Towards the validation of high-throughput sequencing (HTS) for routine plant virus diagnostics: measurement of variation linked to HTS detection of citrus viruses and viroids

Background High-throughput sequencing (HTS) has been applied successfully for virus and viroid discovery in many agricultural crops leading to the current drive to apply this technology in routine pathogen detection. The validation of HTS-based pathogen detection is therefore paramount. Methods Plant infections were established by graft inoculating a suite of viruses and viroids from established sources for further study. Four plants (one healthy plant and three infected) were sampled in triplicate and total RNA was extracted using two different methods (CTAB extraction protocol and the Zymo Research Quick-RNA Plant Miniprep Kit) and sent for Illumina HTS. One replicate sample of each plant for each RNA extraction method was also sent for HTS on an Ion Torrent platform. The data were evaluated for biological and technical variation focussing on RNA extraction method, platform used and bioinformatic analysis. Results The study evaluated the influence of different HTS protocols on the sensitivity, specificity and repeatability of HTS as a detection tool. Both extraction methods and sequencing platforms resulted in significant differences between the data sets. Using a de novo assembly approach, complemented with read mapping, the Illumina data allowed a greater proportion of the expected pathogen scaffolds to be inferred, and an accurate virome profile was constructed. The complete virome profile was also constructed using the Ion Torrent data but analyses showed that more sequencing depth is required to be comparative to the Illumina protocol and produce consistent results. The CTAB extraction protocol lowered the proportion of viroid sequences recovered with HTS, and the Zymo Research kit resulted in more variation in the read counts obtained per pathogen sequence. The expression profiles of reference genes were also investigated to assess the suitability of these genes as internal controls to allow for the comparison between samples across different protocols. Conclusions This study highlights the need to measure the level of variation that can arise from the different variables of an HTS protocol, from sample preparation to data analysis. HTS is more comprehensive than any assay previously used, but with the necessary validations and standard operating procedures, the implementation of HTS as part of routine pathogen screening practices is possible.

AMPLIFIKASI GENE mtDNA CO1 IKAN MALONG (MURAENESOCIDAE) DARI PERAIRAN KOTA TARAKAN DENGAN TEKNIK PCR

Ikan Malong atau di Tarakan lebih dikenal dengan sebutan Ikan Ose merupakan ikan komersil yang tersebar secara luas di laut Indo-west pacific meliputi laut merah, teluk Persia, pantai barat India, dan sri langka hingga Fiji dan Tuvalu, bagian utara jepang dan korea, bagian selatan laut arafura, dan utara Australia. Di Indonesia Ikan Malong tersebar dari pulau Sumatra, Kalimantan, dan Sulawesi. Dengan penyebaran yang begitu luas sayangnya informasi genetik ikan Ose masih sangat terbatas. Penelitian ini dilakukan untuk mengisolasi dan mengamplifikasi gen mtDNA CO1 ikan ose dari perairan Kota Tarakan. Metode penelitian yang dilakukan meliputi isolasi genom mtDNA CO1 dengan mengikuti petunjuk Quick-DNA Tissue/Insect Miniprep Kit (Zymo Research, D6016). Dilanjutkan dengan amplifikasi (perbanyakan) untai gen mtDNA CO1 menggunakan 4 primer cocktail berdasarkan Canadian Center for DNA Barcoding (CCDB), 2006. Kemudian visualisasi produk PCR dengan menggunakan teknik gel elektroforesis. Terdapat dua jenis ikan ose yang dijadikan sampel pada penelitian ini, yaitu Ikan ose dengan perut berwarna kuning (Ose Kuning/Ose-K) dan Ikan ose dengan perut berwarna hitam ( Ose Hitam/Ose-H). Hasil isolasi dan pemurnian genom mtDNA CO1 merujuk pada rasio A260/280. Ekstrak gen mtDNA Ose-K memiliki konsentrasi 67.3 ng/µl dengan nilai rasio A260/280 diperoleh 1.94, dan konsentrasi untuk ekstrak gen mtDNA sampel Ose-H diperoleh 84.5 ng/µl dan 1.97 untuk nilai rasio A260/280. Hasil visualisasi produk PCR setelah di running pada gel elektroforesis diperoleh pita tunggal untuk masing-masing sampel dengan panjang basa sekitar 700 bp. Kata kunci: gen mtDNA CO1, Ikan Ose, pita DNA, rasio A260/280

PSV-36 Optimization of Collection, Storage, and Extraction of Samples for Large-Scale 16s Sequencing Project

Correlations between the microbiome of the horse and various physiological parameters continue to be determined. Most evaluations of the equine microbiome have been regionally focused with limited numbers or variability. In order to elucidate the role of the microbiome on equine health, a large-scale trial has been initiated with a primary objective of analyzing and characterizing the microbiome of the horse. A study of this scope relies on the horse owner to collect samples from various locations and ship them to a centralized lab. Therefore, collection protocols and extraction techniques need to be optimized to maintain sample integrity. A trial was conducted to evaluate the storage conditions and extraction methodologies necessary to develop an optimized method of sample collection, preparation, and extraction. Samples were collected from a single horse and subjected to one of four treatments in duplicate (1-fresh, 2-frozen, 3-stored in 99% EtOH, and 4-stored in a commercially available DNA/RNA transport medium; DNA/RNA Shield®, Zymo Research, Irvine, CA). Frozen samples were placed at -80◦ C immediately following collection and stored for 48-hr. Frozen samples were thawed immediately prior to extraction. All other treatments were stored as dictated by treatment at room temperature for 48-hr prior to extraction to mimic shipping. Samples were processed utilizing a commercially available DNA extraction kit (Quick-DNA™ Fecal/Soil Microbe Miniprep, Zymo Research). DNA extract was analyzed for quantity utilizing a Qubit Fluorometer (ThermoFisher, Waltham, MA), and quality via spectrophotometry (NanoDrop 2000; ThermoFisher, Waltham, MA). Swabs stored in DNA/RNA Shield® yielded higher concentrations of DNA with superior 260/280 values than other treatments. These data indicate that storage of fecal swabs in an appropriate buffer combined with optimized extraction protocols can deliver adequate extracts that can be utilized for 16s sequencing and validates the use of this method for large-scale microbiome analysis.

Assessment of Commercial DNA Cleanup Kits for Elimination of Real-Time PCR Inhibitors in the Detection of Cyclospora cayetanensis in Cilantro

ABSTRACT Inhibited reactions have occasionally been observed when cilantro samples were processed for the detection of Cyclospora cayetanensis using quantitative real-time PCR (qPCR). Partial or total inhibition of PCR reactions, including qPCR, can occur, leading to decreased sensitivity or false-negative results. If inhibition occurs, this implies the need for additional purification or cleanup treatments of the extracted DNA to remove inhibitors prior to molecular detection. Our objective was to evaluate the performance of five commercial DNA cleanup kits (QIAquick purification kit from Qiagen [kit 1], OneStep PCR inhibitor removal by Zymo Research [kit 2], NucleoSpin genomic DNA cleanup XS from Macherey-Nagel [kit 3], DNA IQ system by Promega [kit 4], and DNeasy PowerPlant pro kit from Qiagen [5]) to minimize qPCR inhibition using the U.S. Food and Drug Administration–validated Bacteriological Analytical Manual (BAM) Chapter 19b method for detection of C. cayetanensis in cilantro samples containing soil. Each of the five commercial DNA cleanup kits evaluated was able to reduce the qPCR internal amplification control cycle threshold values to those considered to be normal for noninhibited samples, allowing unambiguous interpretation of results in cilantro samples seeded at both a high oocyst level (200 oocysts) and a low oocyst level (10 oocysts). Of the five kits compared, kits 1, 2, and 3 did not show significant differences in the detection of C. cayetanensis, while significantly higher cycle threshold values, indicating lower recovery of the target DNA, were observed from kits 4 and/or 5 in samples seeded with 200 and 10 oocysts (P < 0.05). This comparative study provides recommendations on the use of commercial cleanup kits which could be implemented when inhibition is observed in the detection of C. cayetanensis in cilantro samples using the BAM Chapter 19b method. HIGHLIGHTS

The Influence of DNA Extraction and Lipid Removal on Human Milk Bacterial Profiles

Culture-independent molecular techniques have advanced the characterization of environmental and human samples including the human milk (HM) bacteriome. However, extraction of high-quality genomic DNA that is representative of the bacterial population in samples is crucial. Lipids removal from HM prior to DNA extraction is common practice, but this may influence the bacterial population detected. The objective of this study was to compare four commercial DNA extraction kits and lipid removal in relation to HM bacterial profiles. Four commercial DNA extraction kits, QIAamp® DNA Microbiome Kit, ZR Fungal/Bacterial DNA MiniPrep™, QIAsymphony DSP DNA Kit and ZymoBIOMICS™ DNA Miniprep Kit, were assessed using milk collected from ten healthy lactating women. The kits were evaluated based on their ability to extract high quantities of pure DNA from HM and how well they extracted DNA from bacterial communities present in a commercial mock microbial community standard spiked into HM. Finally, the kits were evaluated by assessing their extraction repeatability. Bacterial profiles were assessed using Illumina MiSeq sequencing targeting the V4 region of the 16S rRNA gene. The ZR Fungal/Bacterial DNA MiniPrep™ and ZymoBIOMICS™ DNA Miniprep (Zymo Research Corp., Irvine, CA, USA) kits extracted the highest DNA yields with the best purity. DNA extracted using ZR Fungal/Bacterial DNA MiniPrep™ best represented the bacteria in the mock community spiked into HM. In un-spiked HM samples, DNA extracted using the QIAsymphony DSP DNA kit showed statistically significant differences in taxa prevalence from DNA extracted using ZR Fungal/Bacterial DNA MiniPrep™ and ZymoBIOMICS™ DNA Miniprep kits. The only difference between skim and whole milk is observed in bacterial profiles with differing relative abundances of Enhydrobacter and Acinetobacter. DNA extraction, but not lipids removal, substantially influences bacterial profiles detected in HM samples, emphasizing the need for careful selection of a DNA extraction kit to improve DNA recovery from a range of bacterial taxa.

Comparison of Four Commercial Kits for Isolation of Urinary Cell-Free DNA and Sample Storage Conditions

Urinary cell-free DNA (cfDNA) is an attractive body fluid for liquid biopsy. In this study, we compared the efficiencies of four commercial kits for urinary cell-free DNA (cfDNA) isolation and of various sample storage conditions. Urinary cfDNA was isolated from 10 healthy individuals using four commercial kits: QIAamp Circulating Nucleic Acid Kit (QC; Qiagen), MagMAX™ Cell-Free DNA Isolation Kit (MM; Applied Biosystems), Urine Cell-Free Circulating DNA Purification Midi Kit (NU; Norgen Biotek), and Quick-DNA™ Urine Kit (ZQ; Zymo Research). To assess the isolation efficiency, an Agilent 2100 Bioanalyzer with High Sensitivity DNA chips was used, and cfDNA yield was defined as the amount of cfDNA obtained from 1 mL of urine. MM and QC provided the highest cfDNA yield in the 50–300 bp range, and MM and NU gave the highest cfDNA yield in the 50–100 bp range. In particular, the NU kit was efficient for isolation of more fragmented cfDNA in the range of 50–100 bp with the lowest cellular genomic DNA contamination. ZQ had the best cost-efficiency for isolating the same amount of urinary cfDNA. Samples stored at −70 °C with the addition of 10 mM EDTA resulted in the highest cfDNA yield 3 months after sample collection.

Cysteine-cysteine chemokine receptor 5 (CCR5) profile of HIV-infected subjects attending University of Calabar Teaching Hospital, Calabar, Southern Nigeria

Background Cysteine-cysteine chemokine receptor 5 is the main HIV co-receptor involved in the virus and cell-to-cell spread. A variant of the CCR5 gene known as CCR5-Δ32 which is a product of 32 base pair deletion in the gene plays critical role in the infection and progression to AIDS. The study was carried out to determine the CCR5 genotype of HIV-infected subjects attending University of Calabar Teaching Hospital, Calabar. Methods A total of 100 subjects attending HIV clinic, University of Calabar Teaching Hospital were purposively recruited for this study. DNA was extracted from each sample using the Quick gDNA miniprep DNA extraction kit, Zymo Research. Polymerase chain reaction (PCR) was used in the amplification of CCR5 gene in each DNA in a 9700 ABI Thermo cycler and then resolved on 4% agarose gel electrophoresis. Result Out of the 100 samples assessed, 100 (100%) were homozygous for the CCR5 wild type gene (CCR5-wt), while none (0%) was homozygous for the CCR5-Δ32 (mutant type), and heterozygosity was not observed. Conclusion This study observed absence of CCR5-Δ32 deletion gene among the studied subjects in Calabar, implying lack of genetic advantage in HIV infection and possible rapid progression towards AIDS if other precautions are not checked.

PSXIII-18 Conceptus stimuli in peripheral blood mono and polymorphonuclear cells at the beginning of pregnancy

The objective of this experiment was to compare the expression of Interferon-tau Stimulated Genes (ISGs) in peripheral blood mono and polymorphonuclear cells (PBMCs and PMNs) in heifers following insemination. Twenty-nine Nelore heifers had estrous cycle synchronized, and FTAI occurred on D0. Pregnancy diagnosis was performed by ultrasonography on D28 post FTAI. On D0, 10, 14, 16, 18 and 20, blood (25mL) from the jugular vein was collected in heparinized tubes for isolation of PMNs and PBMCs. The isolation was performed using Ficoll®Paque Plus (GE Healthcare). PMNs and PBMCs samples from 8 pregnant and 9 non-pregnant heifers were subjected to RNA extraction using the DirectZol-RNA kit (Zymo-Research) and Trizol (Invitrogen), respectively. The expression of the target genes (ISG15, OAS-1, MX1 and MX2) was normalized in relation to the two reference genes (GAPDH/ACTB for PMNs and GAPDH/PPIA for PBMCs). The abundance of transcripts was evaluated by analysis of variance considering fixed effects of group, day and group by day interaction using the PROC MIXED procedure in SAS. PMNs and PBMCs had a similar expression profile of ISG15 and OAS-1, showing a relative increase (P < 0.05) from D18, and a significant increase in (P < 0.05) expression in pregnant compared to non-pregnant females on D18 and D20. These results were also observed for MX1 in PBMCs. In PMNs, no significant effects for MX1 were found. For MX2, in both cells types, only a group effect (P < 0.05) was observed, indicating a higher expression in pregnant heifers (0.57±0.11 vs. 0.21±0.03) on the days evaluated. When comparing the relative expression of the target genes to D0, no significant (P > 0.1) differences were found between PMNs and PBMCs. In summary, ISG expression is similar in PMNs and PBMCs, specifically for ISG15 and OAS-1, which both seem to be suitable biomarkers for potential early pregnancy determination in heifers.

FIGARO: An efficient and objective tool for optimizing microbiome rRNA gene trimming parameters

ABSTRACTSummaryMicrobiome studies continue to provide tremendous insight into the importance of microorganism populations to the macroscopic world. High-throughput DNA sequencing technology (i.e., Next-generation Sequencing) has enabled the cost-effective, rapid assessment of microbial populations when combined with bioinformatic tools capable of identifying microbial taxa and calculating the diversity and composition of biological and environmental samples. Ribosomal RNA gene sequencing, where 16S and 18S rRNA gene sequences are used to identify prokaryotic and eukaryotic species, respectively, is one of the most widely-used techniques currently employed in microbiome analysis. Prior to bioinformatic analysis of these sequences, trimming parameters must be set so that post-trimming sequence information is maximized while expected errors in the sequences themselves are minimized. In this application note, we present FIGARO: a Python–based application designed to maximize read retention after trimming and filtering for quality. FIGARO was designed specifically to increase reproducibility and minimize trial-and-error in trimming parameter selection for a DADA2–based pipeline and will likely be useful for optimizing trimming parameters and minimizing sequence errors in other pipelines as well where paired-end overlap is required.Availability and implementationThe FIGARO application is freely available as source code at https://github.com/Zymo-Research/figaro.

Optimization ofBrucella abortusProtocols for Downstream Molecular Applications

ABSTRACTWe compared the performances of various DNA extraction kits for their ability to recoverBrucella abortusstrain 19 inoculated intoBrucella-free bovine tissues. Tissues were homogenized in a FastPrep bead homogenizer and extracted in triplicate by using one of five kits (Qiagen DNeasy, GE Illustra, Omega Bio-tek E.Z.N.A., Quanta Extracta, and IBI Science DNA Tissue kit). Whole blood was also taken from animals prior to chemical euthanasia, aliquoted, and then fractioned into buffy coat, red blood cells, and plasma. DNA was extracted from whole blood, buffy coat, and plasma by using four kits (Qiagen DNeasy, Omega Bio-tek E.Z.N.A., IBI Science DNA Blood kit, and 5PRIME PerfectPure). Previously reported primers targeting strain 19 were used to amplify extracted DNA and identify the optimal extraction kit. Real-time PCR was performed, and kits were compared for statistical differences by using quantification cycles as an outcome measure. Omega Bio-tek E.Z.N.A. was superior (P< 0.0068) in its lower quantification cycle values across all tissue kits. The IBI Science DNA Blood kit was superior to Qiagen DNeasy, 5PRIME PerfectPure, and Quanta Extracta (P< 0.0001,P= 0.0004, andP= 0.0013, respectively) but was not different from Omega Bio-tek E.Z.N.A. (P= 1.0). In summary, the optimal extraction kit forB. abortusstrain 19 for tissues is Omega Bio-tek E.Z.N.A., and that for blood and its fractions is the IBI Science Mini Genomic DNA kit. Eluted DNA was also concentrated by using the Zymo Research DNA Clean & Concentrator-25 kit. Concentrated eluted DNA with the target was superior (P= <0.0001) to unconcentrated eluted DNA.