Anelia Kenarova

Community level physiological profiles of bacterial communities inhabiting uranium mining impacted sites.

Bacterial activity and physiological diversity were characterized in mining and milling impacted soils collected from three abandoned uranium mine sites, Senokos, Buhovo and Sliven, using bacterial dehydrogenase activity and Biolog (EcoPlate) tests. The elemental composition of soils revealed high levels of uranium and heavy metals (sum of technogenic coefficients of contamination; TCC(sum) pollution as follows: Sliven (uranium - 374 mg/kg; TCC(sum) - 23.40) >Buhovo (uranium - 139.20mg/kg; TCC(sum) - 3.93) >Senokos (uranium - 23.01 mg/kg; TCC(sum) - 0.86). The physiological profiles of the bacterial community level were site specific, and indicated intensive utilization of polyols, carbohydrates and carboxylic acids in low and medium polluted environments, and i-erithrytol and 2-hydroxy-benzoic acid in the highly polluted environment of Sliven waste pile. Enzymes which take part in the biodegradation of recalcitrant substances were more resistant to pollution than these from the pathways of the easily degradable carbon sources. The Shannon index indicated that the physiological diversity of bacteria was site specific but not in line with the levels of pollution. A general tendency of increasing the importance of the number of utilizable substrates to bacterial physiological diversity was observed at less polluted sites, whereas in highly polluted sites the evenness of substrate utilization rate was more significant. Dehydrogenase activity was highest in Senokos upper soil layer and positively correlated (p<0.01) with the soil organic matter content. The bacterial activity (EcoPlate) and physiological diversity (Shannon index) correlated significantly and negatively with As, Cu, Zn, Pb and U, and Co, Cr, Ni and Mn, respectively. We concluded that the observed site specific shifts in bacterial communities were complex due to both the environmental peculiarities and the bacterial tolerance to the relevant level of pollution, rather than a strong indication of uranium and heavy metals toxicity.

Physiological diversity of bacterial communities from different soil locations on Livingston Island, South Shetland archipelago, Antarctica

Terrestrial food webs of Antarctica are simple and dominated by microorganisms. Soil bacteria play an important role in nutrient cycling, yet little is known about their capacity to utilize different carbon sources and to participate in site nutrient turnover. Biolog EcoPlate™ was applied to study the catabolic activity and physiological diversity of bacteria inhabiting the soil of moss, vascular plants, and fell field habitats from Livingston Island, Antarctica. Additionally, the number of oligotrophic and copiotrophic bacteria was counted by the agar plate method. Results indicated a lack of site-specific distribution of bacterial abundance, in contrast to bacterial catabolic activity and community level physiological profiles. Community level physiological profiles revealed a common capacity of soil bacteria to intensively utilize polyols, which are cryoprotectants widely produced by Antarctic organisms, as well as site-specific phenolic compounds (vegetated habitats), amino acids/amines (moss habitats), carbohydrates and carboxylic acids (fell field habitat). It was concluded that the physiology of soil bacteria is habitat specific concerning both the rate of catabolic activity and pattern of carbon source utilization.

Effects of long-term radionuclide and heavy metal contamination on the activity of microbial communities, inhabiting uranium mining impacted soils

Ore mining and processing have greatly altered ecosystems, often limiting their capacity to provide ecosystem services critical to our survival. The soil environments of two abandoned uranium mines were chosen to analyze the effects of long-term uranium and heavy metal contamination on soil microbial communities using dehydrogenase and phosphatase activities as indicators of metal stress. The levels of soil contamination were low, ranging from ‘precaution’ to ‘moderate’, calculated as Nemerow index. Multivariate analyses of enzyme activities revealed the following: (i) spatial pattern of microbial endpoints where the more contaminated soils had higher dehydrogenase and phosphatase activities, (ii) biological grouping of soils depended on both the level of soil contamination and management practice, (iii) significant correlations between both dehydrogenase and alkaline phosphatase activities and soil organic matter and metals (Cd, Co, Cr, and Zn, but not U), and (iv) multiple relationships between the alkaline than the acid phosphatase and the environmental factors. The results showed an evidence of microbial tolerance and adaptation to the soil contamination established during the long-term metal exposure and the key role of soil organic matter in maintaining high microbial enzyme activities and mitigating the metal toxicity. Additionally, the results suggested that the soil microbial communities are able to reduce the metal stress by intensive phosphatase synthesis, benefiting a passive environmental remediation and provision of vital ecosystem services.

Salmonella Presence—An Indicator of Direct and Indirect Human Impact on Gentoo in Antarctica

ABSTRACT Antarctica remains one of the last areas, where direct human impact is limited. Compared to the rest of the world Antarctic environment could be considered as unpolluted. This explains the significant scientific interest to the effects of touristic activities, and especially during the last decade due to the increased number of tourists visiting diverse parts of the continent. The role of human activity for Salmonella presence in penguins remains unclear. The aim of the present study was to contribute to the knowledge to what extend Salmonella presence in penguins interstitial fauna might be used as an indicator of direct or indirect human impact on the Antarctic ecosystem, by investigating three Gentoo colonies, subjected to different levels of human impact. 16 individual fecal samples were taken per each Gentoo colony. The potentially pathogenic Salmonella typhimurium/enteridis occurred in both studied populations at King George Island at the rates 37,5% and 18,8% respectively, or at rates 85,7% and 60,0% of the positive for Salmonella sp. samples respectively. Unlike both populations at Admiralty bay, King George Island, all samples taken from the Caleta Argentina population at Livingston Island were positive neither for both pathogenic species nor for Salmonell sp.

Natural Communities of Uranium Mining Impacted Area in the Vicinity of the Senokos Village

ABSTRACT Uranium containing wastes accumulated during mine activities have resulted in a multitude of contaminated sites in Bulgaria. The lack of biomonitoring programs limits the environmental impact assessment of uranium impacted areas. The aim of the study was to investigate the health of natural terrestrial (vegetation, soil bacteria and millipedes) and freshwater (macrozoobenthos) communities in the impacted area of former uranium mine Senokos. The mine is one of the forty-nine former uranium mines in Bulgaria, reclaimed in the beginning of the 90s, but the reclamation was compromised due to surface erosion of the protective layers. The vegetation is typical for the region and uranium pollution has not caused any significant adverse affects on it. Adverse affects on soil bacterial communities are recorded only to their activity, but not to the abundance. Soil millipedes are in low density dominated by Pachyiulus cattarensis (Latzel 1884). The benthic community of Luda River is influenced by both uranium loaded sediments and infiltrate water from the mine.

Vertical Distribution of Bacterioplankton in Dolnoto Lake—Seven Rila Lakes

ABSTRACT Temporal and vertical distribution of bacterial abundance (BA) was studied in the high mountain Dolnoto Lake (max depth 11.0 m), the lake at lowest elevation (2 095 m a.s.l.) from the system of the Seven Rila Lakes. The research was performed in July and September, both in 2006 and 2007. Bacteriological analysis was completed with measurements of selected physicochemical parameters such as temperature, oxygen, pH, and inorganic nitrogen and phosphorous concentrations. BA was higher in 2007 (on average 93.92 x 105 cell ml−1), especially in Julq (121.56 x 105 cell ml−1) than in 2006 (on average 17.48 x 105 cell ml−1). The vertical distribution of bacteria depended on temperature, pH and PO4-P, and the most abundant was the subsurface layer of water column in most of the sampling occasions. Bacterial communities from the different vertical layers had different metabolic profiles (EcoPlates Biolog). The lowest physiological diversity was recoded for the subsurface bacterial community.

Functional Diversity of Microorganisms in Heavy Metal-Polluted Soils

In this chapter, we summarize the results from studies designed to assess the impacts of heavy metal pollution on the physiology of soil microorganisms based on a variety of commercially available assays (Biolog and MicroResp) of community substrate use. The results and conclusions from these studies are contradictory, depending on the metal concentrations and speciation, local environmental characteristics, and finally the different interpretations by the authors of the actual levels of pollution. In general, low and moderate levels (according to the Nemerow index) of metal pollution do not affect carbon use ability and functional diversity of the impacted microbial communities, as opposed to high metal pollution levels where significant adverse effects are recorded as functional responses of microbial communities to metal stress. Microbial functional responses to metal stress were observed as reduced catabolic activity and functional diversity, preferential community shifts from one carbon substrate use to another, and/or increased pollution-induced community tolerance. Finally, the microbial responses are summarized in the context of the modifying effects of the local environment on metal toxicity.

Phylogenetic Diversity of Archaea and the Archaeal Ammonia Monooxygenase Gene in Uranium Mining-Impacted Locations in Bulgaria

Uranium mining and milling activities adversely affect the microbial populations of impacted sites. The negative effects of uranium on soil bacteria and fungi are well studied, but little is known about the effects of radionuclides and heavy metals on archaea. The composition and diversity of archaeal communities inhabiting the waste pile of the Sliven uranium mine and the soil of the Buhovo uranium mine were investigated using 16S rRNA gene retrieval. A total of 355 archaeal clones were selected, and their 16S rDNA inserts were analysed by restriction fragment length polymorphism (RFLP) discriminating 14 different RFLP types. All evaluated archaeal 16S rRNA gene sequences belong to the 1.1b/Nitrososphaera cluster of Crenarchaeota. The composition of the archaeal community is distinct for each site of interest and dependent on environmental characteristics, including pollution levels. Since the members of 1.1b/Nitrososphaera cluster have been implicated in the nitrogen cycle, the archaeal communities from these sites were probed for the presence of the ammonia monooxygenase gene (amoA). Our data indicate that amoA gene sequences are distributed in a similar manner as in Crenarchaeota, suggesting that archaeal nitrification processes in uranium mining-impacted locations are under the control of the same key factors controlling archaeal diversity.

Soil Bacterial Abundance and Diversity of Uranium Impacted Area in North Western Pirin Mountain

ABSTRACT The former uranium mine Senocos (Blagoevgrad district, Bulgaria) has been exploited until 1991 when it was closed and later (1994–1997) reclaimed. Recently, the reclamation is compromised due to the erosion of protective layers and the mine wastes continue to affect the area resulting in increased radiation and uranium concentration in mine area. Soil bacterial abundance in more radioactive environment of mine remains unchanged (on average ((8.52±5.1) x 108 cell g−1) compared to the control ((8.76±3.5) x 108 cell g−1) in contrast to their dehydrogenase activity which decreases more than two times. Physiological and species diversity of bacterial mine communities are also affected by the pollution as it is expressed by lower values of Shannon indices compared to the control communities. All carbon sources in BIOLOG assay except 2-hydroxy benzoic acid are available for control bacterial communities and the number of unavailable carbon sources increases linearly with increasing the concentration of uranium in soil. The high levels of radionuclide pollution decrease the biodiversity to 3–4 species (66% of total) in the most polluted point of the mine territory (SPS(5)).