vlog is about Flagellum 

It is a long whip-like structure attached to the bacteria that help them to move towards nutrients or any external stimuli.The flagellum of the bacterium is made of a single protein unit called flagellin.

The flagellum is made of three parts.They are filament,hook and basal body.The filament is the long structure made of helically arranged units of flagellin which act as the propeller.Connecting the filament with the basal body is the wide region called hook.The hook is followed by the basal body which is the motor parts of the flagellum.The motor region uses the ATP derived from protons motive force which helps in the movement of flagellum.

All the bacteria do not possess the flagellum.The bacteria that possess the flagellum may not have the same arrangements and number of flagella.The flagellum may differ in the number and arrangements and following are the types of flagella seen in the bacteria.

Atrichous:No flagella,e.g.klebsiella sp.

Monotrichous: single flagellum present at polar end,e.g.vibrio cholerae.

Amphitricous:single flagellum present at both ends,e.g.Alcaligenes faecalis.

Lophotrichous:Tuft of flagella at one or both the end,e.g.spirilla.

Peritrichous: flagella seen surrounding the entire cell.e.g.salmonella typhi.

Functions of flagellum:

It is the organ of locomotion for bacteria.

It also helps bacteria to move towards the organ or tissue which it infects,e.g.in case of urinary tract infection, the bacteria moves from urethra to bladder with the help of flagella.

Demonstration of flagella in the bacteria 

Dark ground illumination, special staining techniques, electron microscopy, indirect method→swarming growth in the solid agar, Motility under the microscope, Motility in semisolid agar 

Pili 

The pili are rigid hair-like Projection made of protein units called pilin.They are shorter than flagellum and are found mainly in gram-negative bacteria.The pilus has two major functions

It is a virulence factor for bacteria as it helps for the attachment of bacteria to their host cell.The pilus used for attachment is short and is called fimbriae.A special kind of pilus, called sex pilus, helps the bacteria to form conjugation tube during the process of conjugation.

Structure of flagellum

It consists of L ring,p ring,s ring,M ring,hook , filament,rod,basal body.

Arrangements of flagellum

Atrichous→Monotrichous→Amphitrichous→lophotrichous→peritrichous thank you.