Inhibitory effect of thiourea derivatives on the growth of blue-green algae

Microcystin-LR induces histopathological injury and cell apoptosis in the hepatopancreas of white shrimp, Litopenaeus vannamei

Microcystin-LR (MC-LR), a common hepatotoxin produced by bloom-forming cyanobacteria, presents a serious threat to the health of aquatic animals. In this study, we studied the impact of MC-LR on hepatopancreas histopathology, enzyme activity, transcriptome, and apoptosis of Litopenaeus vannamei. Thus, shrimp postlarvae (1.63 ± 0.5 g) exposed to MC-LR at 500 μg/kg caused morphological lesions in the histology of the shrimp hepatopancreas, which exhibited swollen, lighter coloration and unclear edges. Moreover, MC-LR significantly altered the hepatopancreas enzyme activities such as the levels of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), acid phosphatase (ACP), alkaline phosphatase (AKP) and lysozyme (LZM), including the state of apoptosis in hepatopancreas. From the RNA-seq analysis of the hepatopancreas, a total of 728 differentially expressed genes (DEGs) were identified, and their functions in MC-LR treatment group were involved in cellular processes, metabolic processes, biological regulation, cellular components, catalytic activity and binding. The metabolic pathways primarily associated with the DEGs included reactive oxygen species, glycerophospholipid metabolism and the phospholipase D signaling pathway. Overall, q-PCR results indicated that MC-LR led to significant changes in multiple apoptosis genes of shrimp hepatopancreas. This study expand the understanding of the effect of microcystin-LR on commercially farmed crustaceans.

Snapshot of cyanobacterial toxins in Pakistani freshwater bodies

Cyanobacteria are known to produce diverse secondary metabolites that are toxic to aquatic ecosystems and human health. However, data about the cyanotoxins occurrence and cyanobacterial diversity in Pakistan's drinking water reservoirs is scarce. In this study, we first investigated the presence of microcystin, saxitoxin, and anatoxin in 12 water bodies using an enzyme-linked immunosorbent assay (ELISA). The observed cyanotoxin values for the risk quotient (RQ) determined by ELISA indicated a potential risk for aquatic life and human health. Based on this result, we made a more in-depth investigation with a subset of water bodies (served as major public water sources) to analyze the cyanotoxins dynamics and identify potential producers. We therefore quantified the distribution of 17 cyanotoxins, including 12 microcystin congeners using a high-performance liquid chromatography-high-resolution tandem mass spectrometry/mass spectrometry (HPLC-HRMS/MS). Our results revealed for the first time the co-occurrence of multiple cyanotoxins and the presence of cylindrospermopsin in an artificial reservoir (Rawal Lake) and a semi-saline lake (Kallar Kahar). We also quantified several microcystin congeners in a river (Panjnad) with MC-LR and MC-RR being the most prevalent and abundant. To identify potential cyanotoxin producers, the composition of the cyanobacterial community was characterized by shotgun metagenomics sequencing. Despite the noticeable presence of cyanotoxins, Cyanobacteria were not abundant. Synechococcus was the most abundant cyanobacterial genus found followed by a small amount of Anabaena, Cyanobium, Microcystis, and Dolichospermum. Moreover, when we looked at the cyanotoxins genes coverage, we never found a complete microcystin mcy operon. To our knowledge, this is the first snapshot sampling of water bodies in Pakistan. Our results would not only help to understand the geographical spread of cyanotoxin in Pakistan but would also help to improve cyanotoxin risk assessment strategies by screening a variety of cyanobacterial toxins and confirming that cyanotoxin quantification is not necessarily related to producer abundance.