Toxicity microorganism testing

Rationale. Microorganisms were isolated from soil and screened for toxin production according to the scheme in Figure 1. Some of the organisms causing strong inhibition on solid medium were tested for toxin production in liquid medium. Liquid culture will be required to obtain large amounts of material for commercial production of herbicides, however, the ability to produce toxins on solid medium does not necessarily imply toxin production in broth (34). Cyclo-heximide, a phytotoxic but relatively nonspecific antibiotic with little value as a herbicide, is produced by many actinomycetes. Liquid cultures were tested for cycloheximide to determine whether it caused the observed toxicity. 

ATP measured by luciferin-luciferase BL assay was used to examine the effect of toxic substances on whole microbial communities in activated sludge mixed liquid samples [114], It was used to detect whether wastewater had an effect on the biodegradation capability of the resident population of microorganisms. Actually ATP BL represents an important rapid toxicity test that utilizes waste treatment natural microorganisms to determine the toxicity of wastes discharged to the sewer [132],... 

But the most-used toxicity tests are based on bioluminescence inhibition, the responses of which are sometimes difficult to interpret particularly for waste-water quality monitoring. A comparison between a bioluminescence test kit (Microtox) and a respirometry approach for the toxicity study of seven organic and five inorganic toxic compounds was performed [54]. The bioluminescent response proved to have a higher sensitivity to toxicants but was less representative of the effects on activated sludge compared to respirometry, due to the nature of the microorganisms involved in each procedure. 

Monascus colorants have been consumed for hundreds of years and are believed to be safe for human consumption. Tests with a series of microorganisms have demonstrated no mutagenicity. No toxicity was observed in rodents or in fertile chicken eggs. The yellow pigments have an LD50 for mice of 132mg/20g. No ADI is available.11 There has been some concern that some of the strains produced antibiotics which is obviously undesirable for a food colorant, but it is possible to choose strains of Monascus which do not produce antibiotics. 

It seems that large numbers of chemicals, in equally large numbers of test systems, from mammals to insects, vertebrates to invertebrates, microorganisms to plants, exhibit hormetic dose-response relationships. The relationship is not the same as that described earlier for nutrients, in two ways. First, in the case of hormesis the biological response - the toxicity endpoint - is the same in the protective region and in the region of toxicity (i.e., liver cancer incidence is reduced relative to control incidence over a range of low doses, and then as the NOAEL is exceeded, liver cancer incidence increases above that of controls). This is true hormesis. 

Incubations of heptachlor with a mixed culture of soil microorganisms for 12 weeks showed conversion of heptachlor to chlordene, 1-exohydroxychlordene, heptachlor epoxide, and chlordene epoxide. A mixed culture of soil microorganisms, obtained from a sandy loamy soil, degraded heptachlor epoxide to the less toxic 1-exohydroxychlordene. Conversion was about 1% per week during the 12-week test period (Miles et al. 1971). 

The assay microorganisms in Polytox are a blend of bacterial strains originally isolated from wastewater [48]. The Polytox kit (Microbiotest Inc., Nazareth, Belgium), specifically designed to assess the effect of toxic chemicals on biological waste treatment, is based on the reduction of respiratory activity of rehydrated cultures in the presence of toxicants. The commercially available kit is specihcally designed for testing wastewaters. Quantative results can be obtained in just 30 minutes. 

As protozoa and nematodes live in pore water in the soil, most of the methods are adapted from toxicity tests designed for aquatic samples. Among the protozoa the tests with cihates Tetrahymena pyriformis, Tetrahymena thermophiia, Colpoda cucullus, Colpoda inflata, Colpoda steinii, Paramecium caudatum, and Paramecium aurelia have been developed [ 102,112-117]. It is the opinion of some authors that the sensitivity of infusorians is higher than that of microorganisms [115,116]. 

Bitton, G. Toxicity testing in wastewater treatment plants using microorganisms. In Wastewater Microbiology Wiley-Liss New York, 1994, 478 pp. 

Paixao, S.M. and Anselmo, A.M. (2002) Effect of olive mill wastewaters on the oxygen consumption by activated sludge microorganisms an acute toxicity test method, Journal of Applied Toxicology 22 (3), 173-176. 

Because of the numerous benefits of Toxkit assays, they can be used for sample testing even by small analytical laboratories and local monitoring stations for routine toxicity assessments of environmental samples as well as in emergencies. The use of standard organisms means that assays can be standardized and that repeatable results can be obtained in different laboratories. Another, not unimportant aspect is that conducting toxicity assays on microorganisms does not require the consent of an ethical committee.77 Table 9.3 provides information on microbioassays commercially available in kit form (Toxkit).73... 

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