4 April 2014, Nataša Šibanc’s Ph.D. defense titled ‘Biodiversity of Arbuscular Mycorrhizal Fungi and Selected Groups of Rhizosphere Microorganisms from Natural CO2 Springs’


Nataša Šibanc’s Ph.D. defense titled

Biodiversity of Arbuscular Mycorrhizal Fungi and Selected Groups of Rhizosphere Microorganisms from Natural CO2 Springs

was on Friday, 4 April 2014 at 9 am, at University of Ljubljana Biotechnical Faculty, Jamnikarjeva 101. The defense is open to public.

Natasa doktorat


Understanding the processes that regulate the diversity of soil microorganisms is essential for predicting ecosystem responses to environmental changes. Research in natural ecosystems is difficult to conduct due to the specific characteristics of soil, where selection pressures in soils are rarely temporally and spatially oriented and often tend to overlap with other soil characteristics. Natural CO2 springs (mofettes) are extreme ecosystems, where carbon dioxide (CO2) of geological origin reaches the soil surface resulting in long term changes in soil gas composition. Because CO2 vents through the soil, plant roots and soil organisms are the first to be affected by this CO2 source.

For this study on diversity and ecology of communities of soil microorganisms, species-rich and functionally important groups of soil microbes; arbuscular mycorrhizal (AM) fungi, archaea, bacteria, and yeasts were chosen. The AM fungal community composition from selected mofette areas in Slovenia, Italy and the Czech Republic, was determined using Roche 454 GS-FLX pyrosequencing. The community composition of archaea and bacteria from the area of Slovenian mofettes near Stavešinci village was determined using PCR, cloning and Sanger sequencing. Yeasts from the area of Slovenian mofettes were isolated using several isolation techniques and different growth media and identified using molecular approaches.

The most important environmental factors influencing AM fungal, archaeal, and bacterial community composition from natural CO2 springs are the concentration of CO2 in soil air, hypoxia and soil pH. In addition, we have found that AM fungal community composition was different between the two years of sampling, but no significant compositional changes in AM fungal community were observed among different months, or among geographically distant mofettes. AM fungal communities sampled from control locations showed higher biodiversity (according to Hill’s numbers) while no significant difference in biodiversity of archaea and bacteria among locations with different CO2 concentrations was observed. We have identified eight yeast isolates, including the yeast Occultifur species sp. nov., a new, previously undescribed species.

The results of our study show that the emission of geological gas can have significant ecological consequences arising from the changes in the soil microbial community composition. This is shown by a shift towards a greater abundance of anaerobic and methanogenic archaea and bacteria and higher number of fermentative yeast species and also a permanent changes in community composition of all researched microbial groups towards a greater abundance of ecological specialists.