bacterial specialized structures

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3c. Discussion of Bacterial

specialized structures

● Bacterial ̀ cytoskeleton

● appendages & cell wall associated specialized

structures

● Bacterial flagellum (flagella) and chemotaxis

Reading: Ch 3 pg 104; Ch. 3.7 & Ch 4.7 (pages

142-143), & pgs 704, 711 & 726

Shape-determining proteins

FtsZ = Tubulin homolog Present in ALL bacteria

MreB = Actin homolog Absent in coccoid bacteria

CreS “Crescentin” = givesshape to crescent shapedbacteria

The Bacterial have a Cytoskeleton

Special Topic 3.2

Figure 2

Thylakoids =

Carboxysomes = Polyhedral bodies packed with the

enzyme Rubisco for CO2 fixation in autotrophs

Gas vesicles =

Specialized Structures of PhototrophsSee also Fig. 3.37

Figure 18.5

Cyanobacterium (Nostoc )

Prochlorococcus marinus

4

Heterocysts

Fig 18.7B

- Are Specialized cells

containing Nitrogenaseenzyme (an oxygen-sensitivenitrogen-fixing enzyme)

- Found in some Diazotrophs

‘regular’ Nostoc cells

Storage granules

- Organic (e.g.)

- Inorganic (e.g. )

Magnetosomes of magnetotactic bacteria

Membrane-embedded crystals

of Fe3O4

Other Specialized Structures

Figure 3.38

Figure 3.39

Figure 18.33A

Cytoplasmic

Sulfur granules

in Chromatium cells

Anchored in the cell wall

Fimbriae

Pili

- Composed of pilin

monomers- 6 types identified

Sex pili

Type IV pili

Stalks

- Tips secrete adhesion

factors called holdfasts.

Cell appendages

Figure 3.41

‘Stalks’ of the Iron-oxidizing Gallionella sp.

Sex-pili linking 2 mating

cells

Fimbriae & pili on cells

of Porphyromonas gingivalis (Fig. 3.40)



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7

Nannowires & Cannula

Thin flat disc-shaped cells of the

hyperthermophile & barophilicPyrodictium abysii are connected by a

network of thin cannulae (tubes).

Cannula are extensions of the cell’sS-layer, outer membrane & periplasm

See Text Fig 19.10 &

19.11) What is the function of the

cannulae network?

Pyrodictium abysii

For Swimming motility in

liquids

- Can be 1, 2, tufts or all over

cell

- V. long

- Whip-like motion of the

flagella

Chemotaxis & motility using Rotary

Flagella

Figure 3.42a

9 Also see Fig. 2.4

Flagella are complex multi-part structures

are anchored in the cell wall & cell membrane

Movement is in response to a stimuli

Are Driven by a complex motor unit

Energy from the H+ or Na+ Motive Force

*See Fig. 3.43

(By TEM)

Figure 3.44

Chemotaxis – movement of a bacterium

in response to a chemical gradient

‘RUN’)

What is the response

to repellants?

11

Some bacteria e.g Proteus mirabilis use flagella

for a type of motility called swarming

Fig. 18.34; pg 704

Some Gram-positive bacteria can formendospores (e.g Clostridium, Bacillus sp)

Figure 4.26,Pg 142-143



13/09/20

Animation: Chemotaxis: Molecular Events

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Chemotaxis

bacterial specialized structures

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