Fig. 1

Heterologous expression of B. paralicheniformis urease genes in B. subtilis. A Schematic of urease gene loci. (i) shows the native urease genes of the donor and recipient species. Functional categories for each gene are indicated using the colour code given below the schematics. For simplicity, only the last letter of each gene name in the ure cluster is shown. Gene sizes in bp are given above each arrow. The abbreviated terms used in strain denominations throughout this study is shown at the top. (ii) shows the construction of the heterologous expression strains. Deletion of the native ureABC operon is indicated by a crossed-out blue arrow. Introduced genes are shown in simplified schematics using the same colour code. Bent arrows indicate the P_xylA promoter used to drive gene expression. B Urease activity of heterologous expression strains. Urease test broth containing 0.2% xylose were inoculated to an initial OD₆₀₀ of 0.05 from solid media growth and incubated at 30 °C for 24 h in a TECAN Spark microplate reader. Absorbance at 560 nm (A₅₆₀) was monitored to detect the yellow-to-pink colour change of the pH indicator phenol red as a result of urease activity. The composition of the test broth did not support cell growth and OD₆₀₀ remained constant during the experiment, giving no interference with A₅₆₀ measurements. The data are shown as mean ± standard deviation of 2-3 technical repeats and are representative of three independent repeats. Control strains shown in grey symbols are S. pasteurii (S.p.), B. paralicheniformis (B.p.), B. subtilis W168 (W), and its isogenic ureABC deletion (WΔ). The heterologous strains are shown in colour using the nomenclature detailed in panel A