Fig. 7: Met4 and Met32 are required for the assimilation of organosulfur compounds in C. parapsilosis.

The growth of C. parapsilosis CLIB214 and derivative strains disrupted in MET4, MET28, or MET32 was tested in the presence of sulphur-free media supplemented with (i) no sulphur (control, no S); (ii) inorganic sulphur (sulphate, AS), or (iii) organosulfur compounds from different structural classes as only available sulphur source (MOPS, SDS, DMSO). The OD₆₀₀ of the cultures after 8 days at 30 °C is shown. Individual observations are plotted, and the median is indicated by the horizontal bars. The box represents the range of data. For each condition, 3 biological replicates were tested (n = 3), except for L. elongisporus CBS2605 and C. parapsilosis CLIB214, met4Δ and met28Δ in the absence of sulphur, in which 6 biological replicates were tested (n = 6). Detailed information on the mean and standard deviation is available in the Source Data file. One Way ANOVA and Tukey HSD test (F = 222, degrees of freedom = 29) were used for statistical analysis. ns = not significant, ****P ≤ 0.0001. The exact P-values are provided in the Source Data file. L. elongisporus CBS2605 was included as positive control⁶¹. A C. parapsilosis CLIB214 can use both inorganic and organic sulphur sources. Whereas either Met4 or Met28 can sustain growth on inorganic sulphur (AS), Met4 is required for assimilating the organosulfur compounds tested, as shown by the fact that deleting this gene prevented growth on MOPS, SDS, and DMSO. Restoring the wildtype sequence in a met4-disrupted strain recovered this ability (cMET4). B Growth in the absence of cysteine or methionine confirmed that the transcription factor Met32 is not required for the synthesis of sulphur-containing amino acids. However, this protein – like Met4 – is also required for assimilating organic sulphur, as disruption of MET32 specifically abolished growth in media containing organosulfur compounds. Source data (uncropped photographs) are provided as a Source Data file.