Development of a rRNA-Biosensor for the Detection of Toxic Algae (EU Project ALGADEC)

Toxin-producing microalgae have been responsible for great environmental, economic and public health catastrophes throughout history.
These episodes encompass a broad range of phenomena collectively referred to as «harmful algal blooms» (HAB).

 
They include discoloration of waters by mass occurrences of microalgae (true algal blooms that may or may not be «harmful»), toxin-producing species (toxic «blooms» that may be harmful even in low cell concentrations), and several organisms, which are protists but normally referred to as algae. Harmful Algal Blooms (HAB) affect the marine ecosystems in several ways leading to economical losses and/or health problems for humans. They also cause structural changes in the natural food webs that may be indirectly linked to human well being.
 

These “Harmful Algal Blooms” are known to cause a wide range of detrimental effects such as:

• nervous and digestive disturbances through contaminated seafood, which can even lead to death
• physical impairment of fish and shellfish
• cutaneous damage in swimmers
• degradation of habitats

Moreover, these direct effects of toxic algae have important economic impacts for instance in fishing, fish farming and tourism. In the last decades the problem has turned more and more critical, because alteration of ecological systems as a consequence of human activity seems to enhance proliferation of toxin-producing algae. A concentration of only a few cells per litre of some microalgae may produce harmful toxic effects.

Molecular biological tools have, however, greatly enhanced our ability to identify species, to determine the expression of genes regulating key cellular processes, and to estimate gene flow and distribution of species in time and space. We are only just beginning to see routine and innovative uses of these methodologies as applied to HAB species and their interactions with other members of the community. Ribosomal RNA-gene sequences are especially suited to the design of species-specific probes. There are already some 60 rRNA and antibody probes available for some phytoplankton taxa. These have been applied in the microscopic detection of microalgae.

The EU project ALGADEC aims at developing a biological sensor capable of detecting rapidly and specifically the presence of harmful algal species before a bloom occurs. The in-situ specific recognition of algae’s ribosomal RNA is possible by means of a Sandwich Hybridisation on an electrochemical sensor.

• A species specific DNA-probe is immobilised on the surface of the sensor. This probe is called the capture probe
• Isolated rRNA-strands from the target organism bind to the capture probe
• A second probe that carries a digeoxgenin label binds to the RNA of the target organism captured by the first probe on the sensor
• Application of antibody-enzyme complex
• A substrate is added, a biochemical reaction takes place and electrical current is developed which can be measured by the hand held device
• The amount of bound rRNA to the probes is proportional to the electric current

A multi-probe chip will be designed to obtain tailor made sensors containing the most relevant species for a determined area for ease of use by untrained purchasers.

The device will constitute an adequate device for HABs monitoring. In addition, all developments will be performed aiming at the achievement of a cost-effective device in order to enable fish- and shellfish-farmers to check the toxic algal levels of their waters and thus take the corresponding measures to prevent economic loses and to ensure product safety.

For more information please see also: http://www.algadec.net