iBB

Marine microbiomes are prolific sources of bioactive compounds of pharmaceutical value. A new study, published in Marine Drugs, inspected two culture collections comprising 919 host-associated marine bacteria belonging to 55 genera and several unclassified lineages. The study identified numerous isolates with a potentially rich secondary metabolism and inhibitory activities towards human-pathogenic bacteria and fungi. These culture collections, available at iBB-IST and Aveiro University, are a valuable resource of understudied marine bacteria that hold promise for a future, sustainable production of novel drug leads. The work was developed within the SymbioReactor project (DGPM | Fundo Azul program), first-authored by MSc João Almeida and coordinated by Dr Tina Keller-Costa and Prof Rodrigo Costa. The study also involved PhD student Matilde Marques, Dr Dalila Mil-Homens, Prof Miguel Teixeira and Prof Arsénio Fialho from iBB as well collaborators from Aveiro University and Biocant.

B. cenocepacia is a contact-dependent bacterium known for its capacity of causing respiratory infections. Among a panel of adhesins used by B. cenocepacia to contact with host cells, trimeric autotransporter adhesins (TAAs) are of particular interest. In a recent paper published in Cellular Microbiology, a BSRG-iBB team (Andreia Pimenta, Nuno Bernardes, Dalila Mil-Homens and Arsénio M Fialho) together with Michelle Kilcoyne and Lokesh Joshi from the National University of Ireland Galway, Galway, Ireland, were able to uncover the roles of the TAA BCAM2418, as an adhesin and the type of host glycans that serve as recognition targets. This work reveals the importance of BCAM2418 as a mediator of early host-bacteria crosstalk.

Cellular components that contribute to both pathogenesis and drug resistance are among the most promising drug targets in human pathogens. In this study, the uncharacterized drug:H+ antiporter CgTpo4 was shown to play a role in Candida glabrata virulence in the infection model G. mellonella. The underlying mechanism was demonstrated to include a role in AntiMicrobial Peptide (AMP) resistance, compatible with the observed immune response deployed by G. mellonella upon C. glabrata infection. These results, emerging from a collaboration between BSRG members, led by Miguel Cacho Teixeira and including Arsénio Fialho and Dalila Mil-Homens, were just published in International Journal of Molecular Sciences and are expected to contribute to design more suitable antifungal therapeutic strategies.

The role of the bcaC  trimeric autotransporter adhesion (TAA) gene in the virulence of Burkholderia cenocepacia has been disclosed by iBB researchers Andreia Pimenta, Dalila Mil-Homens, Sandra Pinto and Arsénio Fialho in a report published in Microbes and Infection. TAAs are homotrimeric proteins of the outer membrane of many Gram-negative pathogens that play a key role in adhesion to host cells. Two insertional-mutants for TAA bcaC and histidine kinase (HK) BCAM0218 genes were constructed. Findings indicate that bcaC encodes for a large multifunctional TAA that has hemagglutination activity and is also required for maximal host cell adherence. The neighbor BCAM0218 HK encoding gene was identified as a critical player that negatively controls the expression of the bcaC TAA gene. All together, the findings represent a step forward for a better characterization of the subset of B. cenocepacia TAA-encoding genes. This article was selected as the highlighted article of the July 2020 issue of the Microbes and Infection journal.

Zinc surfaces coated with nanostructured ZnO flowers has received increasing attention as a versatile biomaterial for medical applications. A collaborative work between researchers from CQE (Marta Alves, Catarina Santos and Fátima Montemor) and iBB (Dalila Mil-Homens, Sandra Pinto) describes the successful functionalization of these surfaces with cooper (Cu), iron (Fe) or manganese (Mn) oxides (Ox). The in vitro study of  these surfaces,  by fibroblast viability,  hemocompatibility, and  chick  chorioallantoic membrane (CAM) assays revealed the potential brought by CuOx functionalization for anti-cancer applications, with the antagonist behaviour of the surfaces functionalized with MnOx, and in a less extent with FeOx, favouring wound healing in traumatic  processes. Despite the possible correlation between biocompatibility and   hydroxyapatite   precipitation,   no   correlation   could   be   drawn with the corrosion activity, study by immersion and electrochemical techniques, of these surfaces. The study resulted from. The results were published in Colloids and Surfaces B: Biointerfaces.

The effectiveness of Candida glabrata as an emerging human pathogen relies on its ability to acquire azole drug resistance. In a paper just published in Antimicrobial Agents and Chemotherapy, the first time-course evaluation of the global gene expression changes that lead a drug susceptible C. glabrata clinical isolate to step-wise acquisition of resistance to azole drugs was conducted. This work, which results from the collaboration of six different teams under the coordination of Miguel C Teixeira from BSRG-iBB, highlights the multifactorial nature of azole resistance acquisition, including the Epa3 adhesin as a new player, while providing fascinating clues on the underlying evolutionary path. This knowledge is of crucial importance to design more effective antifungal therapy.

The marine bacterial genus Aquimarina is a promising source of novel natural products. A new study published in Marine Drugs demonstrated widespread ability of Aquimarina species to inhibit growth of human-pathogenic microbes such as Candida glabrata and methicillin-resistant Staphylococcus aureus, as well as Vibrio and other marine bacteria relevant to aquaculture. Metabolomics and genomics analyses of Aquimarina strains indicated the presence of novel polyketides and peptides, including cyclic depsipeptide-related compounds. The study further showed that Aquimarina species possess low-abundance distributions across marine biotopes worldwide. It emphasizes the relevance of this member of the microbial rare biosphere as a promising source of novel natural products, supporting future efforts to isolate new bioactive compounds from Aquimarina. The work was developed within the SymbioReactor project (DGPM | Fundo Azul program) led by Prof Rodrigo Costa and Dr Tina Keller-Costa and was first-authored by PhD student Sandra Silva. It also includes former MSc student Patrícia Paula, Dr Dalila Mil-Homens, Prof Miguel Teixeira and Prof Arsénio Fialho from BSRG-iBB as coauthors.

Burkholderia cenocepacia is a human contact-dependent pathogenic bacterium known for its capacity of causing severe opportunistic respiratory infections. B. cenocepacia uses a complex machinery for primary adherence with host cells. In a recent paper published in Scientific Reports, a BSRG-iBB team (Andreia Pimenta, Nuno Bernardes, Dalila Mil-Homens and Arsénio M Fialho) together with Marta M Alves from CQE, IST, have developed a RNASeq-based approach that led to identify adhesion candidate genes that were not previously reported in the context of a B. cenocepacia infection. This study presents a innovative technique in which their use Giant Plasma Membrane Vesicles (GPMVs) from a bronchial epithelial cell line as a cell-like alternative to investigate the steps involved in the adhesion process of B. cenocepacia.

Burkholderia cenocepacia is a human contact-dependent pathogenic bacterium known for its capacity of causing severe and persistent opportunistic respiratory infections. The initial contact between bacteria and the human epithelial cells are crucial for the success of the infection. B. cenocepacia uses very complex machinery for primary adherence with host cells. Among those, the class of trimeric autotransporter adhesins (TAAs) deserves particular attention. In this study, published in MicrobiologyOpen, BSRG-iBB researchers Andreia Pimenta, Dalila Mil-Homens and Arsénio M. Fialho demonstrated that BCAM2418, a TAA from the epidemic strain B. cenocepacia K56-2, shows an on–off switch after an initial colonization period, exhibits a strong expression dependent on the host cell type, and enhances its function on cell adhesion. Moreover, this study found that overexpression of BCAM2418 gene contributes to the bacterial cell adhesion to host cells and is dependent on recognition of O‐linked glycans from the host cell membranes. Overall, this study not only defines the behavior of this particular TAA during the step of bacterial adhesion but also provide insights aiming to determine potential targets for therapeutic proposals.

Acinetobacter baumannii is an important nosocomial pathogen resistant to many antibiotics. The relevance of a bacteriophage capsular depolymerase as a therapeutic agent against A. baumannii has now been unveiled by a collaborative work between researchers from BSRG-iBB (Dalila Mil-Homens, Andreia Pimenta, Arsénio M. Fialho) and the group of Joana Azeredo from the University of Minho. The greater wax moth Galleria mellonella and mice were used as animal models to address the therapeutic efficacy of the depolymerase against the infection. Results show that the enzyme makes bacterial cells fully susceptible to the host complement system killing effect. The depolymerase characterized here fits the new trend of alternative antibacterial agents needed against multidrug resistant pathogens. The work was published in Appl. Environ. Microbiol.