Structure of Bacteria | Part 2 | Flagella | Pili | Capsule

We apologise for the delay in bringing out this video. This is the part 2 video of structure of bacteria. Please watch the part 1 by following the link below.
• Structure of Bacteria ...
Music: www.bensound.com
Narration:
We discussed about different sizes, cell arrangement and shapes of bacteria in the previous video.
In this video, lets discuss about the ultra structure of bacteria and the structures external to the cell wall. The ultra structure of bacteria is all about the arrangement of bio molecules that are seen under the higher magnifications, unlike the structure what we see under the compound microscope.
The structure of a typical bacterial cell looks something like this.
As the bacteria are prokaryotes, the nuclear material is not bound by the membrane.
The other cell organs include ribosomes, cell wall, plasma membrane, pilus, flagellum, cytoplasm and mesosome.
The ultra structure of bacteria include the following 4 components.
Structures external to the cell wall
The cell wall
Structures inside the cell wall
Spores
Flagella
Flagella are thin, and hair like structures. They come through the cell wall and mainly function in motility of bacterial cell. The location of the flagella on the bacterial cell wall, varies depending on the species.
Bacteria with single flagellum is called Monotrichous bacteria.
Bacteria with two flagella located at each ends is called Amphitrichous.
Lophotrichous are the bacteria that has cluster of flagella at one or both ends.
Peritrichous has got many flagella all around the cell wall.
Atrichous does not have flagella at all.
Structure of Flagella:
Falgella has got three basic parts.
Basal body
Hook
Filament
Basal body is structurally complex part of the flagellum. And it is the only part of the flagellum that is inside the cell wall.
The basal body in gram negative bacteria has 4 rings connected to a central rod.
The L ring remains outside and fixed in lipo poly sacharide layer of the cell wall.
The P ring remains next to the L ring and fixed in the peptidoglycan layer.
The S and M rings are placed in the cytoplasmic membrane.
In the gram positive bacteria, as the outer lipo polysacharide layer is almost not present, only the inner S and M ring can be found in the cytoplasmic membrane. The L and P ring are absent in the gram positive bacteria. The basal body acts as a rotary motor and enables the flagellum to move.
Hook:
Hook is the short, and curved structure that connects basal body and filament. Hook is made of multiple copies of single protein called FlgE or also called as flagellar hook protein.
The main function of hook is to transmit the torque generated by the basal body by the rotary motion to the filament.
Filament:
Filament is a helical rod with hallow centre and is usually lengthier than the bacterial cell. It is composed of flagellin protein. The main function of filament is to act as propeller and drive the bacteria.
Pili or Fimbriae (Pilus-singular):
Pili are short, hallow, non-helical and are more in number than flagella. However they do not involve in motility. Beacuse pili are also found in non-motile bacteria.
Pili serve as the port between the two bacteria to transfer the genetic material during the bacterial conjugation. These are known as F pilus.
Some pili help bacteria to attach to epithelial cells of host body during infections. This prevents the bacteria from being washed out by the body fluids and therefore spread the infection.
Capsule:
Capsule is a poly sacharide layer that found outside the cell wall. Many bacterial cells secrete some extra cellular material in the form of a capsule or slime layer.
It is believed that capsule is being hydrophilic, it always keep the bacterial cell surface hydrated and makes it slippery. Therefore help the bacteria escape from phagocytosis.

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Sir can you please add the synthesis of flagella too

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[@usc3697]

Assalamualaikum sir I think there is something wrong
Lophotrichous bacteria have tuft of flagella at one pole and Amphitrichous bacteria have tuft or cluster of flagella at both ends
🎉🎉🎉🎉thank you.
It's ok to done mistake but misconception can leads to something worse.

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Is pili Hallow or Hollow??

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Sorry for the inconvenience.