Upload
ab310
View
227
Download
0
Embed Size (px)
Citation preview
8/6/2019 2011.6.7 Microbe - Introduction
1/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Microbiology : Systematic study of MicroorganismsMicroorganisms : Bacteria, Fungi, Algae,Parasites,Viruses,Prions and Viroids
Basic branches
Bacteriology Study of Bacteria Virology Study of Viruses
Mycology Study of Fungi
Parasitology Study of parasites
Phycology Study of algae
Prions and Viroids .
Applied Branches
Medical Microbiology Study of microorganisms of medical importance Agriculural Microbiology Study of microorganisms in Agriculture
Food Microbiology Study of Microorganisms in Food
Environmental Microbiology Study of Microorganisms in Environment
Industrial Microbiology Study of Microorganisms applied in industries
8/6/2019 2011.6.7 Microbe - Introduction
2/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Medical Microbiology
Branches
Medical Bacteriology Study of Bacteria Medical Virology Study of Viruses
Medical Mycology Study of Fungi Medical Parasitology Study of parasites
Immunology Study of Immunity
Immunity : The resistance offered by host againstmicroorganisms or their parts or products
8/6/2019 2011.6.7 Microbe - Introduction
3/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Identification and Characterization of
Microbes
Cell shape or form is important fordistinguishing different bacteria: Three
Basic shapes:
1. Spherical2. Rod
3. Spiral shape
BACTERIAL MORPHOLOGY
8/6/2019 2011.6.7 Microbe - Introduction
4/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Identification and Characterization
Spherical shaped: Coccus Cocci
Short rods: Coccobacillus - Coccobacilli
Rods: Bacillus Bacilli
Curved rods: Vibrio vibrio
Spiral shaped: Spirillum spirilla
Branched bacteria: Actinomycete Actinomycetes
Irregular: Mycoplasma Mycoplasma
8/6/2019 2011.6.7 Microbe - Introduction
5/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
8/6/2019 2011.6.7 Microbe - Introduction
6/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Different Arrangements of Bacteria
y Cocci in Chains: Streptococci
y Cocci in clusters: Staphylococci
y
Cocci in pairs: Diplococciy Cocci in four: Tetrad
y Bacilli in pair: Diplobacilli
y Bacilli in chains: Streptobacilli
8/6/2019 2011.6.7 Microbe - Introduction
7/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Arrangements
Pairs: diplococci,diplobacilli
Clusters:staphylococci
Chains:streptococci,streptobacilli
8/6/2019 2011.6.7 Microbe - Introduction
8/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
BACTERIA STRUCTURE
BACTERIAL CELL PARTS: Essential for Survival
Cell Wall
Cell membrane
Cytoplasm
Nucleoids
Mesosomes
Ribosomes
8/6/2019 2011.6.7 Microbe - Introduction
9/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
BACTERIA STRUCTURE
BACTERIAL CELL PARTS: Non-Essential forSurvival
Flagellum
Pili
Capsule
Endospore
Intracellular Inclusions
8/6/2019 2011.6.7 Microbe - Introduction
10/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
BACTERIAL CELL PARTS
1. Cell Wall
Cell wall: is the outermost component part.
The thickness of the cell wall ranges from 10-25 nm,
Cell wall is used:
To Protects bacteria against lysis
Allows them to grow over a wide range of osmotic pressures.
It gives Rigidity to bacterial cells, which determines theircharacteristic shape.
The main constituent of bacterial cell wall is a chemically
complex polymer known as peptidoglycan.
8/6/2019 2011.6.7 Microbe - Introduction
11/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Cell Wall
Christian Gram recognized 2 different types of bacteriabased on their staining reaction.
Gram-positive bacteria stain purple and have thicklayers of peptidoglycan combined with teichoic acid.
Gram-negative bacteria stain pink and have muchthinner layer of peptidoglycan covered with an outerlipid membrane.
8/6/2019 2011.6.7 Microbe - Introduction
12/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram Stain Mechanism1. Prepare a thin bacterial smear on glass slide.2. Fix the smear by dry heat
3. Flood the smear with Crystal Violet for 1 min.
4. Wash the slide with tap water
5. Flood the smear with Grams Iodine for 1 min.6. Wash with tap water
7. Decolorize the smear by alcohol for 20-30 sec.
8. Wash slide with water
9. Flood the smear with Safranin
10.Wash with Tap water
11. Air dry slide and Observe under 100X oil immersion
8/6/2019 2011.6.7 Microbe - Introduction
13/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram negativeGram negative Gram positiveGram positive
Heat/DryHeat/Dry
Crystal violet stainCrystal violet stain
IodineIodine FixFix
Safranin stainSafranin stain
AlcoholAlcohol dede-stainstain
8/6/2019 2011.6.7 Microbe - Introduction
14/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram Stain Mechanism
Crystal violet -iodine crystals give blue coloration tocell
Gram-positive Alcohol dehydrates peptidoglycan
CV-crystals do not leave
Gram-negative Alcohol dissolves outer membrane and leaves holes in
peptidoglycan
CV- washes out
8/6/2019 2011.6.7 Microbe - Introduction
15/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.13b, c
8/6/2019 2011.6.7 Microbe - Introduction
16/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Peptidoglycan
The peptidoglycan is a complex, interwoven networkthat
surrounds the entire cell and is composed of threeparts:
1. Sugar (glycan) backbone which is composed of alternating N-acetylmuramic acid andN-acetylglucosamine
2. A set of identical tetrapeptide side chains attachedto the N- acetylmuramic acid.
3. A set of identical peptide cross-bridges betweentwo tetrapeptides.
8/6/2019 2011.6.7 Microbe - Introduction
17/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Peptidoglycan
Polymer of disaccharide
N-acetylglucosamine (NAG) & N-acetylmuramicacid (NAM)
Linked by polypeptides
Figure 4.13a
8/6/2019 2011.6.7 Microbe - Introduction
18/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram-positive cell walls
Special Components of Gram-positive cell walls
Contain significant amount of teichoic andteichuronic acids, which account up to 50% of thedry weight of the cell wall.
Teichoic acids are negatively charged fibers whichprotrude at the outer surface of Gram +ves.
In addition to this some gram-positive walls containpolysaccharide molecules.
8/6/2019 2011.6.7 Microbe - Introduction
19/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram-Positive cell walls
Teichoic acids: two types
Lipoteichoic acid links to plasma membrane
Wall teichoic acid links to peptidoglycan
May regulate movement of cations
Figure 4.13b
8/6/2019 2011.6.7 Microbe - Introduction
20/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram-Negative Cell wall
Special components of Gram-Negative cell walls:
Gram-negative cell walls contain three componentsthat lie outside of the peptidoglycan layer:
Lipopolysaccharide (LPS)
Outer membrane
Lipoprotein
LPS - also known as endotoxin.
The endotoxin is responsible for many of thefeatures of disease, such as fever and shock(especially hypotension) caused by theseorganisms.
8/6/2019 2011.6.7 Microbe - Introduction
21/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram-Negative Cell wall
Periplasmic space = space between inner andouter membrane.
Gram-negative bacteria only have degradativeenzymes located in this area.
Periplasmic enzymes act on the wide variety of
substrates which a GN bacterium encounters innature to convert them to molecules which aretransportable into the cell.
8/6/2019 2011.6.7 Microbe - Introduction
22/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gram-Negative Cell wall
Figure 4.13c
8/6/2019 2011.6.7 Microbe - Introduction
23/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Cell wall less forms in bacteria
L forms : cell wall less forms of bacteria that appearspontaneously or due to treatment with Penicillium.Common in many bacteria E.coli, Neisseria.
Penicillin inhibits peptide bridges in peptidoglycan.
Bacteria can revert back to cell wall forms.
8/6/2019 2011.6.7 Microbe - Introduction
24/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Cell wall less forms in bacteria
Lysozyme are enzymes that digest disaccharide inpeptidoglycan.
Protoplast : Spherical form of Gram Positive
bacterium when treated with lysozyme.Spheroplast : Spherical form of Gram Negative
bacterium when treated with lysozyme.
Mycoplasma: Natural cell wall less forms and they
have Sterols in plasma membrane
Protoplasts and spheroplasts are susceptible toosmotic lysis and are used for research.
8/6/2019 2011.6.7 Microbe - Introduction
25/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Cell wall of Acid-fast bacteria
Mycobacteria have an unusual cell wall,resulting in their inability to be Gram-stained.
These bacteria are said to be acid-fast,
They resist decolorization with acid-alcohol afterbeing stained with Crystal violet.
This is due to the high concentration of lipids,
called as mycolic acids, in the cell wall.
8/6/2019 2011.6.7 Microbe - Introduction
26/49
8/6/2019 2011.6.7 Microbe - Introduction
27/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Plasma Membrane
Figure 4.14a
8/6/2019 2011.6.7 Microbe - Introduction
28/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Plasma MembraneComponents ofPlasma membrane
Phospholipid bilayer
Peripheral proteins
Integral proteins
Transmembrane proteins
Figure 4.14b
8/6/2019 2011.6.7 Microbe - Introduction
29/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Plasma Membrane
Simple diffusion: Movement of a solute from an area ofhigh concentration to an area of low concentration.
Facilitated diffusion: Movement of solutes combinedwith a transporter protein in the membrane.
Movement Across Membranes
8/6/2019 2011.6.7 Microbe - Introduction
30/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Movement Across Membranes
Figure 4.17
8/6/2019 2011.6.7 Microbe - Introduction
31/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Movement Across Membranes
Osmosis Movement of water
across a selectivelypermeable membranefrom an area of high
water concentration to anarea of lower waterconcentration.
Osmotic pressure
The pressure needed tostop the movement ofwater across themembrane.
Figure 4.18a
8/6/2019 2011.6.7 Microbe - Introduction
32/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.18c-e
Movement Across Membranes
8/6/2019 2011.6.7 Microbe - Introduction
33/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Movement Across Membranes
Active transport of substances requires atransporter protein and ATP. Substances such as amino acids, organic acids and
inorganic ions combined with carrier proteins aretransported across membrane and released inside the
cell by this mechanism. Group translocation of substances requires a
transporter protein similar to active transport butthe nutrients being transported undergoes chemical
modification. Sugars and fatty acids are transported by this
mechanism.
8/6/2019 2011.6.7 Microbe - Introduction
34/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
3. Cytoplasm
The cytoplasm is the cellular material outside thenucleus but enclosed by the cell membrane.
Consists of 70% water
~1000 different enzymes
Many ribosomes
It is site of the bacterium for all activities
It is controlled by the information carried in the DNAof the nucleus.
8/6/2019 2011.6.7 Microbe - Introduction
35/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
CytoplasmCytoplasm Cell membrane
Cell Wall
8/6/2019 2011.6.7 Microbe - Introduction
36/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
4. Nucleoid
Genetic material that controls all characteristics ofcell .
Centrally located cellular mass without a nuclearmembrane. Contains a single circular chromosome,in which DNA is located.
8/6/2019 2011.6.7 Microbe - Introduction
37/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
5. Mesosome and Ribosomes
Mesosome =It is an invagination of the cytoplasmic
membrane, which forms septum during cell division.
Site for some respiratory enzymes.
More seen in Bacilli.
Ribosomes =site for protein synthesis. Bacteria
ribosomes are 70S in size with two subunits 50S and
30S.
8/6/2019 2011.6.7 Microbe - Introduction
38/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Ribosomes
Figure 4.19
8/6/2019 2011.6.7 Microbe - Introduction
39/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
BACTERIAL CELL PARTS: Non Essential forSurvival1. Flagella: are long (3-20 ), whiplike appendages
that move the bacteria toward nutrients andother attractants, a process called chemo-taxis.
Made of chains of flagellin
Attached to a protein hook
Anchored to the wall and membrane
The system enables bacteria to detect changes
in concentration of certain chemicals and tomove either toward (positive chemotaxis) oraway (negative chemotaxis) from the substancedepending on its nature.
8/6/2019 2011.6.7 Microbe - Introduction
40/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.8
8/6/2019 2011.6.7 Microbe - Introduction
41/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Flagellar Arrangement in Bacteria:
Monotrichous bacteria that have a single polarflagellum.
Amphitrichous bacteria having flagella at bothends.
Lophotrichous A tuft of flagella in a single
location
Peritrichous bacteria flagella random
distributed all over cell surface.
8/6/2019 2011.6.7 Microbe - Introduction
42/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Flagella Arrangement
Figure 4.7
8/6/2019 2011.6.7 Microbe - Introduction
43/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Motile Cells
Figure 4.9
8/6/2019 2011.6.7 Microbe - Introduction
44/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
2. Fimbriae or pili
Pili are straight rigid rod like appendages. shorter and thinner than flagella, composed ofa single protein pilin.
Function :
Facilitate adherence of bacteria to otherbacterial, red blood cells, or lining of theintestine.
Provide a site for attachment of bacteriophages(bacterial viruses).
Enable bacteria that have a sex pilus to transfergenetic material across a pilus bridge from oneto another by a process known as Conjugation
8/6/2019 2011.6.7 Microbe - Introduction
45/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
3. Capsule Capsule is a thick gelatinous layer produced by the
plasma membrane secreted outside of the cell wall. It is polysaccharide that forms a protective outer
coat to the cell.
Can be detected by negative staining. Plays
important role in bacterial virulence.Function:
Protects bacteria from phagocytosis by white bloodcells inside the body.
Protects bacteria from external toxic substances °radative enzymes.
Provides water molecules to bacteria in dryconditions.
8/6/2019 2011.6.7 Microbe - Introduction
46/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
8/6/2019 2011.6.7 Microbe - Introduction
47/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
4. Endospores
Spore or endospore is a highly resistant,metabolically inactive forms of bacteria.
Endospores are also formed during unfavorabletemperature, pH and gaseous requirement.
Endospore formation is protective measure and notreproductive process.
The genetic material is enclosed in several proteincoats that are resistant to heat, drying, freezing,
toxic chemicals, and radiation. The process of Spore formation is - Sporulation
The process of outgrowth or vegetative growth is Germination
8/6/2019 2011.6.7 Microbe - Introduction
48/49
Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.21a
8/6/2019 2011.6.7 Microbe - Introduction
49/49
Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings
5.Intracytoplasmic inclusions:
Granules: are intracellular inclusions that serve as a storagefor nutrients.
Bacteria store food in reserve form during favorable
conditions, when there is sufficient amount of nutrients &
utilized during unfavorable conditions.
Plasmids: are double stranded extrachromosomal DNA,
particles that carry important genes for antibiotic
resistance, toxin production, and carbohydratefermentation.
Plasmids number may vary from one to many.