17 research outputs found
The changing form of Antarctic biodiversity
Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. Understanding of how this diversity is distributed in marine and terrestrial systems, the mechanisms underlying its spatial variation, and the significance of the microbiota is growing rapidly. Broadly recognizable drivers of diversity variation include energy availability and historical refugia. The impacts of local human activities and global environmental change nonetheless pose challenges to the current and future understanding of Antarctic biodiversity. Life in the Antarctic and the Southern Ocean is surprisingly rich, and as much at risk from environmental change as it is elsewher
Disease-associated glycosylated molecular variants of human C-reactive protein activate complement-mediated hemolysis of erythrocytes in tuberculosis and Indian visceral leishmaniasis
Human C-reactive protein (CRP), as a mediator
of innate immunity, removed damaged cells by activating
the classical complement pathway. Previous studies have
successfully demonstrated that CRPs are differentially induced
as glycosylated molecular variants in certain pathological
conditions. Affinity-purified CRPs from two most
prevalent diseases in India viz. tuberculosis (TB) and
visceral leishmaniasis (VL) have differential glycosylation
in their sugar composition and linkages. As anemia is a
common manifestation in TB and VL, we assessed the
contributory role of glycosylated CRPs to influence hemolysis
via CRP-complement-pathway as compared to
healthy control subjects. Accordingly, the specific binding
of glycosylated CRPs with erythrocytes was established by
flow-cytometry and ELISA. Significantly, deglycosylated
CRPs showed a 7–8-fold reduced binding with erythrocytes
confirming the role of glycosylated moieties. Scatchard
analysis revealed striking differences in the apparent binding constants (104–105M−1) and number of binding
sites (106–107sites/erythrocyte) for CRP on patients’ erythrocytes
as compared to normal. Western blotting along with
immunoprecipitation analysis revealed the presence of
distinct molecular determinants on TB and VL erythrocytes
specific to disease-associated CRP. Increased fragility, hydrophobicity
and decreased rigidity of diseased-erythrocytes
upon binding with glycosylated CRP suggested membrane
damage. Finally, the erythrocyte-CRP binding was shown to
activate the CRP-complement-cascade causing hemolysis,
even at physiological concentration of CRP (10μg/ml).
Thus, it may be postulated that CRP have a protective role
towards the clearance of damaged-erythrocytes in these two
disease
Microbial communities in the subglacial waters of the Vatnajokull ice cap, Iceland
Subglacial lakes beneath the Vatnajokull ice cap in Iceland host endemic communities of microorganisms adapted to cold, dark and nutrient-poor waters, but the mechanisms by which these microbes disseminate under the ice and colonize these lakes are unknown. We present new data on this subglacial microbiome generated from samples of two subglacial lakes, a subglacial flood and a lake that was formerly subglacial but now partly exposed to the atmosphere. These data include parallel 16S rRNA gene amplicon libraries constructed using novel primers that span the v3-v5 and v4-v6 hypervariable regions. Archaea were not detected in either subglacial lake, and the communities are dominated by only five bacterial taxa. Our paired libraries are highly concordant for the most abundant taxa, but estimates of diversity (abundance-based coverage estimator) in the v4-v6 libraries are 3-8 times higher than in corresponding v3-v5 libraries. The dominant taxa are closely related to cultivated anaerobes and microaerobes, and may occupy unique metabolic niches in a chemoautolithotrophic ecosystem. The populations of the major taxa in the subglacial lakes are indistinguishable (>99% sequence identity), despite separation by 6 km and an ice divide; one taxon is ubiquitous in our Vatnajokull samples. We propose that the glacial bed is connected through an aquifer in the underlying permeable basalt, and these subglacial lakes are colonized from a deeper, subterranean microbiome. The ISME Journal (2013) 7, 427-437; doi:10.1038/ismej.2012.97; published online 13 September 201