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- Structural modification of the Pseudomonas aeruginosa alkylquinoline cell–cell communication signal, HHQ, leads to benzofuranoquinolines with anti-virulence behaviour in ESKAPE pathogensPublication . ROSSETTO, VERONICA; Moore-Machacek, Ay'sha; Woods, David F.; Galvão, Helena M.; Shanahan, Rachel M.; Hickey, Aobha; O’Leary, Niall; O’Gara, Fergal; McGlacken, Gerard P.; Reen, F. JerryMicrobial populations have evolved intricate networks of negotiation and communication through which they can coexist in natural and host ecosystems. The nature of these systems can be complex and they are, for the most part, poorly understood at the polymicrobial level. The Pseudomonas Quinolone Signal (PQS) and its precursor 4- hydroxy- 2-heptylquinoline (HHQ) are signal molecules produced by the important nosocomial pathogen Pseudomonas aeruginosa. They are known to modulate the behaviour of co-colonizing bacterial and fungal pathogens such as Bacillus atropheaus, Candida albicans and Aspergillus fumigatus. While the structural basis for alkyl-quinolone signalling within P. aeruginosa has been studied extensively, less is known about how structural derivatives of these molecules can influ-ence multicellular behaviour and population- level decision-making in other co-colonizing organisms. In this study, we investigated a suite of small molecules derived initially from the HHQ framework, for anti-virulence activity against ESKAPE pathogens, at the species and strain levels. Somewhat surprisingly, with appropriate substitution, loss of the alkyl chain (present in HHQ and PQS) did not result in a loss of activity, presenting a more easily accessible synthetic framework for investigation. Virulence profiling uncovered significant levels of inter-strain variation among the responses of clinical and environmental isolates to small-molecule challenge. While several lead compounds were identified in this study, further work is needed to appreciate the extent of strain- level tolerance to small-molecule anti-infectives among pathogenic organisms.
- Culturable yeast diversity associated with industrial cultures of the microalga microchloropsis gaditana and their ability to produce lipids and biosurfactantsPublication . Matos, Madalena; Fernandes, Mónica A.; Costa, Inês; Coelho, Natacha; Santos, Tamara; Rossetto, Veronica; Varela, João; Sá-Correia, IsabelThe marine oleaginous microalga Microchloropsis gaditana (formerly Nannochloropsis gaditana) exhibits a high capacity to thrive in a broad range of environmental conditions, being predominantly utilized as feed in aquaculture. This article reports the characterization of the culturable yeast population present during the scale-up process of M. gaditana cultivation at Necton S.A. facilities, from 5 L flasks until tubular photobioreactors. The 146 yeast isolates obtained, molecularly identified based on D1/D2 and ITS nucleotide sequences, belong to the species Rhodotorula diobovata, R. mucilaginosa, R. taiwanensis, R. sphaerocarpa, Vishniacozyma carnescens, Moesziomyces aphidis, and Meyerozyma guilliermondii. The yeast abundance was found to increase throughout upscaling stages. The yeast populations isolated from microalgal cultures and water samples share phylogenetically close isolates, indicating a possible common source. The impressive high percentage of red yeasts isolated (90%) is consistent with the recognized role of carotenoid pigments in yeast photoprotection. Sixty yeast isolates were tested for lipid (Nile Red staining) and biosurfactant (oil drop dispersion and emulsification index) production. Results revealed that these capacities are common features. Microbial lipids and biosurfactants have promising biotechnological applications. Moreover, biosurfactants can fulfill various physiological roles and provide advantages in natural environments contributing to the promising use of yeasts as probiotics in microalgae production.
- Tailored bacterial co-cultures improve Tisochrysis lutea growth and nutrient profiles under xenic conditions: a new pathway to improve microalgal productionPublication . Santos, Tamara; da Fonseca Simões, Beatriz; Rossetto, Veronica; Pereira, Hugo; Maia, Inês Beatriz; Oliveira, Marta; Esteves Lopes Navalho, João Carlos; Engelen, Aschwin; Varela, JoãoThe marine haptophyte Tisochrysis lutea is a valuable source of high-value compounds, including polyunsaturated fatty acids like docosahexaenoic acid, and pigments (e.g., fucoxanthin). However, high production costs and variability remain major challenges for its large-scale application in aquaculture, pharmaceuticals, and biotechnology industries. Therefore, strategies to enhance biomass production and quality are actively explored. In natural environments, T. lutea establishes mutualistic interactions with bacteria to obtain essential nutrients such as vitamin B12, yet the role of bacteria in industrial cultures remains poorly understood. In this study, 145 bacterial strains were isolated and taxonomically identified from industrial T. lutea cultures, with members of the class Gammaproteobacteria and Actinomycetia being the most prevalent. Forty isolates were screened individually in co-culture with T. lutea revealing strain-specific effects on growth and biochemical composition. Seven beneficial strains were used to design 21 tailored bacterial blends. Several consortia enhanced biomass production (up to 74 %) and increased key bioactive compounds, particularly methylcobalamin (up to 300 %). These findings demonstrate the potential of tailored bacterial consortia to enhance T. lutea productivity and nutritional quality under production-relevant xenic conditions, enabling strategic microbiome modulation for specific industrial goals.