A review of: Yu, V. C., Yu, P. H., Ho, K., and Lee, F. W. (2011) Isolation and Identification of a New Tetrodotoxin-Producing Bacterial Species, Raoultella terrigena, from Hong Kong Marine Puffer Fish Takifugu niphobles. Marine Drugs 9: 2384-2396
Tetrodotoxin (TTX) is one of the most lethal neurotoxins presently known and is familiarly associated with the puffer fish, having been extensively studied in these organisms. Previous research on TTX toxicity has found that puffer fish, grown in closed water systems, are found to be non-toxic but when exposed to open water, become toxic, suggesting that TTX toxicity is the result of microbial colonisation or accumulation. The site of accumulation differs among the (at least) 60 species of puffer fish indigenous to the China Sea, but is most common in the ovaries, liver and intestine.
This study reports the discovery of a new tetrodotoxin producing bacterial species, Raoultella terrigena isolated from the intestines of the pufferfish, Takifugu niphobles. Vibrio were the first reported TTX producing bacterial strain but since then, many new strains have been revealed and identified, in fact, over at least 10 different TTX producing bacterial strains have come to light, in the puffer fish alone, over the last 20 years. The puffer fish is not the only organism that contains TTX producing bacterial strains. It has also been found in starfish, the xanthid crab and in gastropods, among others.
In this study, five bacterial strains were isolated from the intestine of Takifugu niphobles and their toxicity analysed. The methods used to do this included ELISA and mass spectrometry to identify strains with toxicity and determine the presence of TTX. MIDI analysis looked at a match of fatty acid profiles and a BLAST search matched 16S-23S rDNA for microbial identification.
The results of this showed that one of the five strains analysed showed the ability to produce toxin and the mass spectrometry matched the toxin of that strain with the molecular mass of TTX, confirming that the toxin was indeed TTX. The MIDI and BLAST analyses found that the toxin-producing isolated strain fell into the genus Raoultella and was closest matched to Raoultella terrigena, therefore identifying the strain as thus. This is the first time that this bacterial strain has been isolated in the puffer fish.
Whist this paper effectively fulfils the aims of describing the newly discovered TTX-producing bacterial strain and clearly outlining how it was identified, incidentally making the study straightforward to replicate, it doesn’t look into the mechanisms of TTX production in that strain, its synthesis or its role in the toxin production. All of these points would be interesting for further study.
4 comments:
Hi Rachel,
Very interesting post. I recall Colin saying they in a lecture that there was still much uncertainty as to the source of the toxin, but it sounds like they have identified it, at least for one species of puffer fish.
You mentioned that Vibrios were initially postulated as the producers of the toxin. Was this based on previous investigations or was it a hypothesis? I wonder if the TTX gene is plasmid encoded and horizontally transferred t other species of bacteria, and consequently to other host species like the starfish, crab and gastropods you mentioned.
Yes I found TTX interesting, It could also by transferred via transduction. I wonder if new strains are spreading, if resistance to toxins can occur. I also would be intrigued to know if there are nay antidotes in circulation.....
Hey Rachel, Nice post. I know that a lot of bacteria have been identified as producers but one paper I read was talking about the specific areas where TTX is concentrated in organisms (like the liver, ovaries, skin)and how PCR analysis had found no bacterial presence or limited presence to account for the concentrations found. This I guess makes it hard to explain and identify the exact cause for TTX production in each organism.
http://www.sciencedirect.com/science/article/pii/S0041010104002296
Corin- There are currently no antidotes in circulation for this toxin, making it all the more dangerous. The only predatory organisms recorded (as far as I am aware)to be resistant to the toxin is the garter snake. In severe cases the only things hospitals can do it put people on respirators to breath for them in case the their heart stops and I guess wait for the effects of TTX to wear off. I've also read that apparently the heart is the only muscle which is resistant to the effects of the Na+ blocking which TTX incurs.
http://www.springerlink.com/content/p445m58x53816200/
Mario - The statement regarding Vibrios as producers of the TTX toxin was based on previous research. A study published in 2000 found a Vibrio strain, isolated from the highly toxic puffer fish, Fugu vermicularis radiatus, produced tetrodotoxin. Vibrio fisheri from the xanthid crab (Atergatis floridus) and Vibrio alginolyticus from the puffer fish, Fugu vermicularis vermicularis, have also been found to produce TTX.
Reference: Lee, M., Jeong, D., Kim, W., Kim, H., Kim, C., Park, W., Park, Y., Kim, K., Kim, H., and Kim, D. (2000) A Tetrodotoxin-Producing Vibrio Strain, LM-1, from the Puffer Fish Fugu vermicularis radiatus. Appl Environ Microbiol. 66(4): 1698–1701.
Post a Comment