Two mixed bacterial cultures isolated by soil enrichment were capable of utilizing methyl parathion (O,O-dimethyl O-p-nitrophenylphosphorothioate) and parathion (O,O-diethyl O-p-nitrophenylphosphorothioate) as a sole source of carbon. Four isolates from these mixed cultures lost their ability to utilize the pesticides independently in transfers subsequent to the initial isolation. One member of the mixed cultures, a Pseudomonas sp., however, hydrolyzed the pesticides to p-nitrophenol but required glucose or another carbon source for growth. The crude cell extracts prepared from this bacterium showed an optimum pH range from 7.5 to 9.5 for the enzymatic hydrolysis. Maximum enzymatic activity occurred between 35 and 40°C. The enzyme activity was not inhibited by heavy metals, EDTA, or NaN3. Another isolate from the mixed cultures, a Flavobacterium sp., used p-nitrophenol for growth and degraded it to nitrite. Nitrite was assimilated into the cells under conditions during which the nitrogen source was excluded from the minimal growth medium. The hybridization data showed that the DNAs from a Pseudomonas sp. and from the mixed culture had homology with the opd (organophosphate degradation) gene from a previously reported parathion-hydrolyzing bacterium, Flavobacterium sp. The use of the opd gene as a probe may accelerate progress toward understanding the complex interactions of soil microorganisms with parathions.MATERIALS AND METHODS Chemicals. Technical-grade parathion and methyl parathion were obtained from Chem Service (West Chester, Pa.) and from the U.S. Environmental Protection Agency. p-Nitrophenol was purchased from Sigma Chemical Co.
The chlorocarbon mirex undergoes slow, successive loss of chlorine in the field to a series of related compounds that had lost one or more chlorine atoms. Soil samples were recovered 12 years after treatment at 1 part per million (ppm), and ant bait was recovered 5 years after an aircraft crash. As much as 50 percent of the original mirex was recovered at levels of about 0.5 and 640 ppm, respectively. Kepone was present at levels of 0.02 ppm in soil and 10 ppm in the bait or up to 10 percent of the recovered mirex, as determined by combined techniques of chromatography and mass spectrometry. This constitutes the first observation of the degradation of mirex in nature, and demonstrates a pathway for its eventual disappearance from the environment.
Pest management techniques have evolved over the past 50 years. Inorganic chemical pesticides were replaced by synthetic organic chemicals, and now biopesticides constitute a significant part of pest management technology. Requirements for the regulatory approval of pesticides changed dramatically in 1996 with the passage of the Food Quality Protection Act (FQPA). The FQPA directs the U.S. Environmental Protection Agency (EPA) to make more rigorous and conservative evaluation of risks and hazards and mandates a special emphasis on the safety of infants and children. The EPA provides incentives for the industry to register materials that are designated "reduced risk". The future for the registrant industry will include continued reduction in numbers of registrants through mergers and acquisitions. Conventional chemicals will remain as important pest management components, and the processes of combinatorial chemistry and high-throughput bioassays will allow the rapid synthesis and testing of large numbers of candidate compounds. Biopesticides will become more important tools in pest management, with microbial pesticides and transgenic crops being likely to play important crop protection roles. There will be a continuing need for research-based approaches to pest control.
Edible shrimp (Penaeus az&cus) tissue contains approximately 1.2% extractable lipids, the majority of which are phospholipids. Data from the gravimetric quantitation of lipid classes isolated by column chromatography indicated that phosphatidyl choline was the predominant phospholipid and cholesterol the predominant neutral lipid in edible shrimp tissue. Fatty acid distribution data indicated that sphingomyelins contained the greatest percent by weight of unsaturated fatty acids while cholesterol esters contained the greatest proportion of saturated fatty acids. Enzymatic hydrolysis followed by gas liquid chromatography of phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine indicated that fatty acids located at the p position were more highly unsaturated than those at the 01 position.
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