Biological nanostructures associated to iberulites: a SEM study

Abstract

Scanning Electron Microscopy (SEM) is a reliable technique by which geologi cal objects can be screened with magnification ranges between that of optic al microscopy and the nanoscale. It is, therefore, suitable for the study of iberulites, which are pinkish mineral micr ospherules, formed and structured in the troposphere, and composed of complex mineral associations whose pha ses have diverse hygroscopic properties. These mineral phases are mainly silicates, carbonates, sulphates, halides, oxides and phosphates. Othe r minor but not less important compounds are the biological constituents. The sources of such heterogeneous materials ar e the soils of North Africa which, once dispersed into the atmosphere (plumes), undergo physico-chemical transfor mations resulting in the formation of iberulites. Here we report a microscopy research study that analyzes th e biological nanostructures associated to iberulites. A prior selection of iberulite samples was carried out using optical microscopy. Because the material forming iberulites comes from the neighbouring aerosols, their biological constituents should be, a priori , qualitatively similar. However the processes undergone by the iberulites, and their properties, can cause some differences resulting from the role played by these microenvironments as a phys ical support that facilit ates microbial survival and spreading. Dust plumes can have high relative concentrations of remains of composited organisms (plants and diverse microorgani sms) which signify additional loads of viable, yet dormant, biological specimens (bacterial and f ungal spores, algal cysts, plant pollen grains) which move with th ese plumes. These studies, together with future metagenomic data, wi ll improve our knowledge of th e biodiversity of microbial communities integrated in aerolites, a particular class of mi croenvironments with global ecological projection. In addition, they will contribute to establish well-founded strategies for environmental prevention and public health in connection with this issue.