Purification capability of tobacco transformed with enzymes from a methylotrophic bacterium for formaldehyde.

Plants have the ability to remediate environmental pollution. Especially, they have a high purification capability for airpollution. We have measured the purification characteristics of foliage plants for indoor airpollutants--for example, formaldehyde (HCHO), toluene, and xylene--using a tin oxide gas sensor. HCHO is an important intermediate for biological fixation of C1 compounds in methylotrophs. The ribulose monophosphate pathway of HCHO fixation is inherent in many methylotrophic bacteria, which can grow on Cl compounds. Two genes for the key enzymes, HPS and PHI, from the methylotrophic bacterium Mycobacterium gastri MB19 were introduced into tobacco. In this article, the HCHO-removal characteristic of the transformant was examined by using the gas sensor in order to evaluate quantitatively. The purification characteristics of the transformant for toluene, xylene, and styrene were also measured. The results confirmed an increase of 20% in the HCHO-removal capability. The differences of the purification capabilities for toluene, xylene, and styrene were not recognized.

Modeling rhl quorum-sensing regulation on rhamnolipid production by Pseudomonas aeruginosa.

The effect of autoinducer PAI2 on rhamnolipid (RL) production by Pseudomonas aeruginosa was evaluated using an rhlI null mutant of PAO1 added with PAI2 at various concentrations. A model has also been developed to describe the production kinetics regulated by the rhl quorum-sensing system in three steps: First, PAI2 combines with RhlR protein. Second, the activated complex RhlR:PAI2 triggers the transcription (and expression) of the rhlAB operon that encodes for rhamnosyltransferase. Finally, the enzyme catalyzes the RL synthesis. The model describes fairly well the experimental results/profiles from three different studies (this and two others reported in the literature). The overall picture predicted by the model is as follows: The induced enzyme synthesis proceeds at the highest rate following PAI2 addition. The rate decreases with time as the autoinducer is degraded. The enzyme concentration nonetheless continues to increase until reaching the plateau at the exhaustion of autoinducer. Higher added PAI2 concentrations thus give not only higher initial enzyme synthesis rates but also longer induced synthesis. As the enzyme concentration increases with time, the RL production rate also increases, resulting in an accelerated rise in RL concentrations initially. The increase in RL concentrations becomes linear at the exhaustion of PAI2. The best-fit model parameters obtained also provided important insights. To complex half of the intracellular RhlR proteins would require 1.61 microM PAI2, about half of the PAI2 concentration obtained in the stationary-phase culture of wild-type PAO1. On the other hand, to activate the rhamnosyltransferase synthesis at half of its maximum rate would require the binding of 39% of RhlR with PAI2. The maximum RL production rate of the culture was found to be 0.042 g/L.h, and the fully induced culture would require at least 1.61 h to synthesize the enzyme to the necessary level for producing RL at half of the maximum rate.