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Quorum sensing is a mechanism utilized in bacterial strains to communicate between neighboring colonies and assess the strain's population density. Upon surpassing a population density threshold, this mechanism can trigger a population response, such as biofilm production, through the release of signal molecules. Biofilm is an extracellular collection of polysaccharides and proteins that has been observed to provide pathogenic bacteria protection from antibiotic treatment and the body's immune responses. Our lab originally synthesized and tested drug compounds for their potential to reduce or inhibit biofilm production in Staphylococcus aureus (S. aureus) through inhibition of quorum sensing receptor signaling. However, we predicted these tested drug compounds may be reducing biofilm through inhibition of the NorA efflux pump, which has been observed to pump out biofilm forming components. Drug compounds Proline-61, Proline-68, and Tyrosine-16 were tested using a Crystal Violet Assay against three strains of S. aureus, a wildtype (SA-1199), an overexpressor of the NorA efflux pump (SA-1199B), and a knockout strain missing the NorA efflux pump (SA-K1758). All three drugs demonstrated greater significant biofilm inhibition in the overexpressor than in the wildtype strain and no significant inhibition in the knockout, supporting our hypothesis. However, the Crystal Violet Assay only quantifies overall biofilm production and does not measure the specific activity of the NorA efflux pump. We have developed a fluorescence assay utilizing 3-dipropyloxacarbocyanine iodide, a known substrate of NorA, which will allow us to directly quantify NorA activity and its corresponding inhibition, if any, following exposure to our drugs. We hypothesize that Proline-61, Proline-68, and Tyrosine-16 are inhibiting biofilm production in S. aureus through inhibition of the NorA efflux pump. [ABSTRACT FROM AUTHOR]

The soil is a major reservoir for carbon (C) in biosphere, containing globally twice as much C as the atmosphere and three times as much as vegetation. Soil CO2 efflux is highly sensitive to changes in surface temperature and relatively small changes in surface temperature may have a major influence on the magnitude of soil efflux. The potential increase in CO2 release from the soil caused by future elevated temperature may have a positive feedback effect on the atmospheric CO2 and global changes. For estimation of C budgets in target ecosystems, we must be able to account for small-scale spatial variation in soil respiration. Vegetation models require incorporating both temporal and spatial variation of soil respiration and scaling-up the chamber measurements of soil respiration to ecosystem level. In the this study, were compared different underline surfaces due to the soil CO2 emission and identified the main driving factors of soil CO2 emission there. It was created the model which combines the meteorological parameters of whole area and local specific features of each ecosystem. [ABSTRACT FROM AUTHOR]

We investigated isotopic signature of methane efflux from soil surface of Siberian arctic and sub-arctic ecosystems in sites in Siberia. In the boreal ecosystem of the Tura site (64°15'N, 100°13'E) the d13C signature of methane (-43‰ for south facing slope and - 35‰ from north facing slope) showed low methane production potential of investigated soils. Two years of monitoring of the d13CCH4 signatures from surface of ice-wedge polygon of Samoylov island (72°22'N, 126°28'E) showed that the d13C signature were different regarding to temperature and precipitation. The mean of d13CCH4 emitted from the polygon wall ranged from 72.5±1.9‰ to -47.3±1.5‰. The same for polygon center ranged from -67.1±2.0‰ to -62.4±1.7‰. Almost no difference between d13CCH4 signature of years observed could mean that conditions for methane production are possibly quite stable. With respect to methane emission both permafrost ecosystems are thus very contrasting. [ABSTRACT FROM AUTHOR]