The spring bloom in seasonally stratiWed seas is often characterized by a rapid increase in photosynthetic biomass. To clarify how the combined eVects of nutrient and light availability inXuence phytoplankton composition in the oligotrophic Gulf of Aqaba, Red Sea, phytoplankton growth and acclimation responses to various nutrient and light regimes were recorded in three independent bioassays an...

background and objectives: the objective of this study was to monitor the microorganisms isolated from grapes and its derivative traditional products produced in iran. material and methods: four kinds of grapes cultivated summer of 2010 in vineyard of takestan and also grape derived products from shahrod, hamedan and takestan were used for this study.  the samples were cultured in specific medi...

bioleaching is the extraction of metals from their ores through the use of microorganisms. inthis process, the use of native bacteria leads to achieve more yields of metals. so, in the presentstudy, native sulfur-oxidizing bacterium in potentiality of uranium extraction was isolated fromghachin mine in iran and identified by partial gene sequencing. for this purpose, the watersamples were colle...

purpose : identifying the predisposing factors of the infectious keratitis results in understanding the underlying mechanisms of its expansion and severity that is essential for initiation of optimal empirical antimicrobial therapy. this study identified main predisposing factors of bacterial keratitis in a sample of iranian population. methods : ninety patients with bacterial keratitis were pr...

Phytoplankton inhabiting oligotrophic ocean gyres actively reduce their phosphorus demand by replacing polar membrane phospholipids with those lacking phosphorus. Although the synthesis of nonphosphorus lipids is well documented in some heterotrophic bacterial lineages, phosphorus-free lipid synthesis in oligotrophic marine chemoheterotrophs has not been directly demonstrated, implying they are...

Nitrification plays a central role in the nitrogen cycle by determining the oxidation state of nitrogen and its subsequent bioavailability and cycling. However, relatively little is known about the underlying ecology of the microbial communities that carry out nitrification in freshwater ecosystems--and particularly within high-altitude oligotrophic lakes, where nitrogen is frequently a limitin...

Oligotrophic subtropical gyres are the largest oceanic ecosystems, covering >40% of the Earth's surface. Unicellular cyanobacteria and the smallest algae (plastidic protists) dominate CO(2) fixation in these ecosystems, competing for dissolved inorganic nutrients. Here we present direct evidence from the surface mixed layer of the subtropical gyres and adjacent equatorial and temperate regions ...

Abstract. The recycling of scarce nutrient resources in the sunlit open ocean is crucial to ecosystem function. Nitrification directs ammonium (NH4+) derived from organic matter decomposition towards regeneration nitrate (NO3-), an important resource for photosynthetic primary producers. However, technical challenge making nitrification rate measurements oligotrophic conditions combined with re...

The spatial distribution of an uncultured clade of marine diazotrophic -proteobacteria in the Arabian Sea was investigated by the development of a specific primer pair to amplify an internal fragment of nifH by PCR. These organisms were most readily detected in highly oligotrophic surface waters but could also be found in deeper waters below the nutricline. nifH transcripts originating from thi...

Hyperspectral profiles of downwelling irradiance and upwelling radiance in natural waters (oligotrophic and mesotrophic) are combined with inverse radiative transfer to obtain high resolution spectra of the absorption coefficient (a) and the backscattering coefficient (b(b)) of the water and its constituents. The absorption coefficient at the mesotrophic station clearly shows spectral absorptio...