A conserved type IV pilin signal peptide H‐domain is critical for the post‐translational regulation of flagella‐dependent motility

Abstract

SummaryIn many bacteria and archaea, type IV pili facilitate surface adhesion, the initial step in biofilm formation. Haloferax volcanii has a specific set of adhesion pilins (PilA1-A6) that, although diverse, contain an absolutely conserved signal peptide hydrophobic (H) domain. Data presented here demonstrate that these pilins (PilA1-A6) also play an important role in regulating flagella-dependent motility, which allows cells to rapidly transition between planktonic and sessile states. Cells lacking adhesion pilins exhibit a severe motility defect, however, expression of any one of the adhesion pilins in trans can rescue the motility and adhesion. Conversely, while deleting pilB3-C3, genes required for PilA pilus biosynthesis, results in cells lacking pili and having an adhesion defect, it does not affect motility, indicating that motility regulation requires the presence of pilins, but not assembled pili. Mutagenesis studies revealed that the pilin-dependent motility regulatory mechanism does not require the diverse C-terminal region of the PilA pilins but specifically involves the conserved H-domain. This novel post-translational regulatory mechanism, which employs components that promote biofilm formation to inhibit motility, can provide a rapid response to changing environmental conditions. A model for this regulatory mechanism, which may also be present in other prokaryotes, is discussed.

Identification of Haloferax volcanii Pilin N-Glycans with Diverse Roles in Pilus Biosynthesis, Adhesion, and Microcolony Formation

“…Bundles-In H. volcanii, the difference between pili and flagella cannot be easily discerned through electron microscopy, each being about 8 -12 nm in diameter and varying substantially in length (21,34). TEM of ⌬aglB cell-associated filaments and CsCl-purified filaments revealed that their diameters are similar to those of type IV pili or flagella (8 -12 nm) (19).…”

“…However, similar to M. maripaludis, an H. volcanii ⌬aglB strain has remaining surface filaments that are not flagella (19). H. volcanii has six type IV adhesion pilins, PilA1-6, that contain a highly conserved hydrophobic domain required for pilus assembly, adhesion, and motility regulation (20,21). Although each of these pilins can be assembled into a functional pilus in a ⌬pilA [1][2][3][4][5][6] mutant expressing a single pilin in trans, the adhesion phenotypes differ (20).…”

Production of halophilic proteins using Haloferax volcanii H1895 in a stirred-tank bioreactor

“…Therefore, the plasmid pRE5 (Esquivel and Pohlschroder 2014 ;Tripepi et al 2013 ) was used to delete the genes Hvo_1034 and Hvo_1033. The knockout was confirmed by PCR using two primers gene expression after OD = 0.6 was reached.…”

Archaeal membrane-associated proteases: insights on Haloferax volcanii and other haloarchaea

“…In the haloarchaeon H. volcanii the structure and maturation of the S-layer glycoprotein as well as the biogenesis of pili and flagella have been examined (Jarrell et al, 2010; Kaminski et al, 2013; Kandiba et al, 2013; Tripepi et al, 2013; Esquivel and Pohlschroder, 2014). The adequate localization and functionality of these structures requires the participation of different families of proteases which are immersed in the context of the cytoplasmic membrane.…”