Biology subjects

Leong, W.

Publications and source records attributed to Leong, W..

4 recordsLinked to original sources

bioRxiv2026

A beneficial megaplasmid transforms an opportunistic bacterial pathogen to benefit coral by extending their thermal range

Resilient turbid coral reefs, found 1{degrees} north of the equator, experience fewer and less intense bleaching events despite being situated within the worlds busiest shipping port in highly urbanised Singapore. We hypothesised that bacteria within the coral holobiont play a role in maintaining coral diversity within this extreme environment by conferring traits that enhance host tolerance. Eleven Pseudovibrio isolates, whose genomes differ by only four SNPs, were isolated from the scleractinian coral Pachyseris speciosa. A [~]490 kbp megaplasmid (pCJH) was found in 7 of the 11 Pseudovibrio isolates. This study identified an opportunistic Pseudovibrio sp. pathogen of P. speciosa, accelerating bleaching disease. However, presence of the megaplasmid alters the ecological strategy of Pseudovibrio sp. toward mutualism, delaying coral bleaching. The megaplasmid enhances Pseudovibrios host colonisation and establishment of symbiosis through increased attachment and extends its bioactive genetic potential, but reduces fecundity. The Pseudovibrio genomes and megaplasmid encode several diffusible antibiotic biosynthetic gene clusters and contact-dependent inhibition mechanisms, with both types of inhibitory activity shown against local (i.e. P. speciosa) and type-strain Vibrio spp. Interaction analyses in experimentally heat-stressed corals revealed negative associations between Pseudovibrio and Vibrio ASVs corresponding to these cultured isolates. They also showed increased coral thermal tolerance by a full degree (1{degrees}C) when it is associated with the megaplasmid-bearing strain. Together, these findings support the Coral Probiotic Hypothesis that bacteria enhance coral resilience through chemical defense and identifies additional aspects to this symbiosis by a mobile genetic element which could play an important role in coral reef resilience.

microbiology↗

bioRxiv2020

Pseudomonas aeruginosa isolates co-incubated with Acanthamoeba castellanii exhibit phenotypes similar to chronic cystic fibrosis isolates

The opportunistic pathogen, Pseudomonas aeruginosa, is ubiquitous in the environment, and in humans is capable of causing acute and chronic infections. P. aeruginosa, when co-incubated with the bacterivorous amoeba, Acanthamoeba castellanii, for extended periods, produced genetic and phenotypic variants. Sequencing of late-stage amoeba-adapted P. aeruginosa isolates demonstrated single nucleotide polymorphisms within genes that encode known virulence factors, and this correlated with a reduction in expression of virulence traits. Virulence towards the nematode, Caenorhabditis elegans, was attenuated in late-stage amoeba-adapted P. aeruginosa compared to early stage amoeba-adapted and non-adapted counterparts. Late-stage amoeba-adapted P. aeruginosa lost competitive fitness compared to non-adapted counterparts when grown in nutrient rich media. However, non-adapted P. aeruginosa were rapidly cleared by amoeba predation, whereas late-stage amoeba-adapted isolates remained in higher numbers 24 h after ingestion by amoeba. In addition, there was reduced uptake by macrophage of amoeba-adapted isolates and reduced uptake by human neutrophils as well as increased survival in the presence of neutrophils. Our findings indicate that the selection imposed by amoeba on P. aeruginosa resulted in reduced virulence over time. Importantly, the genetic and phenotypic traits possessed by late-stage amoeba-adapted P. aeruginosa are similar to what is observed for isolates obtained from chronic cystic fibrosis infections. This notable overlap in adaptation to different host types suggests similar selection pressures among host cell types. Author SummaryPseudomonas aeruginosa is an opportunistic pathogen that causes both acute infections in plants and animals, including humans and also causes chronic infections in immune compromised and cystic fibrosis patients. This bacterium is commonly found in soils and water where bacteria are constantly under threat of being consumed by the bacterial predators, protozoa. To escape being killed, bacteria have evolved a suite of mechanisms that protect them from being consumed or digested. Here we examined the effect of long-term predation on the genotype and phenotypes expressed by P. aeruginosa. We show that long-term co-incubation with protozoa resulted in mutations in the bacteria that made them less pathogenic. This is particularly interesting as we see similar mutations arise in bacteria associated with chronic infections. Thus, predation by protozoa and long term colonization of the human host may represent similar environments that select for similar losses in gene functions.

microbiology↗

bioRxiv2019

Integrating transcriptomic network reconstruction and QTL analyses reveals mechanistic connections between genomic architecture and Brassica rapa development

Plant developmental dynamics can be heritable, genetically correlated with fitness and yield, and undergo selection. Therefore, characterizing the mechanistic connections between the genetic architecture governing plant development and the resulting ontogenetic dynamics of plants in field settings is critically important for agricultural production and evolutionary ecology. We use a hierarchical Bayesian Function-Valued Trait (FVT) approach to estimate Brassica rapa growth curves throughout ontogeny, across two treatments and in two growing seasons. We find that the shape of growth curves is relatively plastic across environments compared to final height, and that there are trade-offs between growth rate and duration. We determined that combining FVT Quantitative Trait Loci (QTL) and genes/eigengene expression identified via transcriptomic co-expression network reconstructions best characterized phenotypic variation. Further, targeted eQTL analyses identified regulatory hotspots that colocalized with FVT QTL and co-expression network identified genes and mechanistically link FVT QTL with structural trait variation throughout development in agroecologically relevant field settings.

genomics↗

bioRxiv2017

The differential spatiotemporal expression pattern of shelterin genes throughout lifespan

Shelterin forms the core complex of telomere proteins and plays critical roles in protecting telomeres against unwanted activation of the DNA damage response and in maintaining telomere length homeostasis. Although shelterin expression is believed to be ubiquitous for stabilization of chromosomal ends, some evidence suggests that some shelterin subunits have tissue-specific functions. However, very little is known regarding how shelterin subunit gene expression is regulated during development and aging. Using two different animal models, the mouse and zebrafish, we reveal herein that shelterin subunits exhibit distinct spatial and temporal expression patterns that do not correlate with the proliferative status of the organ systems examined. Together, this work shows that the shelterin subunits exhibit distinct spatiotemporal expression patterns, suggesting important tissue-specific functions during development throughout the lifespan.

developmental biology↗