Friend and foe: factors influencing the movement of the bacterium Helicobacter pylori along the parasitism-mutualism continuum.

Understanding the transition of bacterial species from commensal to pathogen, or vice versa, is a key application of evolutionary theory to preventative medicine. This requires working knowledge of the molecular interaction between hosts and bacteria, ecological interactions among microbes, spatial variation in bacterial prevalence or host life history, and evolution in response to these factors. However, there are very few systems for which such broad datasets are available. One exception is the gram-negative bacterium, Helicobacter pylori, which infects upwards of 50% of the global human population. This bacterium is associated with a wide breadth of human gastrointestinal disease, including numerous cancers, inflammatory disorders, and pathogenic infections, but is also known to confer fitness benefits to its host both indirectly, through interactions with other pathogens, and directly. Outstanding questions are therefore why, when, and how this bacterium transitions along the parasitism-mutualism continuum. We examine known virulence factors, genetic predispositions of the host, and environmental contributors that impact progression of clinical disease and help define geographical trends in disease incidence. We also highlight the complexity of the interaction and discuss future therapeutic strategies for disease management and public health in light of the longstanding evolutionary history between the bacterium and its human host

Dissipative Shocks behind Bacteria Gliding

Gliding is a means of locomotion on rigid substrates utilized by a number of bacteria includingmyxobacteria and cyanobacteria. One of the hypotheses advanced to explain this motility mechanism hinges on the role played by the slime filaments continuously extruded from gliding bacteria. This paper solves in full a non-linear mechanical theory that treats as dissipative shocks both the point where the extruded slime filament comes in contact with the substrate, called the filament's foot, and the pore on the bacterium outer surface from where the filament is ejected. We prove that kinematic compatibility for shock propagation requires that the bacterium uniform gliding velocity (relative to the substrate) and the slime ejecting velocity (relative to the bacterium) must be equal, a coincidence that seems to have already been observed.Comment: arXiv admin note: text overlap with arXiv:1402.636

Degradation of reactive red 195 by selected bacteria from textile wastewater

Four selected bacterial strains coded R1, R2, Rc and Rd were successfully isolated from raw textile wastewater. They were screened for their ability to degrade an azo dye of Reactive Red 195 on solid and in liquid dye-containing media. Screening showed that decolourization was best performed under anaerobic condition with the highest colour removal (˜70%) showed by bacterium R2. The partial 16S ribosomal ribonucleic acid (16S rRNA) sequence of bacterium R2 shared 98% sequence similarity to Paenibacillus sp.. Decolourization by this bacterium in a chemically defined medium containing (gL-1) of glucose (1), NH4Cl (0.5), K2HPO4 (7), KH2PO4 (2), MgSO4.7H2O (0.1), CaCl2 (0.02), and Reactive red 195 (0.1), adjusted to pH7 and with (10% v/v) inoculum occurred under partial anaerobic condition at temperature of 37°C. Under optimized condition, bacterium R2 successfully removed more than 95% colour and up to 50% of total organic carbon. No significant change in pH was observed (pH from 7.21 to 7.25) though the anaerobiosis was found to be developed throughout the experiment (redox potential reduced from 2.5 to 0.5 mV). This bacterium produced intracellular (0.033 U/mL) and extracellular (0.026 U/mL) azoreductase enzymes which were found to be stable at pH from 6 to 8 and temperature ranging from 30 ºC to 40ºC. High performance liquid chromatography analysis revealed that biodegradation of Reactive Red 195 under partial anaerobic condition produced at least three types of sulfonated amines which were 4-aminobenzenesulphonic acid (sulphanilic acid), 4-amino-3- hydronapthalenesulphonic acid and 4-amino-5-hydronapthalene-2,7disulphonic acid. The sulphanilic acid can be further degraded to a-ketoglutaric acid, a common Krebs cycle’s intermediate in most aerobic microorganism. Therefore, it can be concluded that the Paenibacillus sp. is of good potential use for the treatment of azo dye-containing wastewater based on its ability to remove colour

Modelling the Mechanics and Hydrodynamics of Swimming E. coli

The swimming properties of an E. coli-type model bacterium are investigated by mesoscale hy- drodynamic simulations, combining molecular dynamics simulations of the bacterium with the multiparticle particle collision dynamics method for the embedding fluid. The bacterium is com- posed of a spherocylindrical body with attached helical flagella, built up from discrete particles for an efficient coupling with the fluid. We measure the hydrodynamic friction coefficients of the bacterium and find quantitative agreement with experimental results of swimming E. coli. The flow field of the bacterium shows a force-dipole-like pattern in the swimming plane and two vor- tices perpendicular to its swimming direction arising from counterrotation of the cell body and the flagella. By comparison with the flow field of a force dipole and rotlet dipole, we extract the force- dipole and rotlet-dipole strengths for the bacterium and find that counterrotation of the cell body and the flagella is essential for describing the near-field hydrodynamics of the bacterium

Persistent and susceptible bacteria with individual deaths

The aim of this paper is to study two models for a bacterial population subject to antibiotic treatments. It is known that some bacteria are sensitive to antibiotics. These bacteria are in a state called persistence and each bacterium can switch from this state to a non-persistent (or susceptible) state and back. Our models extend those introduced in [6] by adding a (random) natural life cycle for each bacterium and by allowing bacteria in the susceptible state to escape the action of the antibiotics with a fixed probability 1-p (while every bacterium in a persistent state survives with probability 1). In the first model we "inject" the antibiotics in the system at fixed, deterministic times while in the second one the time intervals are random. We show that, in order to kill eventually the whole bacterial population, these time intervals cannot be "too large". The maximum admissible length is increasing with respect to p and it decreases rapidly when p<1.Comment: 14 pages, 5 figures, corrected some misprint

Anaerobic degradation of dimethylsulfoniopropionate to 3-S-methylmercaptopropionate by a marine Desulfobacterium strain

Dimethylsulfoniopropionate, an osmolyte of marine algae, is thought to be the major precursor of dimethyl sulfide, which plays a dominant role in biogenic sulfur emission. The marine sulfate-reducing bacterium Desulfobacterium strain PM4 was found to degrade dimethylsulfoniopropionate to 3-S-methylmercaptopropionate. The oxidation of one of the methyl groups of dimethylsulfoniopropionate was coupled to the reduction of sulfate; this process is similar to the degradation of betaine to dimethylglycine which was described earlier for the same strain. Desulfobacterium PM4 is the first example of an anaerobic marine bacterium that is able to demethylate dimethylsulfoniopropionate.

Isoprene oxidation by the gram-negative model bacterium variovorax sp. WS11

Plant-produced isoprene (2-methyl-1,3-butadiene) represents a significant portion of global volatile organic compound production, equaled only by methane. A metabolic pathway for the degradation of isoprene was first described for the Gram-positive bacterium Rhodococcus sp. AD45, and an alternative model organism has yet to be characterised. Here, we report the characterisation of a novel Gram-negative isoprene-degrading bacterium, Variovorax sp. WS11. Isoprene metabolism in this bacterium involves a plasmid-encoded iso metabolic gene cluster which differs from that found in Rhodococcus sp. AD45 in terms of organisation and regulation. Expression of iso metabolic genes is significantly upregulated by both isoprene and epoxyisoprene. The enzyme responsible for the initial oxidation of isoprene, isoprene monooxygenase, oxidises a wide range of alkene substrates in a manner which is strongly influenced by the presence of alkyl side-chains and differs from other well-characterised soluble diiron monooxygenases according to its response to alkyne inhibitors. This study presents Variovorax sp. WS11 as both a comparative and contrasting model organism for the study of isoprene metabolism in bacteria, aiding our understanding of the conservation of this biochemical pathway across diverse ecological niches