Differentiate between flagella and pili

Hello everyone :D

Let's get down to comparing flagella and pili because this is one of the most common questions asked to beginner Microbiologists. So do not worry, I am standing tall for all you beginners out there.

Yeah right, I hope they don't know you are just five one.

Hehehe...shut up.

So let's go.

What do they look like?

Flagella are known to be long, thin, whip like processes whereas pili are short, thick hair like surface appendages.

What are thy made up of?

Both are made up of proteins but they are different. Flagella is made up of a protein known as flagellin and pili are made up of pilin proteins.

What are their types?

Flagella are divided in three types i.e. Bacterial, Eukaryotic and Archeal depending on the cell origin. They are majorly similar in functions but slightly differ in structures.

Pili are divided into two types - 

Conjugative - Also known as sex pili they play an important role in exchange of plasmid and chromosomal DNA between two or more bacterial cells. 

Type IV - These are more into motility and attachment to a substratum. You will come across this pili more often when you study about biofilms. They impart twitching motility to the cell.

How do they move?

Flagella often has a planar wave like movement which either moves sideways or back and forth. Also they move faster as compared to pili.

Pili show a more complicated 3D movement, as in they do not move in a single plane but circularly in all directions.

What are their uses?

Flagella are more involved in movement of the cell but also helps in sensing certain temperatures and chemicals or metals.

Pili as said are useful for surface recognition and attachment, exchange of DNAs and they also act as receptors for certain bacterial viruses. 

Both flagella and pili are antigenic too.

I hope this helps.

High six and tons of love 

-Staph <3