Browsing by Author "Azevedo, Nuno F."

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Biofilms vs. cities and humans vs. aliens – a tale of reproducibility in biofilms
(Elsevier BV, 2021-06) Azevedo, Nuno F.; Allkja, Jontana; Goeres, Darla M.
In recent decades the scientific community has started to appreciate that most microorganisms live in complex 3D structures composed of cells, polysaccharides, and other components such as proteins, extracellular (e)DNA, and lipids. These structures are commonly designated 'biofilms'. Similar to other areas of research, biofilm studies have been affected by a lack of reproducibility. In this article, we propose a new scheme on how to classify the level of reproducibility in biofilms. This consists of four different levels: level 1, no reproducibility; level 2, standard reproducibility; level 3, potential standard reproducibility; and level 4, total reproducibility. Some methods aim to improve reproducibility by focusing on biofilm growth reactors, while others focus on biofilm characterization methods. Moreover, initiatives such as minimum information guidelines and biofilm-centered databases offer alternative strategies to tackle the reproducibility problem. The path to total reproducibility is certainly complex, but novel experimental and computational strategies are bringing us closer to achieving this goal.
Ecology of Legionella pneumophila biofilms: The link between transcriptional activity and the biphasic cycle
(Elsevier BV, 2024-06) Barbosa, Ana; Azevedo, Nuno F.; Goeres, Darla M.; Cerqueira, Laura
There has been considerable discussion regarding the environmental life cycle of Legionella pneumophila and its virulence potential in natural and man-made water systems. On the other hand, the bacterium's morphogenetic mechanisms within host cells (amoeba and macrophages) have been well documented and are linked to its ability to transition from a non-virulent, replicative state to an infectious, transmissive state. Although the morphogenetic mechanisms associated with the formation and detachment of the L. pneumophila biofilm have also been described, the capacity of the bacteria to multiply extracellularly is not generally accepted. However, several studies have shown genetic pathways within the biofilm that resemble intracellular mechanisms. Understanding the functionality of L. pneumophila cells within a biofilm is fundamental for assessing the ecology and evaluating how the biofilm architecture influences L. pneumophila survival and persistence in water systems. This manuscript provides an overview of the biphasic cycle of L. pneumophila and its implications in associated intracellular mechanisms in amoeba. It also examines the molecular pathways and gene regulation involved in L. pneumophila biofilm formation and dissemination. A holistic analysis of the transcriptional activities in L. pneumophila biofilms is provided, combining the information of intracellular mechanisms in a comprehensive outline. Furthermore, this review discusses the techniques that can be used to study the morphogenetic states of the bacteria within biofilms, at the single cell and population levels.
Ecology of Legionella pneumophila biofilms: The link between transcriptional activity and the biphasic cycle
(Elsevier BV, 2024-06) Barbosa, Ana; Azevedo, Nuno F.; Goeres, Darla M.; Cerqueira, Laura
There has been considerable discussion regarding the environmental life cycle of Legionella pneumophila and its virulence potential in natural and man-made water systems. On the other hand, the bacterium's morphogenetic mechanisms within host cells (amoeba and macrophages) have been well documented and are linked to its ability to transition from a non-virulent, replicative state to an infectious, transmissive state. Although the morphogenetic mechanisms associated with the formation and detachment of the L. pneumophila biofilm have also been described, the capacity of the bacteria to multiply extracellularly is not generally accepted. However, several studies have shown genetic pathways within the biofilm that resemble intracellular mechanisms. Understanding the functionality of L. pneumophila cells within a biofilm is fundamental for assessing the ecology and evaluating how the biofilm architecture influences L. pneumophila survival and persistence in water systems. This manuscript provides an overview of the biphasic cycle of L. pneumophila and its implications in associated intracellular mechanisms in amoeba. It also examines the molecular pathways and gene regulation involved in L. pneumophila biofilm formation and dissemination. A holistic analysis of the transcriptional activities in L. pneumophila biofilms is provided, combining the information of intracellular mechanisms in a comprehensive outline. Furthermore, this review discusses the techniques that can be used to study the morphogenetic states of the bacteria within biofilms, at the single cell and population levels.
Interactions of microorganisms within a urinary catheter polymicrobial biofilm model
(Wiley, 2022-09) Allkja, Jontana; Goeres, Darla M.; Azevedo, Andreia S.; Azevedo, Nuno F.
Biofilms are often polymicrobial in nature, which can impact their behavior and overall structure, often resulting in an increase in biomass and enhanced antimicrobial resistance. Using plate counts and locked nucleic acid/2′-O-methyl-RNA fluorescence in situ hybridization (LNA/2′OMe-FISH), we studied the interactions of four species commonly associated with catheter-associated urinary tract infections (CAUTI): Enterococcus faecalis, Escherichia coli, Candida albicans, and Proteus mirabilis. Eleven combinations of biofilms were grown on silicone coupons placed in 24-well plates for 24 h, 37°C, in artificial urine medium (AUM). Results showed that P. mirabilis was the dominant species and was able to inhibit both E. coli and C. albicans growth. In the absence of P. mirabilis, an antagonistic relationship between E. coli and C. albicans was observed, with the former being dominant. E. faecalis growth was not affected in any combination, showing a more mutualistic relationship with the other species. Imaging results correlated with the plate count data and provided visual verification of species undetected using the viable plate count. Moreover, the three bacterial species showed overall good repeatability SD (Sr) values (0.1–0.54) in all combinations tested, whereas C. albicans had higher repeatability Sr values (0.36–1.18). The study showed the complexity of early-stage interactions in polymicrobial biofilms. These interactions could serve as a starting point when considering targets for preventing or treating CAUTI biofilms containing these species.