Evolutionary Stabilization of Cooperative Toxin Production through a Bacterium-Plasmid-Phage Interplay.

Colicins are toxins produced and released by to kill competitors in the gut. While group A colicins employ a division of labor strategy to liberate the toxin into the environment via colicin-specific lysis, group B colicin systems lack cognate lysis genes. In serovar Typhimurium ( Tm), the group B colicin Ib (ColIb) is released by temperate phage-mediated bacteriolysis.

Simulation-Based Exploration of Quorum Sensing Triggered Resistance of Biofilms to Antibiotics.

We present a mathematical model of biofilm response to antibiotics, controlled by a quorum sensing system that confers increased resistance. The model is a highly nonlinear system of partial differential equations that we investigate in computer simulations. Our results suggest that an adaptive, quorum sensing-controlled, mechanism to switch between modes of fast growth with little protection and protective modes of slow growth may confer benefits to biofilm populations.

Differential Equations Models to Study Quorum Sensing.

Mathematical models to study quorum sensing (QS) have become an important tool to explore all aspects of this type of bacterial communication. A wide spectrum of mathematical tools and methods such as dynamical systems, stochastics, and spatial models can be employed. In this chapter, we focus on giving an overview of models consisting of differential equations (DE), which can be used to describe changing quantities, for example, the dynamics of one or more signaling molecule in time and space, often in conjunction with bacterial growth dynamics.

Selection of Functional Quorum Sensing Systems by Lysogenic Bacteriophages in .

Quorum sensing (QS) in coordinates the expression of virulence factors, some of which are used as public goods. Since their production is a cooperative behavior, it is susceptible to social cheating in which non-cooperative QS deficient mutants use the resources without investing in their production. Nevertheless, functional QS systems are abundant; hence, mechanisms regulating the amount of cheating should exist.

Corrigendum: Why Quorum Sensing Controls Private Goods.

[This corrects the article on p. 885 in vol. 8, PMID: 28579979.

Why Quorum Sensing Controls Private Goods.

Cell-cell communication, also termed quorum sensing (QS), is a widespread process that coordinates gene expression in bacterial populations. The generally accepted view is that QS optimizes the cell density-dependent benefit attained from cooperative behaviors, often in the form of secreted products referred to as "public goods." This view is challenged by an increasing number of cell-associated products or "private goods" reported to be under QS-control for which a collective benefit is not apparent.

A Mathematical Model of Quorum Sensing Induced Biofilm Detachment.

Background: Cell dispersal (or detachment) is part of the developmental cycle of microbial biofilms. It can be externally or internally induced, and manifests itself in discrete sloughing events, whereby many cells disperse in an instance, or in continuous slower dispersal of single cells. One suggested trigger of cell dispersal is quorum sensing, a cell-cell communication mechanism used to coordinate gene expression and behavior in groups based on population densities.

Core principles of bacterial autoinducer systems.

Autoinduction (AI), the response to self-produced chemical signals, is widespread in the bacterial world. This process controls vastly different target functions, such as luminescence, nutrient acquisition, and biofilm formation, in different ways and integrates additional environmental and physiological cues. This diversity raises questions about unifying principles that underlie all AI systems.

An approximative approach for single cell spatial modeling of quorum sensing.

Quorum sensing, a special kind of cell-cell communication, has originally been described for well-mixed homogeneous bacterial cultures. However, recent perception supports its ecological relevance for spatially heterogeneous distributed cells, like colonies and biofilms. New experimental techniques allow for single cell analysis under these conditions, which is crucial to understanding the effect of chemical gradients and intercell variations.

Modelling and analysis of a gene-regulatory feed-forward loop with basal expression of the second regulator.

Efficient adaptation strategies to changing environmental conditions are essential for bacteria to survive and grow. Fundamental restructuring of their metabolism is usually mediated by corresponding gene regulation. Here, often several different environmental stimuli have to be integrated into a reasonable, energy-efficient response.

Analysis of N-acylhomoserine lactone dynamics in continuous cultures of Pseudomonas putida IsoF by use of ELISA and UHPLC/qTOF-MS-derived measurements and mathematical models.

In this interdisciplinary approach, the dynamics of production and degradation of the quorum sensing signal 3-oxo-decanoylhomoserine lactone were studied for continuous cultures of Pseudomonas putida IsoF. The signal concentrations were quantified over time by use of monoclonal antibodies and ELISA. The results were verified by use of ultra-high-performance liquid chromatography.

Evidence of autoinducer-dependent and -independent heterogeneous gene expression in Sinorhizobium fredii NGR234.

Populations of genetically identical Sinorhizobium fredii NGR234 cells differ significantly in their expression profiles of autoinducer (AI)-dependent and AI-independent genes. Promoter fusions of the NGR234 AI synthase genes traI and ngrI showed high levels of phenotypic heterogeneity during growth in TY medium on a single-cell level. However, adding very high concentrations of N-(3-oxooctanoyl-)-l-homoserine lactone resulted in a more homogeneous expression profile.

Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22.

The non-essential cation caesium (Cs(+)) is assimilated by all organisms. Thus, anthropogenically released radiocaesium is of concern to agriculture. Cs(+) accumulates owing to its chemical similarity to the potassium ion (K(+)).

Dynamics of glucose and insulin concentration connected to the β-cell cycle: model development and analysis.

Background: Diabetes mellitus is a group of metabolic diseases with increased blood glucose concentration as the main symptom. This can be caused by a relative or a total lack of insulin which is produced by the β-cells in the pancreatic islets of Langerhans. Recent experimental results indicate the relevance of the β-cell cycle for the development of diabetes mellitus.

Spatial heterogeneity of autoinducer regulation systems.

Autoinducer signals enable coordinated behaviour of bacterial populations, a phenomenon originally described as quorum sensing. Autoinducer systems are often controlled by environmental substances as nutrients or secondary metabolites (signals) from neighbouring organisms. In cell aggregates and biofilms gradients of signals and environmental substances emerge.

Dynamics of AHL mediated quorum sensing under flow and non-flow conditions.

Quorum sensing (QS) describes the capability of microbes to communicate with each other by the aid of small molecules. Here we investigate the dynamics of QS-regulated gene expression induced by acylhomoserine lactones (AHLs) in Pseudomonas putida IsoF containing a green fluorescent protein-based AHL reporter. The fluorescence time course of individual colonies is monitored following the external addition of a defined AHL concentration to cells which had previously reached the QS-inactive state in AHL-free medium.

A mathematical model of quorum sensing regulated EPS production in biofilm communities.

Background: Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS). The EPS matrix provides several functional purposes for the biofilm, such as protecting bacteria from environmental stresses, and providing mechanical stability. Quorum sensing is a cell-cell communication mechanism used by several bacterial taxa to coordinate gene expression and behaviour in groups, based on population densities.

Degradation capacity of a 1,2,4-trichlorobenzene mineralizing microbial community for traces of organochlorine pesticides.

A soil-borne microbial community isolated from a contaminated site was previously shown to mineralize 1,2,4-trichlorobenzene (1,2,4-TCB) under aerobic conditions. The key degrader in this community was identified as Bordetella sp. F2.

A mathematical model of mitochondrial swelling.

Background: The permeabilization of mitochondrial membranes is a decisive event in apoptosis or necrosis culminating in cell death. One fundamental mechanism by which such permeabilization events occur is the calcium-induced mitochondrial permeability transition. Upon Ca2+-uptake into mitochondria an increase in inner membrane permeability occurs by a yet unclear mechanism.

Dynamic regulation of N-acyl-homoserine lactone production and degradation in Pseudomonas putida IsoF.

The biocontrol strain Pseudomonas putida IsoF, which was isolated from a tomato rhizosphere, is a known N-acyl-homoserine lactone (AHL) producer with only one LuxI/LuxR-like quorum-sensing (QS) system. The production and degradation of AHLs were analysed in different growth phases of the bacterium. Using the analytical tools of ultra performance liquid chromatography and high resolution MS, it was possible to determine not only the various AHLs synthesized over time but also their degradation products.

Transcription, intercellular variability and correlated random walk.

We develop a simple model for the random distribution of a gene product. It is assumed that the only source of variance is due to switching transcription on and off by a random process. Under the condition that the transition rates between on and off are constant we find that the amount of mRNA follows a scaled Beta distribution.

Sensitivity of the quorum sensing system is achieved by low pass filtering.

Autoinducer sensing, also known as quorum sensing, is the communication of bacteria by autoinducer (small signaling molecules). Cells respond on extremely low concentrations of autoinducer: only one or two molecules per cell are sufficient. At this signal level a high degree of noise is inherent.