Identification of animal species using the partial sequences in the mitochondrial 16S rRNA gene

A practical workflow for forensic species identification using direct sequencing of real-time PCR products

BACKGROUND

Forensic scientists are often required to identify species of unknown biological samples. Although methods based on sequencing of DNA barcode regions are the gold standard for species identification in single-source forensic samples, they are cumbersome to implement as routine work in forensic laboratories that perform many tests, including human DNA typing. We have developed a species identification workflow that incorporates direct sequencing with real-time PCR products (real-time PCR-direct sequencing) as the technical trick for easy testing in forensic practice.

METHOD AND RESULTS

Following our workflow, DNA samples from vertebrates, such as mammals, amphibians, reptiles, birds, and fish, were subjected to species identification using vertebrate universal primers targeting each of the four DNA barcode regions. In real-time PCR melting curve analysis, humans and animals (nonhuman) could be differentiated by comparing melting temperatures, and subsequent real-time PCR-direct sequencing contributed to simplified sequencing. Searches against public DNA databases using the obtained sequences were compatible with the origin of the samples, indicating that this method might be used to identify animal species at the genus level. Furthermore, this workflow was effective in actual casework, which provided rapid test results according to the needs of the investigating agencies.

CONCLUSIONS

The species identification workflow will simply sequence as much as possible and can be integrated into routine forensic practice. The real-time PCR-direct sequencing used in this workflow might be beneficial not only for species identification but also for DNA sequencing by using the Sanger method for a variety of life sciences.

Molecular genetic diversity of some rabbit breeds based on mitochondrial 16S rRNA sequences

<p>The present study was performed to assess the genetic variations among six rabbit breeds in Egypt based on mitochondrial 16S rRNA sequences. The length of partial mitochondrial 16S rRNA in the six rabbit breeds ranged from 546 bp to 558 bp. The sequenced regions were submitted to GenBank/NCBI under accession numbers (MW052052 - MW052057). The average content of A+T was 57% in all breeds. Among breeds, the percentages of genetic distance values were ranged from 0.000 to 0.004. The highest P-distance (0.004) was found between the New Zealand White breed and all other breeds. The results support the suitability of mitochondrial 16S rRNA for genetic diversity analysis of rabbit breeds and the applicability for future research on genetic relationships and the phylogeny of rabbit breeds.</p>

Estimating included animal species in mixed crude drugs derived from animals using massively parallel sequencing

We developed a method that can detect each animal species of origin for crude drugs derived from multiple animal species based on massively parallel sequencing analysis of mitochondrial genes. The crude drugs derived from animals investigated in this study were Cervi Parvum Cornu and Trogopterorum feces, which are derived from a mix of different animal species, two chopped cicada sloughs, and two commercial Kampo drugs. The mitochondrial 12S rRNA, 16S rRNA, and cytochrome oxidase subunit I gene regions were amplified and sequenced using MiSeq. The ratios of haplotype to total number of sequences reads were calculated after sequence extraction and trimming. Haplotypes that exceeded the threshold were defined as positive haplotypes, which were compared with all available sequences using BLAST. In the Cervi Parvum Cornu and Trogopterorum feces samples, the haplotype ratios corresponded roughly to the mixture ratios, although there was a slight difference from mixture ratios depending on the gene examined. This method could also roughly estimate the compositions of chopped cicada sloughs and Kampo drugs. This analysis, whereby the sequences of several genes are elucidated, is better for identifying the included animal species. This method should be useful for quality control of crude drugs and Kampo drugs.

Who killed my dog? Use of forensic genetics to investigate an enigmatic case

Genetic testing of animal biological material has become a valuable tool in forensic investigations, and it is successfully used to identify unknown crime perpetrators, to unmask food frauds, or to clarify cases of animal attacks on humans or other animals. When DNA profiling is not possible due to inadequate amounts of nuclear DNA, mitochondrial DNA (mtDNA) testing is the only viable alternative, as in the case of shed hair samples. In this case, a dog was allegedly killed by wild animals while being hosted in a boarding house. Extraneous hair fragments recovered from the dog’s mouth and paws were subjected to genetic analysis: the cytochrome b gene located on mtDNA was amplified and sequenced in order to determine the species responsible for the killing. The mtDNA analysis provided evidence that the dog was killed by other dogs, thus unmasking a false wild animal attack and putting the case in an entirely different perspective.

Universal mitochondrial 16s rRNA biomarker for mini-barcode to identify fish species in Malaysian fish products

Mislabelling in fish products is a highly significant emerging issue in world fish trade in terms of health and economic concerns. DNA barcoding is an efficient sequencing-based tool for detecting fish species substitution but due to DNA degradation, it is in many cases difficult to amplify PCR products of the full-length barcode marker (~650 bp), especially in severely processed products. In the present study, a pair of universal primers targeting a 198 bp sequence of the mitochondrial 16s rRNA gene was designed for identification of fish species in the processed fish products commonly consumed in Malaysia. The specificity of the universal primers was tested by both in-silico studies using bioinformatics software and through cross-reaction assessment by practical PCR experiments against the DNA from 38 fish species and 22 other non-target species (animals and plants) and found to be specific for all the tested fish species. To eliminate the possibility of any false-negative detection, eukaryotic endogenous control was used during specificity evaluation. The developed primer set was validated with various heat-treated (boiled, autoclaved and microwaved) fish samples and was found to show high stability under all processing conditions. The newly developed marker successfully identified 92% of the tested commercial fish products with 96-100% sequence similarities. This study reveals a considerable degree of species mislabelling (20.8%); 5 out of 24 fish products were found to be mislabelled. The new marker developed in this work is a reliable tool to identify fish species even in highly processed products and might be useful in detecting fish species substitution thus protecting consumers' health and economic interests.

Identification of a broad spectrum of mammalian and avian species using the short fragment of the mitochondrially encoded cytochrome b gene

Mitochondrial DNA (mtDNA), especially the gene for cytochrome b (MT-CYB), has been found to be highly informative for species identification. In this study, we present the results of the analysis of a 127 bp long fragment of MT-CYB, amplified using universal primers, variable enough to be used for species identification and discrimination, even in highly degraded animal samples. The total number of analyzed species in this study was 30, including 17 mammalian and 13 bird species. Using a newly created primer pair, we successfully amplified and sequenced the target sequence in almost all tested species. The amplification was incomplete in just two species, and as a result, partial, but still variable sequences, were obtained. Using the target fragment we successfully identified all tested samples. Initial results suggested that the intraspecies genetic diversity of the target region, in all tested species, was low - from 0 to 4.72%. The interspecies genetic diversity of the target region, crucial for successful discrimination, showed relatively high diversity, ranging from 8.36% to 42.52%. Given its short length, the target region should be used for species determination, particularly in samples that are degraded or are low in DNA quantity.

Establishment of widely applicable DNA extraction methods to identify the origins of crude drugs derived from animals using molecular techniques

We established widely applicable DNA extraction methods to identify the origins of crude drugs derived from animals. Twenty-one samples including 17 kinds of crude drug derived from animals were examined. DNA was extracted from most of the crude drugs by adjustment of the QIAamp^® DNA Mini Kit. DNA extraction was performed successfully using phenol to remove impurities after applying a proteinase treatment. DNA extraction was performed successfully by decalcification treatment using ethylenediaminetetraacetic acid (EDTA), before applying the proteinase treatment for crude drugs having high calcium content, such as those from oyster shell and cuttlefish bone. DNA could not be extracted from sea-ear shell using the EDTA decalcification treatment, but was extracted successfully using a TBONE EX KIT. The mitochondrial 16S ribosomal RNA (rRNA) gene region was amplified, and Basic Local Alignment Search Tool (BLAST) analysis was performed after sequencing. Polymerase chain reaction (PCR) products of approximately 600 bp in length were obtained from all samples except donkey glue, one of the two seahorses, and longgu. Drug origins were determined in all samples by sequence analysis based on the BLAST results, and match rates were >97 %. Moreover, 16 samples had a match rate >99 %. Our DNA extraction methods were widely applicable to evaluation of many crude drugs derived from animals, and proved very useful for identifying the origins of such drugs.

Species identification of bivalve molluscs by pyrosequencing

BACKGROUND

The increase in seafood consumption and the presence of different species of bivalves on the global markets has given rise to several commercial frauds based on species substitution. To prevent and detect wilful or unintentional frauds, reliable and rapid techniques are required to identify seafood species in different products. In the present work, a pyrosequencing-based technology has been used for the molecular identification of bivalve species.

RESULTS

Processed and unprocessed samples of 15 species belonging to the bivalve families Pectinidae, Mytilidae, Donacidae, Ostreidae, Pharide and Veneridae were analysed and correctly identified by the developed pyrosequencing-based method according to the homology between query sequences of the 16S ribosomal RNA (16S rRNA) and cytochrome c oxidase I (COI) genes and their correspondent reference libraries. This technique exhibits great potential in automated and high-throughput processing systems, allowing the simultaneous analysis of 96 samples in shorter execution and turnaround times.

CONCLUSIONS

The correct identification of all the species shows how useful this technique may prove to differentiate species from different products, providing an alternative, simple, rapid and economical tool to detect seafood substitution frauds. © 2016 Society of Chemical Industry.

A new approach to the automatic identification of organism evolution using neural networks

Automatic identification of organism evolution still remains a challenging task, which is especially exiting, when the evolution of human is considered. The main aim of this work is to present a new idea to allow organism evolution analysis using neural networks. Here we show that it is possible to identify evolution of any organisms in a fully automatic way using the designed EvolutionXXI program, which contains implemented neural network. The neural network has been taught using cytochrome b sequences of selected organisms. Then, analyses have been carried out for the various exemplary organisms in order to demonstrate capabilities of the EvolutionXXI program. It is shown that the presented idea allows supporting existing hypotheses, concerning evolutionary relationships between selected organisms, among others, Sirenia and elephants, hippopotami and whales, scorpions and spiders, dolphins and whales. Moreover, primate (including human), tree shrew and yeast evolution has been reconstructed.

Defining management units for European captive aardvarks

The Aardvark (Orycteropus afer) is a very unique, but relatively widespread African mammal. Although some morphological variation has been observed between forest and savannah populations and among different African regions, they are all considered as a single species. However, no modern taxonomic revision is available. All captive aardvarks in Europe are believed to stem from wild born animals from Namibia, but recently several new wild-caught aardvarks from Tanzania have been integrated into the captive population. This raises the question, whether these specimens should be interbred with the existing captive population or whether there is a risk of outbreeding depression. We studied the genetic structure of the captive populations by sequencing two mitochondrial genes (cytochrome b and 16S rRNA) to assess the degree of genetic differentiation between the two source regions. Our data suggest that the aardvarks kept in European zoos belong to the same phylogenetic (mitochondrial) lineage as the differentiation in the two studied mitochondrial markers was extremely low. A more comprehensive analysis of a larger sample with well documented origin (covering the complete geographic range) and with more sensitive genetic markers is needed to infer any final conclusions concerning the aardvark's taxonomy and identification of suitable aardvark management units.

Pet fur or fake fur? A forensic approach

BACKGROUND

In forensic science there are many types of crime that involve animals. Therefore, the identification of the species has become an essential investigative tool. The exhibits obtained from such offences are very often a challenge for forensic experts. Indeed, most biological materials are traces, hair or tanned fur. With hair samples, a common forensic approach should proceed from morphological and structural microscopic examination to DNA analysis. However, the microscopy of hair requires a lot of experience and a suitable comparative database to be able to recognize with a high degree of accuracy that a sample comes from a particular species and then to determine whether it is a protected one. DNA analysis offers the best opportunity to answer the question, 'What species is this?' In our work, we analyzed different samples of fur coming from China used to make hats and collars. Initially, the samples were examined under a microscope, then the mitochondrial DNA was tested for species identification. For this purpose, the genetic markers used were the 12S and 16S ribosomal RNA, while the hypervariable segment I of the control region was analyzed afterwards, to determine whether samples belonged to the same individual.

RESULTS

Microscopic examination showed that the fibres were of animal origin, although it was difficult to determine with a high degree of confidence which species they belonged to and if they came from a protected species. Therefore, DNA analysis was essential to try to clarify the species of these fur samples.

CONCLUSIONS

Macroscopic and microscopic analysis confirmed the hypothesis regarding the analyzed hair belonging to real animals, although it failed to prove with any kind of certainty which actual family it came from, therefore, the species remains unknown. Sequence data analysis and comparisons with the samples available in GenBank showed that the hair, in most cases, belonged to the Canidae family, and in one case only to Felidae.

Performance comparison of genetic markers for high-throughput sequencing-based biodiversity assessment in complex communities

Metabarcode surveys of DNA extracted from environmental samples are increasingly popular for biodiversity assessment in natural communities. Such surveys rely heavily on robust genetic markers. Therefore, analysis of PCR efficiency and subsequent biodiversity estimation for different types of genetic markers and their corresponding primers is important. Here, we test the PCR efficiency and biodiversity recovery potential of three commonly used genetic markers - nuclear small subunit ribosomal DNA (18S), mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (mt16S) - using 454 pyrosequencing of a zooplankton community collected from Hamilton Harbour, Ontario. We found that biodiversity detection power and PCR efficiency varied widely among these markers. All tested primers for COI failed to provide high-quality PCR products for pyrosequencing, but newly designed primers for 18S and 16S passed all tests. Furthermore, multiple analyses based on large-scale pyrosequencing (i.e. 1/2 PicoTiter plate for each marker) showed that primers for 18S recover more (38 orders) groups than 16S (10 orders) across all taxa, and four vs. two orders and nine vs. six families for Crustacea. Our results showed that 18S, using newly designed primers, is an efficient and powerful tool for profiling biodiversity in largely unexplored communities, especially when amplification difficulties exist for mitochondrial markers such as COI. Universal primers for higher resolution markers such as COI are still needed to address the possible low resolution of 18S for species-level identification.

Molecular cloning, bioinformatics analysis and expression of insulin-like growth factor 2 from Tianzhu white yak, Bos grunniens

The IGF family is essential for normal embryonic and postnatal development and plays important roles in the immune system, myogenesis, bone metabolism and other physiological functions, which makes the study of its structure and biological characteristics important. Tianzhu white yak (Bos grunniens) domesticated under alpine hypoxia environments, is well adapted to survive and grow against severe hypoxia and cold temperatures for extended periods. In this study, a full coding sequence of the IGF2 gene of Tianzhu white yak was amplified by reverse transcription PCR and rapid-amplification of cDNA ends (RACE) for the first time. The cDNA sequence revealed an open reading frame of 450 nucleotides, encoding a protein with 179 amino acids. Its expression in different tissues was also studied by Real time PCR. Phylogenetic tree analysis indicated that yak IGF2 was similar to Bos taurus, and 3D structure showed high similarity with the human IGF2. The putative full CDS of yak IGF2 was amplified by PCR in five tissues, and cDNA sequence analysis showed high homology to bovine IGF2. Moreover the super secondary structure prediction showed a similar 3D structure with human IGF2. Its conservation in sequence and structure has facilitated research on IGF2 and its physiological function in yak.

Genetic testing in domestic cats

Varieties of genetic tests are currently available for the domestic cat that support veterinary health care, breed management, species identification, and forensic investigations. Approximately thirty-five genes contain over fifty mutations that cause feline health problems or alterations in the cat's appearance. Specific genes, such as sweet and drug receptors, have been knocked-out of Felidae during evolution and can be used along with mtDNA markers for species identification. Both STR and SNP panels differentiate cat race, breed, and individual identity, as well as gender-specific markers to determine sex of an individual. Cat genetic tests are common offerings for commercial laboratories, allowing both the veterinary clinician and the private owner to obtain DNA test results. This article will review the genetic tests for the domestic cat, and their various applications in different fields of science. Highlighted are genetic tests specific to the individual cat, which are a part of the cat's genome.

Species identification of ten common farm animals based on mitochondrial 12S rRNA gene polymorphisms

Bio-techniques such as genetic manipulation, marker-assisted selection, and identity test have largely facilitated the modern animal production practices. In the present study, we established a reliable and cost-effective molecular method of species identification for common farm animals. We first (re-)analyzed 179 mitochondrial 12S rRNA gene sequences of ten farm animal species to determine the intra-species and species-specific variations. The PCR-RFLP method was subsequently designed to identify these species by using endonucleases BshNI, ScaI, AluI, and BfaI. The poultry and livestock species were first discriminated by one double-digestion of both BshNI and ScaI, which generated different fragment patterns (325 bp and 115 bp for poultry vs. 364 bp and 76 bp for livestock). The ten species could be further discerned according to species-specific restriction pattern by subjecting to digestion of AluI and BfaI, respectively. Our approach would be more reliable by taking the intra-species variations into consideration and could be applied to species identity test, commercial fraud, and wildlife crime.

Inferring the phylogeny of bovidae using mitochondrial DNA sequences: resolving power of individual genes relative to complete genomes

Molecular techniques that assess biodiversity through the analysis of a small segment of mitochondrial genome have been getting wide attention for inferring the mammalian diversity. Due to their highly conserved nature, specific mitochondrial genes offer a promising tool for phylogenetic analysis. However, there is no established criteria for selecting the typical mitochondrial DNA (mtDNA) segments to achieve a greater resolving power. We therefore chose the family Bovidae as a model and compared the tree-topologies resulting from the commonly used and phylogenetically-informative genes including 16S rRNA, 12S rRNA, COI, Cyt b and D-loop with respect to complete mitochondrial genome. The tree topologies from the whole mitochondrial genome of 12 species were not identical albeit similar with those resulting from the five individual genes mentioned above. High bootstrap values were observed for mtDNA compared with that of any single gene. The average pair-wise sequence divergence using different genetic modes was found to be: D-loop (0.229) > Cyt b (0.159) > COI or complete mtDNA (0.143) > 12S rRNA (0.094) > 16S rRNA (0.091). The tree resulting from complete mtDNA clearly separated the 12 taxa of Bovidae into 3 major clusters, one cluster each for subfamily Cervinae and Bovinae and the third cluster comprised the distinctive clades of Caprinae and Antilopinae. However, jumping clades of Antilopinae were observed while using the individual genes. This study showed that Bison bison and Bos Taurus have very close phylogenetic relationship compared to Bubalus bubalis (Bovinae), irrespective of the method used. Our findings suggest that complete mtDNA genome provides most reliable understanding of complex phylogenetic relationships while the reliability of individual gene trees should be verified with high bootstrap support.

Evaluation of the 16S and 12S rRNA genes as universal markers for the identification of commercial fish species in South Africa

The development of DNA-based methods for the identification of fish species is important for fisheries research and control, as well as for the detection of unintentional or fraudulent species substitutions in the marketplace. The aim of this study was to generate a comprehensive reference database of DNA sequences from the mitochondrial 16S and 12S ribosomal RNA (rRNA) genes for 53 commercial fish species in South Africa and to evaluate the applicability of these genetic markers for the identification of fish at the species level. The DNA extracted from all target species was readily amplified using universal primers targeting both rRNA gene regions. Sequences from the 16S and 12S rRNA genes were submitted to GenBank for the first time for 34% and 53% of the fish species, respectively. Cumulative analysis of the 16S rRNA gene sequences revealed mean conspecific, congeneric and confamilial Kimura two parameter (K2P) distances of 0.03%, 0.70% and 5.10% and the corresponding values at the 12S level were 0.03%, 1.00% and 5.57%. K2P neighbour-joining trees based on both sequence datasets generally clustered species in accordance with their taxonomic classifications. The nucleotide variation in both the 16S and 12S sequences was suitable for identifying the large majority of the examined fish specimens to at least the level of genus, but was found to be less useful for the explicit differentiation of certain congeneric fish species. It is recommended that one or more faster-evolving DNA regions be analysed to confirm the identities of closely-related fish species in South Africa.

Genetic differentiation between fake abalone and genuine Haliotis species using the forensically informative nucleotide sequencing (FINS) method

Abalones ( Haliotis species) are a popular delicacy and commonly preserved in dried form either whole or in slices or small pieces for consumption in Asian countries. Driven by the huge profit from trading abalones, dishonest traders may substitute other molluscan species for processed abalone, of which the morphological characteristics are frequently lost in the processed form. For protection of consumer rights and law enforcement against fraud, there is a need for an effective methodology to differentiate between fake and genuine abalone. This paper describes a method (validated according to the international forensic guidelines provided by SWGDAM) for the identification of fake abalone species using forensically informative nucleotide sequence (FINS) analysis. A study of the local market revealed that many claimed "abalone slice" samples on sale are not genuine. The fake abalone samples were found to be either volutids of the genus Cymbium (93%) or the muricid Concholepas concholepas (7%). This is the first report of Cymbium species being used for the preparation and sale as "abalone" in dried sliced form in Hong Kong.

An overview to the investigative approach to species testing in wildlife forensic science

The extent of wildlife crime is unknown but it is on the increase and has observable effects with the dramatic decline in many species of flora and fauna. The growing awareness of this area of criminal activity is reflected in the increase in research papers on animal DNA testing, either for the identification of species or for the genetic linkage of a sample to a particular organism. This review focuses on the use of species testing in wildlife crime investigations. Species identification relies primarily on genetic loci within the mitochondrial genome; focusing on the cytochrome b and cytochrome oxidase 1 genes. The use of cytochrome b gained early prominence in species identification through its use in taxonomic and phylogenetic studies, while the gene sequence for cytochrome oxidase was adopted by the Barcode for Life research group. This review compares how these two loci are used in species identification with respect to wildlife crime investigations. As more forensic science laboratories undertake work in the wildlife area, it is important that the quality of work is of the highest standard and that the conclusions reached are based on scientific principles. A key issue in reporting on the identification of a particular species is a knowledge of both the intraspecies variation and the possible overlap of sequence variation from one species to that of a closely related species. Recent data showing this degree of genetic separation in mammalian species will allow greater confidence when preparing a report on an alleged event where the identification of the species is of prime importance. The aim of this review is to illustrate aspects of species testing in wildlife forensic science and to explain how a knowledge of genetic variation at the genus and species level can aid in the reporting of results.

Reconstructing mammalian phylogenies: a detailed comparison of the cytochrome B and cytochrome oxidase subunit I mitochondrial genes

The phylogeny and taxonomy of mammalian species were originally based upon shared or derived morphological characteristics. However, genetic analyses have more recently played an increasingly important role in confirming existing or establishing often radically different mammalian groupings and phylogenies. The two most commonly used genetic loci in species identification are the cytochrome oxidase I gene (COI) and the cytochrome b gene (cyt b). For the first time this study provides a detailed comparison of the effectiveness of these two loci in reconstructing the phylogeny of mammals at different levels of the taxonomic hierarchy in order to provide a basis for standardizing methodologies in the future. Interspecific and intraspecific variation is assessed and for the first time, to our knowledge, statistical confidence is applied to sequence comparisons. Comparison of the DNA sequences of 217 mammalian species reveals that cyt b more accurately reconstructs their phylogeny and known relationships between species based on other molecular and morphological analyses at Super Order, Order, Family and generic levels. Cyt b correctly assigned 95.85% of mammal species to Super Order, 94.31% to Order and 98.16% to Family compared to 78.34%, 93.36% and 96.93% respectively for COI. Cyt b also gives better resolution when separating species based on sequence data. Using a Kimura 2-parameter p-distance (x100) threshold of 1.5-2.5, cyt b gives a better resolution for separating species with a lower false positive rate and higher positive predictive value than those of COI.