Flow cytometry and capillary electrophoresis analyses in ethanol-stressed Oenococcus oeni strains and changes assessment of membrane fatty acid composition.

AIMS: This study aimed to investigate the dynamics and physiological heterogeneity of Oenococcus oeni under different conditions, cell membrane fluidity and permeability variations, and assessment of changes in cell surface charging rates. METHODS AND RESULTS: Flow cytometry, membrane fatty acid analysis and capillary electrophoresis were performed to study ethanol-induced variations. Different physiological states were assessed, revealing cell subpopulations able to adapt and withstand to environmental stress, in order to recover their functionality. Moreover, total results demonstrated changes in cell surface and membrane fatty acid redistribution with a saturation degree and an unsaturated/saturated fatty acid ratio fairly steady in control and in different ethanol stresses. CONCLUSIONS: This study revealed a great variability among O. oeni strains and the importance to investigate the mechanisms by a multiparametric approach based on the structural and physiological bacterial adjustments in different stresses tolerance. SIGNIFICANCE AND IMPACT OF THE STUDY: Intermediate physiological state assessment in O. oeni with recovery possibility could be an important criterion for potential starter culture application. The flow cytometry application with changes in monitoring membrane fatty acid composition and in surface charging rates allowed the characterization of sorted subpopulations that may contribute to further understanding of diversity and heterogeneity in physiology of bacterial populations.

Design of a dual aptamer-based recognition strategy for human matrix metalloproteinase 9 protein by piezoelectric biosensors.

MMP-9, human matrix metalloproteinase 9, belongs to the family of zinc-dependent peptide-bond hydrolases and is involved in the degradation of the extracellular matrix (ECM). In clinics, it is well known that elevated MMP-9 serum levels are associated with cardiovascular dysfunctions, several aspects of the physiology and pathology of the central nervous system, neuropsychiatric disorders and degenerative diseases related to brain tumors, and excitotoxic/neuroinflammatory processes. Due to the large interest of diagnostics in this protein, efforts to set up sensitive methods to detect MMP-9 for early diagnosis of a number of metabolic alterations are rapidly increasing. In this panorama, biosensors could play a key role; therefore we explored for the first time the development of an aptamer-based piezoelectric biosensor for a sensitive, label free, and real time detection of MMP-9. The detecting strategy involved two different aptamers in a sandwich-like approach able to detect down to 100 pg mL(-1) (1.2 pM) of MMP-9 as detection limit in standard solution. As proof of principle, commercial serum was investigated in terms of possible interferents, their identification and role in MMP-9 detection. The estimated detection limit for MMP-9 is about 560 pg mL(-1) (6.8 pM) in untreated serum.