Paralytic Shellfish Toxins can be Degraded by Bacteria found in Blue Mussels

Pseudoalteromonas, a genus of bacteria found in the toxic blue mussel, has the ability to almost completely degrade (≥90%) Paralytic Shellfish Toxins (PST). PST is a condition that arises from consuming shellfish that have been rendered poisonous due to toxins produced by marine algae, plankton and other forms of marine life.  There were 7 species of bacteria in the genus Pseudoalteromonas isolated from toxic blue mussels which could degrade and detoxify PST efficiently. Though the exact mechanism of degradation is not fully understood, several tests indicated that the PST completely degraded instead of just transforming into an innocuous form (Donovan, et al). The 7 bacteria involved for the test showed over a 90% elimination of the PST in only 5 days. The efficiency of the bacteria could have implications in medicine, such as in providing a new medicine against PST or eliminating PST from the shellfish in the environment. However, more research will need to be conducted in order to understand the exact mechanism of degrading PST by Pseudoalteromonas.— Kevon White
Donovan, C., Garduño, R., Kalmokoff, M., Ku, J., Quilliam, M., Gill, A., 2009. Pseudoalteromonas Bacteria Are Capable of Degrading Paralytic Shellfish Toxins.  Applied and Environmental Microbiology 75, 6919–6923.

 Carrie J. Donovan and colleagues from Dalhousie University first collected toxic blue mussels from the Canadian Food Inspection Agency off the Atlantic Coast of Canada near Nova Scotia. Sixty-nine distinct bacteria were isolated from the digestive glands of the toxic blue mussels and separated into two types, clear and opaque, of nutritional marine 2216 agar plates. The 69 bacterial isolates were then tested with 600 µl of marine broth 2216, 100 µl of toxic algae Alexandrium tamarense extract, and 300 µl of toxic blue mussel extract. A control was made with 100 µl sterile water instead of algae extract. The bacteria were inoculated by centrifuge, and then allowed to incubate at 25 °C in a shaking incubator.  Samples from the starting day to the fifth day were analyzed using high-performance liquid chromatography (HPLC). The samples were then injected in live mice to determine the effectiveness of the detoxification. Gene sequencing, RNA tests, electron microscopy, biochemical tests, and physiological tests were all employed to determine the morphological characteristics of the bacteria.
     Of the 69 isolated bacteria found in the digestive systems of the blue mussel, only one-third of them were found to have a detoxifying effect on PST. Out of that third, only seven—all in the genus Pseudoalteromonas—were found to quickly and effectively remove PST and they eliminated over 90% of it, ranging from 92.28–98.51%. The bacteria did not grow on pure agar plates, possibly indicating that the PST is cometabilized by the bacteria and completely degraded. The exact method of PST’s elimination is not well known but it occurred in both oxygen rich and aerobic environments.   Rats injected with a lethal dose of toxin died in just seven minutes whereas rats that were given any of the seven bacteria lived for at least an hour.  One useful possibility might be to use the bacteria to eliminate biotoxins in shellfish before they are consumed. 

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