Flavobacterium johnsoniae sprB Is Part of an Operon Spanning the Additional Gliding Motility Genes sprC , sprD , and sprF

Abstract

Cells of Flavobacterium johnsoniae move rapidly over surfaces by a process known as gliding motility. Gld proteins are thought to comprise the gliding motor that propels cell surface adhesins, such as the 669-kDa SprB. A novel protein secretion apparatus called the Por secretion system (PorSS) is required for assembly of SprB on the cell surface. Genetic and molecular analyses revealed that sprB is part of a seven-gene operon spanning 29.3 kbp of DNA. In addition to sprB, three other genes of this operon (sprC, sprD, and sprF) are involved in gliding. Mutations in sprB, sprC, sprD, and sprF resulted in cells that failed to form spreading colonies on agar but that exhibited some motility on glass in wet mounts. SprF exhibits some similarity to Porphyromonas gingivalis PorP, which is required for secretion of gingipain protease virulence factors via the P. gingivalis PorSS. F. johnsoniae sprF mutants produced SprB protein but were defective in localization of SprB to the cell surface, suggesting a role for SprF in secretion of SprB. The F. johnsoniae PorSS is involved in secretion of extracellular chitinase in addition to its role in secretion of SprB. SprF was not needed for chitinase secretion and may be specifically required for SprB secretion by the PorSS. Cells with nonpolar mutations in sprC or sprD produced and secreted SprB and propelled it rapidly along the cell surface. Multiple paralogs of sprB, sprC, sprD, and sprF are present in the genome, which may explain why mutations in sprB, sprC, sprD, and sprF do not result in complete loss of motility and suggests the possibility that semiredundant SprB-like adhesins may allow movement of cells over different surfaces.

Helical flow of surface protein required for bacterial gliding motility

“…S4). GldK and GldN are known to be required for secretion of SprB to the cell surface and are part of the PorSS (4,17). GldJ is required for gliding, but its exact function is not known (18).…”

“…F. johnsoniae ATCC 17061 (UW101), CJ1827 (a streptomycinresistant rpsl2 derivative of UW101 used for construction of deletion mutations), and CJ1922 (sprB deletion mutant) were used in this study (17,33,34). The cells were grown in casitone yeast extract (CYE) medium at 25°C with shaking (35) to an optical density of around 1.0 at 600 nm.…”

“…The cells were grown in casitone yeast extract (CYE) medium at 25°C with shaking (35) to an optical density of around 1.0 at 600 nm. For selection and maintenance of the antibiotic-resistant strains, antibiotics were added to the medium at the following concentrations: erythromycin, 100 μg/mL; streptomycin, 100 μg/mL; tetracycline, 20 μg/mL (17,18).…”

On the role, ecology, phylogeny, and structure of dual-family immunophilins

“…Interestingly, three of the Gld genes comprised a putative ATP-binding cassette (ABC) transporter, a multisubunit complex (McBride 2004;Braun and McBride 2005). Additionally, these investigators identified a novel protein secretion system, the Por secretion system (PorSS), in this family, and found that the PorSS genes are in fact a subset of the Gld genes, suggesting a relationship between the secretion system and motility (Rhodes et al 2011;McBride and Zhu 2013). The F. johnsoniae PorSS, for example, is needed for the assembly of the gliding motility apparatus as well as for the secretion of a chitinase.…”

Por Secretion System of Porphyromonas gingivalis

“…The cell surface adhesin SprB protein of F. johnsoniae, which is involved in the formation of swarming colonies on solid agar, is not secreted at the cell surface in the sprT mutant 27 . A recent study 29 showed that sprF has some similarity to porP of P. gingivalis, mutants of which produced no swarming colonies on agar. The SprB protein is produced but not transported to the cell surface of the sprF mutant, as in the sprT mutant.…”