Production of the neurotoxin homoanatoxin-a and detection of a biosynthetic gene cluster sequence (anaC) from an Iranian isolate of Anabaena
Bahareh Nowruzi, Adriana Sturion Lorenzi
Abstract
Lavasan Lake is one of the main water sources for Tehran metropolitan region, besides irrigating 30,000 ha of agricultural land. Cases of animal deaths linked to water ingestion prompted us to study the occurrence of cyanobacteria-related toxic compounds. We investigated the production of microcystins (hepatotoxins) and homoanatoxin-a (neurotoxin) by isolated heterocyst‐forming cyanobacteria using LC-MS and MALDI-TOF mass spectrometry coupled with the detection of biosynthetic gene cluster sequences. The isolates were identified previously by combining morphological analysis and the 16S rRNA gene sequencing. Homoanatoxin-a was detected by LC-MS run at a retention time of 16.3 min, and the protonated molecular ion (m/z 180) was trapped and fragmented by mass spectrometry. The presence of the toxin-producing anaC gene was found in only one Anabaena isolate in agreement with the toxin homoanatoxin-a production. This is the first report of a neurotoxin-producing cyanobacterium isolated from Lavasan Lake.