Taxon interactions control the distributions of cryoconite bacteria colonizing a High Arctic ice cap

Microbial colonization of glacial ice surfaces incurs feedbacks which affect the melting rate of the ice surface. Ecosystems formed as microbe–mineral aggregates termed cryoconite locally reduce ice surface albedo and represent foci of biodiversity and biogeochemical cycling. Consequently, greater understanding the ecological processes in the formation of functional cryoconite ecosystems upon glacier surfaces is sought. Here, we present the first bacterial biogeography of an ice cap, evaluating the respective roles of dispersal, environmental and biotic filtration occurring at local scales in the assembly of cryoconite microbiota. 16S rRNA gene amplicon semiconductor sequencing of cryoconite colonizing a Svalbard ice cap coupled with digital elevation modelling of physical parameters reveals the bacterial community is dominated by a ubiquitous core of generalist taxa, with evidence for a moderate pairwise distance–decay relationship. While geographic position and melt season duration are prominent among environmental predictors of community structure, the core population of taxa appears highly influential in structuring the bacterial community. Taxon co‐occurrence network analysis reveals a highly modular community structured by positive interactions with bottleneck taxa, predominantly Actinobacteria affiliated to isolates from soil humus. In contrast, the filamentous cyanobacterial taxon (assigned to Leptolyngbya/Phormidesmis pristleyi) which dominates the community and binds together granular cryoconite are poorly connected to other taxa. While our study targeted one ice cap, the prominent role of generalist core taxa with close environmental relatives across the global cryosphere indicate discrete roles for cosmopolitan Actinobacteria and Cyanobacteria as respective keystone taxa and ecosystem engineers of cryoconite ecosystems colonizing ice caps.     

173 Role of free cysteines in leptin receptor

Leptin, a 16-kDa adipocytic peptide hormone (product of ob gene), is known to play a key role in the control of body weight and exerts its influence by binding to its long-form receptor (Ob-Rb). Ob-Rb belongs to class I cytokine receptor superfamily and consists of an extracellular, transmembrane, and an intracellular domain. Cysteines including free and disulphide-bonded are known to play a significant role in recognition of leptin by its receptor and are known to be highly conserved in different organisms including human, macaca, mouse, dog, sheep, zebrafish, and medaca. Recently, the crystal structure of leptin-binding domain of human leptin receptor has been determined (1). Using the structural data, we analyzed the role of free cysteines in leptin-binding domain of leptin receptor through docking studies using Rosettadock. The conserved free cysteines namely Cys-604 and Cys-613 were mutated to alanines and this resulted in drastic change in the binding orientation of leptin and its receptor. Based on computational analysis, we propose that cysteines either free or involved in disulphide bridges might play a crucial role during signaling and might be the primary determinant of leptin-receptor interactions, the details of which will be discussed. Currently, understanding the structural basis of leptin and its binding to leptin receptor gains much significance since it might pave the way for designing inhibitors that might be used in controlling obesity.     

Screening of microorganisms producing esterase for the production of (R)-β-Acetylmercaptoisobutyric acid from methyl (R,S)-β-acetylmercaptoisobutyrate

(R)-β-acetylmercaptoisobutyric acid (RAM), a chiral compound, is an important intermediate for the chemical synthesis of various antihypertensive and congestive heart failure drugs. Microorganisms capable of converting (R,S)-β-acetylmercaptoisobutyric acid ((R,S)-ester) to RAM were screened from soil microorganisms. A strain ofPseudomonas sp. 1001 screened from a soil sample was selected to be the best. Cells showed an activity of 540 U/mL from culture broth and the enzyme was thermostable up to 70°C. This strain could produce RAM asymmetrically from (R,S)-ester.     

Mutation analysis in Bardet�CBiedl syndrome by DNA pooling and massively parallel resequencing in 105 individuals

Bardet-Biedl syndrome (BBS) is a rare, primarily autosomal-recessive ciliopathy. The phenotype of this pleiotropic disease includes retinitis pigmentosa, postaxial polydactyly, truncal obesity, learning disabilities, hypogonadism and renal anomalies, among others. To date, mutations in 15 genes (BBS1-BBS14, SDCCAG8) have been described to cause BBS. The broad genetic locus heterogeneity renders mutation screening time-consuming and expensive. We applied a strategy of DNA pooling and subsequent massively parallel resequencing (MPR) to screen individuals affected with BBS from 105 families for mutations in 12 known BBS genes. DNA was pooled in 5 pools of 21 individuals each. All 132 coding exons of BBS1-BBS12 were amplified by conventional PCR. Subsequent MPR was performed on an Illumina Genome Analyzer II? platform. Following mutation identification, the mutation carrier was assigned by CEL I endonuclease heteroduplex screening and confirmed by Sanger sequencing. In 29 out of 105 individuals (28%), both mutated alleles were identified in 10 different BBS genes. A total of 35 different disease-causing mutations were confirmed, of which 18 mutations were novel. In 12 additional families, a total of 12 different single heterozygous changes of uncertain pathogenicity were found. Thus, DNA pooling combined with MPR offers a valuable strategy for mutation analysis of large patient cohorts, especially in genetically heterogeneous diseases such as BBS.