97:10899-10904. and was inhibited, but that of and was not. In addition, the continued manifestation of and in the mutant resulted in the formation of incomplete flagellar filaments that were hollow tubes and consisted primarily of FlaA. Finally, our recent studies have shown that every flagellin unit contributes to the stiffness of the PD166866 periplasmic flagella, and this tightness directly correlates with motility. The regulatory mechanism identified here should allow spirochetes to change the relative percentage of these flagellin proteins and, PD166866 concomitantly, vary the tightness of their flagellar filament. Spirochetes are motile bacteria that are able to swim in highly viscous gel-like environments. The medically important spirochetes include spp. (relapsing fever and Lyme disease), spp. (formerly known as and spp., which cause human and animal gastrointestinal diseases), spp. (leptospirosis), and related subspecies (syphilis, pinta, and yaws), and oral spp. (periodontal disease) (5, 12, 33, 45, 59). The spirochetes swim by means of PD166866 revolving periplasmic flagella (observe referrals 6, 36, and 38 for recent reviews). These organelles reside in the periplasmic space and are attached subterminally to the ends of the cell cylinder. Periplasmic flagella (PFs) are structurally similar to the flagella of additional bacteria, as each consists of a basal body-motor complex, hook, and filament (8, 27, 28, 39, 48, 55). However, the periplasmic flagellar filament is unique and is among the most complex of bacterial flagella. Specifically, in most spirochete varieties, the PFs contain at least one flagellar sheath protein, referred to as FlaA, and one to three core proteins, designated FlaB1, FlaB2, and FlaB3 (6, 35-37). In any given spirochete varieties, each FlaA and FlaB protein is definitely encoded by an individual gene. There is no sequence similarity or antigenic cross-reactivity between FlaA and FlaB proteins (2, 15, 16, 35, 36, 49, 50, 56). The individual periplasmic flagellar proteins have been studied in detail. FlaA proteins are 37 to 44 kDa and are similar between varieties based on amino acid sequences and antigenic cross-reactivity (6, 36, 38, 49). These proteins are likely exported to the periplasmic space by the type II secretion pathway, as their N-terminal amino sequences are cleaved and a typical peptidase I cleavage site is present near the N terminus (4, 18, 49). In contrast, FlaB proteins are exported to the periplasmic space most likely via the flagellum-mediated type III secretion pathway (6, 49). FlaB proteins comprise a family of well-conserved proteins. For example, the FlaB proteins of share 57 to 84% amino acid sequence identities (2, 16, 56). FlaB proteins are generally 33 to 41 kDa, and these proteins immunologically cross-react between one another in a given varieties and also between varieties (2, 6, 36, 49). Because FlaB proteins have sequence similarities to the flagellins of additional bacteria, especially in the N- and C-terminal areas, they are considered to have an identical function in forming the helical flagellar filaments THSD1 that rotate (36, 37, 64). Several studies have shown the PFs and the PFs devoid of the FlaA sheath are left-handed helices and do indeed rotate (7, 21, 35, 37). The rules of flagellar synthesis is definitely complex (1, 10). Studies with the paradigm models and serovar Typhimurium show that a cascade control mechanism is involved in the rules of flagellar genes. Within this hierarchy, the class I genes (and have two flagellin genes (and contains four flagellin genes (has been found in (16, 52, 56) and sigma28 consensus sequences have been recognized upstream PD166866 of several genes, the FlgM homolog has not been found in any spirochete varieties. In contrast to the case for genes, the promoters for genes have sigma70 consensus sequences (4, 18, 26, 32). The rules of these flagellin genes has not been systematically investigated for any spirochete varieties that contains multiple FlaB proteins, such as and varieties. The spirochete and the uncultivable (3, 30-32, 49). As such, has been used to analyze the complex structure of the PFs and the contribution of the individual filament proteins to filament corporation, filament tightness, and motility (35, 37, 53). Earlier experiments have shown that single and most double mutants have decreased motility. Only a double mutant is completely nonmotile (35, 37). With PD166866 this statement, we continued to use to investigate the rules of its multiple flagellin genes and to better understand its.