D'Agostino, P. | Search bioRxiv

bioRxiv2026

Comparative genomics of Dolichospermum circinale strains with differential paralytic shellfish toxin profiles

The cyanobacterium Dolichospermum circinale is a known producer of the neurotoxin saxitoxin and its analogues, collectively known as the paralytic shellfish toxins (PSTs). PSTs vary in potency, and the reported toxin profiles of D. circinale blooms vary in the quantities of individual PSTs, with the regulation of these profiles being poorly understood. In this study, we present the genomes of four D. circinale strains (ACBU01, ACMB03, ACMB13 and FSS-124) with unique PST profiles and perform genome-wide comparisons and specific analysis of the PST-producing biosynthetic gene cluster (sxt) to understand the variability in PST quotas. A reassessment of the previously published D. circinale AWQC131C genome was also performed to collate genomic variation between all strains. Analysis at the nucleotide and amino acid sequence level revealed that toxic strains maintain high genome-wide similarities, corroborated by the analysis of the pan- and variable genomes of each strain. Specifically, the sxt gene sequences were 99-100% identical across all strains. Novel tailoring (sxtSUL, sxtDIOX) and transport (sxtM4) genes were identified within the sxt cluster that were not reported previously in D. circinale. Taken together, these results indicate that the genetic machinery involved in PST production is conserved in this species, suggesting that the regulation of PST biosynthesis in D. circinale does not occur at the genomic level.

microbiology↗

bioRxiv2019

Effect of oral administration of 1,3-1,6 β-glucans in DWV naturally infected newly emerged bees (Apis mellifera L.)

Honeybee pathogens have an important role in honeybee colony mortality and colony losses, most of them are widely spread and necessitate worldwide solutions to contrast honeybees decline. Possible accepted solutions to cope with the spread of honeybees pathogen are focused on the study of experimental protocols to enhance the insects immune defences. Honeybees artificial diet capable to stimulate the immune system is a promising field of investigation as ascertained by the introduction of 1,3-1,6 {beta}-glucans as a dietary supplement. In this work, by collecting faecal samples of honeybees exposed to different dietary conditions of 1,3-1,6 {beta}-glucans (0.5% and 2% w/w), it has been possible to investigate the DWV viral load kinetic without harming the insects. Virological data obtained by a one-step TaqMan RT-PCR highlights the ability of 1,3-1,6 {beta}-glucans to reduce the viral load at 24th day of rearing. Furthermore, results indicated that the diet supplemented with 1,3-1,6 {beta}-glucans was associated with a dose-dependent activation of phenoloxidase. Control group showed a higher survival rate than honeybees exposed to different dietary conditions of 1,3-1,6 {beta}-glucans while no differences have been observed concerning syrup daily consumption.

microbiology↗