Quantitative detection of asbestos fiber in gravelly sand using elastic body-exposure method

Abstract

Chrysotile or crocidolite colloidal solution containing donor plasmid DNA and Escherichia coli cells was subjected to elastic body friction. These acicular clay minerals mediated E. coli antibiotic resistance plasmid transformation. Other clay minerals had no effect on E. coli transformation. The number of E. coli transformants was counted after elastic body exposure with various crocidolite concentrations. There was a correlation between the number of E. coli transformants and crocidolite concentration (between 40 and 1,000 ng/ml). A mixture consisting of sea sand and crocidolite was utilized as a model for quantitative detection of asbestos in gravelly sand. With sea sand containing 0.15-15 mg of crocidolite, a correlation between crocidolite concentration and the number of colonies derived from E. coli transformants was observed. This indicates that measurement of asbestos is possible even when the asbestos sample includes gravelly sand. Fluorescence microscopic observation of crocidolite colloidal solution indicated that crocidolite was present as spherical aggregates having diameters of 6-9 microm. Thus, the number of transformants correlated with that of 6-9 microm crocidolite aggregates.

Transformation of Escherichia coli JM109 using pUC19 by the Yoshida effect

“…Transformation with sepiolite has been published only a few times (Mitsudome et al, 2014;Rodríguez-Beltrán et al, 2012, 2013Tan et al, 2010;Wilharm et al, 2010). Other minerals such as kaolinite and bentonite have been tried but induced undesirable mutations on the host bacterium (Yoshida et al, 2004) and do not promote plasmid transport into E. coli cells (Yoshida and Takebe, 2006). Sepiolite is thus an inexpensive substance not presenting health risks for humans and seems the most suitable choice for a widespread use of tribos transformation on bacteria.…”