Toxicity tests bacterial inhibiting

Toxi-ChromoPad (EBPI, Ontario, Canada) is a simple method for evaluation of the toxicity of solid particles [25,26,32,39]. The test is based on the inhibition of the synthesis of (3-galactosidase in E. coli after exposure to pollutants. The method has been used to measure acute toxicity of sediment and soil and other solid samples. The test bacterial suspension is mixed with homogenized samples and incubated for 2 hours. A drop of the test solution is pipetted onto a fiberglass filter containing an adsorbed substrate. A color reaction indicates the synthesis of enzyme, while a colorless reaction indicates toxicity. It has previously been shown... 

The Microtox assay which measures light inhibition with the bacterium Vibrio fisheri is a well known and useful aquatic toxicity test (see Chapter 1, volume 1 of this book). As previously reported (Blaise et al., 1994) and based on our own experience, it appears more appropriate to determine 60 min IC50 for waste leachates, as opposed to 15 min or 30 min endpoints. IC50s measured after 60 min on MIOM leachates were clearly more sensitive and reproducible than those measured at 30 min and 15 min (Ferrari et ah, 1999). Since WASTOXHAS was applied on (poly)metallic matrices in this study, we also found it more suitable to use zinc sulphate as a reference toxicant to periodically verify the sensitivity of the Microtox bacterial light reagent. 

Bacterial or enzymatic toxicity tests are used to assay the activity of organic compounds including solvents. A survey of environmental bacterial or enzymatic test systems is given by Bitton and Koopman. The principles of these test systems are based on bacterial properties (growth, viability, bioluminescence, etc.) or enzymatic activities and biosynthesis. The toxicity of several solvents were tested in bacterial or enzymatic systems, e.g., pure solvents such as phenol in growth inhibition assays (Aeromonas sp.), solvents in complex compounds such as oil derivates, solvents in environmental samples such as sediments or solvents used in the test systems.The efficiency of several test systems, e.g., Microtox tests or ATP assays, vary, e.g., looking at the effects of solvents. ... 

Historically, respirometers have been used for wastewater biodegradability evaluation. More recently [52], a mobile on-line respirometer was proposed and tested for monitoring the activated sludge inhibition due to industrial discharges in a sewer network. A derived portable device called a Baroxymeter [53], based on monitoring the respiration of a bacterial culture by pressure measurements and using respiration inhibition as a toxicity alert, was proposed for the rapid detection of the toxicity effect of some toxic substances. 

When tested, the antibiotic compounds killed or inhibited the growth of two varieties of E. coli but had no effect on several other types of cells. These results show that in response to bacterial infection the ants elaborated an antibiotic that was selectively toxic to the pathogen. Their defense was tailored closely to their need. It is too soon to know more, but it seems that looking for new antibiotics in ants is a promising idea. Further research should establish whether ant antibiotics will lead to drugs for human use and also reveal whether other crowded species also synthesize antibiotics. 

An agar plate method is presented by Liu et al [47]. On an agar plate covered by a bacterial suspension, an inhibition zone is formed and measured around the spot where the toxic sample has been placed. The duration of the test depends on the growth of the bacterial species (from 3 to 24 hours). This assay is not available in a commercial kit but it is simple to perform as... 

Simple or automated offline or online biodegradability tests can be performed by measuring CO2 or CH4 gas production or O2 consumption [13]. Biosensors may utilize either whole bacterial cells or enzymes to detect specific molecules of hazardous substances. Toxicity can be monitored specifically by whole-cell sensors whose bioluminescence may be inhibited by the... 

An example of the use of a highly specialised cell type to study targeted toxic effects on the cellular metabolism is the recently developed boar spermatozoon motility inhibition test (Andersson et al., 1998). The motility of a spermatozoon depends on the integrity of mitochondrial functions, and thus the action of toxins affecting the energy metabolism is very rapidly detected as reduction of motility. Other end points that can be measured are plasma membrane integrity, astrodome function, and total cellular ATP and NAD reduction. This test has been particularly useful in the detection of certain types of bacterial toxins from various enviromnental and food sources. 

A bacterial assay, the Photobacterium test, based on the inhibition of light emission of a bioluminescent bacterium Vibrio fisheri (ISO, 1998), originally developed to test the toxicity of industrial effluents, gives an indication of the effects of the test agent on the oxidative metabolism of the cell. As a bacterial assay its advantages are rapidity and relatively low costs, but naturally the differences between bacterial and mammalian systems make the interpretation of the results even more difficult than with other short-term tests. 

The use of photosynthetic enzymes isolated from plants has been implemented in a toxicity monitor (LuminoTox, Lab Bell Inc., Shawinigan, Canada). This system can detect a range of compounds such as hydrocarbons, herbicides, phenols, polycyclic aromatic hydrocarbons (PAHs), and aromatic hydrocarbons. These enzymes have been coupled to screen-printed electrode and have been demonstrated to be able to detect triazine and phenylurea herbicides [79]. Other enzyme inhibitions have been used to detect biotoxins from plant, animals, bacterial, algae, and fungal species (e.g., ricin, botulinum toxins, mycotoxins, cyanobacterial toxins). However, since the identity and specificity of the above toxic compound can be very important during the analysis, other sensor systems such as immunosensors may be preferred to give a better indication to toxin type and identity than the use of enzyme inhibition tests. 

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