Summary auto-generated
This paper formally establishes Leptospiraceae as a new bacterial family and describes a new genus, Leptonema, to accommodate strains previously classified as Leptospira serovar illini. Using electron microscopy, researcher Kari Hovind-Hougen examined strains 3055 and A177 and discovered critical morphological differences from true leptospires. These organisms possess cytoplasmic tubules (bundles of 7 nm diameter structures) that are absent in other Leptospira serovars, and their flagellar basal complexes resemble those of gram-positive bacteria rather than gram-negative bacteria like typical leptospires. Additionally, these strains have higher DNA guanine-cytosine content (51-53 mol% versus 35-41 mol% in other Leptospira) and can grow in Trypticase soy broth without supplemental serum, unique among leptospires. The author formalizes Leptospiraceae (previously proposed informally by Pillot in 1965) as a family containing two genera: the established Leptospira Noguchi 1917 and the newly described Leptonema. Leptonema illini serves as the type species for the new genus, with strain 3055 designated as the type strain.
Key findings
- Leptonema illini strains possess cytoplasmic tubules absent in all other Leptospira serovars examined
- Leptonema flagellar basal structures resemble gram-positive bacteria while typical leptospires have gram-negative-type basal complexes
- Leptonema has significantly higher DNA guanine-cytosine content (51-53 mol%) compared to other Leptospira serovars (35-41 mol%)
- Leptonema is the only leptospira capable of growth in Trypticase soy broth without supplemental serum
- The new family Leptospiraceae is formally established containing genera Leptospira and Leptonema based on morphological and biochemical differences
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Abstract
The morphology of the cells of an organism formerly referred to as a member of Leptospira sp. serovar illini has been studied by electron microscopy. Cells of these strains differ morphologically from the cells of leptospires in the following: (i) cells of the former have cytoplasmic tubules which leptospires do not possess, and (ii) the structure of the basal complex on the flagella of the former is similar to that of gram-positive bacteria, whereas the corresponding structure on the flagella of leptospires is similar to that of gram-negative bacteria. Pillot (J. Pillot, thesis, University of Paris, Paris, France, 1965) proposed in 1965 that leptospires should constitute a family, Leptospiraceae. However, Pillot proposed this name in a thesis, which is not considered to be effective publication. Hence, Leptospiraceae is here proposed as the name of a new family. In consequence of the new morphological evidence presented here together with the data from other publications on the deoxyribonucleic acid base composition and serological and cultural properties of cells of strains of Leptospira sp. serovar illini, it is proposed that this family should consist of two genera: Leptospira Noguchi 1917 and Leptonema gen. nov. The type species of Leptonema is Leptonema illini, and the type strain of this species is strain 3055 (= NCTC 11301).