Giuseppe Lo Papa

Salinity and Bacterial Diversity: To What Extent Does the Concentration of Salt Affect the Bacterial Community in a Saline Soil?

In this study, the evaluation of soil characteristics was coupled with a pyrosequencing analysis of the V2-V3 16S rRNA gene region in order to investigate the bacterial community structure and diversity in the A horizon of a natural saline soil located in Sicily (Italy). The main aim of the research was to assess the organisation and diversity of microbial taxa using a spatial scale that revealed physical and chemical heterogeneity of the habitat under investigation. The results provided information on the type of distribution of different bacterial groups as a function of spatial gradients of soil salinity and pH. The analysis of bacterial 16S rRNA showed differences in bacterial composition and diversity due to a variable salt concentration in the soil. The bacterial community showed a statistically significant spatial variability. Some bacterial phyla appeared spread in the whole area, whatever the salinity gradient. It emerged therefore that a patchy saline soil can not contain just a single microbial community selected to withstand extreme osmotic phenomena, but many communities that can be variously correlated to one or more environmental parameters. Sequences have been deposited to the SRA database and can be accessed on ID Project PRJNA241061.

Compartmentalization of gypsum and halite associated with cyanobacteria in saline soil crusts

The interface between biological and geochemical components in the surface crust of a saline soil was investigated using X-ray diffraction, and variable pressure scanning electron microscopy in combination with energy dispersive X-ray spectrometry. Mineral compounds such as halite and gypsum were identified crystallized around filaments of cyanobacteria. A total of 92 genera were identified from the bacterial community based on 16S gene pyrosequencing analysis. The occurrence of the gypsum crystals, their shapes and compartmentalization suggested that they separated NaCl from the immediate microenvironment of the cyanobacteria, and that some cyanobacteria and communities of sulfur bacteria may had a physical control over the distinctive halite and gypsum structures produced. This suggests that cyanobacteria might directly or indirectly promote the formation of a protective envelope made of calcium and sulfur-based compounds.

Saline soils in in Italy: distribution, ecological processes and socioeconomic issues

Soils are crucial for crop production and for the major ecosystem services. They preserve and sustain life. Salinity is one of the main soil threats that reduce soil fertility and affect the crop production. In recent times, a great attention has been paid to the general shortage of arable land, and to the increasing demand for ecological restoration of areas affected by secondary salinization processes. Microorganisms in these habitats may share a strategy, may have developed multiple adaptations for maintaining populations, and cope eventually to extreme conditions by altruistic or cooperative behavior for maintaining their population active. The understanding and the knowledge of the composition and distribution of microorganisms in natural habitats can be interesting for ecological reasons and it is important to develop new restoration strategy of salt-affected soils.

The “genetic erosion” of the soil ecosystem

Abstract This paper takes into consideration the influence of human activities on the loss of pedodiversity in a Mediterranean area due to large scale farming. In particular it examines the quantitative and qualitative soil changes in a period of 53 years (from 1955 to 2008) evaluating the loss of soil diversity at soil subgroups level of the USDA Soil Taxonomy system. The following indices were used: richness; Shannon’s diversity index; Simpson diversity index; Shannon’s evenness index; Simpson’s evenness index. In this case study, considering what we observed in time, the human intervention in soil transformation could increase the diversity in the landscape in an initial phase, but forwarding by large scale farming the result is a huge loss of pedodiversity in time, as diversity indices remarkably have shown. This analysis enabled identification of disappeared soil types, with their unique history of formation. In our opinion this strongly reflects a sort of “genetic erosion” of the soil types, resulting in a substantial weakening of the whole pedo-ecosystem.