Iron reduction by psychrotrophic enrichment cultures

Psychrotrophic (<20 degrees C) enrichment cultures from deep Pacific marine sediments and Alaskan tundra permafrost reduced ferric iron when using organic acids or H(2) as electron donors. The representative culture W3-7 from the Pacific sediments grew fastest at 10 degrees C, which was 5-fold faster than at 25 degrees C and more than 40-fold faster than at 4 degrees C. Fe(III) reduction was also the fastest at 10 degrees C, which was 2-fold faster than at 25 degrees C and 12-fold faster than at 4 degrees C. Overall, about 80% of the enrichment cultures exhibited microbial Fe(III) reduction under psychrotrophic conditions. These results indicated that microbial iron reduction is likely widespread in cold natural environments and may play important roles in cycling of iron and organic matter over geological times.     

Anaerobic transformation of alkanes to fatty acids by a sulfate-reducing bacterium,strain Hxd3

Strain Hxd3, an alkane-degrading sulfate reducer previously isolated and described by Aeckersberg et al. (F. Aeckersberg, F. Bak, and F. Widdel, Arch. Microbiol. 156:5-14, 1991), was studied for its alkane degradation mechanism by using deuterium and (13)C-labeled compounds. Deuterated fatty acids with even numbers of C atoms (C-even) and (13)C-labeled fatty acids with odd numbers of C atoms (C-odd) were recovered from cultures of Hxd3 grown on perdeuterated pentadecane and [1,2-(13)C(2)]hexadecane, respectively, underscoring evidence that C-odd alkanes are transformed to C-even fatty acids and vice versa. When Hxd3 was grown on unlabeled hexadecane in the presence of [(13)C]bicarbonate, the resulting 15:0 fatty acid, which was one carbon shorter than the alkane, incorporated a (13)C label to form its carboxyl group. The same results were observed when tetradecane, pentadecane, and perdeuterated pentadecane were used as the substrates. These observations indicate that the initial attack of alkanes includes both carboxylation with inorganic bicarbonate and the removal of two carbon atoms from the alkane chain terminus, resulting in a fatty acid one carbon shorter than the original alkane. The removal of two terminal carbon atoms is further evidenced by the observation that the [1,2-(13)C(2)]hexadecane-derived fatty acids contained either two (13)C labels located exclusively at their acyl chain termini or none at all. Furthermore, when perdeuterated pentadecane was used as the substrate, the 14:0 and 16:0 fatty acids formed both carried the same numbers of deuterium labels, while the latter was not deuterated at its carboxyl end. These observations provide further evidence that the 14:0 fatty acid was initially formed from perdeuterated pentadecane, while the 16:0 fatty acid was produced after chain elongation of the former fatty acid with nondeuterated carbon atoms. We propose that strain Hxd3 anaerobically transforms an alkane to a fatty acid through a mechanism which includes subterminal carboxylation at the C-3 position of the alkane and elimination of the two adjacent terminal carbon atoms.     

Insecticidal activity of Piper tuberculatum Jacq. extracts: synergistic interaction of piperamides

Abstract

• 1 The insecticidal activity of the neotropical pepper Piper tuberculatum Jacq. and its isolated piperamides was studied. Bioassays with the mosquito Aedes atropalpus L. assessed the relative toxicity of the whole extract of Piper tuberculatum and four of the piperamides, which were isolated and identified, then prepared synthetically.
• 2 The results confirm that P. tuberculatum leaf extracts are as effective as black pepper seed extract and provide an alternative pepper insecticide from a more convenient source, the leaves.
• 3 Experiments with piperamides showed that the tertiary and quaternary mixtures have greater‐than‐additive toxicity compared to single compounds or binary mixtures. One of the four amide compounds, 4,5‐dihydropiperlonguminine, was the most acutely toxic in mosquito larvae bioassays.
• 4 A study of piperamide levels from different P. tuberculatum populations in Costa Rica determined that they were relatively homogeneous. Piper tuberculatum from only one of the five sites had higher levels of one piperamide, 4,5‐dihydropiperine, in both leaf and stem parts. One explanation for differences in the amide concentrations between populations is that one site is ecologically unique compared to the other four.

     

Effect of targeted mutation in collagen V alpha 2 gene on development of cutaneous hyperplasia in tight skin mice.

Collagen V plays a major regulatory role in the formation of heterotypic fibers of the dermis and cartilaginous tissues as well as in the assembly of extracellular matrix. The pN/pN mouse, which is defective in collagen V alpha 2 gene, exhibits skeletal abnormalities, skin fragility, and alterations in the collagen fiber organization, whereas the TSK/+ mouse, which is defective in fibrillin-1, the major component of microfibrils present in the extracellular matrix, develops cutaneous hyperplasia and autoimmunity. We have studied the role of collagen V in the formation of heterotypic collagen fibers in F1 mice, which are obtained by breeding pN/pN with TSK/+ mice. Our results show that F1 progeny neither develop cutaneous hyperplasia nor produce anti-topoisomerase I autoantibodies, unlike TSK/+ mice. The diameter of the collagen fibrils in the skin is also comparable to that found in control mice. Thus, the phenotypic changes observed in the TSK mouse could be reversed by genetic complementation with a collagen V-defective mouse.     

Regulation of Male Sexual Behavior by Progesterone Receptor, Sexual Experience, and Androgen

Recent studies have demonstrated that physiological doses of progesterone may facilitate the androgen-dependent display of male sexual behavior in laboratory rats and three species of lizard. We used mice with a targeted disruption of the progesterone receptor to investigate whether such interactions exist in male mice and whether they may be modified by sexual experience. We found that naive intact male progesterone receptor knockout (PRKO) mice exhibit reduced mount frequencies compared to wild-type (WT) mice. Also unlike WT mice, sexually experienced PRKO males show profound losses in many measures of sexual behavior following castration. In a second experiment, we tested whether male mice heterozygous for a null mutation at the progesterone receptor locus were responsive to testosterone and progesterone treatment. We found that heterozygous males showed a reduced response to testosterone. The data are consistent with experiments indicating that the progesterone receptor is able to facilitate male-typical sex behaviors in other species and suggest novel mechanisms underlying the interaction of androgens and experience.     

Acceptor specificity of the human leukocyte alpha3 fucosyltransferase: role of FucT-VII in the generation of selectin ligands

The alpha3 fucosyltransferase, FucT-VII, is one of the key glycosyltransferases involved in the biosynthesis of the sialyl Lewis X (sLex) antigen on human leukocytes. The sialyl Lewis X antigen (NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential component of the recruitment of leukocytes to sites of inflammation, mediating the primary interaction between circulating leukocytes and activated endothelium. In order to characterize the enzymatic properties of the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been expressed in Trichoplusia ni insect cells. The enzyme is capable of synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from 3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors demonstrate that FucT-VII is able to synthesize both di-fucosylated and tri-fucosylated structures from mono- fucosylated precursors, but preferentially fucosylates the distal GlcNAc within a polylactosamine chain. Furthermore, the rate of fucosylation of the internal GlcNAc residues is reduced once fucose has been added to the distal GlcNAc. These results indicate that FucT-VII is capable of generating complex selectin ligands, in vitro , however the order of fucose addition to the lactosamine chain affects the rate of selectin ligand synthesis.      

Aerobic Mineralization of Trichloroethylene, Vinyl Chloride, and Aromatic Compounds by Rhodococcus Species

Two Rhodococcus strains which were isolated from a trichloroethylene (TCE)-degrading bacterial mixture and Rhodococcus rhodochrous ATCC 21197 mineralized vinyl chloride (VC) and TCE. Greater than 99.9% of a 1-mg/liter concentration of VC was degraded by cell suspensions. [1,2-¹⁴C]VC was degraded by cell suspensions, with the production of greater than 66% ¹⁴CO₂ and 20% ¹⁴C-aqueous phase products and incorporation of 10% of the ¹⁴C into the biomass. Cultures that utilized propane as a substrate were able to mineralize greater than 28% of [1,2-¹⁴C]TCE to ¹⁴CO₂, with approximately 40% appearing in ¹⁴C-aqueous phase products and another 10% of ¹⁴C incorporated into the biomass. VC degradation was oxygen dependent and occurred at a pH range of 5 to 10 and temperatures of 4 to 35°C. Cell suspensions degraded up to 5 mg of TCE per liter and up to 40 mg of VC per liter. Propane competitively inhibited TCE degradation. Resting cell suspensions also degraded other chlorinated aliphatic hydrocarbons, such as chloroform, 1,1-dichloroethylene, and 1,1,1-trichloroethane. The isolates degraded a mixture of aromatic and chlorinated aliphatic solvents and utilized benzene, toluene, sodium benzoate, naphthalene, biphenyl, and n-alkanes ranging in size from propane to hexadecane as carbon and energy sources. The environmental isolates appeared more catabolically versatile than R. rhodochrous ATCC 21197. The data report that environmental isolates of Rhodococcus species and R. rhodochrous ATCC 21197 have the potential to degrade TCE and VC in addition to a variety of aromatic and chlorinated aliphatic compounds either individually or in mixtures.