64 results for Cary, S. Craig, Journal article

  • Investigating diet as the source of tetrodotoxin in Pleurobranchaea maculata

    Khor, Serena; Wood, Susanna A.; Salvitti, Lauren R.; Taylor, David I.; Adamson, Janet E.; McNabb, Paul; Cary, S. Craig (2014)

    Journal article
    University of Waikato

    The origin of tetrodotoxin (TTX) is highly debated; researchers have postulated either an endogenous or exogenous source with the host accumulating TTX symbiotically or via food chain transmission. The aim of this study was to determine whether the grey side-gilled sea slug (Pleurobranchaea maculata) could obtain TTX from a dietary source, and to attempt to identify this source through environmental surveys. Eighteen non-toxic P. maculata were maintained in aquariums and twelve were fed a TTX-containing diet. Three P. maculata were harvested after 1 h, 24 h, 17 days and 39 days and TTX concentrations in their stomach, gonad, mantle and remaining tissue/fluids determined using liquid chromatography-mass spectrometry. Tetrodotoxin was detected in all organs/tissue after 1 h with an average uptake of 32%. This decreased throughout the experiment (21%, 15% and 9%, respectively). Benthic surveys at sites with dense populations of toxic P. maculata detected very low or no TTX in other organisms. This study demonstrates that P. maculata can accumulate TTX through their diet. However, based on the absence of an identifiable TTX source in the environment, in concert with the extremely high TTX concentrations and short life spans of P. maculata, it is unlikely to be the sole TTX source for this species.

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  • Development of a non-lethal biopsy technique for estimating total tetrodotoxin concentrations in the grey side-gilled sea slug Pleurobranchaea maculata

    Khor, Serena; Wood, Susanna A.; Salvitti, Lauren R.; Ragg, Norman L.C.; Taylor, David I.; McNabb, Paul; Cary, S. Craig (2013)

    Journal article
    University of Waikato

    High concentrations of tetrodotoxin (TTX) have been detected in some New Zealand populations of Pleurobranchaea maculata (grey side-gilled sea slug). Within toxic populations there is significant variability in TTX concentrations among individuals, with up to 60-fold differences measured. This variability has led to challenges when conducting controlled laboratory experiments. The current method for assessing TTX concentrations within P. maculata is lethal, thus multiple individuals must be harvested at each sampling point to produce statistically meaningful data. In this study a method was developed for taking approximately 200 mg tissue biopsies using a TemnoEvolution® 18G × 11 cm Biopsy Needle inserted transversely into the foot. Correlation between the TTX concentrations in the biopsy sample and total TTX levels and in individual tissues were assessed. Six P. maculata were biopsied twice (nine days apart) and each individual was frozen immediately following the second sampling. Tetrodotoxin concentrations in biopsy samples and in the gonad, stomach, mantle and the remaining combined tissues and fluids were measured using liquid chromatography-mass spectrometry. Based on the proportional weight of the organs/tissues a total TTX concentration for each individual was calculated. There were strong correlations between biopsy TTX concentrations and the total (r2 = 0.88), stomach (r2 = 0.92) and gonad (r2 = 0.83) TTX concentrations. This technique will enable more robust laboratory studies to be undertaken, thereby assisting in understanding TTX kinetics, ecological function and origin within P. maculata.

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  • Genome sequence of temperate bacteriophage Psymv2 from Antarctic dry valley soil isolate Psychrobacter sp. MV2

    Meiring, Tracy L.; Tuffin, Marla I.; Cary, S. Craig; Cowan, Don A. (2012)

    Journal article
    University of Waikato

    A temperate phage, Psymv2, was isolated from an Antarctic soil bacterium, Psychrobacter sp. MV2. The morphology of Psymv2 was typical of the Siphoviridae, with an isometric head and non-contractile tail. The Psymv2 genome was found to be 35,725 bp in length, had a G + C content of 44.5 %, with 49 protein-coding genes and one tRNA gene predicted. Integration of Psymv2 occurred at an ssrA gene, with the last 27 bases of this gene directly repeated at the prophage ends. The genome was organised in a modular fashion: integration, regulation, packaging, head assembly, tail assembly, host specificity and lysis. While the genome sequence had little similarity on a nucleotide level to previously reported phage sequences, the genome architecture resembled that of Siphoviridae of low G + C Gram-positive bacteria. The closest relatives to Psymv2 were uncharacterized putative prophages within the P. arcticus 273-4 and Acinetobacter baumannii 6013113 genomes. Global alignment of the Psymv2 genome and these prophages revealed significant conservation of the structural modules despite the large spatial divergence of their hosts. A number of unique ORFs were identified in the Psymv2 genome that may contribute to phage and lysogen fitness.

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  • Accuracy assessment of land surface temperature retrievals from Landsat 7 ETM + in the Dry Valleys of Antarctica using iButton temperature loggers and weather station data

    Brabyn, Lars; Zawar-Reza, Peyman; Stichbury, Glen; Cary, S. Craig; Storey, Bryan; Laughlin, Daniel C.; Katurji, Marwan (2013)

    Journal article
    University of Waikato

    The McMurdo Dry Valleys of Antarctica are the largest snow/ice-free regions on this vast continent, comprising 1 % of the land mass. Due to harsh environmental conditions, the valleys are bereft of any vegetation. Land surface temperature is a key determinate of microclimate and a driver for sensible and latent heat fluxes of the surface. The Dry Valleys have been the focus of ecological studies as they arguably provide the simplest trophic structure suitable for modelling. In this paper, we employ a validation method for land surface temperatures obtained from Landsat 7 ETM + imagery and compared with in situ land surface temperature data collected from four transects totalling 45 iButtons. A single meteorological station was used to obtain a better understanding of daily and seasonal cycles in land surface temperatures. Results show a good agreement between the iButton and the Landsat 7 ETM + product for clear sky cases. We conclude that Landsat 7 ETM + derived land surface temperatures can be used at broad spatial scales for ecological and meteorological research.

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  • Pseudovertical Temperature Profiles Give Insight into Winter Evolution of the Atmospheric Boundary Layer over the McMurdo Dry Valleys of Antarctica

    Zawar-Reza, Peyman; Katurji, Marwan; Soltanzadeh, Iman; Dallafior, Tanja; Zhong, Shiyuan; Steinhoff, Daniel; Storey, Bryan; Cary, S. Craig (2013)

    Journal article
    University of Waikato

    Measuring routine vertical profiles of atmospheric temperature is critical in understanding stability and the dynamics of the boundary layer. Routine monitoring in remote areas such as the McMurdo Dry Valleys (MDV) of Antarctica is logistically difficult and expensive. Pseudovertical profiles that were derived from a network of inexpensive ground temperature sensors planted on valley sidewalls (up to 330 m above valley floor), together with data from a weather station and a numerical weather prediction model, provided a long-term climatological description of the evolution of the winter boundary layer over the MDV. In winter, persistent valley cold pools (VCPs) were common, lasting up to 2 weeks. The VCPs were eroded by warm-air advection from aloft associated with strong winds, increasing the temperature of the valley by as much as 25 K. Pseudovertical datasets as described here can be used for model validation.

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  • Abiotic factors influence microbial diversity in permanently cold soil horizons of a maritime-associated Antarctic Dry Valley

    Stomeo, Francesca; Makhalanyane, Thulani P.; Valverde, Angel; Pointing, Stephen B.; Stevens, Mark I.; Cary, S. Craig; Tuffin, Marla I.; Cowan, Don A. (2012)

    Journal article
    University of Waikato

    The McMurdo Dry Valleys collectively comprise the most extensive ice-free region in Antarctica and are considered one of the coldest arid environments on Earth. In low-altitude maritime-associated valleys, mineral soil profiles show distinct horizontal structuring, with a surface arid zone overlying a moist and biologically active zone generated by seasonally melted permafrost. In this study, long-term microenvironmental monitoring data show that temperature and soil humidity regimes vary in the soil horizons of north- and south-facing slopes within the Miers Valley, a maritime valley in the McMurdo Dry Valleys. We found that soil bacterial communities varied from the north to the south. The microbial assemblages at the surface and shallow subsurface depths displayed higher metabolic activity and diversity compared to the permafrost soil interface. Multivariate analysis indicated that K, C, Ca and moisture influenced the distribution and structure of microbial populations. Furthermore, because of the large % RH gradient between the frozen subsurface and the soil surface we propose that water transported to the surface as water vapour is available to microbial populations, eit

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  • Increased Inter-Colony Fusion Rates Are Associated with Reduced COI Haplotype Diversity in an Invasive Colonial Ascidian Didemnum vexillum

    Smith, Kirsty Fiona; Stefaniak, Lauren; Saito, Yasunori; Gemmill, Chrissen E.C.; Cary, S. Craig; Fidler, Andrew E. (2012)

    Journal article
    University of Waikato

    Considerable progress in our understanding of the population genetic changes associated with biological invasions has been made over the past decade. Using selectively neutral loci, it has been established that reductions in genetic diversity, reflecting founder effects, have occurred during the establishment of some invasive populations. However, some colonial organisms may actually gain an ecological advantage from reduced genetic diversity because of the associated reduction in inter-colony conflict. Here we report population genetic analyses, along with colony fusion experiments, for a highly invasive colonial ascidian, Didemnum vexillum. Analyses based on mitochondrial cytochrome oxidase I (COI) partial coding sequences revealed two distinct D. vexillum clades. One COI clade appears to be restricted to the probable native region (i.e., north-west Pacific Ocean), while the other clade is present in widely dispersed temperate coastal waters around the world. This clade structure was supported by 18S ribosomal DNA (rDNA) sequence data, which revealed a one base-pair difference between the two clades. Recently established populations of D. vexillum in New Zealand displayed greatly reduced COI genetic diversity when compared with D. vexillum in Japan. In association with this reduction in genetic diversity was a significantly higher inter-colony fusion rate between randomly paired New Zealand D. vexillum colonies (80%, standard deviation ±18%) when compared with colonies found in Japan (27%, standard deviation ±15%). The results of this study add to growing evidence that for colonial organisms reductions in population level genetic diversity may alter colony interaction dynamics and enhance the invasive potential of newly colonizing species.

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  • The inter-valley soil comparative survey: the ecology of Dry Valley edaphic microbial communities

    Lee, Charles Kai-Wu; Barbier, Béatrice A.; Bottos, Eric M.; McDonald, Ian R.; Cary, S. Craig (2011)

    Journal article
    University of Waikato

    Recent applications of molecular genetics to edaphic microbial communities of the McMurdo Dry Valleys and elsewhere have rejected a long-held belief that Antarctic soils contain extremely limited microbial diversity. The Inter-Valley Soil Comparative Survey aims to elucidate the factors shaping these unique microbial communities and their biogeography by integrating molecular genetic approaches with biogeochemical analyses. Although the microbial communities of Dry Valley soils may be complex, there is little doubt that the ecosystem's food web is relatively simple, and evidence suggests that physicochemical conditions may have the dominant role in shaping microbial communities. To examine this hypothesis, bacterial communities from representative soil samples collected in four geographically disparate Dry Valleys were analyzed using molecular genetic tools, including pyrosequencing of 16S rRNA gene PCR amplicons. Results show that the four communities are structurally and phylogenetically distinct, and possess significantly different levels of diversity. Strikingly, only 2 of 214 phylotypes were found in all four valleys, challenging a widespread assumption that the microbiota of the Dry Valleys is composed of a few cosmopolitan species. Analysis of soil geochemical properties indicated that salt content, alongside altitude and Cu2+, was significantly correlated with differences in microbial communities. Our results indicate that the microbial ecology of Dry Valley soils is highly localized and that physicochemical factors potentially have major roles in shaping the microbiology of ice-free areas of Antarctica. These findings hint at links between Dry Valley glacial geomorphology and microbial ecology, and raise previously unrecognized issues related to environmental management of this unique ecosystem.

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  • Carbon-fixation rates and associated microbial communities residing in arid and ephemerally wet Antarctic Dry Valley soils

    Niederberger, Thomas D.; Sohm, Jill A.; Gunderson, Troy; Tirindelli, Joëlle; Capone, Douglas G.; Carpenter, Edward J.; Cary, S. Craig (2015)

    Journal article
    University of Waikato

    Carbon-fixation is a critical process in severely oligotrophic Antarctic Dry Valley (DV) soils and may represent the major source of carbon in these arid environments. However, rates of C-fixation in DVs are currently unknown and the microorganisms responsible for these activities unidentified. In this study, C-fixation rates measured in the bulk arid soils (<5% moisture) ranged from below detection limits to ∼12 nmol C/cc/h. Rates in ephemerally wet soils ranged from ∼20 to 750 nmol C/cc/h, equating to turnover rates of ∼7–140 days, with lower rates in stream-associated soils as compared to lake-associated soils. Sequencing of the large subunit of RuBisCO (cbbL) in these soils identified green-type sequences dominated by the 1B cyanobacterial phylotype in both arid and wet soils including the RNA fraction of the wet soil. Red-type cbbL genes were dominated by 1C actinobacterial phylotypes in arid soils, with wetted soils containing nearly equal proportions of 1C (actinobacterial and proteobacterial signatures) and 1D (algal) phylotypes. Complementary 16S rRNA and 18S rRNA gene sequencing also revealed distinct differences in community structure between biotopes. This study is the first of its kind to examine C-fixation rates in DV soils and the microorganisms potentially responsible for these activities.

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  • Molecular adaptations to psychrophily: the impact of ‘omic’ technologies

    Casanueva, Ana; Tuffin, Marla I.; Cary, S. Craig; Cowan, Don A. (2010)

    Journal article
    University of Waikato

    The ability of cold-adapted microorganisms (generally referred to as psychrophiles) to survive is the result of molecular evolution and adaptations which, together, counteract the potentially deleterious effects of low kinetic energy environments and the freezing of water. These physiological adaptations are seen at many levels. Against a background of detailed comparative protein structural analyses, the recent surge of psychrophile proteome, genome, metagenome and transcriptome sequence data has triggered a series of sophisticated analyses of changes in global protein composition. These studies have revealed consistent and statistically robust changes in amino acid composition, interpreted as evolutionary mechanisms designed to destabilise protein structures, as well as identifying the presence of novel genes involved in cold adaptation.

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  • Distribution of Pfiesteria piscicida cyst populations in sediments of the Delaware Inland Bays, USA

    Coyne, Kathryn J.; Hare, Clinton E.; Popels, Linda C.; Hutchins, David A.; Cary, S. Craig (2006)

    Journal article
    University of Waikato

    The toxic dinoflagellate, Pfiesteria piscicida, is a common constituent of the phytoplankton community in the Delaware Inland Bays, USA. In this study, molecular methods were used to investigate the distributions of benthic stages (cysts) of P. piscicida in sediment cores from the Delaware Inland Bays. Cores from 35 sites were partitioned into nephloid and anoxic layers and analyzed for P. piscicida by nested amplification of the 18S rDNA gene using P. piscicida-specific primers. The presence of inhibitory substances in the PCR reaction was evaluated by inclusion of an exogenous control DNA in the extraction buffer, thus eliminating samples that may yield false-negative results. Our results indicate a patchy distribution of P. piscicida in sediments of the Delaware Inland Bays, with distinct differences between each of the three bays. Overall, P. piscicida was found more frequently in sediments from Rehoboth Bay compared to Indian River and Little Assawoman Bays. These differences suggest (i) that populations of P. piscicida may be more widely distributed in Rehoboth Bay, (ii) that populations of P. piscicida may have been introduced to Rehoboth Bay at an earlier time, (iii) that past blooms of P. piscicida in Rehoboth Bay estuaries may have seeded the sediments with higher numbers of cysts, and/or (iv) that Rehoboth Bay sediments may be more resistant to clearing due to storm turbulence.

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  • Development of a real-time PCR assay for the detection of the invasive clam, Corbula amurensis, in environmental samples

    Smith, Kirsty Fiona; Wood, Susanna A.; Mountfort, Douglas O.; Cary, S. Craig (2011)

    Journal article
    University of Waikato

    The detection of invasive species soon after an incursion, when the population is confined to a small area and at a low density, maximizes the probability of successful eradication. In response a number of sensitive molecular methods have been developed for identifying the larvae of marine invertebrate pests at extremely low concentrations. In this study we developed a highly sensitive real-time PCR assay targeting the 18S ribosomal DNA for the rapid and accurate identification of the Asian clam Corbula amurensis in environmental samples. Larvae of C. amurensis were spiked into commonly encountered sampling matrices including benthic assemblages, biofilms, sediment grabs and plankton net hauls, and the sensitivity of the assay was assessed. In this study the assay reliably detected one larva in up to 10 g of sediment, and five larvae in 10 g of benthic invertebrate and macro-algal assemblages. Seawater and benthic assemblage samples were collected from four major ports around New Zealand and all were negative for C. amurensis using the real-time PCR assay. This assay has the potential to enhance current surveillance methods, especially regarding morphologically difficult to identify early life-stages. Real-time PCR can be used with high through-put platforms and is extremely sensitive, increasing detection potential during initial stages of incursions.

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  • Co- variation in soil biodiversity and biogeochemistry in northern and southern Victoria Land, Antarctica

    Barrett, John E.; Virginia, R. A.; Wall, Diana H.; Cary, S. Craig; Adams, Byron J.; Hacker, A. L.; Aislabie, Jackie M. (2006)

    Journal article
    University of Waikato

    Data from six sites in Victoria Land (72–77°S) investigating co-variation in soil communities (microbial and invertebrate) with biogeochemical properties showthe influence of soil properties on habitat suitability varied among local landscapes as well as across climate gradients. Species richness of metazoan invertebrates (Nematoda, Tardigrada and Rotifera) was similar to previous descriptions in this region, though identification of three cryptic nematode species of Eudorylaimus through DNA analysis contributed to the understanding of controls over habitat preferences for individual species. Denaturing Gradient Gel Electrophoresis profiles revealed unexpectedly high diversity of bacteria. Distribution of distinct bacterial communities was associated with specific sites in northern and southern Victoria Land, as was the distribution of nematode and tardigrade species. Variation in soil metazoan communities was related to differences in soil organic matter, while bacterial diversity and community structure were not strongly correlated with any single soil property. There were no apparent correlations between metazoan and bacterial diversity, suggesting that controls over distribution and habitat suitability are different for bacterial and metazoan communities. Our results imply that top-down controls over bacterial diversity mediated by their metazoan consumers are not significant determinants of bacterial community structure and biomass in these ecosystems.

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  • Hypolithic microbial communities of quartz rocks from Miers Valley, McMurdo Dry Valleys, Antarctica

    Khan, Nuraan; Tuffin, Marla I.; Stafford, William; Cary, S. Craig; Lacap, Donnabella C.; Pointing, Stephen B.; Cowan, Don A. (2011)

    Journal article
    University of Waikato

    The McMurdo Dry Valleys region of eastern Antarctica is a cold desert that presents extreme challenges to life. Hypolithic microbial colonisation of the subsoil surfaces of translucent quartz rocks represent a significant source of terrestrial biomass and productivity in this region. Previous studies have described hypoliths as dominated by cyanobacteria. However, hypoliths that occur in the lower Dry Valleys such as the Miers, Garwood and Marshall Valleys are unusual as they are not necessarily cyanobacteria-dominated. These hypoliths support significant eukaryal colonisation by fungi and mosses in addition to cyanobacteria- dominated bacterial assemblages and so have considerable ecological value in this barren landscape. Here, we characterise these novel hypoliths by analysis of environmental rRNA gene sequences. The hypolithic community was demonstrated to be distinct from the surrounding soil and non-translucent rocks. Hypoliths supported cyanobacterial signatures from the Oscillatoriales and Nostocales. Other heterotrophic bacterial signatures were also recovered, and these were phylogenetically diverse and spanned 8 other bacterial phyla. Archaeal phylotypes recovered were phylogenetically aYliated with the large group of unclassified, uncultured Crenarcheota. Eukaryal phylotypes indicated that free-living ascomycetous fungi, chlorophytes and mosses (Bryum sp.) were all supported by these hypoliths, and these are thought to be responsible for the extensive eukaryotic biomass that develops around quartz rocks.

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  • Resolving environmental drivers of microbial community structure in Antarctic soils

    Smith, Julie L.; Barrett, John E.; Tusnady, Gabor; Rejto, Lidia; Cary, S. Craig (2009)

    Journal article
    University of Waikato

    Antarctic soils are extremely cold, dry, and oligotrophic, yet harbour surprisingly high bacterial diversity. The severity of environmental conditions has constrained the development of multi-trophic communities, and species richness and distribution is thought to be driven primarily by abiotic factors. Sites in northern and southern Victoria Land were sampled for bacterial community structure and soil physicochemical properties in conjunction with the US and New Zealand Latitudinal Gradient Project. Bacterial community structure was determined using a high-resolution molecular fingerprinting method for 80 soil samples from Taylor Valley and Cape Hallett sites which are separated by five degrees of latitude and have distinct soil chemistry. Taylor Valley is part of the McMurdo Dry Valleys, while Cape Hallett is the site of a penguin rookery and contains ornithogenic soils. The influence of soil moisture, pH, conductivity, ammonia, nitrate, total nitrogen and organic carbon on community structure was revealed using Spearman rank correlation, Mantel test, and principal components analysis. High spatial variability was detected in bacterial communities and community structure was correlated with soil moisture and pH. Both unique and shared bacterial community members were detected at Taylor Valley and Cape Hallett despite the considerable distance between the sites.

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  • Influence of soil properties on archaeal diversity and distribution in the McMurdo Dry Valleys, Antarctica

    Richter, Ingrid; Herbold, Craig W.; Lee, Charles Kai-Wu; McDonald, Ian R.; Barrett, John E.; Cary, S. Craig (2014)

    Journal article
    University of Waikato

    Archaea are the least understood members of the microbial community in Antarctic mineral soils. Although their occurrence in Antarctic coastal soils has been previously documented, little is known about their distribution in soils across the McMurdo Dry Valleys, Victoria Land. In this study, terminal-restriction fragment length polymorphism (t-RFLP) analysis and 454 pyrosequencing were coupled with a detailed analysis of soil physicochemical properties to characterize archaeal diversity and identify environmental factors that might shape and maintain archaeal communities in soils of the three southern most McMurdo Dry Valleys (Garwood, Marshall, and Miers Valley). Archaea were successfully detected in all inland and coastal mineral soils tested, revealing a low overall richness (mean of six operational taxonomic units [OTUs] per sample site). However, OTU richness was higher in some soils and this higher richness was positively correlated with soil water content, indicating water as a main driver of archaeal community richness. In total, 18 archaeal OTUs were detected, predominately Thaumarchaeota affiliated with Marine Group 1.1b (> 80% of all archaeal sequences recovered). Less abundant OTUs (2% of all archaeal sequences) were loosely related to members of the phylum Euryarchaeota. This is the first comprehensive study showing a widespread presence and distribution of Archaea in inland Antarctic soils.

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  • The distribution and identity of edaphic fungi in the McMurdo Dry Valleys

    Dreesens, Lisa L.; Lee, Charles Kai-Wu; Cary, S. Craig (2014)

    Journal article
    University of Waikato

    Contrary to earlier assumptions, molecular evidence has demonstrated the presence of diverse and localized soil bacterial communities in the McMurdo Dry Valleys of Antarctica. Meanwhile, it remains unclear whether fungal signals so far detected in Dry Valley soils using both culture-based and molecular techniques represent adapted and ecologically active biomass or spores transported by wind. Through a systematic and quantitative molecular survey, we identified significant heterogeneities in soil fungal communities across the Dry Valleys that robustly correlate with heterogeneities in soil physicochemical properties. Community fingerprinting analysis and 454 pyrosequencing of the fungal ribosomal intergenic spacer region revealed different levels of heterogeneity in fungal diversity within individual Dry Valleys and a surprising abundance of Chytridiomycota species, whereas previous studies suggested that Dry Valley soils were dominated by Ascomycota and Basidiomycota. Critically, we identified significant differences in fungal community composition and structure of adjacent sites with no obvious barrier to aeolian transport between them. These findings suggest that edaphic fungi of the Antarctic Dry Valleys are adapted to local environments and represent an ecologically relevant (and possibly important) heterotrophic component of the ecosystem.

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  • Enzymic approach to eurythermalism of Alvinella pompejana and its Episymbionts

    Lee, Charles Kai-Wu; Cary, S. Craig; Murray, Alison E.; Daniel, Roy M. (2007)

    Journal article
    University of Waikato

    The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

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  • Development and field assessment of a quantitative PCR for the detection and enumeration of the noxious bloom-former Anabaena planktonica

    Rueckert, Andreas; Wood, Susanna A.; Cary, S. Craig (2007)

    Journal article
    University of Waikato

    Anabaena planktonica is a harmful, bloom-forming freshwater cyanobacterium, which has arrived recently in New Zealand. In the short time since its incursion (<10 yr), A. planktonica has spread rapidly throughout lakes in the North Island. To date, the identification and enumeration of A. planktonica has been undertaken using light microscopy. There is an urgent demand for a highly sensitive and specific quantitative detection method that can be combined with a high sample processing capability in order to increase sampling frequency. In this study, we sequenced 36 cyanobacterial 16S rRNA genes (partial), complete intergenic transcribed spacers (ITS), and 23S rRNA genes (partial) of fresh-water cyanobacteria found in New Zealand. The sequences were used to develop an A. Planktonica specific TaqMan QPCR assay targeting the long ITS1-L and the 5´ terminus of the 23S rRNA gene. The QPCR method was linear (R2 = 0.999) over seven orders of magnitude with a lower end sensitivity of approximately five A. planktonica cells in the presence of exogenous DNA. The quantitative PCR (QPCR) method was used to assess the spatial distribution and seasonal population dynamics of A. planktonica from the Lower Karori Reservoir (Wellington, New Zealand) over a five-month period. The QPCR results were compared directly to microscopic cell counts and found to correlate significantly (95% confidence level) under both bloom and non-bloom conditions. The current QPCR assay will be an invaluable tool for routine monitoring programs and in research investigating environmental factors that regulate the population dynamics and the blooming of A. planktonica.

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  • The microbial olympics

    Youle, Merry; Rohwer, Forest; Stacy, Apollo; Whiteley, Marvin; Steel, Bradley C.; Delalez, Nicolas J.; Nord, Ashley L.; Berry, Richard M.; Armitage, Judith P.; Kamoun, Sophien; Hogenhout, Saskia; Diggle, Stephen P.; Gurney, James; Pollitt, Eric J. G.; Boetius, Antje; Cary, S. Craig (2012)

    Journal article
    University of Waikato

    Every four years, the Olympic Games plays host to competitors who have built on their natural talent by training for many years to become the best in their chosen discipline. Similar spirit and endeavour can be found throughout the microbial world, in which every day is a competition to survive and thrive. Microorganisms are trained through evolution to become the fittest and the best adapted to a particular environmental niche or lifestyle, and to innovate when the 'rules of the game' are changed by alterations to their natural habitats. In this Essay, we honour the best competitors in the microbial world by inviting them to take part in the inaugural Microbial Olympics.

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