Anatoxin-producing and non-toxic strains of Microcoleus sp. coexist in benthic cyanobacterial mats in the Wolastoq (Saint John River, Canada)
Start Date
25-5-2022 11:00 AM
End Date
25-5-2022 11:15 AM
Abstract
The presence of toxigenic benthic cyanobacteria in riverine ecosystems is an increasing concern around the world. In 2018, the death of three dogs along the Wolastoq in New Brunswick, Canada, was attributed to anatoxin exposure after they ingested benthic microbial mats found along the shore. Four samples of the material ingested by the dogs and from the vicinity were collected. Then, 15 non-axenic cyanobacterial isolates were obtained from the same material. Total DNA of the 19 samples was sequenced using Illumina technology. Metagenomic assemblies recovered near-complete Microcoleus genomes from 12 of the sequenced samples. The high average genomic sequence similarity (>95% identity at the nucleotide level) suggests that the 12 genomes are representatives of the same “genomic” Microcoleus species. The genetic repertoire to produce anatoxin-a and dihydroanatoxin-a was identified in 9 of these genomes. The capacity for anatoxin production was confirmed by LC-MS. The overall comparison revealed that genomes of the 9 toxigenic Microcoleus isolates contain a higher number of accessory genes than their 3 non-toxigenic relatives. These differences suggest that toxigenic Microcoleus variants from the Wolastoq would be more responsive to changing environments, nutrient limitation and/or bacteriophage infection. Our results suggest that the two Microcoleus strains inhabited the original benthic mats in similar relative abundances.
Anatoxin-producing and non-toxic strains of Microcoleus sp. coexist in benthic cyanobacterial mats in the Wolastoq (Saint John River, Canada)
The presence of toxigenic benthic cyanobacteria in riverine ecosystems is an increasing concern around the world. In 2018, the death of three dogs along the Wolastoq in New Brunswick, Canada, was attributed to anatoxin exposure after they ingested benthic microbial mats found along the shore. Four samples of the material ingested by the dogs and from the vicinity were collected. Then, 15 non-axenic cyanobacterial isolates were obtained from the same material. Total DNA of the 19 samples was sequenced using Illumina technology. Metagenomic assemblies recovered near-complete Microcoleus genomes from 12 of the sequenced samples. The high average genomic sequence similarity (>95% identity at the nucleotide level) suggests that the 12 genomes are representatives of the same “genomic” Microcoleus species. The genetic repertoire to produce anatoxin-a and dihydroanatoxin-a was identified in 9 of these genomes. The capacity for anatoxin production was confirmed by LC-MS. The overall comparison revealed that genomes of the 9 toxigenic Microcoleus isolates contain a higher number of accessory genes than their 3 non-toxigenic relatives. These differences suggest that toxigenic Microcoleus variants from the Wolastoq would be more responsive to changing environments, nutrient limitation and/or bacteriophage infection. Our results suggest that the two Microcoleus strains inhabited the original benthic mats in similar relative abundances.