No abstract

Phytometabolism of antibiotics is a potentially significant route of human exposure to trace concentrations of antibiotics, prompting concerns about antibiotic resistance. The present study evaluated the metabolism of sulfamethoxazole (SMX), a commonly used sulfonamide antibiotic, by Arabidopsis thaliana. SMX was intensively metabolized by A. thaliana, with only 1.1% of SMX in plant tissues present as the parent compound after 10 days of exposure. Untargeted screening of extractable metabolites revealed that N-glycosylation was the main transformation pathway of SMX in A. thaliana plants, with N4-glycosyl-SMX accounting for more than 80% of the extractable metabolites. Additionally, N4-glycosyl-glycoside SMX accounted for up to 4.4% of the extractable metabolites, indicating glycosylation of N4-glycosyl-SMX. The majority of minor extractable SMX metabolites were also conjugates of the parent compound, such as pterin–SMX and methyl salicylate–SMX conjugates. In 14C-SMX trials, 14C-radioactivity was detected in both extractable and bound residues in plant tissues. Extractable residues, which included 14C-SMX and its soluble metabolites, accounted for 35.8–43.6% of the uptaken 14C-radioactivity, while bound residues were 56.4–64.2%. Approximately 27.0% of the initially applied 14C-radioactivity remained in the culture media at the conclusion of the experiments, composed of both 14C-SMX and its metabolites, likely due to plant excretion.

No abstract

. We interviewed farm managers about their perceptions of wading bird problems and conducted preliminary surveys of wading bird populations at 67 randomly selected channel catfish Ictalurus punctatus pond complexes in northwest Mississippi during December 1995. At a subsample of 24 complexes and 10 other complexes previously surveyed in 1990, we surveyed wading bird populations bimonthly throughout the year in 1996 and observed great blue herons Ardea herodias and great egrets Ardea alba feeding at catfish ponds. Seventy‐five percent of farm managers questioned felt that wading birds were causing losses to their fish stocks, and 74% believed the problem was increasing. Consistent with interview results, 88% of the pond complexes surveyed had one or more wading birds present. Despite reported harassment programs by producers, great blue heron densities at 10 complexes previously surveyed in 1990 had increased by more than eightfold in 1996. Great blue heron densities varied with location, season and time of day, but the average 127‐ha farm supported about 78 herons and 56 great egrets. Despite similar populations, the potential impact of these two species was quite different. Live catfish, averaging 10.3 cm in length (circa 10 g) comprised only 8% of the egret diet by weight, and most of the fish were obtained from fingerling ponds during periods when these fingerlings may be weakened by the bacterial disease, enteric septicemia of catfish. In contrast, live catfish, averaging 16 cm in length (circa 34 g), comprised 44% of the great blue heron diet by weight. Herons foraged from both fingerling and food fish ponds, primarily in the early morning and evening. Based on average population densities and foraging rates, herons at the average 127‐ha farm in northwest Mississippi consumed 114,000 (circa 3,900 kg) catfish, annually. However, further studies are recommended to document production losses.