What is Spirochaetes and Spirilla

Spirochaetes 

have a unique shape, structure and mode of locomotion.

Characteristics: 

They are not stained easily by normal staining methods and thus cannot be designated either gram-negative or gram-positive.

•They are best observed by dark-ground illumination.

•They are slender rods in the from of spirals, like a corkscrew.

•Motility mechanisms is by means of structures called axial filaments.

Certain species inhabit water environments, while others are parasites of arthropods (such as ticks and lice) as well as warm-blooded animals

Members: Examples of spirochaete genera are:

 Borrelia.

 Borrelia recurrentis: causes a relapsing fever in man.

 Borr. vincenti: is the cause of Vincent’s angina in man, an ulcerative condition of the mouth and gums.

 Treponema.

 Treponema pallidum: is the causal organism of syphilis.

 Tr. Pertenue: causes the tropical disease called yaws.

Member’s of spirochaetes cont’d

 Leptospira.

6.3.1: Leptospira icterohaemorragiae: is the cause of a type of jaundice in man called weil’s disease.

•The disease is carried by rats and is encountered in sewer workers.

Other species of Leptospira, with hosts ranging from domestic animals such as the pig to wild animals such as opossums and jackals, give rise to a variety of fevers encountered locally or widely across the world.

Spirilla

Spirilla have a spiral shape, a rigid cell wall, and motility mechanisms based on polar flagella.

Members

 Helicobacter:  is a genus of Gram-negative bacteria possessing a characteristic helix shape.

•They were initially considered to be members of the Campylobacter genus, but since 1989 they have been grouped in their own genus.

•Some species have been found living in the lining of the upper gastrointestinal tract, as well as the liver of mammals and some birds.

Helicobacter cont’d

•The most widely known species of the genus is Helicobacter pylori which infects up to 50% of the human population.

•Some strains of this bacterium are pathogenic to humans as it is strongly associated with peptic ulcers, chronic gastritis, duodenitis, and stomach cancer.

•Helicobacter spp. are able to thrive in the very acidic mammalian stomach by producing large quantities of the enzyme urease which locally raises the pH from  2 to a more biocompatible range of 6 to 7.