The Diverse Applications of Cladistic Analysis of Molecular Evolution, with Special Reference to Nested Clade Analysis

The genetic variation found in small regions of the genomes of many species can be arranged into haplotype trees that reflect the evolutionary genealogy of the DNA lineages found in that region and the accumulation of mutations on those lineages. This review demonstrates some of the many ways in which clades (branches) of haplotype trees have been applied in recent years, including the study of genotype/phenotype associations at candidate loci and in genome-wide association studies, the phylogeographic history of species, human evolution, the conservation of endangered species, and the identification of species

Maximizing viral titer yield at harvest through metabolic process analytical technology (PAT)

This work pertains to the optimization of enterovirus production using MRC5 cultured on microcarriers within a bioreactor. This enterovirus, like other lytic viruses, has a rapid decay rate within a production batch, such that a 30% loss of potency is observed per day. Therefore, to maximize the yield of infectious product from the bioreactor, harvest needs to be timed to maximize the amount of viral production while minimizing the decay. Viral potency assays have slow turnaround times relative to a production batch, making an online process analytical technology (PAT) critical to maximize titers. In pursuit of an online method for tracking viral titer, three different PAT-enabled streams were investigated: dissolved oxygen (DO), viable cell volume (VCV), and oxygen uptake rate (OUR). DO monitoring was the simplest and leverages the ubiquitous DO trends of production, however it remains scale and gassing strategy dependent. Dual-frequency capacitance measurements were utilized to calculate VCV and thereby quantify the magnitude and timing of massive cell lysis that was correlated in time with peak viral potency. OUR, which quantifies the amount of oxygen being consumed per cellular volume, leverages both capacitance and DO measurements (in addition to oxygen mass balances pertaining to the gassing strategy) to provide a holistic scale-independent metabolic PAT readout. The sharp increase we observe in OUR prior to its decline due to cell lysis appears to be related to increased oxygen demand during viral production—this sharp increase precedes peak viral potency and peak specific productivity in our process. Data generated by our PAT tools—DO, VCV, OUR— were compared to potency and specific productivity trends across 22 batches. In this talk, we will discuss the utility and application of the tools, repeatability of our models across datasets, and the strengths and weaknesses of each model. Please click Download on the upper right corner to see the full abstract

1 Modeling Diverse Standpoints in Text Classification: Learning to Be Human by Modeling Human Values

An annotator’s classification of a text not only tells us something about the intent of the text’s author, it also tells us something about the annotator’s standpoint. To understand authorial intent, we can consider all of these diverse standpoints, as well as the extent to which the annotators ’ standpoints affect their perceptions of authorial intent. To model human behavior, it is important to model humans ’ unique standpoints. Human values play an especially important role in determining human behavior and how people perceive the world around them, so any effort to model human behavior and perception can benefit from an effort to understand and model human values. Instead of training humans to obscure their standpoints and act like computers, we should teach computers to have standpoints of their own

Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in McCollom, T. M., Klein, F., Moskowitz, B., Berquo, T. S., Bach, W., & Templeton, A. S. Hydrogen generation and iron partitioning during experimental serpentinization of an olivine-pyroxene mixture. Geochimica Et Cosmochimica Acta, 282, (2020): 55-75, doi:10.1016/j.gca.2020.05.016.A series of laboratory experiments was conducted to investigate serpentinization of olivine–pyroxene mixtures at 230 °C, with the objective of evaluating the effect of mixed compositions on Fe partitioning among product minerals, H2 generation, and reaction rates. An initial experiment reacted a mixture of 86 wt.% olivine and 14 wt.% orthopyroxene (Opx) with the same initial grain size for 387 days. The experiment resulted in extensive reaction (∼53% conversion), and solids recovered at termination of the experiment were dominated by Fe-bearing chrysotile and relict olivine along with minor brucite and magnetite. Only limited amounts of H2 were generated during the first ∼100 days of the experiment, but the rate of H2 generation then increased sharply coincident with an increase in pH from mildly alkaline to strongly alkaline conditions. Two shorter term experiments with the same reactants (26 and 113 days) produced a mixture of lizardite and talc that formed a thin coating on relict olivine and Opx grains, with virtually no generation of H2. Comparison of the results with reaction path models indicates that the Opx reacted about two times faster than olivine, which contrasts with some previous studies that suggested olivine should react more rapidly than Opx at the experimental conditions. The models also indicate that the long-term experiment transitioned from producing serpentine ± talc early in the early stages to precipitation of serpentine plus magnetite, with brucite beginning to precipitate only late in the experiment as Opx was depleted. The results indicate that overall reaction of olivine and Opx was initially relatively slow, but reaction rates accelerated substantially when the pH transitioned to strongly alkaline conditions. Serpentine and brucite precipitated from the olivine-Opx mixture had higher Fe contents than observed in olivine-only experiments at mildly alkaline pH, but had comparable Fe contents to reaction of olivine at strongly alkaline pH implying that higher pH may favor greater partitioning of Fe into serpentine and brucite and less into magnetite. Despite the presence of brucite, dissolved silica activities during the long-term olivine-Opx experiment maintained levels well above serpentine-brucite equilibrium. Instead, silica activities converged on levels close to metastable equilibrium between brucite and olivine. It is proposed that silica levels during the experiment may have been regulated by exchange of SiO2 between the fluid and a silica-depleted, brucite-like surface layer on dissolving olivine.This research was supported by the U. S. National Science Foundation Marine Geology and Geophysics program through grant NSF-OCE 0927744 and by the NASA Astrobiology Institute through Cooperative Agreement NNA15BB02A. Additional support to TMM from the Hanse Wissenschaftskolleg (Delmenhorst, Germany) at an early stage of this project is gratefully acknowledged. FK acknowledges support through Grant NSF-OCE 1427274. The IRM is supported by the Instruments and Facilities Program of the NSF Division of Earth Science. This is IRM contribution 1711. We very much appreciate the comments of Fabrice Brunet, Gleb Pokrovski and an anonymous reviewer that helped us refine our interpretations and improve communication of the results

Many Globally Isolated AD Hybrid Strains of Cryptococcus neoformans Originated in Africa

Interspecific and intervarietal hybridization may contribute to the biological diversity of fungal populations. Cryptococcus neoformans is a pathogenic yeast and the most common fungal cause of meningitis in patients with AIDS. Most patients are infected with either of the two varieties of C. neoformans, designated as serotype A (C. neoformans var. grubii) or serotype D (C. neoformans var. neoformans). In addition, serotype AD strains, which are hybrids of these two varieties, are commonly isolated from clinical and environmental samples. While most isolates of serotype A and serotype D are haploid, AD strains are diploid or aneuploid, and contain two sets of chromosomes and two mating type alleles, MATa and MATα, one from each of the serotypes. The global population of serotype A is dominated by isolates with the MATα mating type (Aα); however, about half of the globally analyzed AD strains possess the extremely rare serotype A MATa allele (Aa). We previously described an unusual population of serotype A in Botswana, in which 25% of the strains contain the rare MATa allele. Here we utilized two methods, phylogenetic analysis of three genes and genotyping by scoring amplified fragment length polymorphisms, and discovered that AD hybrid strains possessing the rare serotype A MATa allele (genotype AaDα) cluster with isolates of serotype A from Botswana, whereas AD hybrids that possess the MATα serotype A allele (AαDa and AαDα) cluster with cosmopolitan isolates of serotype A. We also determined that AD hybrid strains are more resistant to UV irradiation than haploid serotype A strains from Botswana. These findings support two hypotheses: (i) AaDα strains originated in sub-Saharan Africa from a cross between strains of serotypes A and D; and (ii) this fusion produced hybrid strains with increased fitness, enabling the Botswanan serotype A MATa genome, which is otherwise geographically restricted, to survive, emigrate, and propagate throughout the world

Direct Detection and Genotyping of Klebsiella pneumoniae Carbapenemases from Urine by Use of a New DNA Microarray Test

Klebsiella pneumoniae carbapenemases (KPC) are considered a serious threat to antibiotic therapy as they confer resistance to carbapenems, which are used to treat Extended-spectrum beta-lactamase (ESBL) producing bacteria. Here, we describe the development and evaluation of a DNA microarray for detection and genotyping of KPC genes (blaKPC) within 5 hours. To test the whole assay procedure (DNA extraction + DNA microarray assay) directly from clinical specimen, we compared two commercial DNA extraction kits (QIAprep Spin Miniprep Kit (Qiagen), Urine Bacterial DNA Isolation Kit (Norgen)) for the direct DNA extraction from urine samples (dilution series spiked in human urine). A reliable SNP typing from 1×105 CFU/mL urine was demonstrated for Escherichia coli (Qiagen and Norgen) and 80 CFU/mL urine on average for K. pneumoniae (Norgen). The study presents for the first time the combination of a new KPC-microarray with commercial sample preparation for the detection and genotyping of microbial pathogens directly from clinical specimen which paves the way towards tests providing epidemiological and diagnostic data enabling better antimicrobial stewardship