Transition invariants play an important role in the analysis of Petri nets. They determine cycles within a system. In this paper we present a categorical characterization of transition invariants in algebraic high-level (AHL) nets. Thus, when transforming or composing AHL nets using categorical structuring techniques , a suitable transformation or composition of their invariants becomes possibl...

Quorum sensing (QS) is a means of cell-to-cell communication that uses diffusible signaling molecules that are sensed by the population to determine population density, thus allowing co-ordinate gene regulation in response to population density. In Pseudomonas aeruginosa, production of the QS signaling molecule, N-acyl homoserine lactone (AHL), co-ordinates expression of key factors of pathogen...

Quorum-quenching catalysts are of interest for potential application as biochemical tools for interrogating interbacterial communication pathways, as antibiofouling agents, and as anti-infective agents in plants and animals. Herein, the structure and function of AidC, an N-acyl-l-homoserine lactone (AHL) lactonase from Chryseobacterium, is characterized. Steady-state kinetics show that zinc-sup...

Many pathogenic bacteria use quorum sensing (QS) systems to regulate the expression of virulence genes in a density-dependent manner. In one widespread QS paradigm the enzyme LuxI generates a small diffusible molecule of the acyl-homoserine lactone (AHL) family; high cell densities lead to high AHL levels; AHL binds the transcription factor LuxR, triggering it to activate gene expression at a v...

OBJECTIVE Similar to amblyopia in the visual system, "amblyaudia" is a term used to describe persistent hearing difficulty experienced by individuals with a history of asymmetric hearing loss (AHL) during a critical window of brain development. Few clinical reports have described this phenomenon and its consequent effects on central auditory processing. We aim to (1) define the concept of ambly...

The “classical” approach to represent Petri nets by graph transformation systems is to translate each transition of a specific Petri net to a graph rule (behavior rule). This translation depends on a concrete model and may yield large graph transformation systems as the number of rules depends directly on the number of transitions in the net. Hence, the aim of this paper is to define the behavi...

Pseudomonas syringae pv. tomato strain DC3000, a pathogen of tomato and Arabidopsis, occurs as an epiphyte. It produces N-acyl homoserine lactones (AHLs) which apparently function as quorum-sensing signals. A Tn5 insertion mutant of DC3000, designated PsrA(-) (Psr is for Pseudomonas sigma regulator), overexpresses psyR (a LuxR-type regulator of psyI) and psyI (the gene for AHL synthase), and it...

Certain gram-negative pathogens are known to control virulence gene expression through cell-cell communication via small diffusible signal molecules termed autoinducers. This intercellular signal transduction mechanism termed quorum sensing depends on the interaction of an N-acylhomoserine lactone (AHL) auto-inducer molecule with a receptor protein belonging to the LuxR family of positive trans...

We demonstrate an approach to the surface-mediated release of a synthetic N-acylated L-homoserine lactone (AHL) modulator of bacterial quorum sensing (QS). AHL released gradually from thin films of poly(lactide-co-glycolide) (PLG) is shown to activate QS in the model symbiont Vibrio fischeri at levels that exceed those promoted by direct solution-based administration.

one of ahl al-bayt’s methods of interpretation is the intratextual interpretation or the qur’an to qur’an commentary. this method which is based on the interaction and dialogue between the qur’anic verses, is reflected, to a huge extent, in those narratives of ahl al-bayt regarding qur’anic interpretation. the investigation of these narratives, not only leads to the derivation of ahl al-bayt’s ...