DMSP production by coral-associated bacteria

Dimethylsulfoniopropionate (DMSP) is an important molecule in the marine sulfur cycle, produced in large amounts by corals and their dinoflagellate endosymbionts, Symbiodiniaceae. Although corals are known to harbour bacteria that can catabolise DMSP, the recent discovery of bacteria capable of producing DMSP in coastal and deep-sea environments raises the possibility of a bacterial contribution to the DMSP output of corals. Here, 157 bacteria associated with four common coral species were isolated and screened for their ability to produce DMSP by targeting dsyB, a key gene involved in DMSP biosynthesis. Approximately 9% (14 out of 157) of the bacterial isolates harboured dsyB, all being members of the Alphaproteobacteria. The ability of these isolates to produce DMSP was confirmed by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) measurements. A dsyB-harbouring strain, Shimia aestuarii AMM-P-2, was selected for genome sequencing. This strain harbours the complete genetic machinery to (i) assimilate sulfate and synthesise the DMSP precursors, cysteine and methionine; (ii) demethylate DMSP and generate methanethiol; (iii) cleave DMSP, generating dimethyl sulfide (DMS) and acrylate; and (iv) utilise or detoxify acrylate. The impacts of varied environmental factors (temperature, salinity, light and UV radiation) on S. aestuarii AMM-P-2 DMSP biosynthesis were characterised. DMSP levels in S. aestuarii AMM-P-2 increased almost two-fold under both hypersaline conditions (40 PSU) and high UV exposure. DMSP catabolism through the cleavage pathway also increased under these conditions, producing the antioxidants DMS and acrylate, a potential response to the oxidative stress generated. Overall, our results reveal that coral-associated bacteria can synthesize DMSP and may therefore contribute to DMSP production by the coral holobiont

Insights into the cultured bacterial fraction of corals

Bacteria associated with coral hosts are diverse and abundant, with recent studies suggesting involvement of these symbionts in host resilience to anthropogenic stress. Despite their putative importance, the work dedicated to culturing coral-associated bacteria has received little attention. Combining published and unpublished data, here we report a comprehensive overview of the diversity and function of culturable bacteria isolated from corals originating from tropical, temperate, and cold-water habitats. A total of 3,055 isolates from 52 studies were considered by our metasurvey. Of these, 1,045 had full-length 16S rRNA gene sequences, spanning 138 formally described and 12 putatively novel bacterial genera across the Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria phyla. We performed comparative genomic analysis using the available genomes of 74 strains and identified potential signatures of beneficial bacterium-coral symbioses among the strains. Our analysis revealed \u3e 400 biosynthetic gene clusters that underlie the biosynthesis of antioxidant, antimicrobial, cytotoxic, and other secondary metabolites. Moreover, we uncovered genomic features-not previously described for coral-bacterium symbioses-potentially involved in host colonization and host-symbiont recognition, antiviral defense mechanisms, and/or integrated metabolic interactions, which we suggest as novel targets for the screening of coral probiotics. Our results highlight the importance of bacterial cultures to elucidate coral holobiont functioning and guide the selection of probiotic candidates to promote coral resilience and improve holistic and customized reef restoration and rehabilitation efforts

Increasing frailty is associated with higher prevalence and reduced recognition of delirium in older hospitalised inpatients: results of a multi-centre study

Purpose: Delirium is a neuropsychiatric disorder delineated by an acute change in cognition, attention, and consciousness. It is common, particularly in older adults, but poorly recognised. Frailty is the accumulation of deficits conferring an increased risk of adverse outcomes. We set out to determine how severity of frailty, as measured using the CFS, affected delirium rates, and recognition in hospitalised older people in the United Kingdom. Methods: Adults over 65 years were included in an observational multi-centre audit across UK hospitals, two prospective rounds, and one retrospective note review. Clinical Frailty Scale (CFS), delirium status, and 30-day outcomes were recorded. Results: The overall prevalence of delirium was 16.3% (483). Patients with delirium were more frail than patients without delirium (median CFS 6 vs 4). The risk of delirium was greater with increasing frailty [OR 2.9 (1.8–4.6) in CFS 4 vs 1–3; OR 12.4 (6.2–24.5) in CFS 8 vs 1–3]. Higher CFS was associated with reduced recognition of delirium (OR of 0.7 (0.3–1.9) in CFS 4 compared to 0.2 (0.1–0.7) in CFS 8). These risks were both independent of age and dementia. Conclusion: We have demonstrated an incremental increase in risk of delirium with increasing frailty. This has important clinical implications, suggesting that frailty may provide a more nuanced measure of vulnerability to delirium and poor outcomes. However, the most frail patients are least likely to have their delirium diagnosed and there is a significant lack of research into the underlying pathophysiology of both of these common geriatric syndromes

Dimethylsulphoniopropionate (DMSP) metabolism within the coral holobiont

Felicity Kuek studied dimethylsulphoniopropionate (DMSP) metabolism within the coral holobiont focusing on the role of coral-associated bacteria in the production of DMSP, and the possible functions of its catabolic product, acrylate. She found that coral-associated bacteria are important contributors to the total pool of organic sulphur compounds within the holobiont and revealed a novel link between acrylate and the mechanism of calcification of the coral skeleton

Coastal bacterial communities: their potential roles in dimethylsulphide (DMS) production and coral defence

Little is known about the microbial communities in the South China Sea, especially the eastern region and this study aims to expand our knowledge on the diversity of culturable bacterial communities in this area. The Talang-Satang region is situated off the coast of Sematan and is especially important as it is one of the most diverse ecosystems found off Sarawak. Complex microbial communities are known to have significant influence over coral reef ecosystems. Through isolation and identification (16S rDNA) of native microbes from the open ocean, coral surface mucus layer (SML), as well as the surrounding sediment and waters, we were able to determine the species composition and abundance of the culturable bacteria in the South China Sea (Kuching and Kota Kinabalu), the Celebes Sea (Semporna) and the coral reef ecosystem (Talang-talang reef). Comparisons were made with regards to physico-chemical parameters and bacterial communities. The diversity of bacterial communities in these marine environments were analysed through isolation and identification (16S rDNA) of culturable bacteria, as well as preparation of clone libraries and subsequent restriction fragment length polymorphism (RFLP). It was observed that although the majority of bacteria in Kuching, Kota Kinabalu and Semporna are members of the Proteobacteria group, the composition of bacterial communities in these three areas did vary significantly, and the changes were also mirrored in physico-chemical differences. There is also a clear distinction between the different species found in the different parts of the reef system. Isolates found attached to the coral were mostly related to Vibrio spp., presumably attached to the mucus from the water column and surrounding sediment

Diversity and DMS(P) - Related genes in culturable bacterial communities in Malaysian coastal waters

Little is known about the diversity and roles of microbial communities in the South China Sea, especially the eastern region. This study aimed to expand our knowledge on the diversity of these communities in Malaysian waters, as well as their potential involvement in the breakdown or osmoregulation of dimethylsulphoniopropionate (DMSP). Water samples were collected during local cruises (Kuching, Kota Kinabalu, and Semporna) from the SHIVA expedition and the diversity of bacterial communities were analysed through the isolation and identification of 176 strains of cultured bacteria. The bacteria were further screened for the existence of two key genes (dmdA, dddP) which were involved in competing, enzymatically-mediated DMSP degradation pathways. The composition of bacterial communities in the three areas varied and changes were mirrored in physico-chemical parameters. Riverine input was highest in Kuching, which was mirrored by dominance of potentially pathogenic Vibrio sp., whereas the Kota Kinabalu community was more indicative of an open ocean environment. Isolates obtained from Kota Kinabalu and Semporna showed that the communities in these areas have potential roles in bioremediation, nitrogen fixing and sulphate reduction. Bacteria isolated from Kuching displayed the highest abundance (44%) of both DMSP-degrading genes, while the bacterial community in Kota Kinabalu had the highest percentage (28%) of dmdA gene occurrence and the dddP gene responsible for DMS production was most abundant (33%) within the community in Semporna. To the best of our knowledge, this is the first study looking at the diversity of culturable bacteria in coastal waters of East Malaysia and also their potential roles in the DMS(P) cycle

Bacterial communities of talang-talang reef and their potential role in coral defense

Complex microbial communities are known to have significant influence over coral reef ecosystems. The Talang-Satang region is situated off the coast of Sematan and is especially important as it is one of the most diverse ecosystems found off Sarawak. Interestingly, the Talang-talang reef thrives at above-average temperatures of 28-30 °C throughout the year. Through isolation and identification (16S rDNA) of native microbes from the coral, surface mucus layer (SML), as well as the surrounding sediment and waters, we were able to determine the species composition and abundance of the ctilturable bacteria in the coral reef ecosystem. Isolates found attached to the coral are mostly related to Vibrio spp., presumably attached to the mucus from the water column and surrounding sediment. Pathogenic Vibrio spp. and Bacillus spp. were dominant amongst the isolates from the water column and sediment. Known coral pathogens responsible for coral bleaching, V. coralliilyticus and V. shilonii, were isolated from the coral SML and sediment samples respectively. Coral SML isolates are found to be closely related to known nitrogen fixers and antibiotic producers with tolerance towards elevated temperatures and heavy metal contamination. The presence of type I modular polyketides synthase (PKS) genes responsible for clinical and economical macrolide polyketides production, and non-ribosomal peptide synthetase (NRPS) genes with the ability to produce immunosuppressant cyclosporine and other antibiotics were screened using specific PKS and NRPS primers. This specialized microbiota may be important for protecting the corals from pathogens by occupying entry niches and/ or through the production of secondary metabolites (i.e. antibiotics). The community from the coral SML were tested against each other at 28, 30 and 32 °C, and were found to exhibit antimicrobial properties under normal temperatures while pathogenic strains appear more toxic at elevated temperatures. Our results highlight the potential of bacteria associated with the coral SML in producing antibiotics and also indicate their important role in the coral defence

Lihua-jianyan / Huaxue-fence : = Physical testing and chemical analysis : PTCA

Complex microbial communities are known to exert significant influence over coral reef ecosystems. The Talang- Satang National Park is situated off the coast of Sematan and is one of the most diverse ecosystems found off-Sarawak. Interestingly, the Talang-talang reef thrives at above-average temperatures of 28- 30°C throughout the year. Through isolation and identification (16S rRNA) of native microbes from the coral, the surface mucus layer (SML), as well as the surrounding sediment and waters, we were able to determine the species composition and abundance of the culturable bacteria in the coral reef ecosystem. Isolates found attached to the coral are related mostly to Vibrio spp., presumably attached to the mucus from the water column and surrounding sediment. Pathogenic Vibrio spp. and Bacillus spp. were dominant amongst the isolates from the water column and sediment, while known coral pathogens responsible for coral bleaching, Vibrio coralliilyticus and Vibrio shiloi, were isolated from the coral SML and sediment samples respectively. Coral SML isolates were found to be closely related to known nitrogen fixers and antibiotic producers with tolerance towards elevated temperatures and heavy metal contamination, offering a possible explanation why the local corals are able to thrive in higher than usual temperatures. This specialized microbiota may be important for protecting the corals from pathogens by occupying entry niches and/or through the production of secondary metabolites such as antibiotics. The communities from the coral SML were tested against each other at 28, 30 and 32°C, and were also assessed for the presence of type I modular polyketides synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes which are both involved in the production of antibiotic compounds. The bacterial community from the SML exhibited antimicrobial properties under normal temperatures while pathogenic strains appeared toxic at elevated temperatures and our results highlight the role of the coral SML bacterial community in the coral’s defence

Identification and characterization of a peptide from the stony coral Heliofungia actiniformis

Marine organisms produce a diverse range of toxins and bioactive peptides to support predation, competition, and defense. The peptide repertoires of stony corals (order Scleractinia) remain relatively understudied despite the presence of tentacles used for predation and defense that are likely to contain a range of bioactive compounds. Here, we show that a tentacle extract from the mushroom coral, Heliofungia actiniformis, contains numerous peptides with a range of molecular weights analogous to venom profiles from species such as cone snails. Using NMR spectroscopy and mass spectrometry we characterized a 12-residue peptide (Hact-1) with a new sequence (GCHYTPFGLICF) and well-defined β-hairpin structure stabilized by a single disulfide bond. The sequence is encoded within the genome of the coral and expressed in the polyp body tissue. The structure present is common among toxins and venom peptides, but Hact-1 does not show activity against select examples of Gram-positive and Gram-negative bacteria or a range of ion channels, common properties of such peptides. Instead, it appears to have a limited effect on human peripheral blood mononuclear cells, but the ecological function of the peptide remains unknown. The discovery of this peptide from H. actiniformis is likely to be the first of many from this and related species