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The polymerase chain reaction (PCR) is a laboratory technique used for the amplification of a specific DNA fragment in a simple enzyme reaction. The basic PCR method has been modified to expand its application. Development of quantitative PCR (qPCR) has enabled detection and quantification of the target sequence in real time, while it is being synthesized. Another popular variation is reverse transcription polymerase chain reaction (RT-PCR), a technique used to detect and measure RNA. PCR technology has revolutionized the field of molecular biology and medical research. Because of its widespread use, it is important to understand the scientific principles of PCR. The aim of this chapter is to explain the concepts underlying this method and to explore the clinical usefulness and potential of this technique. The chapter also provides detailed protocols on how to undertake PCR in the laboratory, including techniques for RNA isolation, cDNA synthesis, and data analysis. A scenario in which PCR is utilized to answer a research question is also described, as well as guidance on how to troubleshoot experimental problems.

Motivation Designing PCR primers to target a specific selection of whole genome sequenced strains can be a long, arduous and sometimes impractical task. Such tasks would benefit greatly from an automated tool to both identify unique targets, and to validate the vast number of potential primer pairs for the targets in silico. Results Here we present RUCS, a program that will find PCR primer pairs and probes for the unique core sequences of a positive genome dataset complement to a negative genome dataset. The resulting primer pairs and probes are in addition to simple selection also validated through a complex in silico PCR simulation. We compared our method, which identifies the unique core sequences, against an existing tool called ssGeneFinder, and found that our method was 6.5–20 times more sensitive. We used RUCS to design primer pairs that would target a set of genomes known to contain the mcr-1 colistin resistance gene. Three of the predicted pairs were chosen for experimental validation using PCR and gel electrophoresis. All three pairs successfully produced an amplicon with the target length for the samples containing mcr-1 and no amplification products were produced for the negative samples. The novel methods presented in this manuscript can reduce the time needed to identify target sequences, and provide a quick virtual PCR validation to eliminate time wasted on ambiguously binding primers. Availability and implementation Source code is freely available on https://bitbucket.org/genomicepidemiology/rucs. Web service is freely available on https://cge.cbs.dtu.dk/services/RUCS. Supplementary information Supplementary data are available at Bioinformatics online.

The polymerase chain reaction (PCR) is a technology used to exponentially amplify a short, specific DNA region of interest, generating thousands to millions of copies of this specific region, all with a similar sequence and length. It is one of the few techniques that has undoubtedly revolutionized the field of molecular biology and diagnostics. Since the invention of the classical end-point PCR in 1986, the technique has gone through a revolutionary period, with a boost in 1992 due to the invention of real-time or quantitative PCR (qPCR), which allowed for monitoring the PCR reaction in real-time, thereby making the quantification of nucleic acids much more simple, accurate, and sensitive. It is a key technology that is present on almost every bench in a research or diagnostic laboratory. In this chapter we will give an overview of the qPCR technique, starting from its invention, describing the different methodologies and important factors to be taken into account when optimizing and using this widespread nucleic acid-based technique.

A central challenge in the present era of biodiversity loss is to assess and manage human impacts on freshwater ecosystems. Macroinvertebrates are an important group for bioassessment as many taxa show specific responses to environmental conditions. However, generating accurate macroinvertebrate inventories based on larval morphology is difficult and error-prone. Here, DNA metabarcoding provides new opportunities. Its potential to accurately identify invertebrates in bulk samples to the species level, has been demonstrated in several case studies. However, DNA based identification is often limited by primer bias, potentially leading to taxa in the sample remaining undetected. Thus, the success of DNA metabarcoding as an emerging technique for bioassessment critically relies on carefully evaluating primers. We used the R package PrimerMiner to obtain and process cytochrome c oxidase I (COI) sequence data for the 15 most globally relevant freshwater invertebrate groups for stream assessment. Using these sequence alignments, we developed four primer combinations optimized for freshwater macrozoobenthos. All primers were evaluated by sequencing ten mock community samples, each consisting of 52 freshwater invertebrate taxa. Additionally, popular metabarcoding primers from the literature and the developed primers were tested in silico against the 15 relevant invertebrate groups. The developed primers varied in amplification efficiency and the number of detected taxa, yet all detected more taxa than standard ‘Folmer’ barcoding primers. Two new primer combinations showed more consistent amplification than a previously tested ribosomal marker (16S) and detected all 42 insect taxa present in the mock community samples. In silico evaluation revealed critical design flaws in some commonly used primers from the literature. We demonstrate a reliable strategy to develop optimized primers using the tool PrimerMiner. The developed primers detected almost all taxa present in the mock samples, and we argue that high base degeneracy is necessary to decrease primer bias as confirmed by experimental results and in silico primer evaluation. We further demonstrate that some primers currently used in metabarcoding studies may not be suitable for amplification of freshwater macroinvertebrates. Therefore, careful primer evaluation and more region / ecosystem specific primers are needed before DNA metabarcoding can be used for routine bioassessment of freshwater ecosystems.

A Common Primer Multiplex PCR (CP-M-PCR) was developed to detect meat origin of four groups of animal (pig, ruminant, avian and rabbit). This method demonstrated higher sensitivity and efficiency than the conventional multiplex PCR. In this approach, a common forward primer was designed in the 5' end of a homologous region of mitochondrial NADH dehyrogenase subunit 4 (Nad 4) gene sequences of all the animal groups. Specific adapter reverse primers were designed by adding an adapter sequence at the 5' end. The same adapter sequence was used as the common adapter reverse primer. The primers generated specific fragments of 267, 370, 504, and 548 bp lengths for pig, ruminant, avian and rabbit meats, respectively. The use of adapter sequence at the 5' end of the common adapter reverse primers increased the efficiency of the amplification and the application of a common forward primer solved the complexity in multiplex PCR system. Bands of specific amplification can be detected in the PCR assays containing as low as 10(-6) μM of adapter reverse primer. This result indicated that the sensitivity was tremendously increased as compared to the conventional multiplex PCR (10(-3) μM). CP-M-PCR detection limit of the DNA samples was 0.1 ng for the four groups of meats. CP-M-PCR has greatly improved the sensitivity and efficiency of the PCR system for a more reliable and accurate outcome than conventional multiplex PCR system.

Accurate identification of fungal pathogens using a sequence-based approach requires an extraction method that yields template DNA pure enough for polymerase chain reaction (PCR) or other types of amplification. Therefore, the objective of this study was to develop and standardise a rapid, inexpensive DNA extraction protocol applicable to the major fungal phyla, which would yield sufficient template DNA pure enough for PCR and sequencing. A total of 519 clinical and culture collection strains, comprised of both yeast and filamentous fungi, were prepared using our extraction method to determine its applicability for PCR, which targeted the ITS and D1/D2 regions in a single PCR amplicon. All templates were successfully amplified and found to yield the correct strain identification when sequenced. This protocol could be completed in approximately 30 min and utilised a combination of physical and chemical extraction methods but did not require organic solvents nor ethanol precipitation. The method reduces the number of tube manipulations and yielded suitable template DNA for PCR amplification from all phyla that were tested.

Studies of insect assemblages are suited to the simultaneous DNA-based identification of multiple taxa known as metabarcoding. To obtain accurate estimates of diversity, metabarcoding markers ideally possess appropriate taxonomic coverage to avoid PCR-amplification bias, as well as sufficient sequence divergence to resolve species. We used in silico PCR to compare the taxonomic coverage and resolution of newly designed insect metabarcodes (targeting 16S) with that of existing markers [16S and cytochrome oxidase c subunit I (COI)] and then compared their efficiency in vitro. Existing metabarcoding primers amplified in silico75% of insect species with complete mitochondrial genomes available, whereas new primers targeting 16S provided90% coverage. Furthermore, metabarcodes targeting COI appeared to introduce taxonomic PCR-amplification bias, typically amplifying a greater percentage of Lepidoptera and Diptera species, while failing to amplify certain orders in silico. To test whether bias predicted in silico was observed in vitro, we created an artificial DNA blend containing equal amounts of DNA from 14 species, representing 11 insect orders and one arachnid. We PCR-amplified the blend using five primer sets, targeting either COI or 16S, with high-throughput amplicon sequencing yielding more than 6 million reads. In vitro results typically corresponded to in silico PCR predictions, with newly designed 16S primers detecting 11 insect taxa present, thus providing equivalent or better taxonomic coverage than COI metabarcodes. Our results demonstrate that in silico PCR is a useful tool for predicting taxonomic bias in mixed template PCR and that researchers should be wary of potential bias when selecting metabarcoding markers.

Alignment of the Wx-gene and its homolog sequences has been conducted. A dendrogram displaying phylogenetic relationship between Poaceae family members has been built. Transfer of ancient Wx-gene from Zea mays to Dimeria lawsonii has been assumed. Primers for the exons 8–10 of polymorphic region have been designed. In silico PCR analysis has been conducted.

Broad-range and specific 16S rRNA gene PCR is used for detection and identification of bacterial pathogens in clinical specimens from patients with a high suspicion for infection. We describe the development of a broad-range and specific PCR primer, based on bacterial 16S rRNA, for use in routine diagnostic clinical microbiology services. The primers were designed by using conservative regions of 16S rRNA sequences from 10 strains. Ninety-eight clinical strains were isolated from clinical patient specimens. A total of 98 strains of bacteria were identified by phenotypic methods; PCR with newly designed primers and universal primers. All purified PCR products were sequenced using both forward and reverse primers on an automated DNA analyzer. In this study, we evaluated the usefulness of the newly designed primers and the universal primers for the detection of bacteria, and both these techniques were compared with phenotypic methods for bacteria detection. When we also tested 98 strains of clinical isolates with newly designed primers, about 778 bp DNA fragments were amplified and identified from all strains. Of the 98 strains, 94 strains (95.9%) correspond in comparison with phenotypic methods. The newly designed primers showed that the identities of 98 (100%) strains were the same as those obtained by universal PCR primers. The overall agreement between the newly designed primers and universal primers was 100%. The primer set was designed for rapid, accurate, and cheap identification of bacterial pathogens. We think the newly designed primer set is useful for the identification of pathogenic bacteria.

Many yeast experiments require strains modified by recombinant DNA methods. Some experiments require precise insertion of a DNA segment into the genome without a selectable marker remaining. For these applications, we developed a new PCR-based method for marker-free DNA transplant. The current PCR-based method requires the labour-intensive construction of a PCR template plasmid with repeats of the DNA segment flanking URA3. The design of a new vector, IpO, reduces the work in cloning a single copy of the DNA segment between overlapping URA3 fragments present in the vector. Two PCRs are performed that capture the DNA segment and one or the other URA3 fragment. When the PCR products are co-transformed into yeast, recombination between the overlapping URA3 fragments restores URA3 and transposes the cloned DNA segment inside out, creating a repeat-URA3-repeat cassette. Sequences designed into the PCR primers target integration of the cassette into the genome. Subsequent selection with 5-fluoro-orotic acid yields strains that have 'popped out' URA3 via recombination between the DNA repeats, with the result being the precise insertion of the DNA segment minus the selectable marker. An additional advantage of the IpO method is that it eliminates PCR artifacts that can plague the current method's repeat-containing templates.

PCR inhibitors can originate from a variety of sources and can co-extract with the DNA template, resulting in reduced amplification and/or dropped alleles. Currently real time PCR is used to provide a check for the presence of PCR inhibition by monitoring the quality of amplification of an internal control. In this paper we examine the effect of internal control length and sequences on its sensitivity to PCR inhibition by varying concentrations of commonly encountered PCR inhibitors. Data from both amplification and melt curves were evaluated. The results show that while amplicon sequence has minor effects on amplification efficiency and melt curves, amplicon length has a more dramatic effect, regardless of inhibitor type. Given the increasing variety of STR typing kits and their documented differences in performance with respect to inhibition, the data obtained in this study can be used to assist designers of real time PCR kits to adjust their internal PCR controls (IPC) to permit a more targeted estimation of inhibition.

The potato species exhibit gametophytic self-incompatibility system controlled by a single S-locus with multiple S-haplotypes. Each S-haplotype carries two genetically linked genes, S-RNase and SLF, controlling the female and male specificities, respectively. In the style, the S-RNase gene codes for an allele-specific ribonuclease that is involved in the rejection of pollen that carries the same S-haplotype. This gene has five conserved regions (C1–C5) and two hypervariable domains located between C2 and C3 that play a role in S-RNase allele specificity. Presently, eight nucleotide sequences of S-RNase alleles from Solanum tuberosum and S. chacoense have been reported in potato species. In an effort to discriminate these S-RNase alleles and eventually detect new allelic variants, these sequences were analyzed by in silico PCR, using primers designed on the basis of four conserved regions, and were further examined by restriction enzyme patterns. The development of the in silico approach led to the creation of a novel dichotomous key which was able to unequivocally identify the eight potato S-RNase alleles already known and eventually detect putative alleles when the size and/or the restriction pattern of the amplicons were different from those predicted. Experimental data validates the utility and efficiency of the dichotomous key.

Genetic transformation is a widely employed tool in both basic research and commercial plant breeding programs. Its application requires that transgenes be stably integrated and expressed in the plant genome. When transgenic plants are developed, it is essential to determine which plants contain the transgene. Detection methods are usually based on amplification of the target transgene. This paper describes a development of detection method based on conventional and real time polymerase chain reaction (PCR) for simultaneous detection of barley HVA1 transgene and its transcript in transformed durum wheat. Since there exist a high homology between the barley HVA1 gene and the wheat gene, development of a specific sets of primers is needed for PCR-based characterizations, and the study of the transgene. Based on the alignment of the two genes sequences obtained from public databases, several primers were designed to detect and distinguish between the transformed and non-transformed plants. Real time PCR has been employed because of its inherent sensitivity and quantitative nature. It has been possible to design the following primers pairs F2/MMR, F2/R10 and F14/R10 as highly specific and suitable for the detection of HVA1 DNA by conventional and real-time PCR. Nonetheless, the primers used were allowed to reach high efficiencies and did not show any cross-reactivity with DNAs extracted from various plants. The sensitivity achieved was 6.4 pg. The primer pair F2/R10 was considered as highly specific for the detection of both DNA and mRNA of the HVA1 by real-time PCR. The assays proved to be accurate, specific, sensitive and sufficiently reproducible for further application in high-throughput molecular characterization of transgenic lines.Keywords: HVA1, durum wheat, transgenic plant, real time polymerase chain reaction (PCR), droughtAfrican Journal of Biotechnology, Vol. 13(4), pp. 581-592, 22 January, 2014

Quantitative PCR (qPCR) and community fingerprinting methods, such as the Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis,are well-suited techniques for the examination of microbial community structures. The use of phylum and class-specific primers can provide enhanced sensitivity and phylogenetic resolution as compared with domain-specific primers. To date, several phylum- and class-specific primers targeting the 16S ribosomal RNA gene have been published. However, many of these primers exhibit low discriminatory power against non-target bacteria in PCR. In this study, we evaluated the precision of certain published primers in silico and via specific PCR. We designed new qPCR and T-RFLP primer pairs (for the classes Alphaproteobacteria and Betaproteobacteria, and the phyla Bacteroidetes, Firmicutes and Actinobacteria) by combining the sequence information from a public dataset (SILVA SSU Ref 102 NR) with manual primer design. We evaluated the primer pairs via PCR using isolates of the above-mentioned groups and via screening of clone libraries from environmental soil samples and human faecal samples. As observed through theoretical and practical evaluation, the primers developed in this study showed a higher level of precision than previously published primers, thus allowing a deeper insight into microbial community dynamics.

We performed in silico PCR analyses utilizing complete mitochondrial (mtDNA) genome sequences of faba bean (Vicia faba) and two related species, Vigna angularis and Vigna radiata, currently available in GenBank, to infer whether 15 published universal primer pairs for amplification of all 14 cis-spliced introns in genes of NADH subunits (nad genes) are suitable for V. faba and related species. Then, we tested via PCR reactions whether seven out of 15 primer pairs would generate PCR products suitable for further manipulation in 16 genotypes of V. faba representing all botanical varieties of this species (major, minor, equina and subsp. paucijuga) of various levels of improvement (traditional and improved cultivars) originating from Europe, Africa, Asia and south America. We provide new PCR primers for amplification of nad1 intron 2/3 in V. faba, and demonstrate intraspecific variability in primary nucleotide sequences at this locus. Based on outcomes of both in silico predictions and PCR amplification, we report a set of PCR primers for amplification of five introns in nad genes that are promising molecular tools for future phylogeographic and other studies in this species for which unambiguous data on wild ancestors, centre of origin and domestication are lacking. [Projekat Ministarstva nauke Republike Srbije, br. 173005]

Pseudomonas spp. have been known as notorious food spoilage bacteria with ability to produce thermo-tolerant enzymes. They pose serious risk to public health as its most pathogenic member, P. aeruginosa, could cause nosocomial infections affecting peoplewith immunodeficiency. The use of GMF-GMR primers had been reported capable for detecting bacterial moaC of Alcaligenes javaensis JG3. The gene is suspected to be related with dormancy of pathogenic bacteria. This study aimed to investigate specificity of the GMR-GMF as well as a newly designed JMF-JMR pairs of primers (JMF: 5’- GGCGTACATCATCCACACTG-3’ and JMR: 5’-GGCGTTGACCATCTATGACA-3’) for detecting moaC genes of 57 members of Pseudomonas spp. retrieved from http://insilico.ehu.eus/ database using in silico PCR (Polymerase Chain Reaction). The results showed that GMF-GMR primers could selectively amplify 271-bp in silico PCR products from 14 out of 57 members of Pseudomonas spp. tested. However, BLASTn analysis on these 14 amplified DNA sequences showed that they were not part of moaC, yet glpK gene fragment sequences. Meanwhile, the newly designed primers from moaC sequence of strain JG3, JMFJMR, could specifically amplify 214-bp in silico PCR products from 2 out of 57 members of Pseudomonas spp. matched to bacterial moaC gene fragment sequences. As conclusion, based on in silico study JMF-JMR primers are more specific than GMF-GMR ones for detecting moaC gene fragments of members of Pseudomonas spp. studied.

Summary We describe a semi-empirical framework that combines thermodynamic models of primer hybridization with experimentally determined elongation biases introduced by 3′-end mismatches for improving polymerase chain reaction (PCR)-based sequence discrimination. The framework enables rational and automatic design of primers for optimal targeting of one or more sequences in ensembles of nearly identical DNA templates. In situations where optimal targeting is not feasible, the framework accurately predicts non-target sequences that are difficult to distinguish with PCR alone. Based on the synergistic effects of disparate sources of PCR bias, we used our framework to robustly distinguish between two alleles that differ by a single base pair. To demonstrate the applicability to environmental microbiology, we designed primers specific to all recognized archaeal and bacterial genera in the Ribosomal Database Project, and have made these primers available online. We applied these primers experimentally to obtain genus-specific amplification of 16S rRNA genes representing minor constituents of an environmental DNA sample. Our results demonstrate that inherent PCR biases can be reliably employed in an automatic fashion to maximize sequence discrimination and accurately identify potential cross-amplifications. We have made our framework accessible online as a programme for designing primers targeting one group of sequences in a set with many other sequences (http://DECIPHER.cee.wisc.edu).

DNA is a typical organic compound with marked differences from other chemicals and biopolymers because DNA can be amplified by the enzyme polymerase. DNA can be, in principle, amplified from a single copy by the polymerase chain reaction (PCR). In this review, we focus our attention on the chemistry of PCR primers. Because PCR is basic technology in biology research fields, we sometimes use chemically labeled primers without any awareness of the chemistry they leave behind. We would like to emphasize that chemically labeled primers contain a lot of potential for different chemistry ideas and much study is still necessary to advance PCR for single-nucleotide polymorphism (SNP) typing, genetic diagnosis, and other fields. Two categories of primers, affinity-capture primers and signaling primers, are discussed from the viewpoints of their chemical concepts and applications. Affinity-capture primers are used for purification, isolation, and manipulation of PCR products by high specificity and affinity to the cognate molecules by moleculemolecule interactions, whereas signaling primers report the hybridization and/or progress of PCR amplification by a signal change, in most cases by a fluorescence change. The content of this review may be useful for a better understanding of the chemistry of PCR primers and, more importantly, for the invention of novel PCR chemistry.

E. coli is generally a commensal but includes some highly pathogenic strains carrying additional genes in plasmids and/or the chromosome. Based on these genes the pathogenic strains are divided into pathotypes including enteropathogenic (EPEC), enterohemorrhagic (EHEC), enterotoxigenic (ETEC), enteroaggregative (EAEC), enteroinvasive (EIEC) and diffusely adherent (DAEC) E. coli. Here, previously developed multiplex PCR strategies for these strains were integrated into one single step multiplex that differentiates all these E. coli pathotypes, usually based on multiple characteristic PCR products. This multiplex PCR works reliably for colony PCR. Two additional markers were added: one to detect most Enterobacteriacea, which acts as a positive control for successful PCR, and one to distinguish Salmonella. The multiplex correctly classified a set of 45 reference strains by colony PCR and 71 (45+26) strains by in silico PCR. It was then used to interrogate 44 clinical strains from bovine hosts resulting in detection of EAEC and DAEC determinants.

This laboratory exercise demonstrates three different analytical forms of the polymerase chain reaction (PCR) that allow students to genotype themselves at four different loci. Here, we present protocols to allow students to a) genotype a non-coding polymorphic Variable Number of Tandem Repeat (VNTR) locus on human chromosome 5 using conventional PCR, b) perform PCR - Restriction Fragment Polymorphism (PCR-RFLP) analysis to genotype a Single Nucleotide Polymorphism (SNP) of the TAS2R38 gene on human chromosome 7 and c) perform duplex Allele Specific Primer-PCR (ASP-PCR) to genotype SNPs of two enzyme-encoding genes in a single biochemical pathway on human chromosomes 4 and 12. All PCR reactions have been optimized to use a single easily purified sample of the students' own DNA and run under a single thermal cycler program using inexpensive reagents to produce robust and clearly interpretable results on a single agarose gel. As presented here, the lab occupies two lab periods of 2 h, 40 min each: DNA purification followed by PCR reactions set-up on Day 1 and enzyme digestion of the PCR-RFLP and agarose gel analysis on Day 2.

The aim of the present study was to develop a strain-specific polymerase chain reaction (PCR) primer set for the detection of Bifidobacterium bifidum OLB6378 (OLB6378) that can serve as suitable probiotics for infants. The random amplified polymorphic DNA (RAPD)-PCR technique was used to obtain OLB6378-specific PCR products. One OLB6378-specific RAPD-PCR product was obtained after testing 97 RAPD primers, and was sequenced. Thirteen PCR primer sets were designed from the sequence. One PCR primer set was found to amplify one PCR product when genomic DNA of OLB6378 was used as template. The primer set did not amplify any PCR product when the other genomic DNA was used as template. The primer set was tested with 47 strains of B. bifidum and 20 strains of the other Bifidobacterium species. As a result, we developed an OLB6378-specific primer set, one that should be useful not only for the detection of OLB6378 but also for the quantification of OLB6378.

With increasing rates of antibiotic resistance, bacterial infections have become more difficult to treat, elevating the importance of surveillance and prevention. Effective surveillance relies on the availability of rapid, cost-effective, and informative typing methods to monitor bacterial isolates. PCR-based typing assays are fast and inexpensive, but their utility is limited by the lack of targets which are capable of distinguishing between strains within a species. To identify highly informative PCR targets from the growing base of publicly available bacterial genome sequences, we developed pan-PCR. This computer algorithm uses existing genome sequences for isolates of a species of interest and identifies a set of genes whose patterns of presence or absence provide the best discrimination between strains in this species. A set of PCR primers targeting the identified genes is then designed, with each PCR product being of a different size to allow multiplexing. These target DNA regions and PCR primers can then be utilized to type bacterial isolates. To evaluate pan-PCR, we designed an assay for the emerging pathogen Acinetobacter baumannii . Taking as input a set of 29 previously sequenced genomes, pan-PCR identified 6 genetic loci whose presence or absence was capable of distinguishing all the input strains. This assay was applied to a set of patient isolates, and its discriminatory power was compared to that of multilocus sequence typing (MLST) and whole-genome optical maps. We found that the pan-PCR assay was capable of making clinically relevant distinctions between strains with identical MLST profiles and showed a discriminatory power similar to that of optical maps. Pan-PCR represents a tool capable of exploiting available genome sequence data to design highly discriminatory PCR assays. The ease of design and implementation makes this approach feasible for diagnostic facilities of all sizes.

Simple sequence repeats (SSRs) are one of the most informative and widely used molecular markers in plant research. The melon draft genome has provided a powerful tool for SSR marker development in this species in which there are still not enough SSR markers. We therefore developed genome-wide SSR markers from melon, which were used for genetic diversity analysis in melon accessions and comparative mapping with cucumber and watermelon. A total of 44,265 microsatellites from the melon genome were characterized, of which 28,570 SSR markers were developed. In silico PCR analysis with these SSR markers identified 4002 and 1085 with one amplicon in cucumber and watermelon genome, respectively. With these cross-species transferable melon SSR markers, the chromosome synteny between melon and cucumber as well as watermelon was established, which revealed complicated mosaic patterns of syntenic blocks among them. We experimentally validated 384 SSR markers, from which 42 highly informative SSR ones were selected for genetic diversity and population structure analysis among 118 melon accessions. The large number of melon SSR markers developed in this study provides a valuable resource for genetic linkage map construction, molecular mapping, and marker-assisted selection (MAS) in melon. Furthermore, the cross-species transferable SSR markers could also be useful in various molecular marker-related studies in other closely related species in Cucurbitaceae family in which draft genomes are not yet available.

The commonly found oak species Quercus kerrii and the rare species Quercus austrocochinchinensis (subgenus Cyclobalanopsis) are genetically close and found in sympatry in Indo-China with morphological evidences of hybridization. The two species provide an opportunity to investigate the mechanism of speciation and to study how species integrity is maintained in the subgenus Cyclobalanopsis. However, the genomic resources are lacking in Cyclobalanopsis to produce enough molecular markers. We performed RNA-seq on Q. austrocochinchinensis and Q. kerrii by pooling tissues of new and old leaves, roots, and stems. A total of 14,247,444/12,900,500 (Q. austrocochinchinensis/Q. kerrii) clean reads were obtained from 2 × 300 bp Illumina MiSeq sequencing platform. De novo assembly produced 79,312/81,921 contigs representing 49,845/50,767 unigenes. The Ka/Ks estimation and following enrichment analysis identified 24 genes. Most of them were related to biosynthesis and growth, which may be involved in the process of speciation. 5196/5021 primer pairs were successfully designated from 13,762/13,430 putative loci with microsatellite repeats. We selectively screened 215 polymorphic simple sequence repeat (SSR) loci according to the list of 29,893 pairwise orthologous genes predicted by a reciprocal best hits algorithm. From the 215 loci, we selected 102 well-amplified SSR primers for polymorphic SSR locus analysis. We found 18 highly polymorphic loci and suitable for population genetic analysis, with 10 loci that had a diagnostic power that may be useful in studying hybridization. Finally, in silico PCR was performed using two Fagaceae species Quercus robur and Castanea mollissima. Our study provides a set of useful SSR markers and can enable further functional and comparative genomic research on the Quercus subgenus Cyclobalanopsis.

Avoiding complementarity between primers when designing a PCR assay constitutes a central rule strongly anchored in the mind of the molecular scientist. 3’-complementarity will extend the primers during PCR elongation using one another as template, consequently disabling further possible involvement in traditional target amplification. However, a 5’-complementarity will leave the primers unchanged during PCR cycles, albeit sequestered to one another, therefore also suppressing target amplification. We show that 5’-complementarity between primers may be exploited in a new PCR method called COMplementary-Primer-Asymmetric (COMPAS)-PCR, using asymmetric primer concentrations to achieve target PCR amplification. Moreover, such a design may paradoxically reduce spurious non-target amplification by actively sequestering the limiting primer. The general principles were demonstrated using 5S rDNA direct repeats as target sequences to design a species-specific assay for identifying Salmo salar and Salmo trutta using almost fully complementary primers overlapping the same target sequence. Specificity was enhanced by using 3’-penultimate point mutations and the assay was further developed to enable identification of S. salar x S. trutta hybrids by High Resolution Melt analysis in a 35 min one-tube assay. This small paradigm shift, using highly complementary primers for PCR, should help develop robust assays that previously would not be considered.

The taxonomic status of all species of the genus Elizabethkingia was re-evaluated by comparative genomics based on whole-genome sequencing. From these results it is clear that Elizabethkingia endophytica is a later subjective synonym of Elizabethkingia anophelis . In addition, genome-based analysis revealed the misidentification of isolates previously identified by traditional approaches and indicates the presence of two more species. We propose a more rapid identification scheme on the basis of an in silico PCR assay derived from comparative genomics of whole-genome sequences (WGS) from 29 well-curated strains.

Real Time Polymerase Chain Reaction also known as quantitative PCR (q-PCR) is a widely used tool in microbial ecology to quantify gene abundances of taxonomic and functional groups in environmental samples. Used in combination with a reverse transcriptase reaction (RT-q-PCR), it can also be employed to quantify gene transcripts. q-PCR makes use of highly sensitive fluorescent detection chemistries that allow quantification of PCR amplicons during the exponential phase of the reaction. Therefore, the biases associated with 'end-point' PCR detected in the plateau phase of the PCR reaction are avoided. A protocol to quantify bacterial 16S rRNA genes and transcripts from coastal sediments via real-time PCR is provided. First, a method for the co-extraction of DNA and RNA from coastal sediments, including the additional steps required for the preparation of DNA-free RNA, is outlined. Second, a step-by-step guide for the quantification of 16S rRNA genes and transcripts from the extracted nucleic acids via q-PCR and RT-q-PCR is outlined. This includes details for the construction of DNA and RNA standard curves. Key considerations for the use of RT-q-PCR assays in microbial ecology are included.

Background Quantitative (q) PCR by amplification of nucleic acid with a fluorescent dye is widely used. Selection of adequate PCR reagents and devices is relevant to achieve reliable and consistent data. Our main objective was to test the robustness of different commercial SYBR green PCR mixes with respect to specificity and sensitivity of the PCR assay, across various PCR machines (Light Cycler 96, ViiA7) and amplification protocols. Herein, we applied PCR protocols for determining mRNA transcript levels, DNA copy numbers, and DNA genotype. Results First, we set up 70 primer-based assays that targeted immune-related mRNA transcripts. Of the 70 assays 66 (94.3 %) resulted in a single melting curve peak, indicating specificity of the amplification, with PCR mixes from large vendors (Roche, ABI, Bio-Rad). But this was only seen when the PCR protocol that was indicated in the vendor’s guidelines for each particular mix was applied. When deviating from the prescribed protocol, suboptimal melting curves were most often seen when using Roche SYBR green. With respect to PCR yields, the use of ABI mix more often led to lower Cq values. Second, we set up 20 primer-selective PCR assays to target different insertion-deletion and single nucleotide polymorphism regions throughout the genome. The variation in delta Cq between positive and negative DNA samples among the PCR assays was the lowest when using ABI master mix. Finally, the quality of high resolution melting (HRM) assays for DNA genotyping was compared between four commercial HRM PCR mixes (Roche, Bioline, PCR Biosystems, ABI). Only Roche and ABI mixes produced optimal clusters of melting profiles that clearly distinguished genotype variants. Conclusions The current results show a preference for the use of ABI mix when it comes to obtaining higher sensitivity in cDNA analysis and a higher consistency among assays in distinguishing DNA genotypes among different individuals. For HRM assays, it is advisable to use master mix from a relatively large vendor. Electronic supplementary material The online version of this article (doi:10.1186/s13104-016-2093-4) contains supplementary material, which is available to authorized users.

Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen capable of causing severe disease in humans. Rapid and accurate identification and characterization techniques are essential during outbreak investigations. Current methods for characterization of STEC are expensive and time-consuming. With the advent of rapid and cheap whole genome sequencing (WGS) benchtop sequencers, the potential exists to replace traditional workflows with WGS. The aim of this study was to validate tools to do reference identification and characterization from WGS for STEC in a single workflow within an easy to use commercially available software platform. Publically available serotype, virulence, and antimicrobial resistance databases were downloaded from the Center for Genomic Epidemiology (CGE) (www.genomicepidemiology.org) and integrated into a genotyping plug-in with in silico PCR tools to confirm some of the virulence genes detected from WGS data. Additionally, down sampling experiments on the WGS sequence data were performed to determine a threshold for sequence coverage needed to accurately predict serotype and virulence genes using the established workflow. The serotype database was tested on a total of 228 genomes and correctly predicted from WGS for 96.1% of O serogroups and 96.5% of H serogroups identified by conventional testing techniques. A total of 59 genomes were evaluated to determine the threshold of coverage to detect the different WGS targets, 40 were evaluated for serotype and virulence gene detection and 19 for the stx gene subtypes. For serotype, 95% of the O and 100% of the H serogroups were detected at > 40x and ≥ 30x coverage, respectively. For virulence targets and stx gene subtypes, nearly all genes were detected at > 40x, though some targets were 100% detectable from genomes with coverage ≥20x. The resistance detection tool was 97% concordant with phenotypic testing results. With isolates sequenced to > 40x coverage, the different databases accurately predicted serotype, virulence, and resistance from WGS data, providing a fast and cheaper alternative to conventional typing techniques.

Thermal asymmetric staggered PCR is the most widely used technique to obtain the flanking sequences. However, it has some limitations, including a low rate of positivity, and complex operation. In this study, a improved method of it was made based on suppression-PCR and touchdown PCR. The PCR fragment obtained by the amplification was used directly for sequencing after gel purification. Using this improved method, the positive rate of amplified flanking sequences of the ATMT mutants reached 99%. In addition, the time from DNA extraction to flanking sequence analysis was shortened to 2 days with about 6 dollars each sample.

Primer design represents a widely employed gambit in diverse molecular applications including PCR, sequencing and probe hybridization. Variations of PCR, including primer walking, allele-specific PCR and nested PCR provide specialized validation and detection protocols for molecular analyses that often require screening large numbers of DNA fragments. In these cases, automated sequence retrieval and processing become important features and furthermore, a graphic that provides the user with a visual guide to the distribution of designed primers across targets is most helpful in quickly ascertaining primer coverage. To this end, I describe here, PrimerMapper, which provides a comprehensive graphical user interface that designs robust primers from any number of inputted sequences while providing the user with both, graphical maps of primer distribution for each inputted sequence and also a global assembled map of all inputted sequences with designed primers. PrimerMapper also enables the visualization of graphical maps within a browser and allows the user to draw new primers directly onto the webpage. Other features of PrimerMapper include allele-specific design features for SNP genotyping, a remote BLAST window to NCBI databases and remote sequence retrieval from GenBank and dbSNP. PrimerMapper is hosted at GitHub and freely available without restriction.

Analytical PCR experiments preferably use internal probes for monitoring the amplification reaction and specific detection of the amplicon. Such internal probes have to be designed in close context with the amplification primers, and may require additional considerations for the detection of genetic variations. Here we describe Edesign, a new online and stand-alone tool for designing sets of PCR primers together with an internal probe for conducting quantitative real-time PCR (qPCR) and genotypic experiments. Edesign can be used for selecting standard DNA oligonucleotides like for instance TaqMan probes, but has been further extended with new functions and enhanced design features for Eprobes. Eprobes, with their single thiazole orange-labelled nucleotide, allow for highly sensitive genotypic assays because of their higher DNA binding affinity as compared to standard DNA oligonucleotides. Using new thermodynamic parameters, Edesign considers unique features of Eprobes during primer and probe design for establishing qPCR experiments and genotyping by melting curve analysis. Additional functions in Edesign allow probe design for effective discrimination between wild-type sequences and genetic variations either using standard DNA oligonucleotides or Eprobes. Edesign can be freely accessed online at http://www.dnaform.com/edesign2/, and the source code is available for download.

WOS: 000368559100012, PCR is an effective and widely used method for the amplification of target DNA fragments in vitro. The templates that have high guanine-cytosine (GC) content, complex secondary structures, or short tandem repeats are difficult to amplify by the conventional PCR methods. Human genome regulatory regions such as promoters are rich in terms of GC base compositions. To amplify these regions some special modifications or additives are required. Using different PCR strategies such as hot-start/touchdown PCR or the utilization of various additives into the reaction mixture such as organic molecules can improve PCR yield. In the present study we optimized the PCR conditions for the amplification of the human ADAMTS-2 gene promoter region featuring an extremely high GC content and a secondary structure. We show that a combination of three additives, betaine, dimethyl sulfoxide, and 7-deaza GTP, is essential to obtain a correct PCR amplicon. To demonstrate whether the optimized PCR condition was applicable to other GC-enriched regions, a similar procedure was repeated for the amplification of the human URG4/URGCP gene promoter., Scientific and Technological Research Council of Turkey (TUBITAK) [212T200]; Balikesir University Scientific Research Projects Unit (BAP) [2010/39], This work was supported mainly by the Scientific and Technological Research Council of Turkey (TUBITAK, 212T200) and partially by the Balikesir University Scientific Research Projects Unit (BAP, 2010/39).

Diatoms are widely known as brown microalgae generating silicified cell-wall called frustule. The unique frustule ornamentations form occlusion and perforation. An interesting study of frustule formation led us to understand further the variation of thegene of interest (Silicic Acid Transporter/ SIT1) on Bacillariophyceae. The SIT1 gene indicating the frustule formation on diatomhas been studied. As a preliminary study, we used in silico Polymerase Chain Reaction (PCR) analysis to know the gene variation of SIT1. The analysis was conducted using data available from Genebank followed by primer design, comparison of sequence alignment, and in silico PCR. Fourteen extracted SIT1 sequences were aligned and analyzed usingFastPCR program with in silico PCR feature. Our result suggested the primer 7C could be implemented as degenerate primers resulting the in silico amplification of 426-435 bp PCR products. MUSCLE algorithm was furthermore used to align the regions resulted from in silico PCR. A moderate percent...

Low-calorie sweetener, D-tagatose, has sweet characteristic comparable to sucrose. The use of D-tagatose has been deemed as safe, hence D-tagatose is categorized as GRAS material. D-tagatose can be synthesized through isomerization catalyzed by thermostable L-arabinose isomerase encoded by araA gene. Thermostable L-AI can be isolated from thermophilic bacteria, especially from hot spring water source in Sikidang, Dieng Plateau. Determination of capability of bacterial isolates to produce thermostable L-AI can be conducted through gene detection. The method of gene detection involves PCR using a specifically designed primer to amplify the targeted gene. Here, the study was aimed to design primers which amplify specific target within araA gene of partially characterized bacterial strain. The steps involved data mining through NCBI, multiple sequence alignment using CLUSTALW and MUSCLE, primer generation and candidates sorting, in silico PCR and primer characteristics checking by using OligoCalc. The result showed that in the context of this study, CLUSTALW and MUSCLE works in conjunction with each other. There are 4 pairs of primers which could be deduced to amplify the targeted gene. In silico PCR showed that primers iaraAF1 and iaraAR3 are specifically proven to amplify the targeted gene from Bacillus group.

With the advent of molecular-based methods to detect the presence of microbial pathogens, technologies such as the polymerase chain reaction (PCR) and whole genome sequencing have revolutionized the field of food microbiology in ensuring that food products are pathogen free. In addition, these tests can also be applied to strain-specific identification, thus serving as an important tool for differentiating and identifying strains used in food production and as probiotics. The basis of PCR methods is the amplification of select sites in either DNA or RNA molecules such that the level of sensitivity is as low as one microbial cell or virus particle. Since the first days that PCR was rolled out and its potential as a powerful tool for microbial diagnostics was recognized, improvements in its chemistry and the machines that perform these reactions have been impressive. Real-time PCR, which enables concurrent amplification of nucleic acid target sites and the data readout indicating the status of the reaction, has reduced the time of analysis from 2 to 4 h to less than 1 h. Whole genome sequencing can be applied to isolated colonies as well as a nonconventional means as a culture-free detection and identification method. Improvements in these technologies have such potential that the detection and identification of all known microbial pathogens can be accomplished in one reaction. Many different types of molecular-based assays are described in this article.

With the advent of next-generation sequencing and its prolific use in the clinical realm, it would appear that techniques such as PCR would not be in high demand. This is not the case however, as PCR techniques play an important role in the success of NGS technology. Although NGS has rapidly become an important part of clinical molecular diagnostics, whole genome sequencing is still difficult to implement in a clinical laboratory due to high costs of sequencing, as well as issues surrounding data processing, analysis, and data storage, which can reduce efficiency and increase turnaround times. As a result, targeted sequencing is often used in clinical diagnostics, due to its increased efficiency. PCR techniques play an integral role in targeted NGS sequencing, allowing for the generation of multiple NGS libraries and the sequencing of multiple targeted regions simultaneously. We will outline the methods we employ in PCR amplification of targeted genomic regions for cancer mutation hotspots using the Ampliseq Cancer Hotspot v2 panel (Life Technologies, Carlsbad, CA).

The effects of PCR cycle number and DNA polymerase type on 16S rRNA gene pyrosequencing analysis were investigated using an artificially prepared bacterial community (mock community). The bacterial richness was overestimated at increased PCR cycle number mostly due to the occurence of chimeric sequences, and this was more serious with a DNA polymerase having proofreading activity than with Taq DNA polymerase. These results suggest that PCR cycle number must be kept as low as possible for accurate estimation of bacterial richness and that particular care must be taken when a DNA polymerase having proofreading activity is used.

In this study, 3′-flanking sequence between the host plant DNA and the integrated gene construct of pHMW1Dx5 vector in transgenic wheat B73-6-1 was revealed by means of adaptor PCR; thus, the fragment with the length of 3.1 kb was obtained, including a 190-bp wheat genomic DNA, which demonstrates that this HMW-GS gene was located on the wheat chromosome 3B. And the event-specific PCR primers were designed based upon the revealed 3′-flanking sequence; the conventional qualitative PCR and quantitative SYBR real-time PCR detection methods employing these primers were successfully developed. In conventional qualitative PCR assay, the limit of detection was 0.1 % for B73-6-1 wheat genomic DNA for one reaction. In the quantitative SYBR real-time PCR assay, the limit of detection and limit of quantification were 10 and 100 haploid genome copies, respectively. In addition, three mixed blind wheat samples with known B73-6-1 contents were detected using the established real-time PCR systems, and the ideal results indicated that the established event-specific real-time PCR detection systems were reliable, sensitive and accurate.

The polymerase chain reaction (PCR) is a technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. PCR is now a common and often indispensable technique used in medical and biological research labs for a variety of applications. There are three major steps involved in the PCR technique: denaturation, annealing and extension. PCR is useful in the investigation and diagnosis of a growing number of diseases. PCR is also used in forensics laboratories. PCR can identify genes that have been implicated in the development of cancer. The present paper is an attempt to review basics of PCR in relation to its methods, application and use.

Evaluating the specificity of polymerase chain reaction (PCR) primers is an essential step in PCR primer design. The MFEprimer-2.0 server allows users to check primer specificity against genomic DNA and messenger RNA/complementary DNA sequence databases quickly and easily. MFEprimer-2.0 uses a k-mer index algorithm to accelerate the search process for primer binding sites and uses thermodynamics to evaluate binding stability between each primer and its DNA template. Several important characteristics, such as the sequence, melting temperature and size of each amplicon, either specific or non-specific, are reported on the results page. Based on these characteristics and the user-friendly output, users can readily draw conclusions about the specificity of PCR primers. Analyses for degenerate primers and multiple PCR primers are also supported in MFEprimer-2.0. In addition, the databases supported by MFEprimer-2.0 are comprehensive, and custom databases can also be supported on request. The MFEprimer-2.0 server does not require a login and is freely available at http:// biocompute.bmi.ac.cn/CZlab/MFEprimer-2.0. More over, the MFEprimer-2.0 command-line version and local server version are open source and can be downloaded at https://github.com/quwubin/ MFEprimer/wiki/Manual/.

Metabarcoding approaches use total and typically degraded DNA from environmental samples to analyse biotic assemblages and can potentially be carried out for any kinds of organisms in an ecosystem. These analyses rely on specific markers, here called metabarcodes, which should be optimized for taxonomic resolution, minimal bias in amplification of the target organism group and short sequence length. Using bioinformatic tools, we developed metabarcodes for several groups of organisms: fungi, bryophytes, enchytraeids, beetles and birds. The ability of these metabarcodes to amplify the target groups was systematically evaluated by (i) in silico PCRs using all standard sequences in the EMBL public database as templates, (ii) in vitro PCRs of DNA extracts from surface soil samples from a site in Varanger, northern Norway and (iii) in vitro PCRs of DNA extracts from permanently frozen sediment samples of late-Pleistocene age (~16,000-50,000 years bp) from two Siberian sites, Duvanny Yar and Main River. Comparison of the results from the in silico PCR with those obtained in vitro showed that the in silico approach offered a reliable estimate of the suitability of a marker. All target groups were detected in the environmental DNA, but we found large variation in the level of detection among the groups and between modern and ancient samples. Success rates for the Pleistocene samples were highest for fungal DNA, whereas bryophyte, beetle and bird sequences could also be retrieved, but to a much lesser degree. The metabarcoding approach has considerable potential for biodiversity screening of modern samples and also as a palaeoecological tool.

We describe a multiplex tetra-primer amplification refractory mutation system PCR (M-T-ARMS PCR) for detecting three single nucleotide polymorphisms associated with breast cancer, including rs4784227(C>T), rs12196489(G>A) and rs3803662(T>C). Three sets of chimeric primers consisting of a specific sequence fused to a universal sequence at the 5′ end were used in one single PCR reaction, followed by a capillary electrophoresis to separate PCR products and genotyping. We applied this method to test 70 samples from whole blood and mouth swab specimens to demonstrate the performance. All mutations were accurately detected and results were confirmed by direct DNA sequencing. M-T-ARMS PCR coupled with capillary electrophoresis is a simple and accurate assay that allows the simultaneous detection of three mutations in a single tube.

Screening and analysis of collections of DNA molecules is a standard aspect of many DNA computing approaches. We describe the use of three different polymerase chain reaction (PCR) detection methods to screen specific members of a 5-site, 2-variable DNA computing library previously created using parallel overlap assembly of unique sequences generated from the SynDCode program. The three PCR methods (conventional gel-based PCR, SYBR Green real-time PCR and TaqMan real-time PCR) could all successfully identify individual library members separately or in a mixture. The TaqMan approach was also able to identify members in the original library we had not yet sequenced, providing more evidence supporting our hypothesis that the DNA library we generated may be complete. We expect these three approaches will be useful in future screening of other DNA computing libraries and structures.

Summary The base adjacent to the 3′ end of universal PCR primers targeting the 16S rRNA gene is often variable and apparently biases the microbial community composition as represented by PCR-based surveys. To test this hypothesis, four templates of 44 bases each and two complementary primers (21 bases) were designed to differ only in the bases adjacent to the primers, and their amplification efficiencies were evaluated using quantitative PCR. For extension temperatures of 72°C, 73°C and 74°C, improvement in initial amplification efficiency was observed for templates with guanine or cytosine at the position contiguous to the primers. However, no clear preference was observed when extension temperature was lowered to 70°C. Shortening the primers by one base, so that the variable position was located two base pairs downstream from the primer, attenuated but did not eliminate this bias. A conformational change of the quaternary polymerase – primer – template – dNTP complex upon commencing of polymerization is thought to be a rate-limiting step. A possible explanation for the observed bias is the stabilization of this complex by the adjacent guanine or cytosine. Reducing PCR extension temperature to 70°C minimizes amplification biases caused by variable template-contiguous bases to the 3′ end of universal PCR primers. Next-base nucleotide composition should be taken in consideration in designing primers targeting 16S rRNA or other functional genes used in microbial ecology studies.

Optimization of primer sequences for polymerase chain reaction (PCR) and quantitative PCR (qPCR) and reaction conditions remains an experimental challenge. We have developed a resource, PrimerBank, which contains primers that can be used for PCR and qPCR under stringent and allele-invariant amplification conditions. A distinguishing feature of PrimerBank is the experimental validation of primer pairs covering most known mouse genes. Here, we describe a major update of PrimerBank that includes the design of new primers covering 17 076 and 18 086 genes for the human and mouse species, respectively. As a result of this update, PrimerBank contains 497 156 primers (an increase of 62% from the previous version) that cover 36 928 human and mouse genes, corresponding to around 94% of all known protein-coding gene sequences. An updated algorithm based on our previous approach was used to design new primers using current genomic information available from the National Center for Biotechnology Information (NCBI). PrimerBank primers work under uniform PCR conditions, and can be used for high-throughput or genome-wide qPCR. Because of their broader linear dynamic range and greater sensitivity, qPCR approaches are used to reanalyze changes in expression suggested by exploratory technologies such as microarrays and RNA-Seq. The primers and all experimental validation data can be freely accessed from the PrimerBank website, http://pga.mgh.harvard.edu/primerbank/.