Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Biology and Microbiology

First Advisor

Helen N. Westfall


The genus Leptospira belongs to the order Spirochaetales and the family Leptospiraceae. Currently, there are two Leptospira species: L. interrogans, which includes the pathogenic or parasitic organisms; and L. biflexa, all of which are saphrophytic, free-living leptospires. Approximately 240 different serovars, the final taxonomic subdivision of these organisms, have been reported based on antigenic analysis via microscopic agglutination and cross-agglutination absorption tests. These serovars are categorized into serogroups (approximately 60) due to antigenic cross-reactivity. In addition to antigenic analysis, a number of biological and biochemical tests are used to distinguish the two species including: growth at low temperatures, sensitivity to 8-azaguanine and/or the purine derivative 2,6-diaminopurine, the presence or absence of lipase activity, the ability to grow in trypticase soy broth, and the requirement of 1-2% NaCl for growth. These biological and biochemical tests unfortunately do not distinguish between serovars, therefore serology remains the primary means of identification of the specific serovar. The organisms are flexible, right-handed helical rods that are 0.1 um in diameter and 6-12 um in length. The hooks seen at both ends of this negatively stained Leptospira are typical of the organism. Leptospiras are entirely enclosed in the outer cell envelope or sheath (OS). Inside this OS is the protoplasmic cylinder which contains both cytoplasmic and nuclear regions enclosed by the cytoplasmic membrane-cell wall complex. Around the helical protoplasmic cylinder are wound 2 periplasmic flagella (PF), also commonly called axial filaments or endoflagella. Each PF is subterminally attached to the protoplasmic cylinder. Stuart developed an early culture medium in which the nutritional requirements of leptospiras were provided in the form of a rabbit serum supplement. One major drawback of this medium is that variability in rabbit serum leads to inconsistency in maximal growth of the leptospiras. In 1965, Ellinghausen and McCullough developed an albumin medium for leptospiras, which Johnson and Harris improved upon in 1967. Modified Ellinghausen, McCullough, Johnson and Harris (EMJH) medium or the modified albumin medium of Bey and Johnson are the most commonly used media in the United States. The above described albumin media require preparation of separate albumin supplements and chemically defined basal media which makes media preparation both difficult and time consuming. Medium that supports the growth of leptospiras is now commercially available, but its expense often precludes its routine use.

Library of Congress Subject Headings


Escherichia coli



Number of Pages



South Dakota State University