MEDUSA: large scale automatic selection and visual assessment of PCR primer pairs.

MEDUSA is a tool for automatic selection and visual assessment of PCR primer pairs, developed to assist large scale gene expression analysis projects. The system allows specification of constraints of the location and distances between the primers in a pair. For instance, primers in coding, non-coding, exon/intron-spanning regions might be selected. Medusa applies these constraints as a filter to primers predicted by three external programs, and displays the resulting primer pairs graphically in the Blixem (Sonnhammer and Durbin, COMPUT: Appl. Biosci. 10, 301-307, 1994; http://www.cgr.ki.se/cgr/groups/sonnhammer/Blixem.html) viewer. AVAILABILITY: The MEDUSA web server is available at http://www.cgr.ki.se/cgr/MEDUSA. The source code and user information are available at ftp://ftp.cgr.ki.se/pub/prog/medusa.     

SP‐Designer: a user‐friendly program for designing species‐specific primer pairs from DNA sequence alignments

SP‐Designer is an open‐source program providing a user‐friendly tool for the design of specific PCR primer pairs from a DNA sequence alignment containing sequences from various taxa. SP‐Designer selects PCR primer pairs for the amplification of DNA from a target species on the basis of several criteria: (i) primer specificity, as assessed by interspecific sequence polymorphism in the annealing regions, (ii) the biochemical characteristics of the primers and (iii) the intended PCR conditions. SP‐Designer generates tables, detailing the primer pair and PCR characteristics, and a FASTA file locating the primer sequences in the original sequence alignment. SP‐Designer is Windows‐compatible and freely available from http://www2.sophia.inra.fr/urih/sophia_mart/sp_designer/info_sp_designer.php .     

Development of a real-time PCR assay for the detection of Cladosporium fulvum in tomato leaves

Aims: The aim of this study was to develop a sensitive real-time polymerase chain reaction (PCR) assay for the rapid detection of Cladosporium fulvum in tomato leaves. Methods and Results: Three PCR primer pairs were designed based on the nucleotide sequences of: (i) the internal transcribed spacer regions of ribosomal RNA; (ii) a microsatellite region amplified by the microsatellite primer M13; and (iii) the β-tubulin gene of C. fulvum. Each primer pair amplified the expected target DNA fragment from geographically diverse isolates of C. fulvum. No PCR products were amplified with these primer pairs from DNA of other fungal species. Among the three pairs of primers, the primer pair CfF1/CfR1 developed based on the microsatellite region was the most sensitive. Using this sensitive primer pair, a real-time PCR assay was developed to detect early infection of C. fulvum in tomato leaves. Significance and Impact of the Study: DNA regions amplified by the microsatellite primer M13 have a high potential for developing highly sensitive species-specific PCR primers for the detection of phytopathogenic fungi. The real-time PCR assay developed in this study is useful in monitoring early infection of C. fulvum, and can help growers make timely decisions on fungicide application.     

URPD: A Specific Product Primer Design Tool

ABSTRACT: BACKGROUND: Polymerase chain reaction (PCR) plays an important role in molecular biology. Primer design fundamentally determines its results. Here, we present a currently available software for a rather straight-forward way of visualizing the primer design process for infrequent users. RESULTS: URPD (yoUR Primer Design), a web-based specific product primer design tool, combines the NCBI Reference Sequences (RefSeq), UCSC In-Silico PCR, memetic algorithm (MA) and genetic algorithm (GA) primer design methods to obtain specific primer sets. A friendly user interface is accomplished by built-in parameter settings. The incorporated smooth pipeline operations effectively guide both occasional and advanced users. URPD contains an automated process, which produces feasible primer pairs that satisfy the specific needs of the experimental design with practical PCR amplifications. Visual virtual gel electrophoresis and in silico PCR provide a simulated PCR environment. The comparison of Practical gel electrophoresis comparison to virtual gel electrophoresis facilitates and verifies the PCR experiment. Wet-laboratory validation proved that the system provides feasible primers. CONCLUSIONS: URPD is a user-friendly tool that provides specific primer design results. The pipeline design path makes it easy to operate for beginners. URPD also provides a high throughput primer design function. Moreover, the advanced parameter settings assist sophisticated researchers in performing experiential PCR. Several novel functions, such as a nucleotide accession number template sequence input, local and global specificity estimation, primer pair redesign, user-interactive sequence scale selection, and virtual and practical PCR gel electrophoresis discrepancies have been developed and integrated into URPD. The URPD program is implemented in JAVA and freely available at http://bio.kuas.edu.tw/urpd/.     

DNA聚合酶与引物/模板的相互作用对PCR效率的影响

PCR是体外酶促合成特异DNA片段的一种方法,引物的优劣直接关系到PCR的特异性与成功与否。传统的PCR引物设计软件基本上忽略了DNA聚合酶与引物/模板的亲和性对PCR效率的影响。为揭示DNA聚合酶与引物/模板的相互作用是否对PCR的效率有影响,通过构建Taq DNA 聚合酶与不同序列引物/模板DNA相互作用的三维结构模型,采用MM/GBSA方法计算复合物的结合自由能,以结合自由能为参数,为人血清白蛋白基因(Human Serum Albumin gene,HSA gene)和结核杆菌pyrF基因(Mycobacterium tuberculosis pyrF gene)设计了PCR引物。PCR实验结果表明,引物的PCR效率与结合自由能相关：引物与聚合酶的结合自由能越低,PCR实验的效率相对越高。这说明DNA聚合酶与引物/模板的相互作用对PCR效率有重要影响。因此,引物/模板DNA与聚合酶的结合自由能可以作为PCR引物设计的新参数。     

Specific PCR product primer design using memetic algorithm

To provide feasible primer sets for performing a polymerase chain reaction (PCR) experiment, many primer design methods have been proposed. However, the majority of these methods require a relatively long time to obtain an optimal solution since large quantities of template DNA need to be analyzed. Furthermore, the designed primer sets usually do not provide a specific PCR product size. In recent years, evolutionary computation has been applied to PCR primer design and yielded promising results. In this article, a memetic algorithm (MA) is proposed to solve primer design problems associated with providing a specific product size for PCR experiments. The MA is compared with a genetic algorithm (GA) using an accuracy formula to estimate the quality of the primer design and test the running time. Overall, 50 accession nucleotide sequences were sampled for the comparison of the accuracy of the GA and MA for primer design. Five hundred runs of the GA and MA primer design were performed with PCR product lengths of 150–300 bps and 500–800 bps, and two different methods of calculating T_m for each accession nucleotide sequence were tested. A comparison of the accuracy results for the GA and MA primer design showed that the MA primer design yielded better results than the GA primer design. The results further indicate that the proposed method finds optimal or near‐optimal primer sets and effective PCR products in a dry dock experiment. Related materials are available online at http://bio.kuas.edu.tw/ma‐pd/ . © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Molecular diversity analysis of rumen methanogenic Archaea from goat in eastern China by DGGE methods using different primer pairs

Aims:  To screen a pair of primers suitable for denaturing gradient gel electrophoretic (DGGE) analysis of ruminal methanogenic Archaea and to detect the archaeal communities in the rumen of goat.
Methods and Results:  Nine primer pairs for 16S rDNA of methanogenic Archaea , including six for directed polymerase chain reaction (PCR) and three for nested PCR were first evaluated by PCR amplification of the total DNA from rumen fluids and bacteria. The DGGE analysis of rumen fluids was then conducted with three primer sets (344fGC/915r, 1106fGC/1378r and 519f/915rGC) of the nine pairs tested. Good separation and quality of patterns were obtained in DGGE analysis with primer pairs 1106fGC/1378r and 519f/915rGC. A total of 40 DNA fragments were excised from the DGGE gels and their sequences were determined. All fragments belonged to methanogenic Archaea while primer pair 519f/915rGC had better amplification ranges than the other two primer pairs.
Conclusions:  The procedure of DGGE analysis with primer pair 519f/915rGC was more suitable for investigating methanogenic archaeal community in the rumen. The dominant methanogenic Archaea in the rumen of goat was Methanobrevibacter sp. and an unidentified methanogenic Archaea .
Significance and Impact of the Study:  One pair of primers suitable for DGGE analysis of ruminal methanogenic Archaea was obtained and the molecular diversity of ruminal methanogenic Archaea in goat was investigated by PCR-DGGE.     

RTPrimerDB: the real-time PCR primer and probe database

The real-time polymerase chain reaction (PCR) methodology has become increasingly popular for nucleic acids detection and/or quantification. As primer/probe design and experimental evaluation is time-consuming, we developed a public database application for the storage and retrieval of validated real-time PCR primer and probe sequence records. The integrity and accuracy of the data are maintained by linking to and querying other reference databases. RTPrimerDB provides free public access through the Web to perform queries and submit user based information. Primer/probe records can be searched for by official gene symbol, nucleotide sequence, type of application, detection chemistry, LocusLink or Single Nucleotide Polymorphism (SNP) identifier, and submitter's name. Each record is directly linked to LocusLink, dbSNP and/or PubMed to retrieve additional information on the gene/SNP for which the primers/probes are designed. Currently, the database contains primer/probe records for human, mouse, rat, fruit fly and zebrafish, and all current detection chemistries such as intercalating dyes (SYBR Green I), hydrolysis probes (Taqman), adjacent hybridizations probes and molecular beacons. Real-time PCR primer/probe records are available at http://www.realtimeprimerdatabase.ht.st.     

Comparison of primers for the detection of Salmonella enterica serovars using real-time PCR

AIMS: To evaluate the specificity and sensitivity of PCR primers for the detection of Salmonella enterica in a real-time PCR assay using pure cultures. METHODS AND RESULTS: Unenriched whole cells in sterile water were used as template for each PCR. SYBR Green dye was used for the nonspecific detection of dsDNA. The real-time PCR detection limits of five previously published primer sets used in conventional PCR applications were not below 3 x 10(3) CFU per reaction (rxn). A new primer set, Sen, was designed, which detected Salm. enterica Newport down to 6 CFU rxn(-1) in one case, and gave an average detection limit of 35 CFU rxn(-1) over three separate runs. CONCLUSIONS: Primers originally designed for end-point PCR did not have adequate specificity or sensitivity compared with those specifically designed for real-time PCR. SIGNIFICANCE AND IMPACT OF THE STUDY: This study emphasizes the importance of evaluating real-time PCR primer sets in pure cultures prior to testing in field samples. This study will benefit other researchers in selecting an appropriate primer set for real-time PCR detection of Salm. enterica.     

Nano-magnetic primer based electrochemiluminescence-polymerase chain reaction (NMPE-PCR) assay

Here we have developed a novel nano-magnetic primer based electrochemiluminescence-polymerase chain reaction (NMPE-PCR) strategy for detection of genome. The key idea of this method is integrating the two in situ processes: PCR on the surface of magnetic nanoparticles (MNPs) and magnetic beads based ECL readout platform, to avoid some laborious manual operations and achieve rapid yet sensitive detection. At first, the approach employs a pair of functional primers for amplification: one is tris-(2,2'-bipyridyl) ruthenium (TBR) labeled primer; the other one is nano-magnetic primer which is prepared by attaching the primer to the surfaces of MNPs. With the presence of DNA analyte and PCR mixture, the TBR labeled products are directly loaded and enriched on the surface of MNPs during PCR cycling. Then the MNPs-TBR complexes can be analyzed by a magnetic ECL platform without any post-modification or post-incubation. Finally, we used Listeria monocytogenes as the target to examine these desirable properties of this assay, reaching a detection limit of 500 fg/μL for genome in 1 h. The proposed study has provided the evidence as a proof-of-concept, thus having potential for development of automatic mode for detection of specific gene.     

Evaluation of PCR primers for denaturing gradient gel electrophoresis analysis of fungal communities in compost

AIMS: Three previously published fungal specific PCR primer sets, referred to as the NS, EF and NL primer sets, were evaluated for use in compost microbial community analysis by PCR and denaturing gradient gel electrophoresis (DGGE). METHODS AND RESULTS: Primers were first evaluated based on their tolerance to PCR inhibitors. Due to its sensitivity to inhibitors, the NS primer set was determined to require a 10-fold smaller volume addition of compost DNA to PCR than the EF and NL primer sets, based on a logistic regression model for a 75% PCR success rate. Further evaluation of the EF and NL primer sets involved testing the resolution of PCR products from pure fungal cultures on DGGE. The NL primer set, which targets the more variable 28S rDNA, resulted in multiple bands for each pure culture. Thus, the EF primer set was used to monitor the microbial community during compost colonization studies, where three fungi were inoculated onto autoclaved grape pomace and rice straw compost. CONCLUSIONS: Of the three primer sets evaluated, the EF primer set was determined to be the best for PCR-DGGE of compost fungal populations; however, concerns with the EF primer set included the lack of sequence divergence in the targeted region of 18S rDNA and PCR artifacts which interfered with detection of inoculated fungi in the colonization studies. SIGNIFICANCE AND IMPACT OF THE STUDY: There are many factors related to PCR primers that need to be assessed prior to applying PCR-DGGE to fungal communities in complex environments such as compost.     

Specific and sensitive detection of Nosema bombi (Microsporidia: Nosematidae) in bumble bees (Bombus spp.; Hymenoptera: Apidae) by PCR of partial rRNA gene sequences

A polymerase chain reaction (PCR) based method was developed for the specific and sensitive diagnosis of the microsporidian parasite Nosema bombi in bumble bees (Bombus spp.). Four primer pairs, amplifying ribosomal RNA (rRNA) gene fragments, were tested on N. bombi and the related microsporidia Nosema apis and Nosema ceranae, both of which infect honey bees. Only primer pair Nbombi-SSU-Jf1/Jr1 could distinguish N. bombi (323bp amplicon) from these other bee parasites. Primer pairs Nbombi-SSU-Jf1/Jr1 and ITS-f2/r2 were then tested for their sensitivity with N. bombi spore concentrations from 10(7) down to 10 spores diluted in 100 microl of either (i) water or (ii) host bumble bee homogenate to simulate natural N. bombi infection (equivalent to the DNA from 10(6) spores down to 1 spore per PCR). Though the N. bombi-specific primer pair Nbombi-SSU-Jf1/Jr1 was relatively insensitive, as few as 10 spores per extract (equivalent to 1 spore per PCR) were detectable using the N. bombi-non-specific primer pair ITS-f2/r2, which amplifies a short fragment of approximately 120 bp. Testing 99 bumble bees for N. bombi infection by light microscopy versus PCR diagnosis with the highly sensitive primer pair ITS-f2/r2 showed the latter to be more accurate. PCR diagnosis of N. bombi using a combination of two primer pairs (Nbombi-SSU-Jf1/Jr1 and ITS-f2/r2) provides increased specificity, sensitivity, and detection of all developmental stages compared with light microscopy.     

正交设计优化缩叶藓属植物的ISSR-PCR反应体系

目的：建立缩叶藓属（Ptychomitrium）植物ISSR-PCR反应的最佳体系。方法：利用正交设计实验的方法,采用引物562,10号材料Ptychomitrium gardneri为模板对缩叶藓属植物的ISSR-PCR反应体系中的5种主要因素（Mg2＋d、NTPs、引物、模板量、Taq酶量）在4个水平上进行体系优化。结果：确定了缩叶藓属（Ptychomitrium）植物ISSR-PCR反应的最佳体系（25μl）为：Mg2＋浓度为3.2mmol/L、dNTPs浓度为0.96mmol/L、引物浓度为1.04μmol/L、模板量10ng、Taq酶量1.5U。利用该体系,采用引物564在16个材料中能有效扩增。结论：这一优化体系的建立为以后缩叶藓属植物的ISSR遗传多样性的分析奠定了基础。     

EasyExonPrimer

EasyExonPrimer is a web-based software that automates the design of PCR primers to amplify exon sequences from genomic DNA. EasyExonPrimer is written in Perl and uses Primer3 to design PCR primers based on the genome builds and annotation databases available at the University of California, Santa Cruz (UCSC) Genome Browser database (http://genome.ucsc.edu/). It masks repeats and known single nucleotide polymorphism (SNP) sites in the genome and designs standardised primers using optimised conditions. Users can input genes by RefSeq mRNA ID, gene name or keyword. The primer design is optimised for large-scale resequencing of exons. For exons larger than 1 kb, the user has the option of breaking the exon sequence down into overlapping smaller fragments. All primer pairs are then verified using the In-Silico PCR software to test for uniqueness in the genome. We have designed >1000 pairs of primers for 90 genes; 95% of the primer pairs successfully amplified exon sequences under standard PCR conditions without requiring further optimisation. AVAILABILITY: EasyExonPrimer is available from http://129.43.22.27/~primer/. The source code is also available upon request. CONTACT: Xiaolin Wu (forestwu@mail.nih.gov).     

A novel multiplex PCR assay for Salmonella subspecies identification

Aim:  To develop a novel multiplex polymerase chain reaction (PCR) assay with six primer pairs for Salmonella subspecies identification.
Methods and Results:  Five primer pairs were chosen to detect the genes ( fljB , mdcA , gatD , stn and STM4057) responsible for several phenotypic traits or encoding (sub) species-specific regions. A primer pair for invA was added to simultaneously detect Salmonella . The combination of these primer pairs was expected to give unique results to all subspecies, including Salmonella bongori. The multiplex PCR assay was optimized and evaluated with 53 Salmonella strains representing all S. enterica subspecies, S. bongori and five non- Salmonella strains. The multiplex PCR assay revealed that the genotypes were well correlated with the phenotypes in the Salmonella strains tested. The unique band patterns to their subspecies were generated from 94·3% (50/53) of the Salmonella strains, and no product from other strains by the multiplex PCR assay.
Conclusions:  The multiplex PCR assay we developed was found to be a rapid, specific and easy to perform method compared with traditional biochemical tests for Salmonella subspecies identification, especially for rapid screening of large numbers of samples.
Significance and Impact of the Study:  The assay will be useful for characterizing Salmonella isolates from reptiles, which belong to various subspecies, and therefore add to the scientific understanding of reptile-associated Salmonellosis.     

Identification of Lactobacillus crispatus by polymerase chain reaction targeting S-layer protein gene

AIMS: This study aimed to develop a polymerase chain reaction (PCR) method to identify Lactobacillus crispatus. METHODS AND RESULTS: A primer set (CbsA2F-CbsA2R) for amplifying conserved regions of S-layer genes was designed to identify Lact. crispatus and the specificity of this set was compared with that of another primer set (Cri 16SI-Cri 16SII) which has been reported as a species-specific primer set targeting the 16S rRNA gene. Among species in the Lact. acidophilus A1-A4 groups, when KOD polymerase was used for amplification, the primer set CbsA2F-CbsA2R gave PCR products with Lact. crispatus strains only. However, when Taq polymerase was used, this primer set gave products with one Lact. amylovorus strain as well as with Lact. crispatus strains. The primer set Cri 16SI-Cri 16SII gave PCR products with Lact. crispatus strains and two Lact. acidophilus strains, regardless of whether the polymerase used was KOD or Taq. CONCLUSIONS: A PCR targeting the S-layer gene and amplified with KOD polymerase can identify Lact. crispatus accurately and rapidly. SIGNIFICANCE AND IMPACT OF THE STUDY: To the authors' knowledge, this is the first paper to provide a PCR method for the specific identification of Lact. crispatus.     

MethPrimer: designing primers for methylation PCRs

MOTIVATION: DNA methylation is an epigenetic mechanism of gene regulation. Bisulfite- conversion-based PCR methods, such as bisulfite sequencing PCR (BSP) and methylation specific PCR (MSP), remain the most commonly used techniques for methylation mapping. Existing primer design programs developed for standard PCR cannot handle primer design for bisulfite-conversion-based PCRs due to changes in DNA sequence context caused by bisulfite treatment and many special constraints both on the primers and the region to be amplified for such experiments. Therefore, the present study was designed to develop a program for such applications. RESULTS: MethPrimer, based on Primer 3, is a program for designing PCR primers for methylation mapping. It first takes a DNA sequence as its input and searches the sequence for potential CpG islands. Primers are then picked around the predicted CpG islands or around regions specified by users. MethPrimer can design primers for BSP and MSP. Results of primer selection are delivered through a web browser in text and in graphic view.     

Enhancements and modifications of primer design program Primer3

The determination of annealing temperature is a critical step in PCR design. This parameter is typically derived from the melting temperature of the PCR primers, so for successful PCR work it is important to determine the melting temperature of primer accurately. We introduced several enhancements in the widely used primer design program Primer3. The improvements include a formula for calculating melting temperature and a salt correction formula. Also, the new version can take into account the effects of divalent cations, which are included in most PCR buffers. Another modification enables using lowercase masked template sequences for primer design. Availability: Features described in this article have been implemented into the development code of Primer3 and will be available in future versions (version 1.1 and newer) of Primer3. Also, a modified version is compiled under the name of mPrimer3 which is distributed independently. The web-based version of mPrimer3 is available at http://bioinfo.ebc.ee/mprimer3/ and the binary code is freely downloadable from the URL http://bioinfo.ebc.ee/download/.     

SNPbox: a modular software package for large-scale primer design

SUMMARY: We developed a modular software package SNPbox that automates and standardizes the generation of PCR primers and is used in the strategy for constructing single nucleotide polymorphisms (SNPs) maps. In this strategy, the focus of primer design can be either on the validation of annotated public SNPs or on the SNP discovery in exon regions or extended genomic regions, both by resequencing. SNPbox relies on Primer3 for the primer design and combines this program with other publicly available software tools such as BLAST, Spidey and RepeatMasker, and newly developed algorithms. Primer conditions were chosen such that PCR amplifications are uniform for each PCR amplicon facilitating the use of high-throughput genetic platforms. SNPbox can also be used for the design of primer sets for mutation analysis, STR marker genotyping and microarray oligo design. Of the 2500 primer sets designed by SNPbox, 95% successfully amplified genomic DNA under uniform PCR conditions. AVAILABILITY: The software is available from the authors upon request. SUPPLEMENTARY INFORMATION: SNPbox_supplement.     

Comparison of primers for the detection of pathogenic Escherichia coli using real-time PCR

AIMS: To evaluate PCR primers for the detection of pathogenic Escherichia coli in a real-time PCR assay and determine their utility in produce irrigation water testing. METHODS AND RESULTS: Three previously published PCR primer sets and one set designed for this study were tested for their ability to produce amplification products for several pathogenic E. coli serotypes from whole cells as template. Two of the previously published primer sets were chosen for real-time PCR detection limit determination. The coneaeA and PEH detection limit of E. coli O157:H7 was 10(0) and 10(1) CFU rxn(-1) in sterile water respectively. To detect E. coli O157:H7 in sprout irrigation water, the water required dilution due to PCR inhibitors. The detection limit of the coneaeA and PEH was 10(1) and between 10(2) and 10(3) CFU rxn(-1) in diluted sprout irrigation water respectively. CONCLUSIONS: The primer set coneaeA was able to produce an amplification product from each E. coli serotype, except O128:H7 and most sensitive for real-time PCR detection of pathogenic E. coli in diluted sprout irrigation water. SIGNIFICANCE AND IMPACT OF THE STUDY: The necessity of a dissociation analysis to distinguish positive samples from those with fluorescence of random dsDNA generation for real-time PCR in a complex background was established.