Metals and microbes in toxicity testing

Abstract

SynopsisThe use of microorganisms can be a valuable and powerful tool in assessing the toxicity of metals, but a number of factors must be considered if meaningful results are to be obtained. In many instances natural assemblages of microorganisms are preferred to pure cultures as test systems. Similarly, effects on microbial processes such as primary production, respiration, or nitrogen fixation can provide better evaluations of toxicity than are provided by measurements of viability on pure cultures. When possible, more than one measure of activity or viability should be used. In a large number ofcases, the toxicity of a metal is influenced by the chemical species of the metal. The chemical species and the availability of a metal can be influenced markedly by physical and chemical conditions, which include conditions in the field and conditions of the assay itself. Thus, those using microorganisms to assay the toxicity of metals should take care to specify the assay conditions in detail, and they should be sure that the assay conditions are as close as possible to in situ conditions. Moreover, caution should be used when extrapolating from laboratory to field situations, or from one field situation to another.

Incidence of antibiotic and metal resistance and plasmid Carriage in Aeromonas isolated from brown bullhead (latalurus nebulosus)

“…The metal toxicity data should be interpreted cautiously since a number of factors can influence the apparent toxicity of metals in media (Cooney and Pettibone 1986). Pathak et al (1993b) noted that Aer.…”

Bacterial Community Structure and Function along a Heavy Metal Gradient

“…A possible explanation is that bacteria are not exposed to the same concentrations of heavy metal in situ as in laboratory-prepared media. As has already been noted above, components of bacterial growth media can complex heavy metals and remove them from solution, thus reducing their apparent concentrations in the media (4,5). If this were the only factor operating in the present situation, bacteria tested on laboratory media should have been adapted to concentrations of heavy metals in laboratory media that were as high as, if not higher than, concentrations observed in the field.…”

Microtesting appraisal of ATP and cell recovery toxicity end points after acute exposure of Selenastrum capricornutum to selected chemicals

“…Because microalgae are a critical component of the aquatic food web (Neuhold and Ruggerio, 1976;Christensen and Scherfig, 1979), xenobiotic-mediated phytotoxicity is presently receiving increased attention in a variety of environmental investigations (Van Coillie et al, 1983;Couture et al, 1985;Wong and Couture, 1986). In particular, microalgae are sensitive to a wide array of single inorganic (Chiaudani and Vighi, 1978;Rai et al, 1981;Cooney and Pettibone, 1986) and organic (Blanck, 1984;Adams et al, 1985) toxicants, as well as to various interactive mixtures of these (Wong et al, 1982;Blaise et al, 1987;Couture et al, 1987;Munawar et al, 1987). Furthermore, their rapid reactive characteristics make them especially vulnerable to short-term (54-h) exposure to bioavailable chemicals (Hassett et al, 1981;Vymazal, 1984;Harwood et al, 1989).…”