Effect of biosurfactants on crude oil desorption and mobilization in a soil system

Microbially produced biosurfactants were studied to enhance crude oil desorption and mobilization in model soil column systems. The ability of biosurfactants from Rhodococcus ruber to remove the oil from the soil core was 1.4-2.3 times greater than that of a synthetic surfactant of suitable properties, Tween 60. Biosurfactant-enhanced oil mobilization was temperature-related, and it was slower at 15 degrees C than at 22-28 degrees C. Mathematical modelling using a one-dimensional filtration model was applied to simulate the process of oil penetration through a soil column in the presence of (bio)surfactants. A strong positive correlation (R(2)=0.99) was found between surfactant penetration through oil-contaminated soil and oil removal activity. Biosurfactant was less adsorbed to soil components than synthetic surfactant, thus rapidly penetrating through the soil column and effectively removing 65-82% of crude oil. Chemical analysis showed that crude oil removed by biosurfactant contained a lower proportion of high-molecular-weight paraffins and asphaltenes, the most nonbiodegradable compounds, compared to initial oil composition. This result suggests that oil mobilized by biosurfactants could be easily biodegraded by soil bacteria. Rhodococcus biosurfactants can be used for in situ remediation of oil-contaminated soils.     

Adaptive mechanisms of nonspecific resistance to heavy metal ions in alkanotrophic actinobacteria

Sensitivity to heavy metal (HM) exposure has been studied in actinobacterial cultures maintained at the Regional Specialized Collection of Alkanotrophic Microorganisms (acronym IEGM; http://www.iegm.ru/iegmcol). Possible mechanisms of nonspecific resistance of actinobacteria to HMs are discussed, which may be due to their ecological preferences, alkanotrophy, and ability to synthesize biosurfactants. Hydrocarbon-oxidizing strains have been selected that are characterized by high emulsifying activity and resistance to increased (>250 mM) HM concentrations.     

A Nationwide Assessment of the Biodiversity Value of Uganda's Important Bird Areas Network

Abstract:  BirdLife International's Important Bird Areas (IBA) program is the most developed global system for identifying sites of conservation priority. There have been few assessments, however, of the conservation value of IBAs for nonavian taxa. We combined past data with extensive new survey results for Uganda's IBAs in the most comprehensive assessment to date of the wider biodiversity value of a tropical country's IBA network. The combined data set included more than 35,000 site × species records for birds, butterflies, and woody plants at 86 Ugandan sites (23,400 km²), including 29 of the country's 30 IBAs, with data on additional taxa for many sites. Uganda's IBAs contained at least 70% of the country's butterfly and woody plant species, 86% of its dragonflies and 97% of its birds. They also included 21 of Uganda's 22 major vegetation types. For butterflies, dragonflies, and some families of plants assessed, species of high conservation concern were well represented (less so for the latter). The IBAs successfully represented wider biodiversity largely because many have distinctive avifaunas and, as shown by high cross-taxon congruence in complementarity, such sites tended to be distinctive for other groups too. Cross-taxon congruence in overall species richness was weaker and mainly associated with differences in site size. When compared with alternative sets of sites selected using complementarity-based, area-based, or random site-selection algorithms, the IBA network was efficient in terms of the number of sites required to represent species but inefficient in terms of total area. This was mainly because IBA selection considers factors other than area, however, which probably improves both the cost-effectiveness of the network and the persistence of represented species.     

Soil microbiocenosis as an indicator of stability of meadow communities in the environment polluted with heavy metals

The soil microbiota, a key component of natural ecosystems, is considered as a factor determining the stability of meadow communities. The diversity and abundance of the main ecologically significant groups of microorganisms in meadow soils have been studied along a gradient of long-term soil pollution with heavy metals in the Middle Urals. The results provide evidence for stability of the microbial assemblage formed in these soils. It has been found that the functional activity of certain physiological groups of microorganisms (nitrogen-fixing, denitrifying, and cellulolytic bacteria) and the respiratory activity of microbial communities are stimulated under conditions of heavy-metal soil pollution. Probable effects of the observed changes on mineralization of plant remains in meadow communities are discussed.