Characterization of cyanobacterial blooms using metagenomic analysis and microbial ecology

FAINSTEIN, LOLA; ALVAREZ DALINGER, FLORENCIA SOLEDAD; POSSE, ALBA; MACCHIAROLI, NATALIA; KAMENETZKY, LAURA; LOZANO, VERÓNICA LAURA; FIGUEROLA, EVA; GASULLA, JAVIER

Rosario, Santa Fe

Congreso; Congreso de la Sociedad Argentina de Investigaciones en bioquímica y biología molecular (SAIB); 2023

Sociedad Argentina de Investigaciones en bioquímica y biología molecular (SAIB)

Cyanobacterial blooms constitute a global problem, affecting the water quality and producingeconomical losses, along with concerns about their impact on public and environmental health.Their frequency is increasing, boosted by high nutrient load provided by agricultural, industrial anddomestic pollution coupled with global warming. Cyanobacteria are photosynthetic organismsnaturally present in surface water. However, the massive growth affects the whole community ofmicro and macroorganisms. Additionally, on cyanobacterial harmful blooms (CyanoHABs), a widevariety of cyanotoxins are produced by several genera of cyanobacteria, entailing a risk for humanand animal life. Not all the blooms are toxin-producers, abiotic factors conditioning CyanoHABshave been widely studied, but biotic factors, like the biotic interactions, and ecosystem diversityand stability have received less attention. Despite the fact that both diversity and interspecificinteractions are considered to be determining factors of ecosystem stability and that the toxicityprimarily depends on their composition of toxic and non-toxic genotypes. Hepatotoxins of themicrocystins family are by far the most reported cyanotoxins found in CyanoHABs of our country.Nevertheless, recent studies indicated the presence of cyanobacteria capable of producingneurotoxins (saxitoxin and anatoxin), and cytotoxins (cylindrospermopsin).In this project we propose to apply a metagenomic approach focused on two objectives: 1. Theconstruction of co-occurrence networks for a set of freshwater bodies affected by CyanoHABs. Tothis end, we started a year-long campaign last fall on 7 water bodies; including rivers, lagoons, anddams from 5 provinces. To date, we have collected 30 water samples from 12 sampling points andtheir metadata. The samples were filtered and processed to obtain high quality DNA suitable to besequenced. The structure of these networks will give us insights about biotic interactions, andrelationships with physico-chemical factors and stability. 2. Identify toxin biosynthesis gene clustersthat could guide toxin monitoring programs. We have performed long read (ONT) sequencing ofthe metagenome of a sample from El Limón dam (Salta), that provides water supplies to the city ofTartagal. The sequencing produced 7.3M of reads, accounting for 6.1Gb with an average quality of18.9. Preliminary analysis showed the presence of Microcystis, Raphidiopsis raciborskii andPlanktothrix in accordance with microscopy observation. Also, the presence of mycD, critical stepin the biosynthesis of microcystins.The information obtained to date indicates that the proposed metagenomic approach is useful tothe detection of toxigenic strains and the identificación of the cyanotoxin biosynthesis genes. Theanalysis of the complete set of samples will give valuable insights to the understanding of the bioticmechanisms that regulate cyanoHABs and will help the development of monitoring programmes.