TiO2 nanoparticles alter iron homeostasis in Pseudomonas brassicacearum as revealed by PrrF sRNA modulation

TiO2 nanoparticles induced oxidant stress and altered iron homeostasis without having any impact on soil bacterium growth under dark conditions.

Stochastic Resonance in a Bacterium Growth System with Time Delay and Colored Noise

The phenomenon of stochastic resonance in a bacterium growth system that is with two different kinds of time delays and is driven by colored noises is investigated. Based on the extended unified colored noise theory and the method of the probability density approximation, the Fokker–Planck equation and the stationary probability density function are derived. Then via the theory of adiabatic limit, the analytical expression of the signal-to-noise ratio (SNR) is obtained. The different effects of the time delays existed in the nonlinear system and the noise correlation times on the stationary probability density and the signal-to-noise rate are discussed respectively. Finally, numerical simulations are offered and are consistent with approximate analytical results.

Improvement of Anaerobic Operation and Isolation Culture on Hydrogen-Producing and Fermentative Bacteria

Isolation and culture of hydrogen-producing and fermentative bacteria is an important foundation on biohydrogen production process. There are complicated operation and composition in present anaerobic techniques and culture media. Hungate technique was improved and plate of culture bottle was established by comparing anaerobic methods and bacterium growth. Isolation and enrichment culture media were confirmed by the test of different composition and the species and amount of hydrogen-producing and fermentative bacterium. 550 bacterium strains were isolated by the anaerobic operation.

THE GROWTH OF BACTERIOPHAGE

1. An anti-Escherichia coli phage has been isolated and its behavior studied. 2. A plaque counting method for this phage is described, and shown to give a number of plaques which is proportional to the phage concentration. The number of plaques is shown to be independent of agar concentration, temperature of plate incubation, and concentration of the suspension of plating bacteria. 3. The efficiency of plating, i.e. the probability of plaque formation by a phage particle, depends somewhat on the culture of bacteria used for plating, and averages around 0.4. 4. Methods are described to avoid the inactivation of phage by substances in the fresh lysates. 5. The growth of phage can be divided into three periods: adsorption of the phage on the bacterium, growth upon or within the bacterium (latent period), and the release of the phage (burst). 6. The rate of adsorption of phage was found to be proportional to the concentration of phage and to the concentration of bacteria. The rate constant ka is 1.2 x 10–9 cm.8/min. at 15°C. and 1.9 x 10–9 cm.8/min. at 25°. 7. The average latent period varies with the temperature in the same way as the division period of the bacteria. 8. The latent period before a burst of individual infected bacteria varies under constant conditions between a minimal value and about twice this value. 9. The average latent period and the average burst size are neither increased nor decreased by a fourfold infection of the bacteria with phage. 10. The average burst size is independent of the temperature, and is about 60 phage particles per bacterium. 11. The individual bursts vary in size from a few particles to about 200. The same variability is found when the early bursts are measured separately, and when all the bursts are measured at a late time.