Triclosan susceptibility and co-metabolism--a comparison for three aerobic pollutant-degrading bacteria

The antimicrobial agent triclosan is an emerging and persistent environmental pollutant. This study evaluated the susceptibility and biodegradation potential of triclosan by three bacterial strains (Sphingomonas wittichii RW1, Burkholderia xenovorans LB400 and Sphingomonas sp. PH-07) that are able to degrade aromatic pollutants (dibenzofuran, biphenyl and diphenyl ether, respectively) with structural similarities to triclosan. These strains showed less susceptibility to triclosan when grown in complex and mineral salts media. Biodegradation experiments revealed that only strain PH-07 was able to catabolize triclosan to intermediates that included hydroxylated compounds (monohydroxy-triclosan, and dihydroxy-triclosan) and the ether bond cleavage products (4-chlorophenol and 2,4-dichlorophenol), indicating that the initial dihydroxylation occurred on both aromatic rings of triclosan. Additional growth inhibition tests demonstrated that the main intermediate, 2,4-dichlorophenol, was less toxic to strain PH-07 than was triclosan. Our results indicate that ether bond cleavage might be the primary mechanism of avoiding triclosan toxicity by this strain.     

Enrichment of CO2-fixing bacteria in cylinder-type electrochemical bioreactor with built-in anode compartment

Bacterial assimilation of CO2 into stable biomolecules using electrochemical reducing power may be an effective method to reduce atmospheric CO2 without fossil fuel combustion. For the enrichment of the CO2-fixing bacteria using electrochemical reducing power as an energy source, a cylinder-type electrochemical bioreactor with a built-in anode compartment was developed. A graphite felt cathode modified with neutral red (NR-graphite cathode) was used as a solid electron mediator to induce bacterial cells to fix CO2 using electrochemical reducing power. Bacterial CO2 consumption was calculated based on the variation in the ratio of CO2 to N2 in the gas reservoir. CO2 consumed by the bacteria grown in the electrochemical bioreactor (2,000 ml) reached a maximum of approximately 1,500 ml per week. Time-coursed variations in the bacterial community grown with the electrochemical reducing power and CO2 in the mineral-based medium were analyzed via temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region. Some of the bacterial community constituents noted at the initial time disappeared completely, but some of them observed as DNA signs at the initial time were clearly enriched in the electrochemical bioreactor during 24 weeks of incubation. Finally, Alcaligenes sp. and Achromobacter sp., which are capable of autotrophically fixing CO2, were enriched to major constituents of the bacterial community in the electrochemical bioreactor.     

The pleiohomeotic functions as a negative regulator of <Emphasis Type="Italic">Drosophila even-skipped</Emphasis> gene during embryogenesis

Polycomb group (PcG) proteins maintain the spatial expression patterns of genes that are involved in cell-fate specification along the anterior-posterior (A/P) axis. This repression requires cis-acting silencers, which are called PcG response elements (PREs). One of the PcG proteins, Pleiohomeotic (Pho), which has a zinc finger DNA binding protein, plays a critical role in recruiting other PcG proteins to bind to PREs. In this study, we characterized the effects of a pho mutation on embryonic segmentation. pho maternal mutant embryos showed various segmental defects including pair-rule gene mutant patterns. Our results indicated that engrailed and even-skipped genes were misexpressed in pho mutant embryos, which caused embryonic segment defects.     

Ceramide induces serotonin release from RBL-2H3 mast cells through calcium mediated activation of phospholipase A2

Ceramide has been suggested to function as a mediator of exocytosis in response to the addition of a calcium ionophore from PC12 cells. Here, we show that although cell-permeable C(6)-ceramide or a calcium ionophore alone did not increase either the degranulation of serotonin or the release of arachidonic acid (AA) from RBL-2H3 cells, their combined effect significantly stimulated these processes in a time- and dose-dependent manner. This effect was inhibited by the presence of an exogenous calcium chelator and significantly suppressed by the CERK inhibitor (K1) and phospholipase A(2) (PLA(2)) inhibitors. Moreover, cytosolic PLA(2) GIVA (cPLA(2) GIVA) siRNA-transfected RBL-2H3 cells showed a lower level of serotonin release than scramble siRNA-transfected cells. Little is known about the regulation of degranulation proximal to the activation of cytosolic phospholipase A(2) GIVA, the initial rate-limiting step in RBL-2H3 cells. In this study, we suggest that CERK, ceramide-1-phosphate, and PLA(2) are involved in degranulation in a calcium-dependent manner. Inhibition of p44/p42 mitogen-activated protein kinase partially decreased the AA release, but did not affect degranulation. Furthermore, treatment of the cells with AA (ω-6, C20:4), not linoleic acid (ω-6, C18:2) or α-linolenic acid (ω-6, C18:3), induced degranulation. Taken together, these results suggest that ceramide is involved in mast cell degranulation via the calcium-mediated activation of PLA(2).     

Two juvenile hormone esterase-like carboxylesterase cDNAs from a Pandalus shrimp (Pandalopsis japonica): cloning, tissue expression, and effects of eyestalk ablation

Methyl farnesoate (MF), a crustacean juvenile hormone (JH) analog, plays important roles in the regulation of a number of physiological processes such as molting, metamorphosis, and reproduction. Understanding its metabolic pathway is a key for various potential applications in crustacean aquaculture, including artificial seed production and enhancement of growth. Although the synthetic pathway of MF is well established, little is known about its degradation and recycling in crustaceans. In insects, juvenile hormone esterase (JHE), a carboxylesterase, is responsible for JH inactivation. Two cDNAs, encoding JHE-like carboxylesterases (CXEs) from the hepatopancreas and ovary of Pandalopsis japonica, were isolated by using a combination of in-silico data mining from an expressed sequence tag (EST) database and traditional PCR-based cloning. The full length Pj-CXE1 (2084bp) and Pj-CXE2 (1985bp) cDNAs encoded proteins composed of 584 and 581 amino acids, respectively. The active site sequence and domain organization of the Pj-CXEs were highly conserved, including the catalytic triad and other motifs, which suggested that both Pj-CXEs are biologically active carboxylesterases. Phylogenetic analysis of the deduced sequences of Pj-CXEs showed that both were most closely related to the JHEs from non-lepidopteran insects. End-point RT-PCR showed that Pj-CXE1 was expressed primarily in the gonad, whereas Pj-CXE2 was expressed in both the hepatopancreas and hindgut. Quantitative PCR showed that Pj-CXE1 was upregulated in the gonads by eyestalk ablation (ESA). In contrast, ESA had no significant effect on Pj-CXE2 expression in hepatopancreas or gonad. This is the first report of the cloning of two JHE-like CXE cDNAs in decapods and the upregulation of Pj-CXE1 by acute withdrawal of eyestalk neuropeptides. Further study is needed to understand the function of CXEs in MF metabolism and its regulation by eyestalk neuropeptides.     

Immunostick assay for medical diagnosis of rheumatoid arthritis

An immunoassay based on stick-type solid support (immunostick assay) was developed. To demonstrate the medical diagnosis of rheumatoid arthritis (RA), cyclic-citrullinated peptide (CCP), one of specific antigens against RA autoantibodies, was immobilized on the surface of the immunostick, and a color index table was prepared for the determination of CCP-positivity of the test sera. The positivity of RA-positive (n = 31) and RA-negative (n = 20) sera was tested using the immunostick assay and a conventional enzyme-linked immunosorbent assay (ELISA). The statistical agreement of the test results from both methods was analyzed using inter-rater coefficient kappa and Bland-Altman test. The immunostick assay with a color index table was determined to have a high statistical correlation to the conventional ELISA method.