Interaction between long and short particles of tobacco rattle virus

Tobacco rattle virus is a rod-shaped multiparticle virus.Short particles alone are not infectious, long ones are but give rise to the formation of incomplete virus. Mixtures of long and short particles induce the formation of complete virus. The interaction between long and short particles is not strain-specific: if long and short particles of different strains are inoculated together complete virus is also formed. These new strains have properties of both parent strains.The interaction between heterologous long and short particles explains why there are so many different tobacco rattle virus isolates and why no correlation can be found between classifications based on different characteristics

Artificial Neural Networks in Medicine and Biology. A philosophical introduction

Bacillus subtilis possesses a secondary transporter, CitM, that is specific for the complex of citrate and Mg2+ but is also capable of transporting citrate in complex with the heavy metal ions Zn2+, Ni2+ and Co2+. We report on the impact of CitM activity on the toxicity of Zn2+, Ni2+ and Co2+ in B. subtilis. In a citM deletion mutant or under conditions in which CitM is not expressed, the toxic effects of the metals were reduced by the presence of citrate in the medium. In contrast, the presence of citrate dramatically enhanced toxicity when the Mg2+-citrate transporter was present in the membrane. It is demonstrated that the complex of Ni2+ and citrate is transported into the cell and that the uptake is responsible for the enhanced toxicity. At toxic concentrations of the metal ions, the cultures adapted by developing tolerance against these ions. Tolerant cells isolated by exposure to one of the metal ions remained tolerant after growth in the absence of toxic metal ions and were cross-tolerant against the other two toxic ions. Tolerant strains were shown to contain point mutations in the citM gene, which resulted in premature termination of translation