MIDTAL

MICROARRAYS FOR THE DETECTION OF TOXIC ALGAE

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 Obiettivo del progetto (Objective)

Microalgae in marine and brackish waters of Europe regularly cause «harmful effects», considered from the human perspective, in that they threaten public health and cause economic damage to fisheries and tourism. Cyanobacteria cause similar problems in freshwaters. These episodes encompass a broad range of phenomena collectively referred to as «harmful algal blooms» (HABs). They include discoloration of waters by mass occurrences of microalgae (true algal blooms that may or may not be «harmful») to toxin-producing species that may be harmful even in low cell concentrations. A broad classification of HAB distinguishes three groups of toxic organisms. For adequate management of these phenomena, monitoring of microalgae is required. However, the effectiveness of monitoring programmes is limited by the fact that it is time consuming and morphology as determined by light microscopy may be insufficient to give definitive species and toxin attribution. Once cell numbers reach a threshold level, then shellfish are selected to toxin analysis by the mouse bioassay. The mouse bioassay is continued on a daily basis until no more toxin is detected. Molecular and biochemical methods are now available that offer rapid means of both species and toxin detection. In this project we will target rapid species identification using rRNA genes as the target. We include antibodies to specific toxins because even when cell numbers are very low, the toxins can be present and can be accumulated in the shellfish. Microarrays are the state of the art technology in molecular biology for the processing of bulk samples for detection of target RNA/DNA sequences.. The purpose of MIDTAL is to support the common fisheries policy to aid the national monitoring agencies by providing new rapid tools for the identification of toxic algae and their toxins so that they can comply with ECC directive 91/1491/CEE that can be converted to cell numbers and reduce the need for the mouse bioassay.

Introduzione (Teaser)

Algae are an essential part of marine ecosystems. However, their aberrant accumulation may have toxic consequences due to alterations in the chemical composition of marine waters.

Descrizione progetto (Article)

Blooms of toxic or harmful microalgae, commonly referred to as HABs, represent a significant threat to fisheries resources and human health throughout the world. This necessitates the continuous monitoring of this phenomenon to avoid the potential health dangers and economic impacts of contaminated seafood.

Traditionally, phytoplankton monitoring is carried out by identification and enumeration using light microscopy. However, this method, apart from being time consuming, is prone to error due to the phenotypic similarity among various algal species. To distinguish among different species in complex samples, various DNA-based methods such as fluorescent in situ hybridisation (FISH) have been developed.

The EU-funded 'Microarrays for the detection of toxic algae' (MIDTAL) project proposed to develop a universal microarray to test bulk water samples for toxic algal species and their toxins. This method would speed up the laborious identification of individual species.

Following extensive optimisation, MIDTAL partners developed an array with 163 probes covering all the major harmful algal species of current interest in the EU. The array was validated using traditional PCR for specific species and microscopy-based cell counts which showed reasonable agreement. The so called phylochip was considered to be more accurate in cases of small flagellate cells and Pseudo-nitzschia species, which are particularly difficult to quantify by light microscopy.

A further aspect of MIDTAL's work involved the detection of main algae-producing toxins by the use of antibodies on a microarray format. Although not as sensitive as the ELISA, this chip could be utilised in samples of significant toxicity.

Given the importance of toxin-producing algae for human health, directly or through the consumption of contaminated seafood, MIDTAL deliverables will aid the monitoring and prompt identification of toxic species. The high-throughput nature of the proposed method will significantly speed up the whole process, allowing for proper anti-contamination measures to be taken promptly.