Biology subjects

Gan, H. M.

Publications and source records attributed to Gan, H. M..

14 recordsLinked to original sources

bioRxiv2025

Crowning the King of Fruits: Genomic Evidence of Population Structure and Relatedness in Malaysian Durians

Durian (Durio zibethinus), often dubbed the King of Fruits, is a high-value tropical crop native to Southeast Asia and widely cultivated in Malaysia. Revered for its unique flavor yet polarizing for its pungent aroma, durian holds significant cultural and economic importance across the region. Despite this, genomic research on Malaysian durian cultivars remains limited. We performed whole-genome sequencing of several renowned and local durian cultivars, including Musang King (D197), Sultan (D24), Black Thorn (D200), Muar Gold (D101), and Red Prawn (D13) collected from distinct geographic regions across Malaysia. Illumina sequencing yielded approximately 20 to 30x coverage per sample, sufficient for single-nucleotide polymorphism (SNP) detection and population genomic analyses. Principal component analysis (PCA) based on genome-wide SNPs revealed visible population stratification and varying degrees of genetic relatedness among Malaysian durians. Subsequent KING kinship analysis indicated that most cultivars are relatively clonal, with the notable exception of the reference Musang King genome, which appeared genetically heterogeneous compared to other Musang King samples, a finding further supported by population structure inference from admixture analysis and ITS1-5.8S-ITS2 haplotyping. Notably, the Black Thorn cultivar showed no relatedness to Malaysian varieties but exhibited distant genetic similarity to the northern Thai Kan Yao variety. These results provide new genomic insights into the population structure, cultivar differentiation, and potential hybridization among Malaysian durians, forming a valuable foundation for future molecular marker development and breeding programs aimed at different variety authentication and genetic improvement.

genomics↗

bioRxiv2024

Microbiome Dynamics in Tank- and Pond-Reared GIFT Tilapia

Tilapia (Oreochromis spp.) are among the most widely cultivated freshwater finfish species worldwide. The industry increasingly relies on tilapia strains selected for improved growth and other traits, particularly the Genetically Improved Farmed Tilapia (GIFT) strain. Despite the industrys reliance on tilapia, knowledge of microbiome dynamics in reared tilapia remains limited. Understanding normal successional patterns in the microbiome of farmed tilapia is essential to identify characteristics of what constitutes a healthy microbial community. In this study, we assessed the microbiomes of tank and pond-reared GIFT tilapia by analyzing 568 samples, including water, gut, skin, and gill microbiomes of tilapia, from tank systems housing the source GIFT populations in Malaysia, and compared them to those reared in earthen ponds on another farm in Malaysia. A total of 2,307 amplicon sequence variants (ASVs) were identified, encompassing a broad taxonomic diversity of 39 phyla, 86 classes, 180 orders, 299 families, 501 genera, and 399 species. Our findings elucidated distinct microbial community structures between rearing environments and across fish tissues, shedding light on intricate host-microbe interactions shaped by environmental conditions and management practices. The gut microbiome of tank-reared tilapia was dominated by Fusobacteriota (71.14%), in contrast to pond-reared fish (22%), while other taxa, such as Bacteroidota, Firmicutes_A, and Cyanobacteria, also varied markedly between environments and sampling periods. Skin and gill samples showed notable variability in the relative abundances of Fusobacteriota and Deinococcota between the two rearing sites. Principal Coordinates Analysis (PCoA) highlighted the distinct clustering of samples by rearing environment, particularly within gut microbiomes. Biomarkers such as Cyanobiaceae (pond water) and Sphingomonadaceae (tank water) underscored the impact of rearing conditions on microbial composition. These results establish valuable baseline information on the types of bacteria associated with healthy, genetically defined (GIFT) tilapia strains. This foundational information will help identify specific microbial taxa associated with beneficial or detrimental effects on tilapia health and productivity across varying rearing conditions. Such insights can guide the development of targeted microbiome management strategies to enhance tilapia health and optimize performance.

microbiology↗

bioRxiv2023

Complete genome sequence of thermophilic cellulolytic actinobacterium Thermobifida fusca strain UPMC 901 producing thermostable cellulases.

Thermophilic cellulolytic bacteria producing thermostable cellulase have multiple potential industrial and biotechnological applications. In this study, we reported the complete genome sequence of the species Thermobifida fusca UPMC 901 by using nano-pore sequencing technology. The represented genome is 3.76 Mb with a G + C content of 67.4%. The genome is composed of 1 scaffold with 3,193 protein-coding genes. The results indicated that the genome of the Thermobifida fusca gene encodes at least 109 genes for carbohydrate-active enzymes. Of these genes, 38 glycoside hydrolases (GHs), 36 glycosylTransferases (GTs), 21 carbohydrate-binding modules (CBMs), 9 carbohydrate esterases (CEs), and 3 polysaccharide lyases (PL) were identified. In addition, two genes encoding for lytic polysaccharide monooxygenase (LPMO), the copper-dependent enzymes that catalyse oxidative cleavage of recalcitrant crystalline cellulose, that is auxiliary activity (AAs) were also detected in the T. fusca genome. This study represented the ninth genome of the species T. fusca, and the cellulase genes identified will facilitate the exploration of potential sources from T. fusca for industrial and agricultural applications.

microbiology↗

bioRxiv2023

Multiplex PCR detection and Nanopore-based rapid genotyping of tilapia (Oreochromis spp.) pathogens.

BackgroundTilapia aquaculture faces significant threats posed by four prominent pathogens: tilapia lake virus (TiLV), infectious spleen and kidney necrosis virus (ISKNV), Francisella orientalis, and Streptococcus agalactiae. Currently, employed molecular diagnostic methods for these pathogens rely on multiple singleplex PCR reactions, which are time-consuming and expensive. MethodsIn this study, we present an approach utilizing a multiplex PCR (mPCR) assay, coupled with rapid Nanopore sequencing, enabling the one-tube simultaneous detection and one-reaction Nanopore sequencing-based validation of four pathogens. ResultsOur one-tube multiplex assay exhibits a detection limit of 1,000 copies per reaction for TiLV, ISKNV, and S. agalactiae, while for F. orientalis, the detection limit is 10,000 copies per reaction. This sensitivity is sufficient for diagnosing infections and co-infections in clinical samples from sick fish, enabling rapid confirmation of the presence of pathogens. Integrating multiplex PCR and Nanopore sequencing provides an alternative approach platform for fast and precise diagnostics of major tilapia pathogens in clinically sick animals, adding to the available toolbox for disease diagnostics.

genomics↗

bioRxiv2023

A multiplexed RT-PCR Assay for Nanopore Whole Genome Sequencing of Tilapia lake virus (TiLV)

Tilapia lake virus (TiLV) is a highly contagious viral pathogen that affects tilapia, a globally significant and affordable source of fish protein. To prevent the introduction and spread of TiLV and its impact, there is an urgent need for increased surveillance, improved biosecurity measures, and continuous development of effective diagnostic and rapid sequencing methods. In this study, we have developed a multiplexed RT-PCR assay that can amplify all ten complete genomic segments of TiLV from various sources of isolation. The amplicons generated using this approach were immediately subjected to real-time sequencing on the Nanopore system. By using this approach, we have recovered and assembled 10 TiLV genomes from total RNA extracted from naturally TiLV-infected tilapia fish, concentrated tilapia rearing water, and cell culture. Our phylogenetic analysis, consisting of more than 36 TiLV genomes from both newly sequenced and publicly available TiLV genomes, provides new insights into the high genetic diversity of TiLV. This work is an essential steppingstone towards integrating rapid and real-time Nanopore-based amplicon sequencing into routine genomic surveillance of TiLV, as well as future vaccine development.

genomics↗

bioRxiv2022

Genome assembly and analysis of the flavonoid and phenylpropanoid biosynthetic pathways in Fingerroot ginger (Boesenbergia rotunda)

Boesenbergia rotunda (Zingiberaceae), is a high-value culinary and ethno-medicinal plant of Southeast Asia. The rhizomes of this herb have high flavanone and chalcone content. Here we report genome analysis of B. rotunda together with a complete genome sequence as a hybrid assembly. B. rotunda has an estimated genome size of 2.4 Gb which was assembled as 27,491 contigs with N50 size of 12.386 Mb. The highly heterozygous genome encodes 71,072 protein-coding genes and has 72% repeat content, with class I TEs occupying [~]67% of the assembled genome. Fluorescence In Situ Hybridization of the 18 chromosome pairs at metaphase showed six sites of 45S rDNA and two sites of 5S rDNA. SSR analysis identified 238,441 gSSRs and 4,604 EST-SSRs with 49 SSR markers common among related species. Genome-wide methylation percentages ranged from 73% CpG, 36% CHG and 34% CHH in leaf to 53% CpG, 18% CHG and 25% CHH in embryogenic callus. Panduratin A biosynthetic unigenes were most highly expressed in watery callus. B rotunda has a relatively large genome with high heterozygosity and TE content. This assembly and data (PRJNA71294) comprise a source for further research on the functional genomics of B. rotunda, the evolution of the ginger plant family and the potential genetic selection or improvement of gingers.

genomics↗

bioRxiv2022

The First High-Quality Genome Assembly and Data Analysis of the Malaysian mahseer (Tor tambroides)

The Malaysian mahseer (Tor tambroides), one of the most valuable freshwater fish in the world, is mainly targeted for human consumption. The mitogenomic data of this species is available to date, but the genomic information is still lacking. For the first time, we sequenced the whole genome of an adult fish on both Illumina and Nanopore platforms. The hybrid genome assembly had resulted in a sum of 1.5 Gb genomic sequence from the 44,726 contigs found with 44 kb N50 length and BUSCO genome completeness of 84.3%. Four types of SSRs had been detected and identified within the genome with a greater AT abundance than that of GC. Predicted protein sequences had been functionally annotated to public databases, namely GO, KEGG and COG. A maximum likelihood phylogenomic tree containing 53 Actinopterygii species and two outgroups was constructed, providing first insights into the genome-based evolutionary relationship of T. tambroides with other ray-finned fish. These data are crucial in facilitating the study of population genomics, species identification, morphological variations, and evolutionary biology, which are helpful in the conservation of this species.

genomics↗

bioRxiv2020

More from less: Genome skimming for nuclear markers for animal phylogenomics, a case study using decapod crustaceans

Low coverage genome sequencing is rapid and cost-effective for recovering complete mitochondrial genomes for animal phylogenomics. The recovery of high copy number nuclear genes, including histone H3, 18S and 28S ribosomal RNAs, is also possible using this approach. In this study, we explore the potential of the genome skimming (GS) to recover additional nuclear genes from shallow sequencing projects. Using an in silico baited approach, we recover three additional core histone genes (H2A, H2B and H4) from our existing collection of low coverage decapod crustacean dataset (99 species, 69 genera, 38 families, 10 infraorders). Phylogenetic analyses based on various combinations of mitochondrial and nuclear genes for the entire decapod dataset and 40 species of crayfish (Infraorder Astacidea) found that the evolutionary rates for different classes of genes varied widely. The highlight being a very high level of congruence found between trees from the six nuclear genes and those derived from the mitogenome sequences for freshwater crayfish. These findings indicate that nuclear genes recovered from the same genome skimming datasets designed to obtain mitogenomes can be used to support more robust and comprehensive phylogenetic analyses. Further, a search for additional intron-less nuclear genes identified several high copy number genes across the decapod dataset and recovery of NaK, PEPCK and GAPDH gene fragments is possible at slightly elevated coverage, suggesting the potential and utility of GS in recovering even more nuclear genetic information for phylogenetic studies from these inexpensive and increasingly abundant datasets.

evolutionary biology↗

bioRxiv2020

The Crown Pearl: a draft genome assembly of the European freshwater pearl mussel Margaritifera margaritifera (Linnaeus, 1758)

Since historical times, the inherent human fascination with pearls turned the freshwater pearl mussel Margaritifera margaritifera (Linnaeus, 1758) into a highly valuable cultural and economic resource. Although pearl harvesting in M. margaritifera is nowadays residual, other human threats have aggravated the species conservation status, especially in Europe. This mussel presents a myriad of rare biological features, e.g. high longevity coupled with low senescence and Doubly Uniparental Inheritance of mitochondrial DNA, for which the underlying molecular mechanisms are poorly known. Here, the first draft genome assembly of M. margaritifera was produced using a combination of Illumina Paired-end and Mate-pair approaches. The genome assembly was 2,4 Gb long, possessing 105,185 scaffolds and a scaffold N50 length of 288,726 bp. The ab initio gene prediction allowed the identification of 35,119 protein-coding genes. This genome represents an essential resource for studying this species unique biological and evolutionary features and ultimately will help to develop new tools to promote its conservation.

genomics↗

bioRxiv2020

The microbiota of Malaysian fermented fish sauce

Budu is a Malaysian fermented anchovy sauce produced by immersing small fishes into a brine solution for 6 to 18 months. Fermentation of the anchovy sauce is contributed partly by microbial enzymes, but little is known about the microbial community in Budu. Therefore, a better understanding of the Budu microbiome is necessary to better control the quality, consistency and safety of the product. In this study, we collected 60 samples from twenty bottles of Budu produced by seven different manufacturers. We analyzed their microbiota based on V3-V4 16S rRNA amplicon sequencing at the time of opening the bottle as well as 3- and 7-months post-opening. Tetragenococcus was the dominant genus in many samples, reaching a maximum proportion of 98.62%, but was found in low abundance, or absent, in other samples. When Budu samples were not dominated by a dominant taxa, we observed a wider genera diversity such as Staphylococcus, Acinetobacter, Halanaerobium and Bacillus. While the taxonomic composition was relatively stable across sampling periods, samples from two brands showed a sudden increase in relative abundance of the genus Chromobacterium in the 7th month. Based on prediction of metagenome functions, non-Tetragenococcus-dominated samples were predicted to have enriched functional pathways related to amino acid metabolism and purine metabolism compared to Tetragenococcus-dominated microbiome; these two pathways are fundamental fermented quality and health attributes of fish sauce. Within the non-Tetragenococcus-dominated group, contributions towards amino acid metabolism and purine metabolism were biased towards the dominant taxa when species evenness is low, while in samples with higher species evenness, the contributions towards the two pathways were predicted to be evenly distributed between taxa.

molecular biology↗

bioRxiv2019

Found in Space: Nanopore long reads enable the first complete genome assembly of a Malaysian Vibrio parahaemolyticus isolate bearing the pVa plasmid associated with acute hepatopancreatic necrosis disease

BackgroundVibrio parahaemolyticus MVP1 was isolated from a Malaysian aquaculture farm affected with shrimp acute hepatopancreatic necrosis disease (AHPND). Its genome was previously sequenced on the Illumina MiSeq platform and assembled de novo producing a relatively fragmented assembly. Despite identifying the binary toxin genes in the MVP1 draft genome that were linked to AHPND, the toxin genes were localized on a very small contig precluding proper analysis of gene neighbourhood. MethodsThe genome of Vibrio parahaemolyticus MVP1 was sequenced on the Nanopore MinION device to obtain long reads that can span longer repeats and improve genome contiguity. De novo genome assembly was subsequently performed using long-read only assembler (Flye) followed by genome polishing as well as hybrid assembler (Unicycler). ResultsLong-read only assembly produced three complete circular MVP1 contigs consisting of chromosome 1, chromosome 2 and the pVa plasmid that pirABvp binary toxin genes. Polishing of the long read assembly with Illumina short reads was necessary to remove indel errors. The complete assembly of the pVa plasmid could not be achieved using Illumina reads due to the presence of identical repetitive elements flanking the binary toxin genes leading to multiple contigs. Whereas these regions were fully spanned by the Nanopore long reads resulting in a single contig. In addition, alignment of Illumina reads to the complete genome assembly indicated there is sequencing bias as read depth was lowest in low-GC genomic regions. Comparative genomic analysis revealed the presence of a gene cluster coding for additional insecticidal toxins in chromosome 2 of MVP1 that may further contribute to host pathogenesis pending functional validation. Scanning of all publicly available V. parahaemolyticus genomes revealed the presence of a single AinS-family quorum-sensing system in this species that can be targeted for future microbial management. ConclusionsWe generated the first chromosome-scale genome assembly of a Malaysian pirABVp-bearing V. parahaemolyticus isolate. Structural variations identified from comparative genomic analysis provide new insights into the genomic features of V. parahaemolyticus MVP1 that may be associated with host colonization and pathogenicity.

genomics↗

bioRxiv2019

Whole-genome sequencing of five proteobacteria isolated from Lechuguilla Cave, New Mexico, USA: Insights into taxonomy and quorum-sensing

Genomic resources remain scarce for bacteria isolated from oligotrophic caves. We sequenced the genomes of five Proteobacteria isolated from Lechuguilla Cave in New Mexico, USA. Genome-based phylogeny indicates that each strain belongs to a distinct genus. Two Rhizobiaceae isolates possess the genomic potential for the biosynthesis of acyl-homoserine lactone.

genomics↗

bioRxiv2019

Insight into the resistome and quorum sensing system of a divergent Acinetobacter pittii isolate from an untouched site of the Lechuguilla Cave

Acinetobacter are Gram-negative bacteria belonging to the sub-phyla Gammaproteobacteria, commonly associated with soils, animal feeds and water. Some members of the Acinetobacter have been implicated in hospital-acquired infections, with broad-spectrum antibiotic resistance. Here we report the whole genome sequence of LC510, an Acinetobacter species isolated from deep within a pristine location of the Lechuguilla Cave. Pairwise nucleotide comparison to three type strains within the genus Acinetobacter assigned LC510 as an Acinetobacter pittii isolate. Scanning of the LC510 genome identified two genes coding for {beta}-lactamase resistance, despite the fact that LC510 was isolated from a portion of the cave not previously visited by humans and protected from anthropogenic input. The ability to produce acyl-homoserine lactone (AHL) signal in culture medium, an observation that is consistent with the identification of the luxI and luxR homologs in its genome, suggests that cell-to-cell communication remains important in an isolated cave ecosystem.

microbiology↗

bioRxiv2019

Genomic characterization of Vibrio parahaemolyticus from Pacific white shrimp and rearing water reveals novel sequence types and multiple introductions of Photorhabdus insect-related (Pir) toxin-like genes into Malaysia

The Malaysian and global shrimp aquaculture production has been significantly impacted by acute hepatopancreatic necrosis disease (AHPND) typically caused by Vibrio parahaemolyticus harboring the pVA plasmid containing the pirAVpand pirBVpgenes which code for Photorhabdus insect-related (Pir) toxin. The limited genomic resource for V. parahaemolyticus strains from Malaysian aquaculture farms precludes an in-depth understanding of their diversity and evolutionary relationships. In this study, we isolated shrimp-associated and environmental (rearing water) V. parahaemolyticus from three aquaculture farms located in Northern and Central Malaysia followed by whole-genome sequencing of 40 randomly selected isolates on the Illumina MiSeq. Phylogenomic analysis and multilocus sequence typing (MLST) reveal distinct lineages of V. parahaemolyticus that harbor the pirABVpgenes. The recovery of pVA plasmid backbone devoid of pirAVp or pirABVp in some V. parahaemolyticus isolates suggests that the toxin genes are prone to deletion. The new insight gained from phylogenomic analysis of Asian V. parahaemolyticus, in addition to the observed genomic instability of pVa plasmid, will have implications for improvements in aquaculture practices to diagnose, treat or limit the impacts of this disease.

microbiology↗