Aerial Dispersal and Epiphytic Survival of Pseudomonas syringae during a Pretest for the Release of Genetically Engineered Strains into the Environment.

Prospective experimental field evaluation of genetically engineered microorganisms, such as microbial pest control agents, raises issues of how to properly ascertain their fate and survival in the environment. Field trials with recombinant organisms must reflect requirements for sampling and monitoring. Field trials were conducted at Tulelake, Calif., to monitor the numbers of viable cells of a nonrecombinant strain of Pseudomonas syringae that entered the atmosphere and landed on plants and soil during and after an aerosol spray application. An exponential decrease in numbers of viable cells deposited at increasing distances from three sprayed plots was observed. The relative rate of survival of cells sprayed directly on plants was more than 10 times higher than that of cells dispersed through the air to similar adjacent plants. Results are being used to gain experience with the characteristics of a release site that influence containment or dispersal and to develop appropriate sampling methodologies for evaluating survival and dispersal characteristics of genetically engineered bacteria released into the environment. The ability to make predictions about microbial dispersal and survival will reduce the uncertainties associated with environmental releases of recombinant organisms.

A Combined Immunofluorescence-DNA-Fluorescence Staining Technique for Enumeration of Thiobacillus ferrooxidans in a Population of Acidophilic Bacteria.

An antiserum raised against whole cells of Thiobacillus ferrooxidans was allowed to react with a variety of acidophilic and nonacidophilic bacteria in an enzyme-linked immunosorbent assay and an indirect immunofluorescence assay. Both experiments demonstrated that the antiserum was specific at the species level. This preparation was used to evaluate the role of T. ferrooxidans in the microbial desulfurization process. Leaching experiments were performed, and the numbers of T. ferrooxidans cells and other bacteria were estimated by using a combined immunofluorescence-DNA-fluorescence staining technique that was adapted for this purpose. Nonsterile coal samples inoculated with T. ferrooxidans yielded high concentrations of soluble iron after 16 days. After this period, however, T. ferrooxidans cells could no longer be detected by the immunofluorescence assay, whereas the DNA-fluorescence staining procedure demonstrated a large number of microorganisms on the coal particles. These results indicate that T. ferrooxidans is removed by competition with different acidophilic microorganisms that were originally present on the coal.

Some physical factors in toxicological assessment tests.

Many thousand organic compounds are in common use and new ones introduced daily. With many of these materials, little is known about their toxic hazard. For years scientists have been investigating the relation of structure and properties to biological activity. Among the factors relating to toxicity are bioaccumulation and persistence in the organism. In this study, the relation of partition coefficient and solubility to bioaccumulation of some organochlorine compounds was investigated as was also the reactivity of several organophosphates. The work adds confirmation to the relation of molecular parameters to penetration, accumulation, and persistence in toxic action.

Physicochemical properties of some organophosphates in relation to their chronic toxicity.

Organophosphates in increasing amounts and wider varieties of molecular structure are being used to replace the organochlorine pesticides. It has been assumed that the organophosphates as a class would have a minimal chronic toxicity due to rapid hydrolysis and an unfavorable partitioning as regards to lipids. The physicochemical properties of a number of representative organophosphates were determined, including the octanol/water partition coeffecient, hydrolysis, and binding to proteins. Those having a halogenated aryl substitution were found to have partition coefficients not largely different from the organochlorines, suggesting the possibility of fat deposition. Certain of these compounds are sufficiently stable toward hydrolysis to allow bioaccumulation to occur. These preliminary findings appear to indicate a correlation between readily determined physical properties and the potential for chronic effects in this class of compounds.

Studies on the adsorption of selected polychlorinated biphenyl isomers of several surfaces.

The adsorption-desorption characteristics of three selected PCB isomers on a soil and some of its constituents have been determined. The extent of adsorption for all surfaces follows the sequence hexachloro greater than tetrachloro greater dichloro for the isomers chosen. For an individual isomer, the adsorption rates increase in the following sequence: Del Monte, sand, illite clay, Woodburn soil, and humic acid. These results are discussed relative to environmental transport of the chemicals.

Binding of DDT to lecithin.

An interaction between DDT and lecithin is indicated by the reciprocal effects of each compound on the proton magnetic resonance spectrum of the other. The phosphoryl choline moiety of the lecithin and the benzylic proton of the DDT seem to be involved. The most pronounced response in the proton magnetic resonance spectrum of the lecithin produced by increasing concentration s of DDT was a change in the chemical shift of the resonance peak due to the protons of the choline methyl groups. Increasing concentrations of lecithin produced changes in the chemical shift of the resonance peaks of the benzylic proton and adjacent ring protons of the DDT. Equilibrium constant of 0.597 +/-0.015 molal(-1) was obtained for this interaction.