• The Prokaryotic Cell

• Size, shape, arrangement of cells

• Structures external to cell wall

The BacteriaThe BacteriaThe BacteriaThe Bacteria4-a 4-a pps. 77 – 106

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Bacterial Motility4

(Bacterial Motility Quiz)

Membrane Transport4

(Membrane Transport Quiz)

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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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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

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These structures consist of a protein called pilin

Divided into 2 types, different functions

Fimbriae

Pili

Fimbriae vs Pili

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• 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

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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

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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

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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

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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

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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