Selection in Coastal Synechococcus (Cyanobacteria) Populations Evaluated from Environmental Metagenomes

Environmental metagenomics provides snippets of genomic sequences from all organisms in an environmental sample and are an unprecedented resource of information for investigating microbial population genetics. Current analytical methods, however, are poorly equipped to handle metagenomic data, particularly of short, unlinked sequences. A custom analytical pipeline was developed to calculate dN/dS ratios, a common metric to evaluate the role of selection in the evolution of a gene, from environmental metagenomes sequenced using 454 technology of flow-sorted populations of marine Synechococcus, the dominant cyanobacteria in coastal environments. The large majority of genes (98%) have evolved under purifying selection (dN/dS<1). The metagenome sequence coverage of the reference genomes was not uniform and genes that were highly represented in the environment (i.e. high read coverage) tended to be more evolutionarily conserved. Of the genes that may have evolved under positive selection (dN/dS>1), 77 out of 83 (93%) were hypothetical. Notable among annotated genes, ribosomal protein L35 appears to be under positive selection in one Synechococcus population. Other annotated genes, in particular a possible porin, a large-conductance mechanosensitive channel, an ATP binding component of an ABC transporter, and a homologue of a pilus retraction protein had regions of the gene with elevated dN/dS. With the increasing use of next-generation sequencing in metagenomic investigations of microbial diversity and ecology, analytical methods need to accommodate the peculiarities of these data streams. By developing a means to analyze population diversity data from these environmental metagenomes, we have provided the first insight into the role of selection in the evolution of Synechococcus, a globally significant primary producer

Complete Chloroplast Genome Sequences of Important Oilseed Crop Sesamum indicum L

Sesamum indicum is an important crop plant species for yielding oil. The complete chloroplast (cp) genome of S. indicum (GenBank acc no. JN637766) is 153,324 bp in length, and has a pair of inverted repeat (IR) regions consisting of 25,141 bp each. The lengths of the large single copy (LSC) and the small single copy (SSC) regions are 85,170 bp and 17,872 bp, respectively. Comparative cp DNA sequence analyses of S. indicum with other cp genomes reveal that the genome structure, gene order, gene and intron contents, AT contents, codon usage, and transcription units are similar to the typical angiosperm cp genomes. Nucleotide diversity of the IR region between Sesamum and three other cp genomes is much lower than that of the LSC and SSC regions in both the coding region and noncoding region. As a summary, the regional constraints strongly affect the sequence evolution of the cp genomes, while the functional constraints weakly affect the sequence evolution of cp genomes. Five short inversions associated with short palindromic sequences that form step-loop structures were observed in the chloroplast genome of S. indicum. Twenty-eight different simple sequence repeat loci have been detected in the chloroplast genome of S. indicum. Almost all of the SSR loci were composed of A or T, so this may also contribute to the A-T richness of the cp genome of S. indicum. Seven large repeated loci in the chloroplast genome of S. indicum were also identified and these loci are useful to developing S. indicum-specific cp genome vectors. The complete cp DNA sequences of S. indicum reported in this paper are prerequisite to modifying this important oilseed crop by cp genetic engineering techniques

A simple, robust and semi-automated parasite egg isolation protocol

Large-scale parasite quantification is required for improving our understanding of the epidemiology and genetics of host–parasite interactions. We describe a protocol that uses a low-density salt solution for flotation and centrifugation of nematode eggs. Subsequently, sucrose flotation and precipitation are used to obtain clear egg preparations. Most traditional quantification protocols such as the McMaster technique are unsuited for the standardized processing of large numbers of samples and the analysis of large amounts of feces per sample. Consequently, they are suited only for small-scale surveys. Our protocol, which can be used to analyze up to 6 g of feces, results in clear egg preparations that are concentrated in wells of a microtiter plate and that are suited for digital recording and automated counting. Starting from a fecal suspension in the first flotation solution to a digital recording requires approximately 40 min per 24 samples.

Evidence for the evolution of multiple genomes in arbuscular mycorrhizal fungi.

Ancient asexuals directly contradict the evolutionary theories that explain why organisms should evolve a sexual life history. The mutualistic, arbuscular mycorrhizal fungi are thought to have been asexual for approximately 400 million years. In the absence of sex, highly divergent descendants of formerly allelic nucleotide sequences are thought to evolve in a genome. In mycorrhizal fungi, where individual offspring receive hundreds of nuclei from the parent, it has been hypothesized that a population of genetically different nuclei should evolve within one individual. Here we use DNA-DNA fluorescent in situ hybridization to show that genetically different nuclei co-exist in individual arbuscular mycorrhizal fungi. We also show that the population genetics techniques used in other organisms are unsuitable for detecting recombination because the assumptions and underlying processes do not fit the fungal genomic structure shown here. Instead we used a phylogenetic approach to show that the within-individual genetic variation that occurs in arbuscular mycorrhizal fungi probably evolved through accumulation of mutations in an essentially clonal genome, with some infrequent recombination events. We conclude that mycorrhizal fungi have evolved to be multi-genomic

BK virus nephropathy in an immunodeficient patient with chronic lymphocytic leukemia

Background: BK virus, genus polyomavirus, is known as an important cause of nephropathy (BKVN) in renal transplant patients. Cases of BKVN in native kidneys are rare. Objectives: To report a case of BKVN in a patient with chronic lymphocytic leukemia (CLL) and to examine viral and immune parameters. Study design: Quantitative BK virus DNA in plasma and relevant immune parameters were recorded in one CLL patient with BKVN and ten consecutive CLL patients without BKVN. Results: BKVN in the native kidneys of a CLL patient was histologically confirmed. The presence of BKVN correlated with immunologic parameters as well as factors known to cause renal tissue injury. BK viral load levels in the patient steadily increased and exceeded those of the control CLL patients. Conclusions: The results document a pathogenic role for BK virus in native kidneys of immuno-compromised CLL patients and indicate a role for quantitative BK virus DNA detection for early management of BKVN in native kidneys. Published by Elsevier B.V