Form ID Research Articles

Rubisco kinetic adaptations to extreme environments.

Photosynthetic and chemosynthetic extremophiles have evolved adaptations to thrive in challenging environments by finely adjusting their metabolic pathways through evolutionary processes. A prime adaptation target to allow autotrophy in extreme conditions is the enzyme Rubisco, which plays a central role in the conversion of inorganic to organic carbon. Here, we present an extensive compilation of Rubisco kinetic traits from a wide range of species of bacteria, archaea, algae, and plants, sorted by phylogenetic group, Rubisco type, and extremophile type. Our results show that Rubisco kinetics for the few extremophile organisms reported up to date are placed at the margins of the enzyme's natural variability. Form ID Rubisco from thermoacidophile rhodophytes and form IB Rubisco from halophile terrestrial plants exhibit higher specificity and affinity for CO2 than their non-extremophilic counterparts, as well as higher carboxylation efficiency, whereas form ID Rubisco from psychrophile organisms possess lower affinity for O2. Additionally, form IB Rubisco from thermophile cyanobacteria shows enhanced CO2 specificity when compared to form IB non-extremophilic cyanobacteria. Overall, these findings highlight the unique characteristics of extremophile Rubisco enzymes and provide useful clues to guide next explorations aimed at finding more efficient Rubiscos.

MagMD: Database summarizing the metabolic action of gut microbiota to drugs

An increasing number of studies have reported that microbiome can affect drug response by altering pharmacokinetics and pharmacodynamics of formation of toxic metabolites. With the development of metagenomic sequencing, gut microbial composition as well as the metabolic function are drawing more and more attention for the patient stratification. The established microbiota databases provide useful information about the gut microbe-drug interactions. However, these databases generally lacked the detailed effects on substance and the metabolites, which are helpful in elucidating the mechanisms underlying drug biotransformation and personalized medicine. To address these issues, in this study, we developed Metabolic action of gut Microbiota to Drugs (MagMD), a database and a web-service covering 32, 678 records of interactions between 2,146 gut microbes, 36 enzymes and 219 substrates (mainly drugs). The detailed annotations for each entry, including the taxonomic level of microbes, the molecular form and PubChem ID of drugs from PubChem Compound Database, types of microbial secreted enzymes and the original reference links can also be accessed from the web service. Availability and implementationMagMD is a publicly available resource, constantly updated. It has an intuitive web interface and can be freely accessed at http://www.unimd.org/magmd.

Distribution of Chromophytic Phytoplankton in the Eddy-Induced Upwelling Region of the West Pacific Ocean Revealed Using rbcL Genes.

Marine chromophytic phytoplankton are a diverse group of algae and contribute significantly to the total oceanic primary production. However, the spatial distribution of chromophytic phytoplankton is understudied in the West Pacific Ocean (WPO). In this study, we have investigated the community structure and spatial distribution of chromophytic phytoplankton using RuBisCO genes (Form ID rbcL). Our results showed that Haptophyceae, Pelagophyceae, Cyanophyceae, Xanthophyceae, and Bacillariophyceae were the dominant groups. Further, chromophytic phytoplankton can be distinguished between upwelling and non-upwelling zones of the WPO. Surface and 75 m depths of a non-upwelling area were dominated by Prochlorococcus strains, whereas chromophytic phytoplankton were homogenously distributed at the surface layer in the upwelling zone. Meanwhile, Pelagomonas-like sequences were dominant at DCM (75 m) and 150 m depths of the upwelling zone. Non-metric multidimensional scaling (NMDS) analysis did not differentiate between chromophytic phytoplankton in the upwelling and non-upwelling areas, however, it showed clear trends of them at different depths. Further, redundancy analysis (RDA) showed the influence of physicochemical parameters on the distribution of chromophytic phytoplankton. Along with phosphate (p < 0.01), temperature and other dissolved nutrients were important in driving community structure. The upwelling zone was impacted by a decrease in temperature, salinity, and re-supplement of nutrients, where Pelagomonas-like sequences outnumbered other chromophytic groups presented.

Dissolved inorganic carbon determines the abundance of microbial primary producers and primary production in Tibetan Plateau lakes.

Climate change globally accelerates the shrinkage of inland lakes, resulting in increases in both water salinity and dissolved inorganic carbon (DIC). The increases of salinity and DIC generate contrasting effects on microbial primary producers and primary production, however, their combined effects remain unclear in aquatic ecosystems. We hypothesized that increased DIC mitigates the constraints of enhanced salinity on microbial primary producers and primary production. To test this, we employed isotope labeling and molecular methods to explore primary production and four dominant types of microbial primary producers (form IA, IB, IC and ID) in lakes on the Tibetan Plateau. Results showed that DIC was positively correlated with the abundance of the form IAB and ID microbial primary producers and primary production (all P <0.001) and offset salinity constraints. Structural equation models elucidated that DIC substantially enhanced primary production by stimulating the abundance of form ID microbial primary producers. The abundance of form ID primary producers explained more variations (14.6%) of primary production than form IAB (6%) and physicochemical factors (6.8%). Diatoms (form ID) played a determinant role in primary production in the lakes by adapting to high DIC and high salinity. Our findings suggest that inland lakes may support higher primary productivity in future climate change scenarios.

Inorganic carbon concentrating mechanisms in free-living and symbiotic dinoflagellates and chromerids.

Photosynthetic dinoflagellates are ecologically and biogeochemically important in marine and freshwater environments. However, surprisingly little is known of how this group acquires inorganic carbon or how these diverse processes evolved. Consequently, how CO2 availability ultimately influences the success of dinoflagellates over space and time remains poorly resolved compared to other microalgal groups. Here we review the evidence. Photosynthetic core dinoflagellates have a Form II RuBisCO (replaced by Form IB or Form ID in derived dinoflagellates). The invitro kinetics of the Form II RuBisCO from dinoflagellates are largely unknown, but dinoflagellates with Form II (and other) RuBisCOs have inorganic carbon concentrating mechanisms (CCMs), as indicated by invivo internal inorganic C accumulation and affinity for external inorganic C. However, the location of the membrane(s) at which the essential active transport component(s) of the CCM occur(s) is (are) unresolved; isolation and characterization of functionally competent chloroplasts would help in this respect. Endosymbiotic Symbiodiniaceae (in Foraminifera, Acantharia, Radiolaria, Ciliata, Porifera, Acoela, Cnidaria, and Mollusca) obtain inorganic C by transport from seawater through host tissue. In corals this transport apparently provides an inorganic C concentration around the photobiont that obviates the need for photobiont CCM. This is not the case for tridacnid bivalves, medusae, or, possibly, Foraminifera. Overcoming these long-standing knowledge gaps relies on technical advances (e.g., the invitro kinetics of Form II RuBisCO) that can functionally track the fate of inorganic C forms.

On Idempotent Units in Commutative Group Rings

Special elements as units, which are defined utilizing idempotent elements, have a very crucial place in a commutative group ring. As a remark, we note that an element is said to be idempotent if r^2=r in a ring. For a group ring RG, idempotent units are defined as finite linear combinations of elements of G over the idempotent elements in R or formally, idempotent units can be stated as of the form id(RG)={∑_(r_g∈id(R))▒〖r_g g〗: ∑_(r_g∈id(R))▒r_g =1 and r_g r_h=0 when g≠h} where id(R) is the set of all idempotent elements [3], [4], [5], [6]. Danchev [3] introduced some necessary and sufficient conditions for all the normalized units are to be idempotent units for groups of orders 2 and 3. In this study, by considering some restrictions, we investigate necessary and sufficient conditions for equalities:i.V(R(G×H))=id(R(G×H)),ii.V(R(G×H))=G×id(RH),iii.V(R(G×H))=id(RG)×Hwhere G×H is the direct product of groups G and H. Therefore, the study can be seen as a generalization of [3], [4]. Notations mostly follow [12], [13].

46.4: Compact Stereoscopic Augmented Reality Goggle with Single Display Panel

A light path for stereoscopic near eye display utilizing single display panel has been proposed and embedded in an existing snow goggle for AR display function with its original form factor and ID design intact. The prototype demonstrates sufficient quality to display numbers or symbols for data information or guiding.

Diversity and Spatial Distribution of Chromophytic Phytoplankton in the Bay of Bengal Revealed by RuBisCO Genes (rbcL)

Phytoplankton are the basis of primary production and play important roles in regulating energy export in marine ecosystems. Compared to other regions, chromophytic phytoplankton are considerably understudied in the Bay of Bengal (BOB). Here, we investigated community structure and spatial distribution of chromophytic phytoplankton in the BOB by using RuBisCO genes (Form ID rbcL). High throughput sequencing of rbcL genes revealed that diatoms, cyanobacteria (Cyanophyceae), Pelagophyceae, Haptophyceae, Chrysophyceae, Eustigamatophyceae, Xanthophyceae, Cryptophyceae, Dictyochophyceae, and Pinguiophyceae were the most abundant groups recovered in the BOB. Abundances and distribution of diatoms and Pelagophyceae were further verified using quantitative PCR analyses which showed the dominance of these groups near the Equator region (p < 0.01) where upwelling was likely the source of nutrients. Further, redundancy analysis demonstrated that temperature was an important environmental driver in structuring distributions of Cyanophyceae and dominant chromophytic phytoplankton. Morphological identification and quantification confirmed the dominance of diatoms, and also detected other cyanobacteria and dinoflagellates that were missing in our molecular characterizations. Pearson’s correlations of these morphologically identified phytoplankton with environmental gradients also indicated that nutrients and temperature were key variables shaping community structure. Combination of molecular characterization and morphological identification provided a comprehensive overview of chromophytic phytoplankton. This is the first molecular study of chromophytic phytoplankton accomplished in the BOB, and our results highlight a combination of molecular analysis targeting rbcL genes and microscopic detection in examining phytoplankton composition and diversity.

Autotrophic microbial community succession from glacier terminus to downstream waters on the Tibetan Plateau.

Glaciers harbour diverse microbes and autotrophic microbes play a key role in sustaining the glacial ecosystems by providing organic carbon. The succession of glacier-originated autotrophic microbes and their effects on downstream aquatic ecosystems remain unknown. We herein investigated the shift of autotrophic microbial communities in waters (not biofilms) along a glacier meltwater transect consisting of a glacier terminus outflow (subglacial), a glacial stream, two glacier-fed lakes (upper and lower) and their outflow on the Tibetan Plateau. The autotrophic community was characterized by cbbL gene using qPCR, T-RFLP and clone library/sequencing methods. The results demonstrated that form IC and ID autotrophic microbes exhibited a much higher abundance than form IAB in all waters along the transect. Form IAB autotrophic abundance in waters gradually decreased, while the form IC exhibited a substantial increase in the upper lake waters, and ID exhibited a substantial increase in the lower lake waters. The water form IC autotrophic community structure exhibited a distinguished shift from the glacier terminus outflow to the stream, while the form ID showed a dramatic shift from the stream to the lower lake. Our results revealed the succession patterns of glacier-originated autotrophic microbial communities and possible effects on downstream aquatic ecosystems.

Rubisco carboxylation kinetics and inorganic carbon utilization in polar versus cold-temperate seaweeds.

Despite the high productivity and ecological importance of seaweeds in polar coastal regions, little is known about their carbon utilization mechanisms, especially the kinetics of the CO2-fixing enzyme Rubisco. We analyzed Rubisco carboxylation kinetics at 4 °C and 25 °C in 12 diverse polar seaweed species (including cold-temperate populations of the same species) and the relationship with their ability to use bicarbonate, by using 13C isotope discrimination and pH drift experiments. We observed a large variation in Rubisco carboxylation kinetics among the selected species, although no correlation was found between either the Michaelis-Menten constant for CO2 (Kc) or Rubisco content per total soluble protein ([Rubisco]/[TSP]) and the ability to use bicarbonate for non-green seaweeds. This study reports intraspecific Rubisco cold adaptation by means of either higher Rubisco carboxylation turnover rate (kcatc) and carboxylase efficiency (kcatc/Kc) at 4 °C or higher [Rubisco]/[TSP] in some of the analyzed species. Our data point to a widespread ability for photosynthetic bicarbonate usage among polar seaweeds, despite the higher affinity of Rubisco for CO2 and higher dissolved CO2 concentration in cold seawater. Moreover, the reported catalytic variation within form ID Rubisco might avert the canonical trade-off previously observed between Kc and kcatc for plant Rubiscos.

Jumps of computably enumerable equivalence relations

We study computably enumerable equivalence relations (or, ceers), under computable reducibility ≤, and the halting jump operation on ceers. We show that every jump is uniform join-irreducible, and thus join-irreducible. Therefore, the uniform join of two incomparable ceers is not equivalent to any jump. On the other hand there exist ceers that are not equivalent to jumps, but are uniform join-irreducible: in fact above any non-universal ceer there is a ceer which is not equivalent to a jump, and is uniform join-irreducible. We also study transfinite iterations of the jump operation. If a is an ordinal notation, and E is a ceer, then let E(a) denote the ceer obtained by transfinitely iterating the jump on E along the path of ordinal notations up to a. In contrast with what happens for the Turing jump and Turing reducibility, where if a set X is an upper bound for the A-arithmetical sets then X(2) computes A(ω), we show that there is a ceer R such that R≥Id(n), for every finite ordinal n, but, for all k, R(k)≱Id(ω) (here Id is the identity equivalence relation). We show that if a,b are notations of the same ordinal less than ω2, then E(a)≡E(b), but there are notations a,b of ω2 such that Id(a) and Id(b) are incomparable. Moreover, there is no non-universal ceer which is an upper bound for all the ceers of the form Id(a) where a is a notation for ω2.

Acquisition and metabolism of carbon in the Ochrophyta other than diatoms.

The acquisition and assimilation of inorganic C have been investigated in several of the 15 clades of the Ochrophyta other than diatoms, with biochemical, physiological and genomic data indicating significant mechanistic variation. Form ID Rubiscos in the Ochrophyta are characterized by a broad range of kinetics values. In spite of relatively high K0.5CO2 and low CO2 : O2 selectivity, diffusive entry of CO2 occurs in the Chrysophyceae and Synurophyceae. Eustigmatophyceae and Phaeophyceae, on the contrary, have CO2 concentrating mechanisms, usually involving the direct or indirect use of [Formula: see text] This variability is possibly due to the ecological contexts of the organism. In brown algae, C fixation generally takes place through a classical C3 metabolism, but there are some hints of the occurrence of C4 metabolism and low amplitude CAM in a few members of the Fucales. Genomic data show the presence of a number of potential C4 and CAM genes in Ochrophyta other than diatoms, but the other core functions of many of these genes give a very limited diagnostic value to their presence and are insufficient to conclude that C4 photosynthesis is present in these algae.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'.

CO2-dependent carbon isotope fractionation in the dinoflagellate Alexandrium tamarense

The carbon isotopic composition of marine sedimentary organic matter is used to resolve long-term histories of pCO2 based on studies indicating a CO2-dependence of photosynthetic carbon isotope fractionation (εP). It recently was proposed that the δ13C values of dinoflagellates, as recorded in fossil dinocysts, might be used as a proxy for pCO2. However, significant questions remain regarding carbon isotope fractionation in dinoflagellates and how such fractionation may impact sedimentary records throughout the Phanerozoic. Here we investigate εP as a function of CO2 concentration and growth rate in the dinoflagellate Alexandrium tamarense. Experiments were conducted in nitrate-limited chemostat cultures. Values of εP were measured on cells having growth rates (μ) of 0.14–0.35d−1 and aqueous carbon dioxide concentrations of 10.2–63μmolkg−1 and were found to correlate linearly with μ/[CO2(aq)] (r2=0.94) in accord with prior, analogous chemostat investigations with eukaryotic phytoplankton. A maximum fractionation (εf) value of 27‰ was characterized from the intercept of the experiments, representing the first value of εf determined for an algal species employing Form II RubisCO—a structurally and catalytically distinct form of the carbon-fixing enzyme. This value is larger than theoretical predictions for Form II RubisCO and not significantly different from the ∼25‰ εf values observed for taxa employing Form ID RubisCO. We also measured the carbon isotope contents of dinosterol, hexadecanoic acid, and phytol from each experiment, finding that each class of biomarker exhibits different isotopic behavior. The apparent CO2-dependence of εP values in our experiments strengthens the proposal to use dinocyst δ13C values as a pCO2 proxy. Moreover, the similarity between the εf value for A. tamarense and the consensus value of ∼25‰ indicates that the CO2-sensitivity of carbon isotope fractionation saturates at similar CO2 levels across all three ecologically prominent clades of eukaryotic phytoplankton. This continuity of εf across taxa may help to explain why there is no coherent signature of phytoplankton evolutionary succession in Phanerozoic carbon isotope records.

A comprehensive framework for functional diversity patterns of marine chromophytic phytoplankton using rbcL phylogeny.

Marine chromophytes are taxonomically diverse group of algae and contribute approximately half of the total oceanic primary production. To understand the global patterns of functional diversity of chromophytic phytoplankton, robust bioinformatics and statistical analyses including deep phylogeny based on 2476 form ID rbcL gene sequences representing seven ecologically significant oceanographic ecoregions were undertaken. In addition, 12 form ID rbcL clone libraries were generated and analyzed (148 sequences) from Sundarbans Biosphere Reserve representing the world’s largest mangrove ecosystem as part of this study. Global phylogenetic analyses recovered 11 major clades of chromophytic phytoplankton in varying proportions with several novel rbcL sequences in each of the seven targeted ecoregions. Majority of OTUs was found to be exclusive to each ecoregion, whereas some were shared by two or more ecoregions based on beta-diversity analysis. Present phylogenetic and bioinformatics analyses provide a strong statistical support for the hypothesis that different oceanographic regimes harbor distinct and coherent groups of chromophytic phytoplankton. It has been also shown as part of this study that varying natural selection pressure on form ID rbcL gene under different environmental conditions could lead to functional differences and overall fitness of chromophytic phytoplankton populations.

Phytoplankton community diversity is influenced by environmental factors in the coastal East China Sea

Surface seawater was collected in four different seasons in the coastal East China Sea adjacent to the Yangtze River Estuary and phytoplankton community diversity was analysed using rbcL genetic markers. Phytoplankton diversity (Shannon Index) was found to be highest in autumn and lowest in summer, which was mainly controlled by seawater temperature, river runoff, the Taiwan Warm Current and possibly other environmental factors. For taxa characterized by Form IAB rbcL, the abundance of Chlorophyta was much greater than those of Proteobacteria and Cyanobacteria throughout the year with the most dominant taxa being Bathycoccus prasinos (Chlorophyta) in spring and Micromonas sp. (Chlorophyta) in other seasons. For taxa identified by Form ID rbcL, Coscinodiscophyceae (diatoms) constituted the largest group (most clones) in the phylogenetic tree. Dinophysis fortii (a dinoflagellate) was found to be the most abundant species in winter and spring and Skeletonema spp. (a diatom) dominated the phytoplankton community in summer and autumn. The seasonal dominance of Dinophysis fortii agreed well with the recently increasing proportion of dinoflagellates in the phytoplankton community in the coastal East China Sea. The abundance of Dinophysis fortii was negatively correlated with seawater temperature, suggesting that harmful algal blooms caused by this species may primarily occur in spring.

Diversity and spatial distribution of autotrophic communities within and between ice‐covered Antarctic lakes (McMurdo Dry Valleys)

AbstractWe compared the spatial distribution and diversity of autotrophic microbial communities among four permanently ice‐covered, chemically stratified lakes located in the Taylor (Lakes Bonney‐east and west lobes, Fryxell), and Wright (Lake Vanda) Valleys of the McMurdo Dry Valleys (Victoria Land, Antarctica). Clone libraries were constructed for major carbon fixation genes (rbcL isoforms IA/B and ID; cbbM; nifJ). Real time quantitative polymerase chain reaction assays were also developed for each of these markers of autotrophy to assess the influence of lake physicochemical factors on spatial trends in major photosynthetic and chemolithoautotrophic groups. Both lobes of Lake Bonney were dominated by Ribulose‐1, 5‐bisphosphate carboxylase oxygenase (RubisCO) form ID rbcL (haptophytes and stramenopiles), while Lake Fryxell was dominated by rbcL form ID‐harboring cryptophytes. Lake Vanda was the least productive lake and was dominated by form IA/B rbcL (cyanobacteria and chlorophytes) and form ID rbcL (stramenopiles). Autotrophic carbon fixation genes from photosynthetic organisms were generally positively correlated with light availability. Chemolithoautotrophic organisms harboring form II RubisCO were detected in only two of the four lakes (west lobe Lake Bonney and Fryxell) and were associated with the presence of either sulfide (Fryxell) or dimethylated sulfur compounds (west lobe Lake Bonney).

Variability of chromophytic phytoplankton in the North Pacific Subtropical Gyre

Eukaryotic phytoplankton play important roles in regulating productivity and material export in oligotrophic ocean ecosystems. In this study, we examined the vertical and temporal variability in planktonic Chromalveolate (hereafter chromophyte) assemblages over a 2-year period (2007–2009) at Station ALOHA (22°45′N, 158°W) in the North Pacific Subtropical Gyre (NPSG). Polymerase chain reaction (PCR) amplification, cloning, and sequencing of form ID rbcL genes from samples collected at nearly monthly intervals provided information on the diversity, abundances, and variability associated with chromophytic phytoplankton. Despite persistently oligotrophic conditions, the euphotic zone of this habitat supported a phylogenetically diverse assemblage of chromophytic algae, including representatives of various genera of diatoms, pelagophytes, prymnesiophytes, and dinoflagellates. Quantitative PCR (qPCR) amplification of diatom, prymnesiophyte, and pelagophyte rbcL phylotypes revealed that the population structure of these assemblages was highly variable in time, with gene abundances often varying more than an order of magnitude between successive months. Diatom rbcL genes were typically the most abundant in both the upper and lower regions of the euphotic zone, while rbcL gene abundances of the prymnesiophytes and pelagophytes were significantly greater (One-way ANOVA, P<0.05) in the lower regions of the euphotic zone (75–125m) than in the upper euphotic zone (5–45m). Similarly, we observed elevated concentrations of 19-hexanoxyfucoxanthin and 19-butanoxyfucoxanin (diagnostic pigments of prymnesiophytes and pelagophytes, respectively) in the lower euphotic zone, while concentrations of fucoxanthin (a diagnostic diatom pigment) demonstrated less vertical structure. Analyses of samples collected using sediment traps deployed at 150m revealed that members of diatoms, prymnesiophytes, and pelagophytes all contributed to material export out of the upper ocean. None of the phytoplankton groups displayed significant seasonality in gene abundances or fluxes over the period of observations. Our study confirms that diatoms are ubiquitous and diverse members of the euphotic zone phytoplankton assemblage in the NPSG, while prymnesiophytes and pelagophytes appear to capitalize on the relatively nutrient-enriched but low light conditions characteristic of the deeper euphotic zone waters. The combined use of molecular- and pigment-based tools demonstrated that despite persistently oligotrophic conditions chromophytic plankton are perennial contributors to upper ocean biomass and particle export in the NPSG.

O058 FIRST EXPERIENCE WITH EXTRAAMNIOTIC INTRAUTERINE PROSTAGLANDIN F2 ALPHA FOR MID TRIMESTER PREGNANCY TERMINATION – RARE CASE OF SEVERE COMPLICATION: A CASE REPORT

International Journal of Gynecology & ObstetricsVolume 119, Issue S3 p. S281-S281 Free communication (oral) presentations O058 FIRST EXPERIENCE WITH EXTRAAMNIOTIC INTRAUTERINE PROSTAGLANDIN F2 ALPHA FOR MID TRIMESTER PREGNANCY TERMINATION – RARE CASE OF SEVERE COMPLICATION: A CASE REPORT A.P. Andreeva, A.P. AndreevaSearch for more papers by this authorM. Tsankova, M. TsankovaSearch for more papers by this authorB. Marinov, B. MarinovSearch for more papers by this author A.P. Andreeva, A.P. AndreevaSearch for more papers by this authorM. Tsankova, M. TsankovaSearch for more papers by this authorB. Marinov, B. MarinovSearch for more papers by this author First published: 22 October 2012 https://doi.org/10.1016/S0020-7292(12)60488-3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume119, IssueS3Abstracts of XX FIGO World Congress of Gynecology and ObstetricsOctober 2012Pages S281-S281 RelatedInformation

Diversity and Expression of RubisCO Genes in a Perennially Ice-Covered Antarctic Lake during the Polar Night Transition

The autotrophic communities in the lakes of the McMurdo Dry Valleys, Antarctica, have generated interest since the early 1960s owing to low light transmission through the permanent ice covers, a strongly bimodal seasonal light cycle, constant cold water temperatures, and geographical isolation. Previous work has shown that autotrophic carbon fixation in these lakes provides an important source of organic matter to this polar desert. Lake Bonney has two lobes separated by a shallow sill and is one of several chemically stratified lakes in the dry valleys that support year-round biological activity. As part of an International Polar Year initiative, we monitored the diversity and abundance of major isoforms of RubisCO in Lake Bonney by using a combined sequencing and quantitative PCR approach during the transition from summer to polar winter. Form ID RubisCO genes related to a stramenopile, a haptophyte, and a cryptophyte were identified, while primers specific for form IA/B RubisCO detected a diverse autotrophic community of chlorophytes, cyanobacteria, and chemoautotrophic proteobacteria. Form ID RubisCO dominated phytoplankton communities in both lobes of the lake and closely matched depth profiles for photosynthesis and chlorophyll. Our results indicate a coupling between light availability, photosynthesis, and rbcL mRNA levels in deep phytoplankton populations. Regulatory control of rbcL in phytoplankton living in nutrient-deprived shallow depths does not appear to be solely light dependent. The distinct water chemistries of the east and west lobes have resulted in depth- and lobe-dependent variability in RubisCO diversity, which plays a role in transcriptional activity of the key gene responsible for carbon fixation.

Synthesis of novel PVA crosslink mixed matrix scaffolds and adsorption of copper ions from waste water

Mixed matrix scaffolds were composed through uniform distributed of ion exchange resins (H+ form Amberjet, ID 780 &mgr;m) into the stereo-structural chitosan matrix prepared by dissolving chitosan powder with a middle molecular weight into acetic solutions. Along the synthesis processes of mixed matrix scaffolds, 4 wt% of chitosan solutions containing of resin particles were homogeneous crosslinked with aqueous polyvinyl alcohol (PVA) solutions to produce PVA crosslink mixed matrix scaffolds. Specifically, ion exchange resin particles suspending in a viscous PVA crosslink chitosan solution were poured into cylindrical aluminum containers to prepare PVA crosslink chitosan mixed matrix scaffolds through the freeze-gelation process. PVA crosslink mixed matrix scaffolds were then utilized for removal of copper ions from waste water. The uniform distribution of ion exchange resins embedded in the stereo structure of chitosan matrices can clearly be observed on the images of the scanning electron micrograph (SEM). The adsorption processes were operated by adsorbing copper ions of waste water onto the amine functional groups (–NH2) exposed on the external and porous stereo-structural surfaces of chitosan matrices as well as the sulfonate functional groups at the outer surface of ion exchange resins respectively. Adsorption experiment were carried out at 25°C and pH 6.0 over the concentration ranging from 200 to 3000 mg Cu2+/l. The maximum adsorption capacity for PVA crosslink mixed matrix scaffolds were 93.5 mg Cu2+/g-adsorbents at the initial copper ion concentration of 2500 mg Cu2+/l. The adsorption isotherm curve could be simulated by Langmuir adsorption model. The desorption ratio of copper ions of PVA crosslink chitosan mixed matrix scaffolds was 97.9% at a low initial copper ion concentration of 200 mg Cu2+/l. As the initial copper ion concentrations increased, desorption ratio decreased.