TOPIC 3: The Bacterial Cell

Morphology

The study of the internal structure

1. Shape

2. Size

What are ways to categorize bacteria?

1. Cocci (Round/Spherical)

2. Bacillus (Rods)

3. Spirillum & Spirochete (Spiral)

What are the major shapes/forms of bacteria?

Cocci

Round or spherical bacteria

Diplococci

Round or spherical bacteria that is in pairs and facing each other and may also come in a lanceolate (leaf-like) or coffee-bean form

Streptococcus pneumoniae

Provide an example of lanceolate (leaf-like) shaped bacteria.

Neisseria Gonorrhoeae

Identify the coffee-bean shaped bacteria.

Streptococci

Round or spherical bacteria in chains and occur along a single axis

Streptococcus Pyogenes

What is an example of a streptococci?

Staphylococci

Round or spherical bacteria that has an irregular shape or grape-like clusters

Staphylococcus Aureus

What is an example of a staphyloccoci, which is known to be a causative agent of acne and food poisoning?

Tetrad

Round or spherical bacteria that come in groups of 4

Gaffkya Tetragena

What is an example of a tetrad?

Sarcina

Round or spherical bacteria that are in cubical pockets of 8 (may look like 4 under a microscope but has a shadow at the back to differentiate from a tetrad)

Sarcina Lutea

What is an example of a sarcina, which is known to be a normal flora of the skin and large intestines?

Bacillus

Rod shaped bacteria

Fusiform Bacillus

Rod shaped bacteria that are spindle-like in shape

Wide in the middle and tapers at both ends

Diplobacilli

Rod shaped bacteria that occur in pairs

Snapping

Type of diplobacilli that is v-shaped

Slipping

Type of diplobacilli that is parallel

Streptobacilli

Rod-shaped bacteria that occurs in chains

Bacillus Subtilis

What is an example of a streptobacilli, which does not cause any disease and is a common lab contaminant?

Coccobacilli

Rod-shaped bacteria that is plump and oval

Escherichia Coli

What is a type of coccobacilli, which is normal flora of the lower intestine?

Vibrio

Rod-Shaped bacteria that is comma shaped/curved rod

Vibrio Cholerae

What is an example of a vibrio, which causes cholera?

Spirillum

Spiral organisms that remain rigid in motion

Camplyobacter Jejuni

What is an example of a spirillum, which is a causative agent of diarrhea?

Spirochete

Bacteria with a spiral shape with long axis that bends when in motion; different genus are differentiated by the tightness of the coiling

1. Genus Treponema

2. Genus Leptospira

3. Genus Borrelia

Types of spirochete genus

Genus Treponema

Type of spirochete genus that is tightly coiled with the characteristics corkscrew appearance

Treponema Pallidum

What is an example of a corkscrew shape bacteria that causes syphilis, STD?

Genus Leptospira

Type of spirochete genus that is less tightly coiled with sharp hook like bends at the ends of the cell

Leptospira interrogans

What is an example of a leptospira bacteria?

Genus Borrelia

Type of spirochete genus that is much less tightly coiled which have the appearance of an extremely long, undulating, bacillary form

Borrelia burgdorferi

What is an example of a borrelia, which causes lime disease, virus, ticks?

Micron (μ)

What is the old unit for measuring bacteria size?

Micrometer (μm)

What is the metric system unit for measuring bacteria size?

1/1000th mm

1/25000th in

1 μm = ____ mm or ____ in

Width: 0.25-1 μm

Length: 1-3 μm

What is the size of bacteria generally?

0.4-2 μm

Size of cocci (in μm)

0.2-4 μm x 0.5-20 μm

Size of bacilli (in μm)

Haemophilus influenzae; 0.3-1 μm

What is the smallest known pathogenic bacilli and what is its size?

Bacillus anthracis; 1.5 μm across by 4 μm long

What is the largest known pathogenic bacilli and what is its size?

1-14 μm

Size of spirals (in μm)

1. External Structures

Ultrastructures of Bacteria

Flagellum

Long, whiplike structures that extend beyond the surface of the cell and glycocalyx and propel the cell through its environment

Proteus Species

What bacteria species sometimes swarm as a thin film of growth?

H (Hauch) Antigen

Flagella antigen; refers to the swarming growth in culture

False

True or False: Flagella can be seen with an ordinary stain.

1. Long, thin filaments

2. Hook

3. Basal body

Three parts of the flagella

Long, thin filament

Part of the flagella that is the whiplike shaft that extends out into the cell’s environment; composed of many identical globular molecules of a protein called flagellin

Flagellin

What are the identical globular molecules of a protein that composes the long, thin filament of the flagella?

Hook

Part of the flagella that is a curved structure where the base of the filament is inserted

Basal Body

Part of the flagella that anchors the filament and hook to the Cell Wall (CW) by means of a rod and a series of either 2 or 4 rings; Together the hook, rod, and rings allow the filament to rotate 360

Gram Positive Bacteria

The image shows the cell membrane of what bacteria type?

Gram Negative Bacteria

The image shows the cell membrane of what bacteria type?

Messea’s Classification

Classifies the various flagellar arrangements

1. Monotrichous

2. Lophotrichous

3. Amphitrichous

4. Peritrichous

5. Atrichous

According to Messea’s Classification, what are the flagellar arrangements prokaryotes may have?

Monotrichous

Flagellar arrangement in which cells have a single flagellum

1. Vibrio cholerae

2. Campylobacter jejuni

3. Pseudomonas aeruginosa

What are examples of monotrichous bacteria?

Lophotrichous

Flagellar arangement in which cells have a tuft of flagella at only one end of the cell

Amphitrichous

Flagellar arrangement in which cells have flagella at both ends

Pseudomonas species

What species of bacteria are mostly lophotrichous?

Peritrichous

Flagellar arrangement in which flagella cover the surface of the cell

1. Salmonella typhi

2. Proteus vulgaris

What are examples of peritrichous bacteria?

Atrichous

Flagellar arrangement that has no flagella

1. Shigella dysenteriae

2. Klebsiella pneumoniae

What are examples of atrichous bacteria?

Helical

Some spiral bacteria have amphitrichous flagella that spiral tightly around the cell (instead of protruding into the surrounding environment). This produces what type of movement for spirochetes?

Endoflagella

Some spiral bacteria have amphitrichous flagella that spiral tightly around the cell (instead of protruding into the surrounding environment). This is considered what which form an axial filament that wraps around the cell between the cell membrane and outer membrane?

Motility of the cell wherein it can flee from a harmful environment or to a more favorable environment with food and light available

What is the function of the flagella?

Phase Variation

Mechanism in which when bacteria sense that antibodies are developing, it will change to its antigenic structure so that it will not be killed by the antibodies

Microfibrils: Pili & Fimbriae

Nonmotile extensions of prokaryotes unlike flagella

Fimbriae

• Hairlike, sticky, proteinaceous, bristle-like projections

• Used by Gram (-) bacteria to adhere to one another and to substances in the environment (adhesins)

• May be hundreds

• Usually shorter than flagella

Neisseria gonorrhoeae

What is an example of a bacteria with fimbriae, which adheres to host surfaces like the mucous membranes of the reproductive tract?

Pilus

• Tubules composed of a protein called pilin

• Longer than fimbriae but shorter than flagella

• Typically 1-10 present per cell

• Used in moving across a substrate or towards another bacterium

• Sex/conjugal -__ mediate the transfer of DNA from one cell to the other

Pilin

What protein is pilus composed of?

1. Serve as adhesins, lectins

2. Conduit for the passage of DNA

3. Surface translocation

What are the importances of microfibrils (fimbriae and pili)?

Adhesins

(Importance of microfibrils)

Proteins that allow bacteria to attach to host cells

Lectins

(Importance of microfibrils)

Any class of proteins which bind specifically to certain sugars and cause agglutination to particular cell types, specific for fimbriae

Conduit for passage of DNA

(Importance of Microfibrils)

Via sex/conjugal pili

Surface translocation

(Importance of Microfibrils)

Slow twitching or gliding motion for non-flagellated material like cocci

Fimbriae.

Identify (1)

Pili

Identify (2)

Flagellum

Identify (3)

Sex/Conjugal Pili

Identify the structure between the bacteria.

Gram (+) has a thick peptidoglycan layer

What is the difference between the two types of prokaryotic cell wall (Gram (+) and Gram (-) bacteria)?

Cell Envelope

Consists of the membrane structures surrounding the cytoplasm; the outermost structures

1. Cell Wall/Murein Layer

2. Periplasm (in Gram (-) bacteria only)

3. Outer membrane (in Gram (-) bacteria only)

4. Cytoplasmic/cell membrane

What is the cell envelope compoed of?

Cell Wall/Murein Layer

Component of the cell envelope that is composed of the peptidoglycan macromolecule

1. Periplasm

2. Outer membrane

Components of the cell envelope that is only found in Gram (-) bacteria

Cytoplasmic/cell membrane

Component of the cell envelope that encloses the cytoplasm and some produce capsules and slime layers

Glycocalyx (Glycocalyces)

Surface adherence structure that is a polypeptide or polysaccharide, either an amino acid or sugar, enriched coating that covers the outside of many eukaryotic and prokaryotic cells that functions as a barrier between cells and its surroundings

1. Capsule

2. Slime Layer

2 Kinds of Glycocalyx

Capsule

Kind of glycocalyx made up of organized repeating units of organic chemicals firmly attached to the cell surface

Slime Layer

Kind of glycocalyx that is loose, water-soluble

Capsule

Identify the type of glycocalyx.

Slime layer

Identify the type of glycocalyx.

1. Protect the cell from desiccation (removal of moisture)

2. Feature of numerous pathogenic prokaryotes

3. Important in organisms’ ability to survive and cause disease

What is the significance of glycocalyces?

Vi antigen

Heat labile somatic antigen of capsules thought to be associated to virulence or severity and harmfulness of a disease in bacteria