The lipA gene encoding an extracellular lipase from Pseudomonas cepacia was cloned and sequenced. Downstream from the lipase gene an open reading frame was identified, and the corresponding gene was named limA. lipA was well expressed only in the presence of limA. limA exerts its effect both in cis and in trans and therefore produces a diffusible gene product, presumably a protein of 344 amino acids. Replacement of the lipA expression signals (promoter, ribosome-binding site, and signal peptide-coding sequences) by heterologous signals from gram-positive bacteria still resulted in limA-dependent lipA expression in Escherichia coli, Bacillus subtilis, and Streptomyces lividans.

Arsenolipids are the major arsenic species present in marine oils. Several structures of arsenolipids have been elucidated the last 5 years, demonstrating the chemical complexity of this trace element in the marine environment. Several commercial fish oils and marine oils, ranging in total arsenic concentrations from 1.6 to 12.5 mg kg(-1) oil, were analyzed for arsenolipids using reversed-phase high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The arsenolipids were quantified using three different arsenic-containing calibration standards; dimethylarsinate (DMA), triphenylarsinoxide (Ph₃AsO) and a synthesized arsenic-containing hydrocarbon (AsHC) (dimethylarsinoyl nonadecane; C₂₁H₄₃AsO). The observed variation in signal intensity for arsenic during the gradient elution profile in reversed-phase HPLC was compensated for by determining the time-resolved response factors for the arsenolipids. Isotopes of germanium ((74)Ge) and indium ((115)In) were suited as internal standards for arsenic, and were used for verification of the arsenic signal response factors during the gradient elution. Dimethylarsinate was the most suitable calibration standard for the quantification of arsenolipids, with recoveries between 91% and 104% compared to total arsenic measurements in the same extracts. A range of marine oils was investigated, including oils of several fish species, cod liver and seal, as well as three commercial fish oils. The AsHCs - C₁₇H₃₈AsO, C₁₉H₄₂AsO and C₂₃H₃₈AsO - were identified as the major arsenolipids in the extracts of all oils by HPLC coupled with quadrupole time-of-flight mass spectrometry (qTOF-MS). Minor amounts of two arsenic-containing fatty acids (AsFAs) (C₂₃H₃₈AsO₃ and C₂₄H₃₈AsO₃) were also detected in the oils. The sum of the AsHCs and the AsFAs determined in the present study accounted for 17-42% of the total arsenic in the oils.

Selenium (Se) is an essential element with a small difference between physiological and toxic doses. To provide more effective and safe Se dosing regimens, as compared to dosing with ionic selenium, nanoparticle formulations have been developed. However, due to the nano-formulation, unexpected toxic effects may occur. We used metabolite pattern determination in urine to investigate biological and/or toxic effects in rats administered nanoparticles and for comparison included ionic selenium at an equimolar dose in the form of sodium selenite. Low doses of 10 and 100 fold the recommended human high level were employed to study the effects at borderline toxicity. Evaluations of all significantly changed putative metabolites, showed that Se nanoparticles and sodium selenite induced similar dose dependent changes of the metabolite pattern. Putative identified metabolites included increased decenedioic acid and hydroxydecanedioic acid for both Se formulations whereas dipeptides were only increased for selenite. These effects could reflect altered fatty acid and protein metabolism, respectively.

The present study describes the use of a simple solid-phase extraction procedure for the extraction of arsenic-containing hydrocarbons from fish oil followed by analysis using gas chromatography (GC) coupled to inductively coupled plasma mass spectrometry (ICPMS). The procedure permitted the analysis of a small sample amount, and the method was applied on a range of different commercial fish oils, including oils of anchovy (Engraulis ringens), Atlantic herring (Clupea harengus), sand eel (Ammodytes marinus), blue whiting (Micromesistius poutassou) and a commercial mixed fish oil (mix of oils of Atlantic herring, Atlantic cod (Gadus morhua) and saithe (Pollachius virens)). Total arsenic concentrations in the fish oils and in the extracts of the fish oils were determined by microwave-assisted acid digestion and ICPMS. The arsenic concentrations in the fish oils ranged from 5.9 to 8.7 mg kg(-1). Three dominant arsenic-containing hydrocarbons in addition to one minor unidentified compound were detected in all the oils using GC-ICPMS. The molecular structures of the arsenic-containing hydrocarbons, dimethylarsinoyl hydrocarbons (C17H38AsO, C19H42AsO, C23H38AsO), were verified using GC coupled to tandem mass spectrometry (MS/MS), and the accurate masses of the compounds were verified using quadrupole time-of-flight mass spectrometry (qTOF-MS). Additionally, total arsenic and the arsenic-containing hydrocarbons were studied in decontaminated and in non-decontaminated fish oils, where a reduced arsenic concentration was seen in the decontaminated fish oils. This provided an insight to how a decontamination procedure originally ascribed for the removal of persistent organic pollutants affects the level of arsenolipids present in fish oils.

Monocolonization of germ-free (GF) mice enables the study of specific bacterial species in vivo. Lactobacillus acidophilus NCFMTM (NCFM) is a probiotic strain; however, many of the mechanisms behind its health-promoting effect remain unknown. Here, we studied the effects of NCFM on the metabolome of jejunum, cecum, and colon of NCFM monocolonized (MC) and GF mice using liquid chromatography coupled to mass-spectrometry (LC-MS). The study adds to existing evidence that NCFM in vivo affects the bile acid signature of mice, in particular by deconjugation. Furthermore, we confirmed that carbohydrate metabolism is affected by NCFM in the mouse intestine as especially the digestion of oligosaccharides (penta- and tetrasaccharides) was increased in MC mice. Additionally, levels of α-tocopherol acetate (vitamin E acetate) were higher in the intestine of GF mice than in MC mice, suggesting that NCFM affects the vitamin E acetate metabolism. NCFM did not digest vitamin E acetate in vitro, suggesting that direct bacterial metabolism was not the cause of the altered metabolome in vivo. Taken together, our results suggest that NCFM affects intestinal carbohydrate metabolism, bile acid metabolism and vitamin E metabolism, although it remains to be investigated whether this effect is unique to NCFM.