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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  • Spatial modelling of wetness for the Antarctic Dry Valleys

    Stichbury, Glen; Brabyn, Lars; Green, T.G. Allan; Cary, S. Craig (2011)

    Journal article
    University of Waikato

    This paper describes a method used to model relative wetness for part of the Antarctic Dry Valleys using Geographic Information Systems (GIS) and remote sensing. The model produces a relative index of liquid water availability using variables that influence the volume and distribution of water. Remote sensing using Moderate Resolution Imaging Spectroradiometer (MODIS) images collected over four years is used to calculate an average index of snow cover and this is combined with other water sources such as glaciers and lakes. This water source model is then used to weight a hydrological flow accumulation model that uses slope derived from Light Detection and Ranging (LIDAR) elevation data. The resulting wetness index is validated using three-dimensional visualization and a comparison with a high-resolution Advanced Land Observing Satellite image that shows drainage channels. This research demonstrates that it is possible to produce a wetness model of Antarctica using data that are becoming widely available.

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  • Distribution and abiotic influences on hypolithic microbial communities in an Antarctic Dry Valley

    Cowan, Don A.; Pointing, Stephen B.; Stevens, Mark I.; Cary, S. Craig; Stomeo, Francesca; Tuffin, Marla I. (2010)

    Journal article
    University of Waikato

    The Miers Valley within the McMurdo Dry Valleys of Antarctica supports abundant quartz and marble substrates for hypolithons—microbial colonists on the underside of these translucent rocks. Three physically distinct hypolithic community types have been identified: cyanobacteria dominated (Type I), fungus dominated (Type II) or moss dominated (Type III). The distribution of the three types was mapped across much of the ~75 km2 area of the upper Miers Valley and correlated this with the measurements of selected micro-environmental variables. Type I hypolithons were most common and occurred at all altitudes up to 824 m, whilst Type II and Type III hypolithons were less abundant and restricted to lower altitudes on the valley floor (<257 m, respectively). Whilst all colonized quartz effectively filtered incident UVB irradiance, transmittance levels for UVA and PAR varied markedly and were significant in determining hypolith type. Notably, the Type I hypolithons occurred under rocks with a significantly lower transmittance of photosynthetically active radiation than Type II and III hypolithons. Altitude and aspect were also significant factors determining hypolith type, and a role for altitude-related abiotic variables in determining the distribution of Type I, II and III hypolithons is proposed.

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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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  • Microbial community composition of transiently wetted Antarctic Dry Valley soils

    Niederberger, Thomas D.; Sohm, Jill A.; Gunderson, Troy E.; Parker, Alexander E.; Tirindelli, Joëlle; Capone, Douglas G.; Carpenter, Edward J.; Cary, S. Craig (2015-01-28)

    Journal article
    University of Waikato

    During the summer months, wet (hyporheic) soils associated with ephemeral streams and lake edges in the Antarctic Dry Valleys (DVs) become hotspots of biological activity and are hypothesized to be an important source of carbon and nitrogen for arid DV soils. Recent research in the DV has focused on the geochemistry and microbial ecology of lakes and arid soils, with substantially less information being available on hyporheic soils. Here, we determined the unique properties of hyporheic microbial communities, resolved their relationship to environmental parameters and compared them to archetypal arid DV soils. Generally, pH increased and chlorophyll a concentrations decreased along transects from wet to arid soils (9.0 to ~7.0 for pH and ~0.8 to ~5 μg/cm3 for chlorophyll a, respectively). Soil water content decreased to below ~3% in the arid soils. Community fingerprinting-based principle component analyses revealed that bacterial communities formed distinct clusters specific to arid and wet soils; however, eukaryotic communities that clustered together did not have similar soil moisture content nor did they group together based on sampling location. Collectively, rRNA pyrosequencing indicated a considerably higher abundance of Cyanobacteria in wet soils and a higher abundance of Acidobacterial, Actinobacterial, Deinococcus/Thermus, Bacteroidetes, Firmicutes, Gemmatimonadetes, Nitrospira, and Planctomycetes in arid soils. The two most significant differences at the genus level were Gillisia signatures present in arid soils and chloroplast signatures related to Streptophyta that were common in wet soils. Fungal dominance was observed in arid soils and Viridiplantae were more common in wet soils. This research represents an in-depth characterization of microbial communities inhabiting wet DV soils. Results indicate that the repeated wetting of hyporheic zones has a profound impact on the bacterial and eukaryotic communities inhabiting in these areas.

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  • The ecological dichotomy of ammonia-oxidizing archaea and bacteria in the hyper-arid soils of the Antarctic Dry Valleys

    Magalhães, Catarina M.; Machado, Anna; Frank-Fahle, Béatrice; Lee, Charles Kai-Wu; Cary, S. Craig (2014-09-30)

    Journal article
    University of Waikato

    The McMurdo Dry Valleys of Antarctica are considered to be one of the most physically and chemically extreme terrestrial environments on the Earth. However, little is known about the organisms involved in nitrogen transformations in these environments. In this study, we investigated the diversity and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in four McMurdo Dry Valleys with highly variable soil geochemical properties and climatic conditions: Miers Valley, Upper Wright Valley, Beacon Valley and Battleship Promontory. The bacterial communities of these four Dry Valleys have been examined previously, and the results suggested that the extremely localized bacterial diversities are likely driven by the disparate physicochemical conditions associated with these locations. Here we showed that AOB and AOA amoA gene diversity was generally low; only four AOA and three AOB operational taxonomic units (OTUs) were identified from a total of 420 AOA and AOB amoA clones. Quantitative PCR analysis of amoA genes revealed clear differences in the relative abundances of AOA and AOB amoA genes among samples from the four dry valleys. Although AOB amoA gene dominated the ammonia-oxidizing community in soils from Miers Valley and Battleship Promontory, AOA amoA gene were more abundant in samples from Upper Wright and Beacon Valleys, where the environmental conditions are considerably harsher (e.g., extremely low soil C/N ratios and much higher soil electrical conductivity). Correlations between environmental variables and amoA genes copy numbers, as examined by redundancy analysis (RDA), revealed that higher AOA/AOB ratios were closely related to soils with high salts and Cu contents and low pH. Our findings hint at a dichotomized distribution of AOA and AOB within the Dry Valleys, potentially driven by environmental constraints.

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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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  • 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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  • Ancient origins determine global biogeography of hot and cold desert cyanobacteria

    Bahl, Justin; Lau, Maggie C.Y.; Smith, Gavin J.D.; Vijaykrishna, Dhanasekaran; Cary, S. Craig; Lacap, Donnabella C.; Lee, Charles Kai-Wu; Papke, Thane; Warren-Rhodes, Kimberley A.; Wong, Fiona K.Y.; McKay, Christopher P.; Pointing, Stephen B. (2010)

    Journal article
    University of Waikato

    Factors governing large-scale spatio-temporal distribution of microorganisms remain unresolved, yet are pivotal to understanding ecosystem value and function. Molecular genetic analyses have focused on the influence of niche and neutral processes in determining spatial patterns without considering the temporal scale. Here, we use temporal phylogenetic analysis calibrated using microfossil data for a globally sampled desert cyanobacterium, Chroococcidiopsis, to investigate spatio-temporal patterns in microbial biogeography and evolution. Multilocus phylogenetic associations were dependent on contemporary climate with no evidence for distance-related patterns. Massively parallel pyrosequencing of environmental samples confirmed that Chroococcidiopsis variants were specific to either hot or cold deserts. Temporally scaled phylogenetic analyses showed no evidence of recent inter-regional gene flow, indicating populations have not shared common ancestry since before the formation of modern continents. These results indicate that global distribution of desert cyanobacteria has not resulted from widespread contemporary dispersal but is an ancient evolutionary legacy. This highlights the importance of considering temporal scales in microbial biogeography.

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