Posted 25 April 2012 - 12:20 AM
I want to isolate thiobacillus species from soil. I need to add elemental sulfur to culture media but it is not soluble.what can I do?
Posted 13 June 2012 - 12:01 AM
Elemental sulfur won't solubilize, but in these media it is not expected to happen... as note from DSMZ:
Note: Elemental sulfur melts and then aggregates during autoclaving at 121 °C thereby
making it unusable by microorganisms. Hence, it is important to sterilize the sulfur
powder separately from the liquid medium. This can be achieved by filling screw cap
tubes (18 x 100 mm, borosilicate glass) with sulfur powder (approx. 2/3 volume) to which
1 or 2 drops of distilled water is added. The screw cap should not be tightly closed. The
tubes are heated in a water bath to 90-100 °C for 3 hours on each of 3 successive days.
The sterilized sulfur can be stored at room temperature in the dark for several months.
They state that the sulfur remains at the liquid-air-interface in freshly prepared sterile medium while as a result of growth most of the sulfur gets coated by bacteria and sinks to the bottom of the tube.
To use thiosulfate, you have to use relatively high pH media, around 4.4, because it is not stable at low pH.