What is slime layer and bacterial capsule?

Many bacterial cells secrete some extracellular material in the form of a capsule or a slime layer. A slime layer is loosely associated with the bacterium and can be easily washed off, whereas a capsule is attached tightly to the bacterium and has definite boundaries.

What is the purpose of capsules and slime layers in bacteria?

A slime layer is a non-rigid matrix that is easily deformed and is not able to exclude India Ink. Biofilms are composed of many cells and their outer barriers. The primary functions of both capsules and slime layers are for protection and adhesion.

What is a slime capsule in bacteria?

Capsule. Capsule or slime layer is used to describe glycocalyx which is a thin, high molecular weight secretory substance present in many bacteria external to cell wall (Fig. 7.6). It is composed of polysaccharide, polypeptide, or both. Capsules contain water which protects the bacteria against desiccation.

What is the function of slime layer in bacteria?

The slime layer is an easily removed, diffuse, unorganized layer of extracellular material which surrounds the bacterial cell. It is usually composed of polysaccharides and it may serve to trap nutrients, to aid in cell motility, to bind cells together or to adhere to smooth surfaces.

Is capsule thicker than slime layer?

The capsule is composed of polysaccharides. The Slime layer is composed of glycoprotein, glycolipids, and exopolysaccharide. It is thicker than the slime layer. It is a thin layer.

Is capsule present in all bacteria?

Not all bacterial species produce capsules; however, the capsules of encapsulated pathogens are often important determinants of virulence. Encapsulated species are found among both Gram-positive and Gram-negative bacteria.

How do bacteria move?

Many bacteria move using a structure called a flagellum. Each cell may have several flagella and some bacteria can rotate them at up to 1,500 times per second so that they act in a similar way to a propeller, allowing a bacterium to travel 10 times its length every second.

What is the main function of flagella?

Flagellum is primarily a motility organelle that enables movement and chemotaxis. Bacteria can have one flagellum or several, and they can be either polar (one or several flagella at one spot) or peritrichous (several flagella all over the bacterium).

What is the function of the slime capsule?

The slime layer’s job is to protect bacteria cells from environmental threats including antibiotics and desiccation. Bacteria can adhere to smooth surfaces like prosthetic implants and catheters, as well as other smooth surfaces like Petri dishes, due to the slime layer.

Which bacteria are spore forming?

Spore-forming bacteria include Bacillus (aerobic) and Clostridium (anaerobic) species. The spores of these species are dormant bodies that carry all the genetic material as is found in the vegetative form, but do not have an active metabolism.

Why do bacteria move?

Getting warmer: With no brain to supply motivation, a bacterium instead must rely on chemical cues from its environment to provide an impetus to move. This process, known as chemotaxis, is completely involuntary. Bacteria simply respond to the tugs and pulls of their environment to take them to useful places.

Why are bacteria capsules and slime layers important?

Capsules and slime layers. Capsules can protect a bacterial cell from ingestion and destruction by white blood cells ( phagocytosis ). While the exact mechanism for escaping phagocytosis is unclear, it may occur because capsules make bacterial surface components more slippery, helping the bacterium to escape engulfment by phagocytic cells.

What kind of material does a bacterial cell secrete?

Many bacterial cells secrete some extracellular material in the form of a capsule or a slime layer. A slime layer is loosely associated with the bacterium and can be easily washed off, whereas a capsule is attached tightly to the bacterium and has definite boundaries.

What is the name of the gelatinous layer of bacteria?

A gelatinous layer of polysaccharide or polypeptide is called Glycocalyx. These polysaccharides may be composed of a single type of sugars (homopolysaccharide) or several types of sugars (heteropolysaccharides) and lies outside the cell envelope of bacteria. If glycocalyx is firmly attached to the cell wall it is referred to as a capsule.

How are bacteria capsules seen under a light microscope?

Capsules can be seen under a light microscope by placing the cells in a suspension of India ink. The capsules exclude the ink and appear as clear halos surrounding the bacterial cells. Capsules are usually polymers of simple sugars (polysaccharides), although the capsule of Bacillus anthracis is made of polyglutamic acid.