic Structures• Plasma membrane– Encloses the cell– Regulates material
into and out of cell
• Cell Wall– Supports cell and
determines its shape
• Capsule– Slime layer– Protects– Helps to not dry out– Helps attach to other
cells5/03/2012 11Masdiana Padaga
Prokaryotic Structures• Flagella
– Used to swim/move– Spins like a
propeller or whip like
• Pilli– Hair or threadlike
structures– Help stick to other
cells for mating or animal cells for food and protection
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Cytoplasm • Composed largely of water, together with proteins,
nucleic acid, lipids and small amount of sugars and salts
• Ribosomes: numerous, 15-20nm in diameter with 70S; distributed throughout the cytoplasm; sensitive to streptomycin and erythromycin site of protein synthesis
Plasmids: extrachromosomal genetic elements
Inclusions: sources of stored energy, e,g volutin
Plasmid Plasmids
are small , circular/line , extrachromosomal ,double-stranded DNA molecules 。
capable of self-replication and contain genes that confer some properties such as antibiotic resistance , virulence. Inclusions of Inclusions of
BacteriaBacteriaInclusions are aggregates
of various compounds that are normally involved in storing energy reserves or building blocks for the cell.
accumilate when a cell is grown in the presence of excess nutrients
granulose
Cell membran
e
• Site of biosynthesis of DNA, cell wall polymers and membrane lipids. Selective permeability and transport of solutes into cells
• Electron transport and oxidative phosphorylation• Excretion of hydrolytic exoenzymes
Nucleus
• Lacking nuclear membrane, absence of nucleoli, hence known as nucleic material or nucleoid, one to several per bacterium.
Prokaryotic Cell Structure
Glycocalyx - term to describe substances that surround bacterial cells
1. Capsule if substance is organized and firmly
attached to cell wall 2. Slime Layer
if substance is unorganized and loosely attached to cell wall
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Capsules and slime layers
These are structures surrounding the outside of the cell envelope. They usually consist of polysaccharide; however, in certain bacilli they are composed of a polypeptide (polyglutamic acid). Capsules are often lost during in vitro culture.
Attachment Protection from phagocytic
engulfment. Resistance to drying. Depot for waste products. Reservoir for certain
nutrients. protection
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Polar monotrichousPseudomonas
Polar amphitrichousSpirillium Lophotrichous
Spirillum
PeritrichousSalmonella
Flagella:
SEM of peritrichous strain Proteous
Note: bacteria without flagella are called atrichous.5/03/2012 19Masdiana Padaga
In Gram-negative Bacteria
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In Gram-positive Bacteria
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• Flagella consist of a number of proteins including flagellin
Identification of Bacteria
Pathogenesis Motility of bacteria
Motility• Almost all Spiral bacteria are
motile• About 1/2 of Bacilli are
motile• Almost all Cocci are non-
motile• Bacteria move toward
attractive stimuli and away from harmful substances and waste products in the process known as chemotaxis.
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Pilli or fimbrae• Filamentous appendages that are
shorter, straighter and more numerous that flagella
• Conjugation pilli found in certain group of bacteria.
• Used for genetic material transfer.
• The transfer process is called conjugation.
• Antibiotic resistance transfer.• Atatchment pilli, Help bacteria
adhare to the surfaces, such as cell surfaces and interface of water and air.
• It helps in colonization and pathogenicity.
• found mostly in Gram (-) Bacteria5/03/2012 24Masdiana Padaga
E. coli (pathogenic)5/03/2012 25Masdiana Padaga
Cell Wall• Main structural component -
Peptidoglycan
• Peptidoglycan– repeating dissacharide units– polypeptides
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Gram-Positive
Peptidoglycan
Cell Membrane
Peptidoglycan
Cytoplasmic membrane
Another cell
Gram-Negative
Outer Membrane
MembranePeptidoglycan
Peptidoglycan
Periplasm
Periplasmic space
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Bac
teria
l Cel
l Wal
ls
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Gram (+) Cell Wall• NAM N-acetylmuramic acid• NAG N- acetylglucosamine• tetrapeptide side chains• pentaglycine crossbridges• teichoic acid
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Gram (-) Cell Wall
• NAM• NAG• Tetrapeptide side chains• pentaglycine• 2nd Outer membrane
– Lipopolysaccharides (LPS)• Lipid A• O Antigen
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Functions of Cell Wall• Maintaining the cell's characteristic shape- the
rigid wall compensates for the flexibility of the phospholipid membrane and keeps the cell from assuming a spherical shape
• Countering the effects of osmotic pressure• Providing attachment sites for bacteriophages• Providing a rigid platform for surface
appendages- flagella, fimbriae, and pili all emanate from the wall and extend beyond it
• Play an essential role in cell division• Be the sites of major antigenic determinants
of the cell surface 。• Resistance of Antibiotics
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Cell Membrane (Plasma Membrane)
• 2 structural component– double layer of phospholipids– proteins
• Fluid Mosaic Model
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cytoplasmic membrane
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Functions of Cell Membrane
• 1. Selective barrier (selectively permeable)
• 2. Secretes exoenzymes– amylases– lipases– peptidases– CAN NOT UNDERGO PHAGOCYTOSIS
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Functions of Cell Membrane
• 3. E.T.S. is located here• 4. Enzymes for cell wall synthesis• 5. If photosynthesis, enzymes are
located on membranous structures called thylakoids
• 6. Mesosomes - invagination of cell membrane attached to DNA (Binary Fission)?
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Endospores (spores)
• Dormant cell Dormant cell • Resistant to adverse Resistant to adverse
conditions conditions - high temperatures- high temperatures- organic solvents- organic solvents
• Produced when starvedProduced when starved• Contain calcium dipicolinateContain calcium dipicolinate DPA, DPA, DDipicolinic acidipicolinic acid• BacillusBacillus and and ClostridiumClostridium
Identification of Bacteria
Pathogenesis Resistance
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Microscope • Light Microscope• Electron Microscope• Darkfield Microscope• Phase Contrast
Microscope• Fluorescence Microscope• Confocal Microscope )
Method
Staining Methods Simple staining; Differential staining (Gram
stain, Acid-fast stain), Special staining( Negative
stain, Spore stain, Flagella stain)
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Gram Stain• 1884 Hans Christian Gram• most important stain used in
Bacteriology
• Divides all Bacteria into 2 groups:– Gram (+)– Gram (-)
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Gram Staining
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Results• Gram (+) Purple• Gram (-) Red• Difference - due to
structure of cell wall– Gram (+) Thick cell wall– Gram (-) Thin cell wall
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