Table 1.
Strains used in this study.
Fig 1.
The color development of T. rubrum on Tr1 media depends on the pH.
A-D: T. rubrum strain STRB012 grown on Tr1 medium in a 9 cm split plate. On right side of the plate the pH was adjusted to 3.5 and on the left side to 8.5 A, B: 20 day after inoculation a yellow to beige pigmentation is visible. C, D: 33 days after inoculation. At high pH a strong wine-red pigmentation is visible, whereas on low pH a brownish to beige pigmentation is visible. E-F: The four T. rubrum strains STRB008, STRB012, 193 and 1049 were inoculated on Tr1 medium with pH adjusted to 3.5 (left plate), 6 (middle) and 8.5 (right). E: 20 days after inoculation the first strains have a wine-pigmentation. F: 33 days after inoculation all strains have a wine-red pigmentation at high pH, whereas all strains stay whitish to beige under acid conditions.
Table 2.
Overview of the pigment color of the T. rubrum grown on two different media for four weeks.
Fig 2.
A: Color change in 800 μl liquid media of strain STRB008. The liquid culture is originally yellow (left tube). After adding 100 μl 10% HCl the medium clears up (middle). By adding 100 μl 1M NaOH the liquid medium turns wine-red (right). B: The color change can be reversed and re-reversed by adding alternately acid or alkaline. The original liquid medium of strains STRB012 is wine-red (left tube). After adding 0.5 ml of 10% HCl the color changes to yellow (middle). By adding 1.5 ml 1M KOH the color change can be reversed to wine-red (right). C-H: Liquid cultures of strain STRB012 over a period of 4 weeks. The pH was adjusted to 3.5 (left flask), 6 (middle) or 8 (right). C: One day after inoculation the culture liquid is transparent with a slight yellow coloration. D: One week after inoculation the pH 6 trial has the highest growth rate, followed by the one of pH 8. Only minor changes of the culture liquid are visible. F: After two weeks of inoculation a yellow coloration had develops in the pH 6 trial. G: After 3 weeks the liquid of the pH 3.5 trial is transparent, reddish in the pH 6 and yellowish at the pH 8 trial. After 4 weeks the culture liquid of the pH 6 and 8 trial is reddish. I, J: Comparison of the culture liquid of strain STRB012 with culture liquid after adding 200μl 0.2M NaOH. I: Comparison of culture liquid 3 weeks after inoculation. From left to right: pH 3.5 trial, pH 3.5 with NaOH, pH 6 trial, pH 6 trial with NaOH, pH 8 trial and pH 8 trial with NaOH. An obvious color change to red is seen only in the pH 6 trial. J: Comparison 4 weeks after inoculation. A weak color change is observed in the pH 3.5 trial and an obvious change is seen in the pH 6 and 8 trial.
Fig 3.
Change of the pH induced by T. rubrum observed over an period of 4 weeks.
Before inoculation of the fungus, the pH was adjusted to 3.5, 6 or 8 and the pH was measured every second day. Each combination of fungal strain and pH has been performed in triplicate. A: T. rubrum strain STRB012 in Tr1 liquid medium. B: T. rubrum strain STRB008 in Tr1 liquid medium. C: T. rubrum strain STRB012 in SC medium.
Fig 4.
Chemical structures of Xanthomegnin (PubChem CID: 3032411), Viopurpurin (#73759973) and Vioxanthin (#119072), the three main pigments of T. rubrum.
These compounds give T. rubrum the characteristic red pigmentation. They are belong to the family of 1,4-naphthoquinone and are synthesized from polyketides. The structural data of Xanthomegnin (PubChem CID: 3032411), Viopurpurin (#73759973) and Vioxanthin (#119072) were downloaded from NCBI PubChem database as xml file. Afterwards the files were converted with the Linux Babel software to pdb files, converted with Gnome GChemPaint software to a svg vector graphic and arranged with GNU program Inkscape.
Table 3.
Comparison of the three main pigments of T. rubrum.