What are the structures found outside a bacterium?

Question

What are the structures found outside a bacterium?

Answer 1

Pili: A pilus is a hairlike appendage found on the surface of many bacteria. All pili are primarily composed of oligomeric pilin proteins.

Pili connect the bacterium to another of its species, or to another bacterium of a different species, and build a bridge between the cytoplasms of either cell. That enables the transfer of plasmids between the bacteria.

Flagellum: a whip-like structure for locomotion.

Answer 2

first structure is flagella..bacterial flagella are smaller then eukaryotic flagella..the flagella of bacterial cells are 15 to 20 nm in diameter and upto 20 micrometer long and are also simpler in organisation...they help in locomotion of cell....according to presence of flagella bacteria are classified as...

1.monotrichous...there is single flagellum at one pole of cell

2.lophotrichous...there are several flagella at one pole

3,amphitrichous...the cell bears atleast one flagellum at each pole

4.petritrichous...there are flagella all over the surface of cell

pili are elongated,fewer,thicker,tubular structures..they help in conjugation and are present only in gram negative bacteria..they are non motile but adhesive structures which enable bacteria to stick firmly to other bacteria,to a surface or to some eukaryote such as mold,plant,animal cells or epithelial cells of alimentary respiratory and urinary tracts...

fimbriae are small bristle like fibres emerging out of the cell..these are 3 to 10 nm in diameter..there are about 300 to 400 fimbriae in very cell..they are persent in both gram positive nad gram negative bacteria..some type of fimbriae are involved in attaching bacteria to solid surfaces such as rocks in streams and host tissues...they also help in mutual clinging of bacteria......

Answer 3

External structures of a bacterium may include:

1. Appendages: flagella, pili, fimbriae

2. Glycocalyx: capsule, slime layer