The Spirochetes (3)

Family 1: SPIROCHAETACEAE

Genus 3: Cristispira

Cristispira sp.

Cristispira is a genus of large spirochetes, with unclear divisions into different species.  The organism was first found by Cretes when he found the organism inhabiting the digestive tract of oysters.  It wasn’t until 1910; however that Gross proposed the establishment of the genus Cristispira. They are generally found in the digestive tracts, specifically the crystalline styles, of both freshwater and marine mollusks. This is a commensal relationship, where the microbe gets nutrients and shelter, and the mollusk is neither harmed or benifited.  However, not all mollusks in a population will contain Cristispira, and when an organism is host to the microbe there are generally no other bacteria found. They are currently distinguished from other spirochetes only by their physical structure, as they have not yet been cultured in the lab.  Individual cells have a diameter between .4 and 10 μm and can grow up to 150 μm in length. They are also characterized by the presence of a “crista”, a crest like structure.The crista can be seen under the microscope and appears as a bundle of filaments bound to the outer sheath. Cristispira is a facultative anaerobe, and has an optimum temperature of 15˚ C. Currently, there is no biochemical or genetic data for Cristispira but scientists are trying to find the link between the microbe and the crystalline style in order to cultivate them in the lab.

A study was done in 1981 to study the unique relationship between Cristispira and its host using a scanning electron microscope (SEM). Scanning electron microscopy was employed to observe the physical interactions between Cristispira spp. and the crystalline style of the Chesapeake Bay oyster (Crassostrea virginica Gmelin 1791). Cristispira organisms were found associated with both the inner and outer layers of the posterior two-thirds of the style. The spirochetes possessed blunt-tipped ends, a cell diameter range of 0.6 to 0.8 ,um, and distended spirochetal envelopes which followed the contour of the cells. Transmission electron microscopy showed that the distension of the envelope was probably due to the containment of numerous axial filaments. In addition, they were found to possess two distinct spiral shapes which were dependent on whether their location was inside or on the surface of the style. (http://aem.asm.org/content/42/2/336.full.pdf)

Cristispira pectinis

Habitat: Harmless parasites of freshwater and marine molluscs and some gastropods.

Oxygen Relationships: Unknown

Major character: Have never been isolated; have unusually large number of periplasmic flagella

Species: Main species are, C. balbianii, C. anodontae, C. pinnae, C. pectinis.