engleski

Characterization of bacteria in nickel-rich kaolinite, montmorillonite, and saponite mixture form Gornje Orešje, Croatia

A sample of nickel (Ni)-rich clay from Gornje Orešje (POSILOVIĆ, 2009), Croatia was analysed mineralogically and bacteriologically. The light greyish-green sample of alteration product of peridotite mother rocks was recognized as a mixture of kaolinite, montmorillonite, saponite and negligible quantity of quartz and calcite. The abundance of total heterotrophic bacteria grown at 22°C was 7.0±0.8 log colony-forming unit (CFU)/mL of wet clay. The population of carbapenem-resistant bacteria grown at 35°C was present at abundance of 3.9±0.6 log CFU/mL. According to the Bruker MALDI-TOF MS analysis, the population of carbapenem-resistant bacteria was represented by Stenotrophomonas sp. with intrinsic resistance, and Pseudomonas sp. with acquired resistance to carbapenems. The results suggest that Ni-rich clay is a habitat of dense bacterial population, including those resistant to last-resort antibiotics. Scanning Electron Microscopy analysis (Fig. 1) confirmed that bacteria were mostly restricted to the edges of montmorillonite sheets, which probably represent the sites of easy access of bacteria to the cations present in mineral.

bacteria ; clay ; environment

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