We carry out ecotoxicity testing using our multispecies, microbial ecotoxicity tests MARA and LumiMARA. These bioassays include strains from marine, freshwater and terrestrial environments to provide a more genetically diverse alternative to single species bacterial tests. They provide a rapid and reliable analysis of toxicity.
Bacteria are good candidates for ecotoxicity testing because of a number of factors, including their small size, their rapid growth rate and their ease of handling. The use of bacterial bioassays to assess toxicity is well established, and single species bacterial tests are commonly used across a broad range of industry and environmental applications as they are convenient to use, and give rapid results.
The best known tests make use of the naturally luminescent bacteria Aliivibrio fischeri (previously known as Vibrio fischeri). These tests are based on the fact that exposure to toxins disrupts the bacteria's respiratory processes, which in turn results in a reduction in light output. Reduction in light output is an easily measurable response that can be used to assess the acute toxicity of samples.
MARA and LumiMARA: multispecies microbial ecotoxicity tests
NCIMB's MARA and LumiMARA bioassays make use of the genetic diversity of microbes and the ease with which they can be handled, to take the concept of the microbial bioassay a step beyond single species testing.
Single species bacterial testing is generally based around assessment of the acute toxicity response of a single marine species. In contrast, testing using both MARA and LumiMARA gives a measure of acute and chronic toxicity, encompasing marine, freshwater and terrestrial species of bacteria in addition to a yeast.
MARA: for assessment of chronic toxicity
The MARA test assesses toxicity by measuring the growth of ten bacterial species and one yeast, following 18 hours of incubation in the presence of a concentration gradient of the test sample.
As MARA measures impact on growth after a period of incubation, rather than the immediate effect of exposure to the sample on respiratory processes, it gives an indication of chronic toxicity.
LumiMARA: for assessment of acute toxicity
LumiMARA assesses toxicity on the basis of the reduction in luminescence of 11 species of bacteria following exposure to a concentration gradient of the test sample.
The test includes nine marine and two fresh water species from a variety of habitats and, similarly to single species tests that use Aliivirio fischeri, gives a measure of acute toxicity of the sample tested.
Benefits of MARA and LumiMARA for ecotoxicity testing
- Using MARA and LumiMARA as an alternative to single-species bacterial testing is a very simple means of increasing the breadth and genetic diversity of ecotoxicity testing, whilst retaining other benefits of using a microbial test.
- Each strain within the MARA and LumiMARA test can respond differently to toxins present in a sample, and this creates a unique profile or "fingerprint" for each sample, which can be used to assess changes in toxicity over time or between locations.