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ResearchBlogging.orgFor some reason, I’ve a real hankering for Japanese food at the moment. I’ve no idea why – perhaps it’s due to me going through some old photos from when I toured across the country visiting labs about ten years ago. In one of them, I’m standing underneath a large fibreglass puffer fish outside a restaurant (no, I’m not going to post it).

Puffer fish, in case you didn’t know, is quite the delicacy in many parts of Asia. In Japan, it’s known as fugu. I didn’t eat any, though. Why not? Well, the fish is one of the most poisonous animals in the world. It must be skilfully prepared, or it’s potentially lethal: a slight tingling of the lips, and it’s goodnight. Deaths are rare nowadays, but I didn’t want to take the risk. I try to avoid eating anything that might kill me (although I did once – and only once – eat a kebab).

The root of the problem is tetrodotoxin (TTX), a lethal neurotoxin found in many animals. It currently has no known antidote. The animals themselves are not poisonous; the TTX is probably produced by symbiotic bacteria that live within them. Indeed, if you grow a puffer fish in an enclosed water system, it contains no TTX. Release it into open water, or feed it toxic puffer fish liver, and it becomes poisonous. Numerous different TTX-producing species have been identified, including those from the Pseudomonas, Vibrio and Actinomyces.

I found a paper last week in Marine Drugs in which a group of researchers have isolated a species of bacteria not previously known to produce TTX from within the intestines of the Hong Kong marine puffer fish Takifugu niphobles. This species was identified as Raoultella terrigena, a Gram-negative, rod-shaped bacterium.

Five bacterial strains were successfully isolated from the fish’s intestines, but only one was able to produce any toxic effects. The presence of TTX was confirmed by mass spectrometry. The identity of the strain was suggested initially by comparing its membrane fatty acid profile to other species on record and confirmed by ribosomal DNA sequence comparison.

The authors of the paper stress that although a TTX-producing species of bacteria was found within a puffer fish, there is no direct proof that it’s the bacteria making the fish poisonous, although it seems likely. Given some of the odd symbioses we’ve reported on this blog, it wouldn’t surprise me. I think I’ll stick to puffer fish grown in sterile water for the time being…

Benjamin Thompson

Yu VC, Yu PH, Ho KC, & Lee FW (2011). Isolation and Identification of a New Tetrodotoxin-Producing Bacterial Species, Raoultella terrigena, from Hong Kong Marine Puffer Fish Takifugu niphobles. Marine drugs, 9 (11), 2384-96 PMID: 22163191

Image Credit: Joi on Flickr
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Written by Benjamin Thompson

16/01/2012 at 8:33 pm

One Response

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  1. As a note, deaths are basically unheard of for fugu prepared by a licenced cook. The very few deaths that do occur are due to dense people who catch a fugu and thinks they know how to prepare it just by following pictures in a book, advice from their cousin who once worked as waiter in a fugu restaurant or something like that. When you consider that it’s not a rare treat around here — fugu is sold in every fishmonger and with fugu restaurants in most neighbourhoods — the real risk is probably smaller than for eating buffet food or Korean barbecue.

    The most dangerous food in Japan? Mochi, small blocks of sticky rice cakes. It’s good, but really very sticky, and every year you have old people especially choking on the mochi in their soup. of course, chewy rice doesn’t have the dramatic flair of deadly poisonous fish so mochi gets off scot free while fugu gets the bum rap.

    Janne

    22/01/2012 at 1:06 am


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