Nucleotide Base Composition Research Articles

Next-generation sequencing yields complete mitochondrial genome assembly of peaceful betta fish, Betta imbellis (Teleostei: Osphronemidae)

The complete mitochondrial genome (mitogenome) of the peaceful betta (Betta imbellis) was obtained using next-generation sequencing. The sample of B. imbellis was collected from its native habitat in Southern Thailand. The mitogenome sequence was 16,897 bp in length, containing 37 genes with identical order to most teleost mitogenomes. Overall nucleotide base composition of the complete mitogenome was determined as AT bias. Phylogenetic analysis of B. imbellis showed a closer relationship with bubble-nesting fighting fish. This annotated mitogenome reference can be utilized as a bioresource for phylogenetic studies to support betta conservation programs.

Identification and Characterization of Staphylococcus aureus 16S rRNA gene isolated from different Food Specimens from South Indian Region

Staphylococcus aureus (S. aureus) associated food-borne diseases have global impact on human health. Genome wide analyses have shown that S. aureus contains specific endotoxin expressing gene and produce toxic proteins which is responsible for food contamination. Appropriate detection of pathogens is one of the major tool to avoid infection rate and reduce the health and socio-economic burden to human being. In addition, inappropriate handing the specimens, misdiagnosis and limited standard medical support could directly influence the infection rate.
 The objective of this study was to identify S. aureus from different food specimens from Hyderabad, India. A total of 70 random bacterial nutrient agar medium pure plates were made based on different morphological appearance of bacterial colonies. Preliminary identification of S. aureus based on standardized morphological method showed specific golden yellow colonies. Biochemical assay also verified bacterial specimens. Furthermore, molecular characterization was performed on the basis of polymerase chain reaction (PCR) and sequencing of 16S rRNA gene of S. aureus. Newly sequenced 16S rRNA gene sequences showed 100% homology to S. aureus, analyzed using NCBI-BLAST tool.
 The phylogenetic analysis and nucleotide base composition studies performed using 39 sequences of 16S rRNA gene from different isolates of Staphylococcus, including Staphylococcus aureus. For the purpose, 16S rRNA gene sequences were retrieved from the NCBI in FASTA format. The phylogenetic analysis was performed using Maximum Likelihood method and revealed the relationships and percent similarity of Staphylococcus aureus 16S rRNA gene. 
 Keywords: Food-borne diseases; 16S rRNA gene; Maximum Likelihood; Phylogenetic analysis; Staphylococcus aureus.

DNA barcoding and phylogenetics of freshwater fish fauna of Ranganadi River, Arunachal Pradesh.

Arunachal Pradesh, the largest state of North-East India covers almost 60.93% of the Eastern Himalayan hotspot. Fish diversity and species identification is utmost important for fisheries management. But, in some cases morphological characteristics based identification is difficult for a non-specialist to perform. In view of the above, the present study emphasized on the assessment of DNA barcoding, phylogenetics and genetic diversity of fish species in the Ranganadi River, Arunachal Pradesh, India. India. Arunachal Pradesh, the largest state of North-East India covers almost 60.93% of the Eastern Himalayan hotspot. Altogether 114 specimens, representing 22 species, belonging to 3 orders and 5 families were successfully barcoded and found to be 98-100% identical from both GenBank and BOLD databases. Out of these 22 fish species, it was found that one species assessed was Endangered, three species as Near Threatened and one species as Vulnerable. A Neighbour Joining (NJ) tree was constructed using Rstudio for the purpose of a phylogenetic analysis of the identified species. The barcoding gap analysis using K2P, P-distance and Jukes-Cantor was done to detect the presence of cryptic species and barcoding success. The nucleotide base composition and genetic distance analysis were also performed, using MEGA 6.0. DNA Sequence Polymorphism v6.12.03 analysis revealed the nucleotide diversity (p) and haplotype diversity (Hd). The Hd for the whole dataset was found to be 0.975, which showed high genetic diversity in the Ranganadi River. Both morphological key identifying characters and molecular data corroborated the phylogenetic analysis. This COI barcode library, generated in the present study, not only helped in species identification and molecular study, but also in cryptic species identification.

Characterization of the complete mitochondrial genome of Euspira gilva with phylogenetic analysis

Here, we determined the complete mitogenome sequence of Euspira gilva (Littorinimorpha: Naticidae). The complete mitochondrial genome is circular and 16,119 bp in length, containing 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. All PCGs and rRNA genes are encoded on the heavy strand while tRNA genes are distributed in both the strands. The overall nucleotides base composition of the heavy strand is A (31.80%), G (14.72%), C (13.72%), and T (39.76%), with an A + T bias (71.56%). All of the PCGs had ATG as their start codon. The common termination codon is TAA, except for nd4l terminated with TAG. The 22 tRNA genes could be folded into a typical clover-leaf secondary structure. As seen from the phylogenetic tree, E. gilva has a more close relationship with Neverita didyma and Glossaulax reiniana.

The complete mitochondrial genome of a Green macroalgae species: Ulva meridionalis (Ulvales: Ulvaceae)

Ulva meridionalis, a green macroalgae, is one of the causal species for green tides in Japan and spread into the coast of China. During this research, we sequenced the complete mitochondrial genome of U. meridionalis. The mitogenome is 62,887 bp in length, including 28 encoding genes and 29 tRNA genes. Compared with the Ulva species from mitogenome, the gene order and organization of this mitogenome are similar to most of other determined Ulva mitogenomes, with the nucleotide base composition of A 33.6%, T 32.2%, C 16.2%, and G 18.0%. Phylogenetic analysis shows U. meridionalis is closely related to Ulva flexuosa.

The complete mitochondrial genome of the hybrid offspring Epinephelus fuscoguttatus ♀ × Epinephelus tukula ♂

The hybrid offspring Epinephelus fuscoguttatus ♀ × E. tukula ♂ showed heterosis in terms of growth and disease resistance. The mitochondrial genome is 16,629 bp in length and consists of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a control region. The difference of total length is mainly caused by the difference of length in non-coding region. The nucleotide base composition is A = 29.15%, G = 15.62%, T = 26.91%, C = 28.32%, A + T = 56.06%, and C + G = 43.94%. The phylogenetic analysis using neighbour-joining (NJ) method showed that the hybrid offspring has a closer relationship to E. fuscoguttatus × E. lanceolatus.

Complete mitochondrial genome of the East Asian fish-eating bat: Myotis ricketti (Chiroptera, Vespertilionidae)

I report the complete mitochondrial genome (mitogenome) of the East Asian fish-eating bat (Myotis ricketti or M. pilosus), also known as the Rickett’s big footed bat. The total length of the circular M. ricketti mitogenome is 17,098 base pairs, containing 13 protein-coding genes (PCGs), two ribosomal RNAs, 22 transfer RNAs, and a non-coding control region (D-loop region). The gene order and organisation of this mitogenome are similar to most of other determined vertebrate mitogenomes, with the nucleotide base composition of A 34.22%, T 30.32%, C 22.80%, and G 12.66%. Besides, the mitogenomic D-loop region contains 29 copies of a tandem repeat sequence of six nucleotides (CATACG). The phylogenetic analysis indicates that M. ricketti is closely related to M. macrodactylus and M. petax. This study will contribute to the investigations of phylogeny and evolution for Myotis and its relevant taxa.

The complete mitochondrial genome of Paracheirodon axelrodi (Characiformes: Characidae) and phylogenetic studies of Characiformes

The Paracheirodon axelrodi is an important freshwater fish in the Amazon basin of South America, more expensive than Paracheirodon innesi. Here, we describe the complete 17,100 base pair (bp) mitochondrial genome of Paracheirodon axelrodi mohavensis. The mitogenome has a nucleotide base composition of A (29.62%), T (29.41%), G (15.39%), and C (25.62%), and encodes 13 protein subunits, 22 tRNAs, a 12S rRNA of 952 bp and 16S rRNA of 1665 bp, and a 1433 bp D-loop control region, each located in the conserved mtDNA structure typical for Characidae fishes. All protein-coding genes have initiation codons of ATG, ND1, ND2, CO2, ND3, ND4L, ND5, ND6 and Cytb ended by TAA as a stop codon, ND4 ended by AGA as a stop codon, CO1 ended by AGG as a stop codon, ATP8 and CO3 ended by TAG as a stop codon, ATP6 ended by ATT as a stop codon. This characterised mitogenome may help inform management practices for Paracheirodon axelrodi mohavensis by facilitating future studies on how allopatric populations of this imperilled species are evolving across refuge habitats.

First report of the complete mitochondrial genome and phylogenetic analysis of Aphrodita australis (Aphroditidae, Annelida)

In this study, the complete mitochondrial genome of the Aphrodita australis was sequenced. The complete mitochondrial genome was circular and 15,288 bp in length, consisted of a typical set of 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and 1 non-coding control region. All these genes are in the heavy strand. The non-coding control region is 672 bp in length, and located between tRNA-Ser and tRNA-Leu. The overall nucleotides base composition of the heavy strand is 31.02% for A, 22.76% for C, 12.49% for G, and 33.73% for T, with a slight A + T-rich feature (64.75%). All of the PCGs begin with ATG as their start codon and the cox 3, cytb and nad 3 are terminated with TAA, atp8, nad4, nad 4l, and nad 6 are terminated with TAG, while others are terminated by incomplete codon T. Seen from the phylogenetic tree, A. australis has a more close relationship with Goniada japonica than other species.

The mitochondrial genome of the marine gastropod Neverita didyma (Roding, 1798) (Mollusca: Gastropoda)

In this study, the complete mitochondrial genome of the Neverita didyma (Mollusca: Gastropoda) was sequenced. The mitochondrial genome is 15,252 bp in length, containing 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes. The overall nucleotides base composition of the heavy strand is 30.47% for A, 14.09%% for C, 15.89%for G, and 39.56% for T with an AT-rich feature (70.03%). All the protein-coding genes begin with an ATG codon, the common termination codon is TAA, except for nd2 and nd4l terminated with TAG and nd5 terminated by incomplete codon TA. Seen from the phylogenetic tree, Naticarius hebraeus, and N. didyma from the same Superfamily (Naticoidea) clustered into one branch. The data would provide useful data for further studies on population genetics and molecular systematics.

The complete mitochondrial genome of an eelpout Lycodes ygreknotatus (Teleostei: Zoarcidae)

Here, we report the complete mitochondrial genome of the eelpout Lycodes ygreknotatus. The mitogenome is 16,486 bp in length and has the typical vertebrate mitochondrial gene arrangement, which contains 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and one D-loop region. The overall nucleotide base composition of L. ygreknotatus is 26.29%, 25.32%, 30.43%, and 17.96% for A, T, C, and G, respectively. Phylogenetic analysis of 14 fish species showed that L. ygreknotatus and Lycodes toyamensis were clustered into one branch.

The phylogenomic position of the Critically Endangered Largetooth Sawfish Pristis pristis (Rhinopristiformes, Pristidae), inferred from the complete mitochondrial genome

The complete mitogenome of the Critically Endangered Largetooth Sawfish Pristis pristis (Rhinopristiformes, Pristidae) is presented in this study. The genome is 16,912 bp in length with a nucleotide base composition of 32.0% A, 26.5% C, 13.2% G, and 28.3% T, containing 37 genes typical of vertebrates. Two start (GTG and ATG) and two stop (TAG and TAA/T) codons are found in the protein-coding genes. The 22 tRNA genes range from 66 bp (tRNA-Ser2) to 75 bp (tRNA-Leu1). The tRNA-Pro gene is duplicated with an unknown sequence between the two copies. Bayesian phylogenetic reconstruction showed that P. pristis clusters with the Pristis clade with strong posterior probability (100%).

The polyphyly of Plasmodium: comprehensive phylogenetic analyses of the malaria parasites (order Haemosporida) reveal widespread taxonomic conflict.

The evolutionary relationships among the apicomplexan blood pathogens known as the malaria parasites (order Haemosporida), some of which infect nearly 200 million humans each year, has remained a vexing phylogenetic problem due to limitations in taxon sampling, character sampling and the extreme nucleotide base composition biases that are characteristic of this clade. Previous phylogenetic work on the malaria parasites has often lacked sufficient representation of the broad taxonomic diversity within the Haemosporida or the multi-locus sequence data needed to resolve deep evolutionary relationships, rendering our understanding of haemosporidian life-history evolution and the origin of the human malaria parasites incomplete. Here we present the most comprehensive phylogenetic analysis of the malaria parasites conducted to date, using samples from a broad diversity of vertebrate hosts that includes numerous enigmatic and poorly known haemosporidian lineages in addition to genome-wide multi-locus sequence data. We find that if base composition differences were corrected for during phylogenetic analysis, we recovered a well-supported topology indicating that the evolutionary history of the malaria parasites was characterized by a complex series of transitions in life-history strategies and host usage. Notably we find that Plasmodium, the malaria parasite genus that includes the species of human medical concern, is polyphyletic with the life-history traits characteristic of this genus having evolved in a dynamic manner across the phylogeny. We find support for multiple instances of gain and loss of asexual proliferation in host blood cells and production of haemozoin pigment, two traits that have been used for taxonomic classification as well as considered to be important factors for parasite virulence and used as drug targets. Lastly, our analysis illustrates the need for a widespread reassessment of malaria parasite taxonomy.

Complete mitochondrion genome of the endangered Mohave tui chub Siphateles bicolor mohavensis (Cypriniformes: Cyprinidae)

The Mohave tui chub (Siphateles bicolor mohavensis) is an endangered cyprinid fish endemic to the Mojave Desert region of southeastern California, USA. Here, we describe the complete 16,607 base pair (bp) mitochondrial genome of S. b. mohavensis. The mitogenome has a nucleotide base composition of A (29.08%), T (26.91%), G (17.58%), and C (26.43%), and encodes 13 protein subunits, 22 tRNAs, a 12S rRNA of 956 bp and 16S rRNA of 1691 bp, and a 929 bp D-loop control region, each located in the conserved mtDNA structure typical for cyprinid fishes. All protein-coding genes have initiation codons of ATG or GTG, and only the ND1, CO1, ATPase8, NDL4, ND4, ND5, and ND6 genes have complete stop codons. Phylogenetic analyses confirmed the relationship of S. b. mohavensis to several genera of cyprinids (e.g. Gila, Acrocheilus) also endemic to western North America. This characterized mitogenome may help inform management practices for S. b. mohavensis by facilitating future studies on how allopatric populations of this imperiled species are evolving across refuge habitats.

Phylogenomic re-assessment of the thermophilic genus Geobacillus

Geobacillus is a genus of Gram-positive, aerobic, spore-forming obligate thermophiles. The descriptions and subsequent affiliations of the species in the genus have mostly been based on polyphasic taxonomy rules that include traditional sequence-based methods such as DNA–DNA hybridization and comparison of 16S rRNA gene sequences. Currently, there are fifteen validly described species within the genus. The availability of whole genome sequences has provided an opportunity to validate and/or re-assess these conventional estimates of genome relatedness. We have applied whole genome approaches to estimate the phylogenetic relatedness among the sixty-three Geobacillus strains for which genome sequences are currently publicly available, including the type strains of eleven validly described species. The phylogenomic metrics AAI (Average Amino acid Identity), ANI (Average Nucleotide Identity) and dDDH (digital DNA–DNA hybridization) indicated that the current genus Geobacillus is comprised of sixteen distinct genomospecies, including several potentially novel species. Furthermore, a phylogeny constructed on the basis of the core genes identified from the whole genome analyses indicated that the genus clusters into two monophyletic clades that clearly differ in terms of nucleotide base composition. The G+C content ranges for clade I and II were 48.8–53.1% and 42.1–44.4%, respectively. We therefore suggest that the Geobacillus species currently residing within clade II be considered as a new genus.

The phylogenomic position of the Winghead Shark Eusphyra blochii (Carcharhiniformes, Sphyrnidae) inferred from the mitochondrial genome

The complete mitogenome of the Winghead Shark Eusphyra blochii (Carcharhiniformes: Sphyrnidae) is determined in this study, which is 16,727 bp with a nucleotide base composition: 31.6% A, 25.7% C, 13.0% G and 29.7% T, containing 37 genes with the typical gene arrangement pattern and translate orientation in vertebrates. Two start codons (ATG and GTG) and two stop codons (TAG and TAA/T) are found in the protein-coding genes. The 22 tRNA genes range from 67 bp (tRNA-Cys and tRNA-Ser2) to 75 bp (tRNA-Leu1). The phylogenetic position showed that E. blochii clustered with the Sphyrna clade with strong posterior probability (100%).

The phylogenomic position of the smooth lanternshark Etmopterus pusillus (Squaliformes: Etmopteridae) inferred from the mitochondrial genome

In this study, the complete mitogenome of the Smooth lanternshark Etmopterus pusillus (Squaliformes: Etmopteridae) was firstly determined. It was 16,729 bp, consisting of 13 protein-coding genes (PCGs), 22 tRNA genes, 2 rRNA genes and 1 putative control region with typical order to that of most other vertebrates. Its nucleotide base composition is 31.3% A, 23.0% C, 14.3% G and 31.5% T. Two start codons (GTG and ATG) and two stop codons (TAG and TAA/T) were used in the protein-coding genes. The phylogenetic results showed that E. pusillus was clustered to Squaliolus aliae (Dalatiidae) and suggested that Dalatiidae was polyphyletic.

Complete mitochondrial genome and the phylogenetic position of the smalleye pygmy shark Squaliolus aliae (Squaliformes: Dalatiidae)

The complete mitogenome of the smalleye pygmy shark Squaliolus aliae (Squaliformes: Dalatiidae) is presented in this study firstly. It is 16,717 bp with a nucleotide base composition of 30.7% A, 26.2% C, 14.7% G and 28.5% T, containing 37 genes and a control region with typical order as vertebrate. There are 23bp short intergenic spaces and 28bp overlaps locating in gene junctions. 2 rRNA genes are located in heavy strand. Twenty-two tRNA genes range from 67bp (tRNA-Cys) to 75 bp (tRNA-Leu1). Two initial codons (ATG and GTG) and two terminal codons (TAA and T) are found in protein-coding genes. The phylogenetic result shows that S. aliae in this study is clustered to the (Somniosus pacificus + Squalidae).

The complete mitogenome of Schizopygopsis stoliczkai (Cypriniformes: Cyprinidae) from Western China

In this study, we firstly sequenced the complete mitochondrial genome of Schizopygopsis stoliczkai (Cypriniformes: Cyprinidae) from the Yarkand River, Xinjiang, China. The mitogenome is 16,833 bp in length, composed of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 2 non-coding regions (origin of light-strand replication and control region). The gene content and order is in accord with the common vertebrate form. The nucleotide base composition of H-strand is 28.4% A, 27.0% T, 26.1% C, and 18.5% G. The phylogenetic analysis based on the complete mitochondrial sequences showed that S. stoliczkai was clustered into Schizopygopsis clade.

The complete mitochondrial genome of the Azuma emmnion

The complete mitochondrial genome of the Azuma emmnion has been determined. The total length of a complete nucleotide sequence of the mitochondria is 16 522 bp, which contained 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and one D-loop region. Its nucleotide sequence and composition of A. emmnion mitochondrion was similar to most other vertebrates. Nucleotide base composition of mitochondrial genome was the following: 25.58% for A, 18.22% for G, 27.67% for C, 28.53% for T. The phylogenetic analysis result, which based on the complete mitogenomes of of A. emmnion and other 11 fish species, indicated that A. emmnion and Pholis crassispina clustered into one branch.