Biology subjects

Heddi, B.

Publications and source records attributed to Heddi, B..

3 recordsLinked to original sources

bioRxiv2025

Biotope-dependent High Level Resistance to Reactive Oxygen Species, Antibiotic Tolerance, and Virulence of Staphylococcus aureus

The human and livestock pathogen Staphylococcus aureus poses a major clinical challenge due to antibiotic treatment failure. Its resilience is mainly attributed to antibiotic resistance and tolerance mechanisms related to persistence. Here we investigate how two infection-relevant biotopes, milk and serum, shape S. aureus pathogenic properties and capacity to withstand environmental stresses. Milk-versus serum-adapted bacteria show gross differences in envelope physical properties, membrane fatty acid composition and rigidity, and pigment production, and display distinct proteomic profiles. Compared to serum, milk adaptation of S. aureus confers extreme resistance to ROS damage, pronounced antimicrobial tolerance, and accelerated killing in an insect infection model. High level S. aureus pigmentation in whole milk is stimulated by milk lipids, and is responsible for high ROS resistance. The remarkable robustness of S. aureus in a milk biotope may signal the need to adjust antibiotic regimens when treating mastitis infections in humans and livestock.

microbiology↗

bioRxiv2025

Improving Electrochemical Aptasensor Sensitivity for Bacillus cereus Spore Detection in Food Safety Applications

Rapid detection of Bacillus cereus spores is critical for preventing food contamination and spoilage. Many existing methods detect B. cereus cells instead of spores, and cannot be applied directly in foods. Here, combination of aptamers that bind different moieties at the surface of B. cereus spore with rapid electrochemical detection is presented. When different DNA aptamers were immobilized on screen printed gold electrode, they showed higher binding capacity for B. cereus spores than individual aptamers suggesting a synergic effect. The biosensor exhibited a wide dynamic range (102 - 107 CFU/mL) of low limits of detection ([~]1 CFU/mL) using just 15 L of sample. Validation in spiked salad, using direct spore sensing in rinse water and comparing it to the culturing method, confirmed its sensitivity and specificity. This aptamer-combined approach achieving the rapid (15 min) and single-step detection may also be suitable for detecting other foodborne pathogens.

microbiology↗

bioRxiv2020

Harnessing intrinsic fluorescence for typing of secondary structures of DNA

DNA is polymorphic since, despite its ubiquitous presence as a double-stranded helix, it is able to fold into a plethora of other secondary structures both in vitro and in cells. Despite the considerable advances that have been made in understanding this structural diversity, its high-throughput investigation still faces severe limitations. This mainly stems from the lack of suitable label-free methods, combining a fast and cheap experimental workflow with high information content. Here, we explore the use of intrinsic fluorescence emitted by nucleic acids for this scope. After a preliminary assessment of the suitability of this phenomenon for tracking the conformational changes of DNA, we examined the intrinsic steady-state emission spectra of an 89-membered set of synthetic oligonucleotides with reported conformation (G-quadruplexes, i-motifs, single- and double stranded DNA) by means of multivariate analysis. Specifically, principal component analysis of emission spectra resulted in successful clustering of oligonucleotides into three corresponding conformational groups, albeit without discrimination between single- and double-stranded structures. Linear discriminant analysis of the same training set was exploited for the assessment of new sequences, allowing the evaluation of their G4-forming propensity. Our method does not require any labelling agent or dye, avoiding the related intrinsic bias, and can be utilized to screen novel sequences of interest in a high-throughput and cost-effective manner. In addition, we observed that left-handed (Z-) G4 structures were systematically more fluorescent than most other G4 structures, almost reaching the quantum yield of 5'-d[(G3T)3G3]-3' (G3T), the most fluorescent G4 structure reported to date. This property is likely to arise from the similar base-stacking geometry in both types of structures.

biophysics↗