The First Data on the Complete Genome of a Tetrodotoxin-Producing Bacterium

Tetrodotoxin (TTX)-producing bacteria have attracted great interest as a model system for study of the TTX biosynthetic route. Here, we report the complete genome of the TTX-producing bacterium Bacillus sp. 1839. The genome of the strain Bacillus sp. 1839, previously isolated from the TTX-bearing marine ribbon worm Cephalothrix cf. simula, was obtained using second generation Illumina and third generation nanopore sequencing technologies. Phylogenetic analysis has classified this strain as Cytobacillus gottheilii.

The Microbial Community of Tetrodotoxin-Bearing and Non-Tetrodotoxin-Bearing Ribbon Worms (Nemertea) from the Sea of Japan

A potent marine toxin, tetrodotoxin (TTX), found in a great variety of marine and some terrestrial species, leaves intriguing questions about its origin and distribution in marine ecosystems. TTX-producing bacteria were found in the cultivable microflora of many TTX-bearing hosts, thereby providing strong support for the hypothesis that the toxin is of bacterial origin in these species. However, metagenomic studies of TTX-bearing animals addressing the whole microbial composition and estimating the contribution of TTX-producing bacteria to the overall toxicity of the host were not conducted. The present study is the first to characterize and compare the 16S rRNA gene data obtained from four TTX-bearing and four non-TTX-bearing species of marine ribbon worms. The statistical analysis showed that different nemertean species harbor distinct bacterial communities, while members of the same species mostly share more similar microbiomes. The bacterial species historically associated with TTX production were found in all studied samples but predominated in TTX-bearing nemertean species. This suggests that deeper knowledge of the microbiome of TTX-bearing animals is a key to understanding the origin of TTX in marine ecosystems.

Stable Tetrodotoxin Production by Bacillus sp. Strain 1839

For the first time, tetrodotoxin (TTX) was detected in a bacterial strain after five years of cultivation in laboratory conditions since its isolation from the animal host. A reliable method suitable for bacterial samples, high-performance liquid chromatography with tandem mass spectrometry, was used for toxin detection in spore and vegetative cultures of Bacillus sp. 1839. TTX was detected in a spore culture of the strain.

Tetrodotoxin-Producing Bacteria: Detection, Distribution and Migration of the Toxin in Aquatic Systems

This review is devoted to the marine bacterial producers of tetrodotoxin (TTX), a potent non-protein neuroparalytic toxin. In addition to the issues of the ecology and distribution of TTX-producing bacteria, this review examines issues relating to toxin migration from bacteria to TTX-bearing animals. It is shown that the mechanism of TTX extraction from toxin-producing bacteria to the environment occur through cell death, passive/active toxin excretion, or spore germination of spore-forming bacteria. Data on TTX microdistribution in toxic organs of TTX-bearing animals indicate toxin migration from the digestive system to target organs through the transport system of the organism. The role of symbiotic microflora in animal toxicity is also discussed: despite low toxin production by bacterial strains in laboratory conditions, even minimal amounts of TTX produced by intestinal microflora of an animal can contribute to its toxicity. Special attention is paid to methods of TTX detection applicable to bacteria. Due to the complexity of toxin detection in TTX-producing bacteria, it is necessary to use several methods based on different methodological approaches. Issues crucial for further progress in detecting natural sources of TTX investigation are also considered.

Identification of tetrodotoxin-producing bacteria from goby Yongeichthys criniger

Toxic goby fish (Yongeichthys criniger) containing tetrodotoxin (TTX), from Zhanjiang, Guangdong province, China, were screened for TTX-producing bacteria. Two toxic bacterial strains were isolated from the liver of Y. criniger and respectively denoted XC3-3 and XL-1. TTX production by the strains was confirmed by mouse bioassay, enzyme-linked immunosorbent assay and high performance liquid chromatography coupled with mass spectrometry. Based on morphological, physiological and biochemical characteristics and 16S rDNA phylogenetic analysis, strain XC3-3 was identified as Enterobacter cloaca and XL-1 was closely related to Rahnella aquatilis. These findings show for the first time that TTX-producing bacteria are symbiotic bacteria in goby and suggest that bacterial strains are at least partially responsible for TTX accumulation in Y. criniger.

Production level of tetrodotoxin in Aeromonas is associated with the copy number of a plasmid

Tetrodotoxin (TTX) has been identified from taxonomically diverse organisms. Artificial synthesis of TTX has been reported, but the biosynthetic pathway of TTX remains elusive. In this study, we found TTX producing ability was associated with the copy number of plasmid pNe-1 in Aeromonas strain Ne-1 during fermentation, suggesting that at least one gene encoding a TTX-synthesis enzyme is located on this plasmid. Compared with bacterial genomes, plasmids are small and easier to screen for genes associated with TTX biosynthesis. The approximately 100 kb genome of pNe-1 was sequenced. The plasmid contains 60 complete open reading frames (orfs) of which 32 (53.3%) encode hypothetical proteins. Seven genes are related to the type IV secretion system (T4SS) and 2 genes are related to transposons, indicating that the TTX-producing bacterium Aeromonas might have the ability to transfer the TTX biosynthesis gene via the conjugation and contagion of plasmid pNe-1. In addition, we unexpectedly found that Aeromonas Ne-1 contains unknown TTX-degrading materials, indicating there is a homeostatic mechanism to maintain a stable amount of TTX in the bacterium. These results will help us to better understand TTX biosynthesis, the bacterial origin of TTX, and TTX degradation.

Isolation and identification of a new tetrodotoxin-producing bacterial species, Raoultella terrigena, from Hong Kong marine puffer fish Takifugu niphobles

Puffer fish, Takifugu niphobles, collected from the Hong Kong coastal waters were screened for tetrodotoxin-producing bacteria. A Gram-negative, non-acid-fast, non-sporing and rod shaped bacterial strain (designated as gutB01) was isolated from the intestine of the puffer fish and was shown to produce tetrodotoxin (TTX). Based on the Microbial Identification (MIDI) and 16S-23S rDNA internal transcribed spacer (ITS) phylogenetic analysis, the strain was identified as Raoultella terrigena. The TTX production ability of the strain was confirmed by mouse bioassay, ELISA and mass spectrometry (MALDI-TOF). Our results reiterate that the TTX found in puffer fish was likely produced by the associated bacteria and TTX are widely produced amongst a diversity of bacterial species.