Computationally Designed Anti-LuxP DNA Aptamer Suppressed Flagellar Assembly- and Quorum Sensing-Related Gene Expression in Vibrio parahaemolyticus.

(1) Background: Quorum sensing (QS) is the chemical communication between bacteria that sense chemical signals in the bacterial population to control phenotypic changes through the regulation of gene expression. The inhibition of QS has various potential applications, particularly in the prevention of bacterial infection. QS can be inhibited by targeting the LuxP, a periplasmic receptor protein that is involved in the sensing of the QS signaling molecule known as the autoinducer 2 (AI-2). The sensing of AI-2 by LuxP transduces the chemical information through the inner membrane sensor kinase LuxQ protein and activates the QS cascade. (2) Methods: An in silico approach was applied to design DNA aptamers against LuxP in this study. A method combining molecular docking and molecular dynamics simulations was used to select the oligonucleotides that bind to LuxP, which were then further characterized using isothermal titration calorimetry. Subsequently, the bioactivity of the selected aptamer was examined through comparative transcriptome analysis. (3) Results: Two aptamer candidates were identified from the ITC, which have the lowest dissociation constants (Kd) of 0.2 and 0.5 micromolar. The aptamer with the lowest Kd demonstrated QS suppression and down-regulated the flagellar-assembly-related gene expression. (4) Conclusions: This study developed an in silico approach to design an aptamer that possesses anti-QS properties.

Influence of Symbiotic Probiont Strains on the Growth of Amphora and Chlorella and Its Potential Protections Against Vibrio spp. in Artemia.

The emerging aquaculture industry is in need of non-antibiotic-based disease control approaches to minimize the risk of antibiotic-resistant bacteria. Bacterial infections mainly caused by Vibrio spp. have caused mass mortalities of fish especially during the larval stages. The objectives of this study were to verify the potential of symbiotic probiont strains, isolated from microalgae (Amphora, Chlorella, and Spirulina) for suppressing the growth of Vibrio spp. and at the same time ascertain their abilities to enhance microalgal biomass by mutualistic interactions through microalgae-bacteria symbiosis. In addition, in vivo studies on Artemia bioencapsulated with probiont strains (single strain and mix strains) and microalgae were evaluated. The selected potential probionts were identified as Lysinibacillus fusiformis strain A-1 (LFA-1), Bacillus sp. strain A-2 (BA-2), Lysinibacillus fusiformis strain Cl-3 (LFCl-3), and Bacillus pocheonensis strain S-2 (BPS-2) using 16s rRNA. The cell densities of Amphora culture supplemented with BA-2 and Chlorella culture supplemented with LFCl-3 were higher than those of the controls. Artemia bioencapsulated with mix strains (LFA-1 + BA-2 + LFCl-3 + BPS-2) and Amphora demonstrated the highest survival rate compared to the controls, after being challenged with V. harveyi (60 ± 4%) and V. parahaemolyticus (78 ± 2%). Our study postulated that BA-2 and LFCl-3 were found to be good promoting bacteria for microalgal growth and microalgae serve as a vector to transport probiotic into Artemia. Moreover, mixture of potential probionts is beneficial for Artemia supplementation in conferring protection to Artemia nauplii against pathogenic Vibrios.

Chemical Composition and Evaluation of the α-Glucosidase Inhibitory and Cytotoxic Properties of Marine Algae Ulva intestinalis, Halimeda macroloba, and Sargassum ilicifolium.

Seaweed has tremendous potentials as an alternative source of high-quality food products that have attracted research in recent times, due to their abundance and diversity. In the present study, three selected seaweed species commonly found in the Malaysian Peninsular, Ulva intestinalis, Halimeda macroloba, and Sargassum ilicifolium, were subjected to preliminary chemical screening and evaluated for α-glucosidase inhibitory and cytotoxic activities against five cancer cell lines. Chemical composition of U. intestinalis, H. macroloba, and S. ilicifolium methanolic extracts was evaluated by Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Our results revealed the highest total carotenoids (162.00 µg g-1 DW), chlorophyll a (313.09 ± 2.53 µg g-1 DW), and chlorophyll b (292.52 ± 8.84 µg g-1 DW) concentrations in U. intestinalis. In the α-glucosidase inhibitory activity, S. ilicifolium demonstrated the lowest efficacy with an IC50 value of 38.491 ppm compared to other species of seaweed. H. macroloba extract, on the other hand, was found to be the most cytotoxic toward MCF-7 and HT 29 cells with IC50 of 37.25 ± 0.58 and 21.32 ± 0.25 µg/mL, respectively, compared to other cell lines evaluated. Furthermore, H. macroloba extract was also found to be less toxic to normal cell (3T3) with IC50 of 48.80 ± 0.11 µg/mL. U. intestinalis extract exhibited the highest cytotoxicity toward Hep G2 cells with IC50 of 23.21 ± 0.11 µg/mL, whereas S. ilicifolium was less toxic to MDA- MB231 cell with IC50 of 25.23 ± 0.11 µg/mL. Subsequently, the GC-MS analysis of the methanolic extracts of these seaweed samples led to the identification of 27 metabolites in U. intestinalis, 22 metabolites in H. macroloba, and 24 metabolites in S. ilicifolium. Taken together, the results of this present study indicated that all the seaweed species evaluated are good seaweed candidates that exhibit potential for cultivation as functional food sources for human consumption and need to be promoted.

Phylogenetics and population genetics of Plotosus canius (Siluriformes: Plotosidae) from Malaysian coastal waters.

Plotosus canius (Hamilton, 1822) is a significant marine species in Malaysia from nutritional and commercial perspectives. Despite numerous fundamental research on biological characteristics of P. canius, there are various concerns on the level of population differentiation, genomic structure, and the level of genetic variability among their populations due to deficiency of genetic-based studies. Deficiency on basic contexts such as stock identification, phylogenetic relationship and population genetic structure would negatively impact their sustainable conservation. Hence, this study was conducted to characterize the genetic structure of P. canius for the first time through the application of mitochondrial Cytochrome Oxidase I (COI) gene, cross amplification of Tandanus tandanus microsatellites, and a total of 117 collected specimens across five selected populations of Malaysia. The experimental results of the mitochondrial analysis revealed that the haplotype diversity and nucleotide diversity varied from 0.395-0.771 and 0.033-0.65 respectively. Moreover, the statistical analysis of microsatellites addressed a considerable heterozygote insufficiency in all populations, with average observed heterozygosity (Ho ) value of 0.2168, which was lower than the standard heterozygosity in marine populations (Ho = 0.79). This alongside the high Fis values estimation, high pairwise differentiation among populations and low within population variations are supposed to be associated with small sample size, and inbreeding system. Besides, the significant finding of this study was the sharing of common haplotype KR086940, which reflects a historical genetic connectivity between Peninsular Malaysia and Borneo populations due to the geological history of Southeast Asia during Pleistocene era. Demographic analyses showed that all populations were in an equilibrium state with no significant evidence of population expansion. To put it briefly, the current study has managed to provide an initial genomic database toward understanding of the genetic characterization, phylogenetic, molecular diversification and population structure in P. canius, and should be necessary highlighted for appropriate management and conservation of species. Further studies must be carried out involving more geographical and sampling sites, larger population size per site, and utilization of species specific microsatellites loci.