Suppressor mutants from MotB-D24E and MotS-D30E in the flagellar stator complex of Bacillus subtilis

Abstract

The bacterial flagellar motor is mainly energized by either a proton (H + ) or sodium ion (Na + ) motive force and the motor torque is generated by interaction at the rotor-stator interface. MotA/MotB-type stators use H + as the coupling ion, whereas MotP/ MotS-and PomA/PomB-type stators use Na + . Bacillus subtilis employs both H + -coupled MotA/MotB and Na + -coupled MotP/MotS stators, which contribute to the torque required for flagellar rotation. In Escherichia coli, there is a universally conserved Asp-32 residue of MotB that is critical for motility and is a predicted H + -binding site. In B. subtilis, the conserved aspartic acid residue corresponds to Asp-24 of MotB (MotB-D24) and Asp-30 of MotS (MotS-D30). Here we report the isolation of two mutants, MotB-D24E and MotS-D30E, which showed a nonmotile and poorly motile phenotype, respectively. Up-motile mutants were spontaneously isolated from each mutant. We identified a suppressor mutation at MotB-T181A and MotP-L172P, respectively. Mutants MotB-T181A and MotP-L172P showed about 50% motility and a poorly motile phenotype compared to each wild type strain. These suppressor sites were suggested to indirectly affect the structure of the ion influx pathway.

Na + -induced structural transition of MotPS for stator assembly of the Bacillus flagellar motor

“…The D30A substitution inhibited motility in soft agar (fig. S6), in agreement with a previous report ( 28 ). MotPS D30A observed by HS-AFM looked very similar in its entire architecture to wild-type MotPS ( Fig.…”

Isolation of dextran‐hydrolyzing intestinal bacteria and characterization of their dextranolytic activities

“…Most bacterial dextranase producers have the ability to synthesize several aglucosidases with different sub-cellular localizations and substrate specificities simultaneously. [28][29][30] Two extracellular dextranases (D 1 and D 2 ) and one intracellular dextranase (D 4 ) from Pseudomonas sp. strain UQM 733 have been isolated.…”

“…Dextranase activity has also been detected in both the intra-and extracellular fractions of B. oralis Ig4a obtained from human dental plaque. 28 In addition, there are couple of reports about cloning and expression of the dextranase from Bacteroides spp., such as B. thetaiotaomicron 489 and B. thetaiotaomicron VPI-5482. 31,32 Dextranase from B. thetaiotaomicron VPI-5482 showed endodextranase activity to synthesize isomaltooligosaccharides (DP>4) as well as cyclic form of oligomers.…”

Metabolites Produced by Kaistia sp. 32K Promote Biofilm Formation in Coculture with Methylobacterium sp. ME121

“…We recorded a video of the observed movements for about 5 s and the moving distance per second (40 frames), using a digital color camera (Leica DF310 FX). The speed of each swimming cell was calculated by using 2D movement measurement capture 2D-PTV software (Digimo, Tokyo, Japan) and analysis of the captured movie [ 23 ].…”