Isolation and characterization of bacteria from the copepod Pseudocaligus fugu ectoparasitic on the panther puffer Takifugu pardalis with the emphasis on TTX

A total of 50 bacterial isolates was obtained from the copepod Pseudocaligus fugu, which is a common parasite, collected from the body surface of the panther puffer Takifugu pardalis. On the basis of colony characteristics, these bacterial isolates were grouped into six types, of which only two (Types-I and -II) showed a high affinity for adhesion to the carapace of the banana shrimp Penaeus merguiensis. These two types of adhesive bacteria were identified through 16S rRNA sequence analysis as Shewanella woodyi (Type-I) and Roseobacter sp. (Type-II). Representative isolates of these two adhesive bacteria were examined for tetrodotoxin (TTX) production by high-performance liquid chromatography (HPLC)–fluorometric system, gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry (LC–MS). It was rather unexpectedly revealed that TTX and anhydroTTX were present in the supernatant of culture of the Type-II isolate Roseobacter sp.