Quorum sensing (QS) plays an important role during infection for the opportunistic human pathogen Pseudomonas aeruginosa. Quorum sensing inhibition (QSI) can disrupt this initial event of infection without killing bacterial cells, and thus QS inhibitors have been suggested as novel approaches for anti-infective therapy. Cinnamaldehyde (CAD) is a P. aeruginosa biofilm inhibitor and disperser of preformed biofilms. In this study, the combined use of CAD and colistin (COL) revealed a synergistic activity, but this was not the case for CAD combined with carbenicillin, tobramycin (TOB), or erythromycin in checkerboard assays for P. aeruginosa. CAD demonstrated QSI activity by repression of the expression of lasB, rhlA and pqsA in GFP reporter assays. Approximately 70% reduction in GFP production was observed with the highest CAD concentration tested in all the QS reporter strains. TOB also showed strong QSI when combined with CAD in reporter assays. Combination treatments revealed an additive activity of CAD with COL and TOB in biofilm inhibition (75.2% and 83.9%, respectively) and preformed biofilm dispersion (~90% for both) when compared to the individual treatments. Therefore, a proposed method to mitigate P. aeruginosa infection is a combination therapy of CAD with COL or CAD with TOB as alternatives to current individual drug therapies.

Background: Reef-building corals are acutely threatened by ocean warming, calling for active interventions to reduce coral bleaching and mortality. Corals associate with a wide diversity of bacteria which can influence coral health, but knowledge of specific functions that may be beneficial for corals under thermal stress is scant. Under the oxidative stress theory of coral bleaching, bacteria that scavenge reactive oxygen (ROS) or nitrogen species (RNS) are expected to enhance coral thermal resilience. Further, bacterial carbon export might substitute the carbon supply from algal photosymbionts, enhance thermal resilience and facilitate bleaching recovery. To identify probiotic bacterial candidates, we sequenced the genomes of 82 pure-cultured bacteria that were isolated from the emerging coral model Galaxea fascicularis. Results: Genomic analyses showed bacterial isolates were affiliated with 37 genera. Isolates such as Ruegeria, Muricauda and Roseovarius were found to encode genes for the synthesis of the antioxidants mannitol, glutathione, dimethylsulfide, dimethylsulfoniopropionate, zeaxanthin and/or β-carotene. Genes involved in RNS-scavenging were found in many G. fascicularis-associated bacteria, which represents a novel finding for several genera (including Pseudophaeobacter). Transporters that are suggested to export carbon (semiSWEET) were detected in seven isolates, including Pseudovibrio and Roseibium. Further, a range of bacterial strains, including strains of Roseibium and Roseovarius, revealed genomic features that may enhance colonisation and association of bacteria with the coral host, such as secretion systems and eukaryote-like repeat proteins. Conclusions: Our work provides an in-depth genomic analysis of the functional potential of G. fascicularis-associated bacteria and identifies novel combinations of traits that may enhance the coral’s ability to withstand coral bleaching. Identifying and characterising bacteria that are beneficial for corals is critical for the development of effective probiotics that boost coral climate resilience.

Contact surfaces have been identified as one of the main routes for pathogen transmission. The efficacy to kill both viruses and bacteria on touch surfaces is critical to reducing the rampant spread of harmful pathogens. Copper is one such material that has been traditionally used for its antimicrobial properties. However, most contact/touch surfaces are made up of steel or aluminum due to their structural properties. Therefore, coating high-touch components with copper is one possible solution to improve antibacterial efficacy. In this study, copper was coated on both stainless steel and aluminum substrates using a cold spray process which is a fast and economic coating technique. The coated samples in both as-deposited and heat-treated states were exposed to Escherichia coli and Staphylococcus aureus bacteria, and their efficacy was compared with bulk copper plate. It was found that both bacterial cells responded differently to the different coating properties such as coating thickness, porosity, hardness, surface roughness, oxide content, and galvanic coupling effect. These correlations were elucidated in light of various results obtained from antibacterial and bacterial attachment tests, and materials characterizations of the coatings. It is possible to tailor copper coating characteristics to render them more effective against targeted bacteria.