Категории: Все - prokaryotes - shape - cell - structure

по Anson Choong 7 лет назад

167

Prokaryotes

Prokaryotes, a diverse group of microorganisms, exhibit a range of sizes from the smallest at 0.3 μm to very large ones measuring up to 600 x 80 μm. Their cell walls differ significantly between Gram-positive and Gram-negative bacteria.

Prokaryotes

Prokaryotes

Size

very large
600 x 80 μm
Average
0.6 μm
Smallest
0.3 μm

Shape

Additional
No fixed shape
Pleomorphic
Unusual

Triangular

Square

Star shape

Spiral
Spirochete
Spirullum
Bacilli
Pallisades
Streptobacilli
Diplobacilli
Cocci
Sarcianae
Tetradcocci
Staphyllococci
Sreptococci
Diplococci

Structure external to cell wall

Pili
join bacterial cells in preparation for the transfer of DNA
only one or two per cell
Longer than fimbriae
Fimbriae
a few to several hundred
evenly dsitributed over entire surface of the cell
at the pole of the cell
Axial Filaments
spiral around cell
Bundle of fibrils arises at the end of the cell
Flagella
Type of motility

Swarm

rapid wavelike movement

Tumbles

runs interrupted by periodic,abrupt, random changes in direction abrupt, random changes in direction

Run or Swim

moves in one direction for a length of time of time

Number & Arrangement

Petritrichous

Spread over entire surface of cell

Lophotrichous

Cluster of flagella at one or both ends

Subtopic

Amphitrichous

one flagellum at each end of cell

Monotrichous

one flagellum

Glycocalyx
Functions

Protect cell from dehydration

Attachment to various surface

Protection from phagocytosis

Made of sugar

EPS

Unorganized

Slime layer

organized

capsule

Cell wall

Gram negative

high

outer membrane

absent

peptidoglycan layer

stain red

Gram positive
Lipopolysaccharide

none

Outer membrane
Periplasmic space

Absent

Teichoic acid

present

Peptidoglycan layer

many layer

Gram reaction

stain purple