Search

Summary: The Gypsum Hill (GH) springs on Axel Heiberg Island in the Canadian high Arctic are host to chemolithoautotrophic, sulfur‐oxidizing streamers that flourish in the high Arctic winter in water temperatures from −1.3 to 7°C with ~8% salinity in a high Arctic winter environment with air temperatures commonly less than −40°C and an average annual air temperature of −15°C. Metagenome sequencing and binning of streamer samples produced a 96% complete Thiomicrorhabdus sp. metagenome‐assembled genome representing a possible new species or subspecies. This is the most cold‐ and salt‐extreme source environment for a Thiomicrorhabdus genome yet described. Metaproteomic and metatranscriptomic analysis attributed nearly all gene expression in the streamers to the Thiomicrorhabdus sp. and suggested that it is active in CO2 fixation and oxidation of sulfide to elemental sulfur. In situ geochemical and isotopic analyses of the fractionation of multiple sulfur isotopes determined the biogeochemical transformation of sulfur from its source in Carboniferous evaporites to biotic processes occurring in the sediment and streamers. These complementary molecular tools provided a functional link between the geochemical substrates and the collective traits and activity that define the microbial community's interactions within a unique polar saline habitat where Thiomicrorhabdus‐dominated streamers form and flourish. [ABSTRACT FROM AUTHOR]

Environmental oxidation and microbial metabolism drive production of acid mine drainage (AMD). Understanding changes in the microbial community, due to geochemical and seasonal characteristics, is fundamental to AMD monitoring and remediation. Using direct sequencing of the 16S and 18S rRNA genes to identify bacterial, archaeal, and eukaryotic members of the microbial community at an AMD site in Northern Ontario, Canada, we found a dynamic community varying significantly across winter and summer sampling times. Community composition was correlated with physical and chemical properties, including water temperature, pH, conductivity, winter ice thickness, and metal concentrations. Within Bacteria, Acidithiobacillus was the dominant genus during winter (11%-57% of sequences) but Acidiphilium was dominant during summer (47%-87%). Within Eukarya, Chrysophyceae (1.5%-94%) and Microbotrymycetes (8%-92%) dominated the winter community, and LKM11 (4%-62%) and Chrysophyceae (25%-87%) the summer. There was less diversity and variability within the Archaea, with similar summer and winter communities mainly comprising Thermoplasmata (33%-64%) and Thermoprotei (5%-20%) classes but also including a large portion of unclassified reads (∼40%). Overall, the active AMD community varied significantly between winter and summer, with changing community profiles closely correlated to specific differences in AMD geochemical and physical properties, including pH, water temperature, ice thickness, and sulfate and metal concentrations. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the pathogenesis of infectious diseases requires comprehensive knowledge of the proteins expressed by the pathogen during in vivo growth in the host. Proteomics provides the tools for such analyses but the protocols required to purify sufficient quantities of the pathogen from the host organism are currently lacking. Here, we present a rapid immunomagnetic protocol for the separation of Francisella tularensis, a highly virulent bacterium and potential biowarfare agent, from the spleens of infected mice. In less than one hour, bacteria can be isolated in quantities sufficient to carry out meaningful proteomic comparisons with in vitro grown bacteria. Furthermore, the isolates are virtually free from contaminating host proteins. Two-dimensional gel analysis revealed a host induced proteome in which 78 proteins were differentially expressed in comparison to in vitro grown controls. The results obtained clearly demonstrate the complexity of the adaptive response of F. tularensis to the host environment, and the difficulty of mimicking such behavior in vitro. [Copyright &y& Elsevier]

Abstract: We characterized the bacterial community from an AMD tailings pond using both classical culturing and modern direct sequencing techniques and compared the two methods. Acid mine drainage (AMD) is produced by the environmental and microbial oxidation of minerals dissolved from mining waste. Surprisingly, we know little about the microbial communities associated with AMD, despite the fundamental ecological roles of these organisms and large-scale economic impact of these waste sites. AMD microbial communities have classically been characterized by laboratory culturing-based techniques and more recently by direct sequencing of marker gene sequences, primarily the 16S rRNA gene. In our comparison of the techniques, we find that their results are complementary, overall indicating very similar community structure with similar dominant species, but with each method identifying some species that were missed by the other. We were able to culture the majority of species that our direct sequencing results indicated were present, primarily species within the Acidithiobacillus and Acidiphilium genera, although estimates of relative species abundance were only obtained from direct sequencing. Interestingly, our culture-based methods recovered four species that had been overlooked from our sequencing results because of the rarity of the marker gene sequences, likely members of the rare biosphere. Further, direct sequencing indicated that a single genus, completely missed in our culture-based study, Legionella, was a dominant member of the microbial community. Our results suggest that while either method does a reasonable job of identifying the dominant members of the AMD microbial community, together the methods combine to give a more complete picture of the true diversity of this environment. [Copyright &y& Elsevier]

The discovery of polygonal terrain on Mars underlain by ice heightens interest in the possibility that this water-bearing habitat may be, or may have been, a suitable habitat for extant life. The possibility is supported by the recurring detection of terrestrial microorganisms in subsurface ice environments, such as ice wedges found beneath tundra polygon features. A characterization of the microbial community of ice wedges from the high Arctic was performed to determine whether this ice environment can sustain actively respiring microorganisms and to assess the ecology of this extreme niche. We found that ice wedge samples contained a relatively abundant number of culturable cells compared to other ice habitats (∼105 CFU·mL−1). Respiration assays in which radio-labeled acetate and in situ measurement of CO2 flux were used suggested low levels of microbial activity, though more sensitive techniques are required to confirm these findings. Based on 16S rRNA gene pyrosequencing, bacterial and archaeal ice wedge communities appeared to reflect surrounding soil communities. Two Pseudomonas sp. were the most abundant taxa in the ice wedge bacterial library (∼50%), while taxa related to ammonia-oxidizing Thaumarchaeota occupied 90% of the archaeal library. The tolerance of a variety of isolates to salinity and temperature revealed characteristics of a psychrotolerant, halotolerant community. Our findings support the hypothesis that ice wedges are capable of sustaining a diverse, plausibly active microbial community. As such, ice wedges, compared to other forms of less habitable ground ice, could serve as a reservoir for life on permanently cold, water-scarce, ice-rich extraterrestrial bodies and are therefore of interest to astrobiologists and ecologists alike. Key Words: Ice wedge-Cryo-environments-Astrobiology-Microbial respiration-Biodiversity. Astrobiology 12, 347-360. [ABSTRACT FROM AUTHOR]

Abstract: Francisella tularensis subspecies tularensis is one of the most virulent of bacterial pathogens for humans. Protective immunity against the pathogen can be induced in humans and some, but not all, mouse strains by vaccination with live, but not killed, vaccines. In mice, this protection is mediated predominantly by CD4+ and CD8+ T cells. This is thought to be the case too for humans. Nevertheless, it is possible that successful vaccination elicits antigen-specific antibodies that can serve as correlates of protection. To test this hypothesis we examined the repertoire of antibodies induced following successful immunization of BALB/c and CH3/HeN mice versus unsuccessful vaccination of C57BL/6 and DBA⧹2 mice with F. tularensis Live Vaccine Strain or following unsuccessful vaccination of BALB/c mice with highly related subspecies, F. novicida. The results showed that successful vaccination elicited antibodies to at least six proteins that were not recognized by antisera from vaccinated but unprotected mice. [Copyright &y& Elsevier]