The Prokaryotic Cell Size, shape, arrangement of cells Structures external to cell wall The Bacteria...
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Transcript of The Prokaryotic Cell Size, shape, arrangement of cells Structures external to cell wall The Bacteria...
• The Prokaryotic Cell
• Size, shape, arrangement of cells
• Structures external to cell wall
The BacteriaThe BacteriaThe BacteriaThe Bacteria4-a 4-a pps. 77 – 106
2
Bacterial Motility4
(Bacterial Motility Quiz)
Membrane Transport4
(Membrane Transport Quiz)
Log on to: www.microbiologyplace.com
Animations Animations
3
Histones
Organelles (Golgi, ER, cilia, etc.)
Polysaccharide cell walls
Binary fission Mitotic spindle
Peptidoglycan cell walls
No organelles
No histones
Not in a membrane
One circular chromosome Paired chromosomes
In nuclear membrane
Prokaryote vs EukaryoteProkaryote vs Eukaryote“Prenucleus” “True nucleus”
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Vast heterogeneous group
Include bacteria, archaea
Ubiquitous in nature
Very small
Unicelluar
The Prokaryotic WorldThe Prokaryotic World
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Differentiated by many factorsMorphology (shape)
Chemical composition (~staining)
Nutritional requirements
Biochemical activities
Sources of energy
Go through your Lab Manual and list Ex #s next to each of the factors above
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• Coccus (plural = cocci; berries)– Spherical cells
• Bacillus (plural = bacilli; small staffs)– Rod-shaped, often motile– Large surface area to volume and adsorption
is more effective
• Coccobacillus– Cells not perfectly round (as cocci) – Have ‘blunted’ ends, ‘oval’ shape
Morphology, ShapesMorphology, Shapes
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• Spirillum (plural = spirilla)– Spiral or curved bodies, one or more ‘twists’– Rigid, fairly inflexible– Often motile by external flagella
• Spirochetes – Also ‘spiral’ shaped, but more flexible – Motile by an internal flagellum, axial filament
• Vibrio– Comma shaped cells, motile via flagella
8Figures 4.1a, 4.2a, 4.2d, 4.4b, 4.4c
• Average size: 0.2 -1.0 µm 2 - 8 µm• Basic shapes
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• Arrangement & groupings - useful identification characteristics
• Cells can remain attached to each other as bacteria divide
• Cocci tend to display more variation in grouping than rods– Cocci divide along more than one axis– Rods only divide along their short axis
Arrangements, GroupingsArrangements, Groupings
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• Diplococci = pairs of cocci
• Streptococci = chains of cocci
• Staphylococci = clusters of geometrically arranged cocci (sometimes grape-like)
• Tetrads = ‘packets’ of 4 cells
• Sarcinus = ‘packets’ of 8 cells
• Diplobacilli = pairs of cells
• Streptobacilli = chains of cells
11Figures 4.1, 4.2
12Figure 4.5
– Star-shaped Stella– Square Haloarcula
• Most bacteria are monomorphic
• A few are pleomorphic (Corynebacterium)
Unusual shapesUnusual shapes
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Structures External to the Cell WallStructures External to the Cell Wall
Glycocalyx
Flagella
Axial filaments
Fimbriae, pili
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Glycocalyx
Cell wall
FimbriaePili
Flagellum
• The outer surface covered in– Polysaccharide, protein, polyalcohols, amino
sugars, spp specific
• Functions include:– Attachment– Protection from desiccation– Protection from ‘attack’
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GlycocalyxGlycocalyx
Figure 4.6
• Capsules are– Closely associated
with cells– Does not ‘wash’ off
easily
• Slime layer is– More diffuse, easily
washed off
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Capsules
Slime layers
2 Types of Glycocalyx
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• Glycocalyx can be thick or thin, rigid or flexible
• Observe with India ink– See dark cells with ‘clear outline’ around them– Stain does not penetrate glycocalyx
Stain? See Ch 3, Fig 3.13a, p 72 & LM
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• Streptococcus mutans – Produces a slime layer– Forms a surface that allows other bacteria to
aggregate on tooth surfaces– Results in dental plaque
• Vibrio cholerae– Attach to intestinal villi of host– Results in cholera
FunctionsFunctionsAttachment
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• Capsules and slime layers are hydrophilic
– Bind ‘extra’ water in the environment
– Contribute to protection from desiccation
• Also provide protection from loss of nutrients
– Holds nutrients within the layer
Avoid Desiccation
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It is difficult to engulf a bacterium that has a capsule
Avoid Phagocytosis
• Streptococcus pneumoniae
– Able to cause pneumonia and ‘kill’ patient
– Non-encapsulated cannot cause pneumonia
• Klebsiella colonize respiratory tract
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Bacteria Disease
1. Bacillus anthracis
2. Streptococcus pneumoniae
3. Klebsiella
4. Streptococcus mutans
Capsules and Virulence
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• A tail-like structure – Projects from the cell body of bacteria– Functions in movement
• Bacterial example:– Helicobacter pylori
• Uses multiple flagella to propel itself• Through mucus lining to reach stomach
epithelium
Flagella Flagella
Singular: Flagellum; whip
Figure 4.6
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Rotate like screws
Provide several kinds of bacterial motility
Flagella are Helical Filaments
• Consist of protein: flagellin
• Attach to a protein ‘hook’
• Connects to ‘basal body’ rings
• Gram + microbes have 2 basal body rings
• Gram negative have 4 rings
24Figure 4.8b
Note: 4 rings vs 2 in Gram +
Gram negative bacterium
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• Via rotation of the basal body
• Rotational ‘speed’ can increase or decrease
• Moves bacteria through liquid media
Flagella and Motility
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• Monotrichous (polar) – One flagellum– Vibrio cholera
• Amphitrichous – Have a single flagellum on each end– Only one operates at a time– Allows bacteria to reverse course rapidly
Flagella Variation
• Lophotrichous (one or both ends of cell)– Have multiple flagellum at same ‘spot’– Act in concert to move bacteria in single direction
• Peritrichous – Have a flagella projecting in all directions– Escherichia coli
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Flagella ArrangementFlagella Arrangement
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Flagella: Run, Tumble
• Move in one direction called a ‘run’
• Change in direction called ‘tumbles’ – Interruptions in a run, changes direction– Caused by reversal of flagella rotation
• Bacteria with many flagella– Proteus– Swarms, wavelike movement across media
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Figure 4.9
View animation: Bacterial Motility4
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Running and Tumbling
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• Move toward or away from stimuli: TAXIS– Due to chemical stimuli: chemotaxis– Or, light: phototaxis
• If toward the stimuli, called an attractant– And the bacteria moves towards it with many
‘runs’ and few ‘tumbles’
• If away from the stimuli, called a repellent– The frequency of ‘tumbles’ increases as it moves
away from the stimulus
Taxis
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33
The flagellar protein called H antigen is used to identify serovars
Flagella and Virulence
– Among Gram negative bacteria
– (e.g., E. coli O157:H7)
– At least 50 different H antigens for E. coli
– Associated with foodborne epidemics (Ch 1, p. 20)
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• Endoflagella, movement only
• In spirochetes
• Anchored at one end of a cell
• Rotation causes cell to move in spiral motion
Fig 4.10
Axial Filaments
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• Spirochetes– Move through body
fluids– Treponema pallidum
• Syphilis – Borrelia burgdorferi
• Lyme disease
Fig 26.10
Fig 23.13
Axial Filaments and Virulence
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Fimbriae & PiliFimbriae & Pili
• Are short, thin appendages
• Fimbriae allow attachment to initiate disease
• Pili join cells to transfer DNA from one cell to another called:
Fig 4.11
Fig 8.25Conjugation
37
These structures consist of a protein called pilin
Divided into 2 types, different functions
Fimbriae
Pili
Fimbriae vs Pili
38
• Occur at poles of cells, or all over
• Number from a few to >hundreds
• Enable a cell to adhere to surfaces
• Example:
– Neisseria gonorrhoreae
– Causes gonorrhea
– Fimbriae helps colonize mucus membranes
Fimbriae Characteristics
Fig 4.11
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Usually longer than fimbriae
Number only one or 2
Pili join cells to transfer DNA
Process called conjugation
Pili Characteristics
Fig 8.25
40
Q’sQ’s
a. Flagellab. Pili
1. The structure used by bacteria to transfer genetic information is:
c. Glycocalyxd. Ribosome
2. Prokaryotic cellsa. Have a single chromosome
b. Lack a nuclear membrane
c. Divide by binary fission
d. Have cell walls containing peptidoglycan
e. All of the above
41
1. Which is not a function of glycocalyx
Q’sQ’s
a. It forms pseudopodia for faster mobility of an organism
b. It can protect a bacterial cell from drying outc. It can contribute to the disease-causing
processd. It allows a bacterium to stick to a host
2. All of these are involved in bacterial attachment except:a. Fimbriaeb. Pili
c. Capsulesd. Axial filaments
42
Q’sQ’s
1. The cell arrangement shown here is:a. Streptococcus
b. Staphylococcus
c. Diplococcus
d. Tetradse. Sarcinae
2. The plane in which a bacterium divides determines the arrangement.
True False
43
Q’sQ’s
1. What is taxis?a. Movement towards a stimulus
b. Movement toward or away from a stimulus
c. Movement towards light
d. Movement away from a stimulus
2. What are the 3 parts of a flagellum?a. Tubulin, flagellin, basal body
b. Flagellin, filament, hook
c. Filament, hook, basal body
d. Tubulin, hook, filament
44
Q’sQ’s
1. Which of the following is NOT a structure found in prokaryotic cells?
a. Flagella b. Pili
c. Ciliad. Axial filamentse. Peritrichous flagella