Strain-dependent motility defects and suppression by a flhO mutation for B. subtilis bactofilins

Abstract

Objective Bactofilins can assemble into polymeric structures and play important roles in cell shape maintenance, chromosome segregation and motility. Bacillus subtilis bactofilins BacE and BacF were shown to be important for swimming motility in strain PY79, and single gene deletions were reported to be lethal, in contrast to a double bacEF deletion. Results Extending this work, we show that motility defects vary between different B. subtilis strains, with strain 168 showing no defect in motility, and 3610 showing delayed induction of swimming. Generation of single gene deletions in PY79 was possible by transferring corresponding deletions from 168. In the natural isolate 3610, gene deletions also showed a negative effect on biofilm formation, revealing an additional function for BacE and BacF. A spontaneous arising suppressor mutation in PY79 was mapped to the flhO gene, a constituent of the flagellum, which obtained an 18 amino acid extension at its C-terminus. Our findings show that bactofilin gene deletions lead to different motility phenotypes dependent on the strain background, and affect biofilm formation in the natural isolate 3610. Our data reinforce the idea of a connection between bactofilins and motion via the flagellum, and suggest that they operate in a switch like manner.

A Machine Learning-Empowered Workflow to Discriminate Bacillus subtilis Motility Phenotypes

“…Therefore, we utilized this strain as a negative control, and the colony area extension here results from an increase in the cell density and does not rely on active flagella movement. As shown prior to this study, the effect of a bactofilin double mutant on motility is present in PY79, but not in 168 or W3610, indicating strain-specific differences in the regulation of flagella biosynthesis as described in [4].…”

“…The dataset contains three replicates with each nine technical replicates for the strains PY79, 168 and the flagella mutant PY79 yhbEF, resulting in 81 colonies. These data were already partially published in [4]. Biomedical datasets are often even smaller; therefore, we include only nine colonies of the supermotile strain W3610 and the lab strain BG214.…”

“…It has been known for more than a century that colony morphology can be strikingly different between pathogenic and non-pathogenic strains of bacteria and should therefore be decisive in characterizing bacteria isolated from patients [1][2][3]. B. subtilis is a model organism for Gram-positive bacteria and is known for its different mobility, depending on the respective strain [4,5]. To access the characteristic phenotypic differences of the colony formation present in Bacillus subtilis, a set of wild-type and domesticated laboratory strains are used (see Table 1).…”

Halofilins as Emerging Bactofilin Families of Archaeal Cell Shape Plasticity Orchestrators

“…Besides the HalA, HalB, and bactofilin assemblages, our map contains a fourth, smaller group radiating from the bactofilin cluster (BacEF). This cluster consists of bacterial and archaeal bactofilin-like proteins with 13 windings, represented by homologs of BacEF (UniProtKB P39132 and P39133) from Bacillus subtilis (30, 43) and the uncharacterized protein from Methanobacterium bryantii (UniProtKB A0A2A2H537).…”

“…Next, we collected time lapses with epifluorescence across multiple generations to assess whether HalA and HalB structures are dynamically regulated throughout the cell cycle. Like BacEF bactofilins that orchestrate flagella placement (30, 43), HalB foci are relatively static across the scale of minutes (Fig. 3C, Movie S3).…”