Engineered single- and multi-cell chemotaxis pathways in E. coli

We have engineered the chemotaxis system of Escherichia coli to respond to molecules that are not attractants for wild-type cells. The system depends on an artificially introduced enzymatic activity that converts the target molecule into a ligand for an E. coli chemoreceptor, thereby enabling the cells to respond to the new attractant. Two systems were designed, and both showed robust chemotactic responses in semisolid and liquid media. The first incorporates an asparaginase enzyme and the native E. coli aspartate receptor to produce a response to asparagine; the second uses penicillin acylase and an engineered chemoreceptor for phenylacetic acid to produce a response to phenylacetyl glycine. In addition, by taking advantage of a ‘hitchhiker' effect in which cells producing the ligand can induce chemotaxis of neighboring cells lacking enzymatic activity, we were able to design a more complex system that functions as a simple microbial consortium. The result effectively introduces a logical ‘AND' into the system so that the population only swims towards the combined gradients of two attractants

Critical review on biofilm methods

Biofilms are widespread in nature and constitute an important strategy implemented by microorganisms to survive in sometimes harsh environmental conditions. They can be beneficial or have a negative impact particularly when formed in industrial settings or on medical devices. As such, research into the formation and elimination of biofilms is important for many disciplines. Several new methodologies have been recently developed for, or adapted to, biofilm studies that have contributed to deeper knowledge on biofilm physiology, structure and composition. In this review, traditional and cutting-edge methods to study biofilm biomass, viability, structure, composition and physiology are addressed. Moreover, as there is a lack of consensus among the diversity of techniques used to grow and study biofilms. This review intends to remedy this, by giving a critical perspective, highlighting the advantages and limitations of several methods. Accordingly, this review aims at helping scientists in finding the most appropriate and up-to-date methods to study their biofilms.The authors would like to acknowledge the support from the EU COST Action BacFoodNet FA1202

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

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Model</p> <p>We mathematically model quorum sensing and EPS production in a growing biofilm under various environmental conditions, to study how a developing biofilm impacts quorum sensing, and conversely, how a biofilm is affected by quorum sensing-regulated EPS production. We investigate circumstances when using quorum-sensing regulated EPS production is a beneficial strategy for biofilm cells.</p> <p>Results</p> <p>We find that biofilms that use quorum sensing to induce increased EPS production do not obtain the high cell populations of low-EPS producers, but can rapidly increase their volume to parallel high-EPS producers. Quorum sensing-induced EPS production allows a biofilm to switch behaviours, from a colonization mode (with an optimized growth rate), to a protection mode.</p> <p>Conclusions</p> <p>A biofilm will benefit from using quorum sensing-induced EPS production if bacteria cells have the objective of acquiring a thick, protective layer of EPS, or if they wish to clog their environment with biomass as a means of securing nutrient supply and outcompeting other colonies in the channel, of their own or a different species.</p

Influence of Uranium on Bacterial Communities: A Comparison of Natural Uranium-Rich Soils with Controls

This study investigated the influence of uranium on the indigenous bacterial community structure in natural soils with high uranium content. Radioactive soil samples exhibiting 0.26% - 25.5% U in mass were analyzed and compared with nearby control soils containing trace uranium. EXAFS and XRD analyses of soils revealed the presence of U(VI) and uranium-phosphate mineral phases, identified as sabugalite and meta-autunite. A comparative analysis of bacterial community fingerprints using denaturing gradient gel electrophoresis (DGGE) revealed the presence of a complex population in both control and uranium-rich samples. However, bacterial communities inhabiting uraniferous soils exhibited specific fingerprints that were remarkably stable over time, in contrast to populations from nearby control samples. Representatives of Acidobacteria, Proteobacteria, and seven others phyla were detected in DGGE bands specific to uraniferous samples. In particular, sequences related to iron-reducing bacteria such as Geobacter and Geothrix were identified concomitantly with iron-oxidizing species such as Gallionella and Sideroxydans. All together, our results demonstrate that uranium exerts a permanent high pressure on soil bacterial communities and suggest the existence of a uranium redox cycle mediated by bacteria in the soil

Efficacy Enhancement of Trisodium Phosphate against spoilage and pathogenic bacteria in model biofilms and on adipose tissue

NatuurwetenskappeMikrobiologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Methanogenic digestion of <I>Lignocellulose </I>residues under conditions of high-rate acidogenic fermentation

IngenieursweseProsesingenieurswesePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Shifts in community composition provide a mechanism for maintenance of activity of soil yeasts in the presence of elevated copper levels

NatuurwetenskappeMikrobiologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Effect of bacteriocins pediocin PD-1, plantaricin 423, and Nisin on biofilms of <I>Oenococcus oeni </I>on a stainless steel surface.

NatuurwetenskappeMikrobiologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Dynamics of a microbial biofilm in a rotating biological contactor for the treatment of winery effluent

Wastewater from wine-related industries is characterised by high variability in COD and pH. Disposal of these effluents with little or no treatment could lead to heavy financial penalties or pollution of soil and water resources. A pilot-scale rotating biological contactor (RBC) was evaluated for the treatment of winery effluent, with specific focus on the biofilms that formed on the RBC discs. On average, the RBC reduced the influent COD of the winery effluent by 23% (from 3 828 mg/&#8467; to 2 910 mg/&#8467;) and increased the pH by 0.95 units (from 5.77 to 6.13) at an average retention time of 1h. Similar results were obtained during evaluations at a wine-bottling plant where thick active biofilms, containing mostly yeasts, formed on the discs and proved stable and resilient to various physical and chemical shocks. WaterSA Vol.30 (3) 2004: 407-41