Sulfur Oxidizing Bacterial Broth

This particular media was designed to detect the presence of a group of bacteria that is able to oxidize sulfur, or reduced forms of sulfur, and produce sulfuric acid that has the potential to corrode metallic and concrete structures. It is aerobic and slightly purple in color with few white salt precipitants at the bottom. This media will turn grey, green and finally yellow in the presence of sulfur-oxidizing bacteria with no change in turbidity. The amount of white or yellow salts can also increase at the bottom due to the presence of sulfur oxidizing bacteria.  This media is very acidic in nature, which makes it very specific for the right kind of bacteria that could take up to four weeks to show a positive reaction depending on salt content and concentration.


 Frequently Asked Questions

1- After I ordered this media I noticed it was slightly turbid and with precipitants at the bottom. Why is this?

SOB media can show light turbidity and precipitants, which are just undissolved salts, due to its very acidic nature. Before performing a serial dilution, it is recommended to keep one vial as a negative control and as a point of reference for any positive reaction other vials might show.  Remember, the color change is the main way to determine the presence or absence of sulfur oxidizing bacteria.

2-I understand that these bacteria can take some time to grow. Is there something I can do to help their growth rate?

Incubating it at the right temperature (28°C to 32°C) and inoculating extra amounts of air (1mL) every other day can potentially help most species of sulfur-oxidizing bacteria.

3-Will this media turn different colors in the presence of contaminants?

No, most common contaminants won’t grow in this media because its acidic nature prevents it. However, it could turn dark purple or even blue if an inoculated liquid sample has a basic pH.

4- What could be considered as signs of sulfur oxidizing bacteria in my system?

The main sign is a very low pH in your system due to a high concentration of sulfuric acid. If your environment or system is constantly being exposed to sulfur or hydrogen sulfide, there is a chance that these microorganisms are present in your system.

5-I haven’t heard about these bacteria in the oil and gas industry, why?

Despite the fact that these bacteria are not one of the most common agents for MIC, they are starting to show relevance in structures that are exposed to acidic waters, particularly in the mining industry and off shore facilities.

6-How should I store this media?

The best way to store this media is under refrigeration at approximately 4°C. However, it can be stored at room temperature (25°C), in a well-ventilated area with no direct contact to sunlight. It is a very stable media and it can last up to 6 months if store under proper conditions. The best indicator that the media has expired is a drastic change in its color from light purple to almost transparent.

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