Sorption and transport of 17beta-estradiol and testosterone in undisturbed soil columns.

Land-applied domestic animal wastes contain appreciable amounts of 17beta-estradiol (henceforth, estradiol) and testosterone. These sex hormones may be transported through soil to groundwater and streams, where they may adversely affect the environment. Previous column transport studies with these hormones used repacked soil and did not consider preferential flow. We, therefore, determined the sorption and transport characteristics of estradiol and testosterone in undisturbed soil columns (15-cm i.d. by 32-cm height). In the sorption experiment, isotherms for estradiol and testosterone were nonlinear with Freundlich exponents (n) less than one. Sorption of both hormones decreased with soil depth, and estradiol sorbed more strongly than testosterone. Average estradiol Freundlich sorption coefficients (K(f)) values were 36.9 microg(1 - n) mL(n) g(-1) for the 0- to 10-cm soil depth and 25.7 microg(1 - n) mL(n) g(-1) for the 20- to 30-cm soil depth. Average testosterone K(f) values were 26.7 microg(1 - n) mL(n) g(-1) for the 0- to 10-cm soil depth and 14.0 microg(1 - n) mL(n) g(-1) for the 20- to 30-cm soil depth. In the transport experiment, 27% of the estradiol and 42% of the testosterone leached through the soil columns. Approximately 50% of the remaining soil-bound hormones were sorbed in the top 10 cm of soil. In almost all instances, breakthrough concentrations of estradiol, testosterone, and a chloride tracer peaked simultaneously. Simultaneous breakthrough and HYDRUS-1D transport parameters indicated both chemical and physical nonequilibrium processes affected hormone transport. This suggests hormones placed on soil surfaces may contaminate groundwater under conditions of preferential flow.

Phytoremediation of pyrene in a Cecil soil under field conditions.

We evaluated the effects of annual ryegrass (Lolium multiflorum Lam.) and phosphorus (P) availability on the dissipation of pyrene added at a concentration of approximately 600 mg kg-1 dry soil in the top 7.5 cm of a Cecil loamy sand (fine, kaolinitic, thermic Typic Kanhapludults) in a 10-month experiment under field conditions in Clemson, South Carolina. Plastic canopies were installed to prevent flooding of plots and raindrop dispersion of pyrene. Treatment factors were pyrene, vegetation, and available P levels. Each of the eight treatments had four replicates. The soil was adjusted to low and high P concentrations (an average of 41 and 66 kg extractable P ha-1, respectively). After a 175-d lag period for all treatments, the rate of pyrene removal followed first-order kinetics. The first-order rate constant was significantly higher in nonvegetated (0.098 d-1) than vegetated treatments (0.034 d-1). These data suggest that the presence of easily biodegradable organic matter from plant roots slowed the removal rate of pyrene. The levels of available P did not affect the rate of pyrene dissipation. Pyrene decreased below the detection limit of 6.25 mg kg-1 dry soil in all treatments after 301 d.

Putative temporal variability of Escherichia coli ribotypes from yearling steers.

Escherichia coli is a ubiquitous component of the intestinal microflora of warm-blooded animals, and is an indicator of fecal contamination of surface waters. Ribotype profiling of E. coli is one of several genotypic methods that has been developed to determine the host origin of fecal bacteria. Like most genotypic methods of source tracking, ribotyping requires a host origin database to identify environmental isolates. To determine the extent of temporal variability of ribotypes and its effect on a host origin database, E. coli isolates were obtained from fecal samples of two herds of Black Angus steers at a long-term experimental site at four sampling times from October 1999 to July 2000. Fecal samples were taken from six randomly chosen steers at each time. At a similarity index of 90% as calculated by unweighted pair-group method using arithmetic averages (UPGMA), 240 ribotypes were identified from 451 E. coli isolates. Only 20 ribotypes (8.3%), comprising 33% of the total isolates, were shared among sampling times and were considered resident ribotypes. Two of the twenty resident ribotypes appeared at three sampling times, and the remaining eighteen appeared at two. The majority of the ribotypes, therefore, were transient and unique to each sampling time and steer. Both the apparent turnover of E. coli ribotypes and a clonal diversity index of 0.97 (indicative of extensive ribotype variability) suggest the necessity of ribotyping a large number E. coli isolates per host to establish a host origin database that is independent of temporal variability, or complete enough to be effective.

Association of carbon disulfide with plants in the family Fabaceae.

We examined 40 taxa from nine genera within the subfamily Mimosoideae; 29 (73%) from six genera produced carbon disulfide (CS2). In addition, 19 of 40 taxa (48%) produced carbonyl sulfide (OCS). Of nine mimosoid taxa that produced CS2, all possessed a djenkolic acid and a cysteine lyase. Of three mimosoid taxa that did not produce CS2, two lacked a cysteine lyase and one lacked both a lyase and a djenkolic acid. Of 16 taxa from 14 genera from the other two subfamilies of the Fabaceae, the Caesalpinioideae and Papilionoideae, none produced CS2. The results suggest that CS2 production is common in the Mimosoideae and uncommon in the Caesalpinioideae and Papilionoideae and that plants in the Mimosoideae that do produce CS2 must possess both a djenkolic acid and a cysteine lyase for this production to occur.

Presence of a Vanadium Nitrogenase in Azotobacter paspali.

There have been no previous studies on the genetics of Azotobacter paspali, an aerobic bacterium which forms a highly specific diazotrophic association with Bahia grass (Paspalum notatum). We constructed A. paspali strains defective in the molybdenum nitrogenase so that alternative N(2)ases could be studied. The cosmid vector pTBE and genomic DNA fragments ( approximately 50 kb) of A. paspali ATCC 23367 were used to construct a gene library in Escherichia coli. Recombinant cosmids containing sequences homologous to molybdenum nitrogenase nifDK structural genes were identified by hybridization. A 2.9-kb fragment bearing the putative nifDK genes of A. paspali was subcloned and mutagenized in vitro by the insertion of a kanamycin resistance gene cassette. The mutation was recombined into the chromosome of A. paspali with the suicide vector pCU101. One resultant mutant strain, AP2, was incapable of diazotrophic growth in a molybdenum-containing medium (Nif) without vanadium but grew well in a molybdenum-deficient medium with vanadium. The nitrogenase system in AP2 reduced acetylene to ethylene and produced ethane as 2.4% of the total products. Molybdenum levels as low as 10 nM prevented the diazotrophic growth of AP2, even in the presence of vanadium at levels up to 10 muM. These results are consistent with the existence of a vanadium nitrogenase system in A. paspali.

The Role of Microbes Associated with Chicken Litter in the Suppression of Meloidogyne arenaria.

The role of microbes associated with chicken litter in the suppression of Meloidogyne arenaria in amended soil was investigated. Amended soil treatments were prepared, including combinations of sterile and nonsterile chicken litter and soil. Microbial biomass in different treatments was compared by measuring carbon dioxide evolution. There was less CO evolved in sterile litter than in nonsterile litter treatments. Tomato seedlings cv. Rutgers were transplanted into soil mixtures and inoculated with 2,000 M. arenaria eggs. After 10 days, fewer second-stage juveniles (J2) had penetrated the roots in soils amended with nonsterile litter than sterile litter. The effects of sterile and nonsterile litter-amended soil solutions on M. arenaria eggs and J2 were observed over a period of 6 days. A lower percentage of eggs remained apparently healthy in nonsterile than in sterile-amended soil solutions over 6 days. Microbial degradation of the egg shells was apparent. Fewer J2 survived in sterile- and nonsterile-amended-soil solutions as compared to water controls.

Growth of genetically engineered Pseudomonas aeruginosa and Pseudomonas putida in soil and rhizosphere.

The effect of the addition of a recombinant plasmid containing the pglA gene encoding an alpha-1,4-endopolygalacturonase from Pseudomonas solanacearum on the growth of Pseudomonas aeruginosa and Pseudomonas putida in soil and rhizosphere was determined. Despite a high level of polygalacturonase production by genetically engineered P. putida and P. aeruginosa, the results suggest that polygalacturonase production had little effect on the growth of these strains in soil or rhizosphere.

Styrofoam cup-membrane assembly for studying microorganism-root interactions.

An assembly consisting of Styrofoam cups with membranes of varying porosities was developed to study microorganism-root interactions. The assembly permitted uniform distribution of a bacterium in soil and was simple, easy to use, and disposable. In tests with the bacterium Pseudomonas solanacearum, little difference in P. solanacearum survival was observed in the rhizosphere or nonrhizosphere of tomato.

Microtechnique for isolating fecal coliforms from soil.

A most-probable-number microtitration technique for isolating fecal coliforms from soil was developed. A correlation coefficient of 0.86, with a 95% confidence interval of 0.76 less than zeta less than 0.92, was obtained when this technique was compared with the standard elevated-temperature fecal coliform most-probable-number procedure.