Biology subjects

Kwong, W. K.

Publications and source records attributed to Kwong, W. K..

7 recordsLinked to original sources

bioRxiv2026

Discovery and characterisation of OMVs produced by the bee gut microbiota

Bacteria use diverse mechanisms to interact with each other and with eukaryotic hosts, thereby shaping microbiome composition and influencing host health. One of these mechanisms is the production of outer membrane vesicles (OMVs), nanoscale structures that bud off from bacterial cells into the extracellular space. OMVs can deliver bioactive cargoes, including enzymes, RNA and DNA, enabling functions such as cell-to-cell communication, nutrient acquisition and immunomodulation. However, the role of OMVs in beneficial host-associated microbiomes remains unclear. Here, we investigated OMV production in the gut bacteria of the western honey bee (Apis mellifera), which forms a highly conserved and stable microbial community. Using electron microscopy, fluorescence labelling, and nanoparticle tracking analysis, we detected OMV production in every gram-negative species of the bee gut microbiota that we investigated. Vesicles were observed in gut contents of wild and laboratory-inoculated bees, but absent in bees lacking a microbiota. OMVs contained nucleic acids, with more RNA than DNA. Bacterial strains varied in OMV properties, including abundance, size, and zeta potential. These findings indicate that OMVs are likely significant mediators of interbacterial and host-microbe interactions in the bee gut.

microbiology↗

bioRxiv2026

Vertical inheritance and loss-driven evolution of secretion systems in the bee gut microbiota

The stability of gut bacterial communities is determined by complex inter-cellular interactions such as competition, cooperation and host dynamics. A mechanism proposed to mediate these interactions is bacterial secretion systems: specialized protein complexes that secrete effector molecules into neighbouring cells or the surrounding environment to influence community stability. However, the forces driving secretion system distribution and evolution in host-associated microbiomes remain unclear. Here, we show that secretion systems in the bee gut microbiome are predominantly vertically inherited and evolve primarily through recurrent gene loss rather than horizontal acquisition. Using comparative genomic analysis, we found that bee gut symbionts mostly encode type I, V, and VI secretion systems. In contrast, the pathogen-associated type II and III systems are missing, but they retain evolutionarily related pili and flagella. We found weak association between the presence of specific secretion systems and the bee hosts, suggesting that these systems are maintained for interbacterial interactions rather than host-specific adaptation. Co-phylogenetic analyses show congruence between bacterial strain phylogenies and most secretion system phylogenies, indicating a vertical mode of transmission. Only a subtype of the type VI system in the Orbaceae and the type IV system in Snodgrassella spp. show evidence of horizontal transmission. The lack of horizontal transfers means that losses of secretion systems is a permanent evolutionary event in almost all lineages of the bee gut microbiota. Our study provides a uniquely comprehensive analysis of secretion systems across an entire gut bacterial community, giving insight into how microbiomes evolve and maintain functional interactions within host-associated environments.

evolutionary biology↗

bioRxiv2024

Implications of gen(om)e duplications on the expansion and evolution of the GPCR signalling pathway

Gene and genome duplications are important evolutionary events associated with the emergence of gene families and novel biological functions. G protein-coupled receptors (GPCRs) constitute the largest family of membrane proteins, and their associated signalling pathways control crucial physiological functions such as neurotransmission, endocrine activity, and immunity. However, the duplication history of the entire pathway across evolutionary time is unknown. Here, we performed a comprehensive analysis of the duplication events of the main interactors of the GPCR signalling cascade. We show that different components of the pathway evolved under distinct frequencies of duplication events, with G proteins and GPCRs exhibiting higher frequencies than the downstream mediators and regulators. We also found that GPCRs are evolutionarily younger than G proteins and that most receptors evolved before their ligands. Additionally, the GPCR signalling system experienced significant gene expansion through duplication during the emergence of placental mammals, which played an important role in all human body systems, particularly concerning ligands and G proteins. These results indicate that the expansion and diversification of the GPCR signalling pathway was based on independent and discrete duplication events of its main components, suggesting that the maintenance of duplicate genes within the pathway may have been mediated by the selection of complementary duplication and divergence processes between the signalling components at specific evolutionary stages.

evolutionary biology↗

bioRxiv2022

Cooperative host-microbe metabolism of a plant toxin in bees

During pollination, bees are exposed to a myriad of xenobiotics, including plant metabolites, which may exert a wide range of effects on their health. Although bees encode enzymes that help in the metabolism of xenobiotics, they still have reduced detoxification gene diversity when compared to other insects, and may rely on other components of their physiology, such as the microbiota, to degrade potentially toxic molecules. In this study, we show that amygdalin, a cyanogenic glycoside found in honey bee-pollinated almond trees, can be metabolized by both bees and members of the gut microbiota. In microbiota-deprived bees, amygdalin is degraded into prunasin, leading to prunasin accumulation in the midgut and hindgut. In microbiota-colonized bees, on the other hand, amygdalin is degraded even further, and prunasin does not accumulate in the gut, suggesting that the microbiota contribute to the full degradation of amygdalin into hydrogen cyanide. In vitro experiments demonstrated that amygdalin degradation by bee gut bacteria is strain-specific and not characteristic of a particular genus or species. We found strains of Bifidobacterium, Bombilactobacillus and Gilliamella that can degrade amygdalin, and the degradation mechanism appears to vary since only some strains produce prunasin as an intermediate. Finally, we investigated the basis of degradation in Bifidobacterium wkB204, a strain that fully degrades amygdalin. We found overexpression and secretion of several carbohydrate-degrading enzymes, including one in glycoside hydrolase family 3 (GH3). We expressed this GH3 in Escherichia coli and detected prunasin as a byproduct when cell lysates were cultured with amygdalin, supporting its contribution to amygdalin degradation. These findings demonstrate that both host and microbiota can act together to metabolize dietary plant metabolites. How amygdalin degradation into hydrogen cyanide affects bee health remains to be elucidated.

ecology↗

bioRxiv2020

Taxonomy of the apicomplexan symbionts of coral, including Corallicolida ord. nov., reassignment of the genus Gemmocystis, and description of new species Corallicola aquarius gen. nov. sp. nov. and Anthozoaphila gnarlus gen. nov. sp. nov.

Corals (Metazoa; Cnidaria; Anthozoa) have recently been shown to play host to a widespread and diverse group of intracellular symbionts of the phylum Apicomplexa. These symbionts, colloquially called corallicolids, are mostly known through molecular analyses, and no formal taxonomy has been proposed. Another apicomplexan, Gemmocystis cylindrus (described from the coral Dendrogyra cylindrus), may be related to corallicolids, but lacks molecular data. Here, we isolate and describe motile trophozoite (feeding) corallicolids cells using microscopic (light, SEM, and TEM) and molecular phylogenetic analysis to provide the basis for a formal description. Phylogenetic analyses using nuclear and plastid rRNA operons, and three mitochondrial protein sequences derived from single cell transcriptomes, all confirm that these organisms fall into a discrete deep-branching clade within the Apicomplexa not closely related to any known species or major subgroup. As a result, we assign this clade to a new order, Corallicolida ord. nov., and family, Corallicolidae fam. nov. We describe a type species, Corallicola aquarius gen. nov. sp. nov. from its Rhodactis sp. host, and also describe a second species, Anthozoaphila gnarlus gen. nov. sp. nov., from the coral host Madracis mirabilis. Finally, we propose reassigning the incertae sedis taxon G. cylindrus from the order Agamococcidiorida to the Corallicolida, based on similarities in morphology and host localization to that of the corallicolids.

microbiology↗

bioRxiv2019

Highly reduced genomes of protist endosymbionts show evolutionary convergence

Genome evolution in bacterial endosymbionts is notoriously extreme: the combined effects of strong genetic drift and unique selective pressures result in highly reduced genomes with distinctive adaptations to hosts [1-4]. These processes are mostly known from animal endosymbionts, where nutritional endosymbioses represent the best-studied systems. However, eukaryotic microbes, or protists, also harbor diverse bacterial endosymbionts, but their genome reduction and functional relationships with their more diverse hosts are largely unexplored [5-7]. We sequenced the genomes of four bacterial endosymbionts from three species of diplonemids, poorly-studied but abundant and diverse heterotrophic protists [8-10]. The endosymbionts come from two intracellular families from different orders, Rickettsiaceae and Holosporaceae, that have invaded diplonemids multiple times, and their genomes have converged on an extremely small size (605-632 kbp), similar gene content (e.g., metabolite transporters and secretion systems), and reduced metabolic potential (e.g., loss of energy metabolism). These characteristics are generally found in both families, but the diplonemid endosymbionts have evolved greater extremes in parallel. Their modified type VI secretion systems are likely involved in the manipulation of host metabolism (e.g., interactions with host mitochondria) or defense against bacterial infections, although their similar effector/immunity proteins may also allow for co-occurring Holosporaceae species in one diplonemid host. Finally, modified cellular machinery like ATP synthase without oxidative phosphorylation and reduced flagella present in both diplonemid endosymbionts and nutritional animal endosymbionts indicates that intracellular mechanisms have converged in bacterial endosymbionts with various functions and from different eukaryotic hosts across the tree of life.

evolutionary biology↗

bioRxiv2018

A widespread coral-infecting apicomplexan contains a plastid encoding chlorophyll biosynthesis

The Apicomplexa are an important group of obligate intracellular parasites that include the causative agents of human diseases like malaria and toxoplasmosis. They evolved from free-living, phototrophic ancestors, and how this transition to parasitism occurred remains an outstanding question. One potential clue lies in coral reefs, where environmental DNA surveys have uncovered several lineages of uncharacterized, basally-branching apicomplexans. Reef-building corals form a well-studied symbiotic relationship with the photosynthetic dinoflagellate Symbiodinium, but identification of other key microbial symbionts of corals has proven elusive. Here, we used community surveys, genomics, and microscopy to identify an apicomplexan lineage, which we name corallicola, that was found in high prevalence (>80%) across all major groups of corals. In-situ fluorescence and electron microscopy confirmed that corallicola lives intracellularly within the tissues of the coral gastric cavity, and possesses clear apicomplexan ultrastructural features. We sequenced the plastid genome, which lacked all genes for photosystem proteins, indicating that corallicola harbours a non-photosynthetic plastid (an apicoplast). However, the corallicola plastid differed from all other known apicoplasts because it retains all four genes involved in chlorophyll biosynthesis. Hence, corallicola shares characteristics with both its parasitic and free-living relatives, implicating it as an evolutionary intermediate, and suggesting that a unique ancestral biochemistry likely operated during the transition from phototrophy to parasitism.

microbiology↗