List Three Forms of Motility in Bacteria

In this list three forms of motility in bacteria post we have briefly explained about locomotion, motility in bacteria (flagellar movement, spirochaetal movement and gliding movement).

Locomotion

Locomotion is important to all organisms for various purposes like to find food, to mate, to escape from predators, for survival purpose, etc. and altogether, they influence in locomotive organ evolution process in animals.

Locomotive organs are different in nature from one species to other. Muscles play important role in movement of the animals. In higher animals along with muscles, bones also associate for the movement. Animal movements can differentiate as walk, run, swim, fly, crawl and jump. 

Motility in bacteria can classify as flagellar, spirochaetal and gliding movement. Single cell organisms also show crawling like movement often called amoeboidal movement as well as they show cillary movement, flagellar movement. 

Nature of movement is different in plants in which roots, branches, leaves move in response to environmental abiotic factors but overall the plant is non-movable. Here we discuss the different types of locomotion or movement and their mechanisms briefly.

Types of Motility in Bacteria

Motility in bacteria can defined as an ability to move from one place to another. The organs which helps for the locomotion is called as locomotive organs. Ex: limbs, flagella, cilia, etc.

Prokaryotic and eukaryotic single cell organism does movement for their survival, growth and reproduction. Bacteria are single cell prokaryotic organisms. They show three different types of movements. They are

Flagellar movement

Bacteria can move in liquids with help of flagellum. Depends on number of flagella, arrangement over cell surface, bacteria were named differently like monotrichous, lophotrichous, amphitrichous and peritrichous. According to the arrangement they are classified into different classes and those bacteria are motile.

Locomotion in Bacteria

Structure of Flagellum

Flagellum is a lash-like cell surface appendages and it consists of protein flagellin. It generally divided into 3 portions and they are basal body, hook and filament.

Basal body is implanted in cell wall. Basal body of the flagellum has M (motor) ring, S (stator) ring and C ring. M and s ring together bind with peptidoglycan layer of the bacteria whereas c ring present in the cytoplasmic region.

Basal body is connected with the filament by hook. Flagellum can rotate either clockwise or anticlockwise.

Further basal body has around 40 proteins including ‘mot’ proteins and ‘fli’ proteins which are essential in the active movement through proton pumping mechanism. Ex. for flageller bacteria Vibrio, Spirillum, Salmonella, Klebsiella, etc.

Spirochetal movement

Spirochetes are Class V bacteria. The movement of Spirochetes is called as spirochetal movement. Spirochetes are long right handed helically shaped bacteria.

Axial fibrils and periplasmic flagellum, present in the periplasmic region of the bacteria, overlapped together and run one sub-polar end to other of the Spirochetes. 

The mechanism of Spirochetal movement is not clear; however the proposed anticlockwise rotation of the flagellum can lead the bacterial movement. Classical example for this type movement is Treponemapallidum.

Locomotion in Bacteria

Structure of Spirochetes

Gliding movement

Group of gliding bacteria show non-flagellum based gliding movement. Fimbriae like appendages (pili), present at polar region, involve in the gliding movement with the help of motor system A and S along chemosensory system ‘Frz’.

Here coordinated movement of two different motor systems, known as S and A system, response for the motility of bacteria.

But their mode of action is unclear. Ex. Myxococcus, cyanobacterium, Oscillatoria. But other hypotheses like generation of contractile waves or surface tension or pushing by secreted slime was also proposed as possible mechanisms of gliding.

Locomotion in Bacteria

Gliding movement of Treponema Pallidum

Further Readings

Reference