Structure and Function

Fig.4. To-Scale Photograph
of B. burgdorferi

B. burgdorferi is relatively large compared to other bacteria: 

it has an average length of 20-30 µm and width of 0.2-0.5 µm.

B. burgdorferi is one of the few bacteria whose genome has been fully sequenced. 

The bacterium contains a linear chromosome, consisting of 901,725 base pairs, 

each one with 853 genes encoded with proteins that are accounted for 

DNA replication, transcription, translation, and solute transport.

In addition to this, B. burgdorferia also contains 21 other linear and circular plasmids 

that add up to total of 533,000 base pairs of DNA.

B. burgdorferi is a Gram-negative bacterium. 

This means that the crystal violet dye used in Gram stain test colours the bacterium red or pink, as opposed to dark blue or violet colouring of Gram-positive bacteria. 

This difference is due to the presence of an additional outer membrane of 

Gram-negative bacteria.

Fig. 5. A colony of B. burgdorferi dyed in pink by the Crystal violet dye used in 

Gram staining protocol

B. burgdorferi’s morphology can be divided into two parts: the cell cylinder and 

periplasmic flagella, whip, hair-like structures.

The  helically-shaped cylinder of a B. burgdorferi is coated by a slime layer, 

which prevents the bacterium to be digested 

once inside the host's body.

Fig.6. Morphology of
Borrelia Burgdorferi

Attached at each end of B. burgdorferi are 

7 to 11 periplasmic flagella 

that overlap in the centre of the cell.

In most bacteria, the cell shape is determined by their peptidoglycan layer 

(a chemical compound consisting of sugars and amino acids that form the cell wall). 

Although this is also holds true for B. burgdorferi, 

it has been proved through various experiments that the flagella are the main cause for the cell’s unique shape. 

Without them, B. burgdorferi would be a rod-shaped bacillus. 

Due to the presence of the periplasmic flagella, 

B. burgdorferi is able to maintain its helical shape.