Relapsing Fevers: Neglected Tick-Borne Diseases.

Relapsing fever still remains a neglected disease and little is known on its reservoir, tick vector and physiopathology in the vertebrate host. The disease occurs in temperate as well as tropical countries. Relapsing fever borreliae are spirochaetes, members of the Borreliaceae family which also contain Lyme disease spirochaetes. They are mainly transmitted by Ornithodoros soft ticks, but some species are vectored by ixodid ticks. Traditionally a Borrelia species is associated with a specific vector in a particular geographical area. However, new species are regularly described, and taxonomical uncertainties deserve further investigations to better understand Borrelia vector/host adaptation. The medical importance of Borrelia miyamotoi, transmitted by Ixodes spp., has recently spawned new interest in this bacterial group. In this review, recent data on tick-host-pathogen interactions for tick-borne relapsing fevers is presented, with special focus on B. miyamotoi.

Selected phenotypic features of BR91, a unique spirochaetal strain isolated from the Culex pipiens mosquito.

Growth temperature range, resistance to selective antibiotics, activities of 23 enzymes, protein fingerprints and fatty acids composition of the spirochaetal strain BR91, isolated from the Culex pipiens mosquito, were tested. The spirochaetes were grown in BSK-H Complete liquid medium. The optimal in vitro growth temperature of the strain was 33 °C. Strain BR91 was sensitive to trimethoprim, nalidixic acid, 5-fluorouracil, and tolerated phosphomycin. The strain produced acid and alkaline phosphatase, esterase (C4), esterase-lipase (C8), leucine arylamidase, naphthol-AS-BI-phosphohydrolase and α-fucosidase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) assay revealed several major proteins in the size range of 13-16 kDa, 22-30 kDa and 37-131 kDa. Fatty acid methyl ester (FAME) analysis showed that C14:0, C16:0, C18:1 ω9c and summed feature 5 (C18:2 ω6,9c and/or C18:0 anteiso) are major fatty acids. This study highlights certain phenotypic differences between strain BR91 and the Lyme disease spirochaete Borrelia burgdorferi, and supports the hypothesis that strain BR91 represents a unique taxonomical entity in a system of spirochaetal species.

Acetogenesis from H2 plus CO2 by spirochetes from termite guts.

Pure cultures of termite gut spirochetes were obtained and were shown to catalyze the synthesis of acetate from H2 plus CO2. The 16S ribosomal DNA sequences of two strains were 98 percent similar and were affiliated with those of the genus Treponema. However, neither was closely related to any known treponeme. These findings imply an important role for spirochetes in termite nutrition, help to reconcile the dominance of acetogenesis over methanogenesis as an H2 sink in termite hindguts, suggest that the motility of termite gut protozoa by means of attached spirochetes may be based on interspecies H2 transfer, and underscore the importance of termites as a rich reservoir of novel microbial diversity.

Variation amongst human isolates of Brachyspira (Serpulina) pilosicoli based on biochemical characterization and 16S rRNA gene sequencing.

Brachyspira pilosicoli (formerly Serpulina pilosicoli) causes swine spirochaetosis and can also be isolated fro human faeces, although its role in human disease remains unclear. The genetic and biochemical variations amongst 19 isolates of human spirochaetes from five different countries were evaluated and compared to those found amongst swine isolates of B. pilosicoli. All isolates were negative for beta-glucosidase and all but one were positive for hippurate hydrolysis, which are characteristics typical of B. pilosicoli. The isolates showed variation in indole production and alpha-galactosidase and alpha-glucosidase activity, other characteristics which can be used to identify B. pilosicoli. The DNA sequences of part of the 16S rRNA gene differed from each other and from that of B. pilosicoli by 0-3 bp out of 283 bp. It is concluded that there is considerable variation amongst human intestinal spirochaetes. Since few of the isolates reported here match the current criteria for B. pilosicoli, it is concluded that this species is more heterogeneous than previously appreciated. However, it cannot be excluded that some isolates may belong to uncharacterized related Brachyspira/Serpulina species.

Spirochete chemotaxis, motility, and the structure of the spirochetal periplasmic flagella.

Spirochetes have a unique motility system that is characterized by flagellar filaments contained within the outer membrane sheath. Direct evidence using video microscopy has recently been obtained which indicates that these periplasmic flagella (PF) rotate in several spirochetal species. This rotation generates thrust. As shown for one spirochete, Spirochaeta aurantia, motility is driven by a proton motive force. Spirochete chemotaxis has been most thoroughly studied in S. aurantia. This spirochete exhibits three distinct behaviours, runs of smooth swimming, reversals and flexing. These behaviours are modulated by addition of attractants such that S. aurantia swims towards higher concentrations of attractants in a spatial gradient. Unlike the prototypical bacterium, Escherichia coli, chemotaxis in S. aurantia involves fluctuations in membrane potential. The PF of a number of spirochetes have been examined in considerable detail. For most species, the PF filaments are complex, consisting of an assembly of several different polypeptides. There are several antigenically related core polypeptides surrounded by an outer layer consisting of a different polypeptide. Borrelia burgdorferi and Spirochaeta zuelzerae represent exceptions where the filaments are composed of a single major polypeptide species. The genes encoding the filament polypeptides from several spirochete species have been cloned and analysed. Apparently, the outer layer polypeptides of S. aurantia, Treponema pallidum and Serpulina hyodysenteriae are transcribed from sigma-70-like promoters, whereas the core polypeptide genes are transcribed from sigma-28-like promoters. A gene encoding the hook polypeptide in Treponema phagedenis has been cloned and analysed. The product of this gene shows significant similarity to the E. coli hook protein, FlgE, and homologs have been identified in T. pallidum and B. burgdorferi.(ABSTRACT TRUNCATED AT 250 WORDS)

Cristispira from oyster styles: complex morphology of large symbiotic spirochetes.

Crystalline styles (digestive organs) of bivalve mollusks provide the habitat for highly motile bacteria. Styles from freshly-collected oysters, Crassostrea virginica, were studied by electron microscopy; Cristispira spirochetes were abundant in these organs. Detailed study reveals these spirochetes to be among the most complex prokaryotic cells known. More than 600 periplasmic flagella and an adhering outer lipoprotein membrane (e.g., a 270 degrees sillon) form the ultrastructural basis for the "crista," first described by light microscopy. Unique rosette structures corresponding to the "chambers" or "ovoid inclusions" of light microscopy were detected at the periphery of all protoplasmic cylinders. Polar organelles and linearly aligned flagellar insertions are conspicuous. In size and complexity, Cristispira more resembles Pillotina, Diplocalyx, Clevelandina and Hollandina (large spirochetes symbiotic in termites) than it does Treponema. Cristispira pectinis (Gross, 1910), the type species; Spirillum ostrea (Noguchi, 1921); and another, less frequent bacterial symbiont are the predominant inhabitants of the dense style matrix. The ultrastructure of the spirillum and an electron micrograph of the third bacterium are shown.

Possible evolutionary significance of spirochaetes.

Large symbiotic spirochaetes of the family Pillotaceae (e.g. pillotinas) are found in dry wood and subterranean termites (Hollande & Garagozlou 1967). These morphologically distinctive spirochaetes comprise several genera. Some of them contain microtubules within their protoplasmic cylinders. They demonstrate a variety of relations with their termite and protist hosts. Some are free-living within the lumen of the intestine, some tend to be associated with filamentous and other bacteria, some are found regularly coursing between the numerous undulipodia ( = eukaryotic flagella, cilia, and other (9 + 2) organelles of motility) of hypermastigotes and polymastigotes. Still other smaller termite spirochaetes are regularly attached to protists via specialized attachment sites. Some even form motility symbiosis with their host protists. The analogy between the behaviour of host-associated spirochaetes and the possible steps in the origin of the undulipodia and mitotic system of eukaryotes is discussed briefly.

Pillotinas and hollandinas: distribution and behaviour of large spirochaetes symbiotic in termites.

Pillotina spirochaetes have been observed in the hindguts of wood-eating cockroaches (Cryptocercus punctulatus), and in 25 out of 28 species of termites examined. They were especially abundant in 21 species of dry wood termites of the family Kalotermitidae, from Europe, North America and Australia. These included many species of Kalotermes and one or a few of the following: Glyptotermes, Bifidotermes, Neotermes, Ceratokalotermes, Paraneotermes, Cryptotermes, Porotermes, Marginitermes, Pterotermes, Zootermopsis, Reticulitermes, Coptotermes, Heterotermes, and nasutitermitids. Identifications of pillotinas were made on the basis of large size (0.5--2 micromtere in diameter, 50 to greater than 100 micrometers in length) and wave pattern; these were verified by electron microscopy in K. schwarzi, Pterotermes occidentis and others. Pillotinas were also present in all species of subterranean termites (Family Rhinotermitidae) examined, and in the most primitive Australian termite, Mastotermes darwiniensis (Family Mastotermitidae). They were not observed in damp wood termites (Family Hodotermidiae). Pillotinas are invariably associated with a rich, complex xylophagous microbial community composed primarily of motile prokaryotes, and hypermastigote and polymastigote flagellates. Some have been previously described by those primarily concerned with termite hindgut protozoa. Observations were made on their modes of behaviour, division, and microbial associates. A new genus of spirochaetes, Hollandina, is also described. It is distinguished from Pillotina by a smaller size and several ultrastructural features, but is otherwise closely related taxonomically. Evidence is provided to support Hollande and Gharagozlou's (1967) concept that the pillotinas and hollandinas deserve the taxonomic status of 'family' and that they should be classified with the cristispire siprochaetes a-cording to the scheme developed by Hovind-Hougen (1976). Spirochaetes are treated as a Phylum of the Kingdom Monera (Prokaryota) in the five kingdom system of Whittaker (1969).