Acetic acid bacteria are used in the commercial production of lactobionic acid (LacA). However, the lactose-oxidizing enzyme of these bacteria remains unidentified. Lactose-oxidizing activity has been detected in bacterial membrane fractions and is strongly inhibited by d-glucose, suggesting that the enzyme was a membrane-bound quinoprotein glucose dehydrogenase, but these dehydrogenases have been reported to be incapable of oxidizing lactose. Thus, we generated m-GDH-overexpressing and -deficient strains of Komagataeibacter medellinensis NBRC3288 and investigated their lactose-oxidizing activities. Whereas the overexpressing variants produced ~2–5-fold higher amounts of LacA than the wild-type strains, the deficient variant produced no LacA or d-gluconic acid. Our results indicate that the lactose-oxidizing enzyme from acetic acid bacteria is membrane-bound quinoprotein glucose dehydrogenase.
Developmental mechanisms of segmentation appear to be varied among insects in spite of their conserved body plan. Although the expression patterns of the segment polarity genes in all insects examined imply well conserved function of this class of genes, expression patterns and function of the pair-rule genes tend to exhibit diversity. To gain further insights into the evolution of the segmentation process and the role of pair-rule genes, we have examined expression and function of an ortholog of the Drosophila pair-rule gene even-skipped (eve) in a phylogenetically basal insect, Gryllus bimaculatus (Orthoptera, intermediate germ cricket). We find that Gryllus eve (Gb'eve) is expressed as stripes in each of the prospective gnathal, thoracic, and abdominal segments and as a broad domain in the posterior growth zone. Dynamics of stripe formation vary among Gb'eve stripes, representing one of the three modes, the segmental, incomplete pair-rule, and complete pair-rule mode. Furthermore, we find that RNAi suppression of Gb'eve results in segmentation defects in both anterior and posterior regions of the embryo. Mild depletion of Gb'eve shows a pair-rule-like defect in anterior segments, while stronger depletion causes a gap-like defect showing deletion of anterior and posterior segments. These results suggest that Gb'eve acts as a pair-rule gene at least during anterior segmentation and also has segmental and gap-like functions. Additionally, Gb'eve may be involved in the regulation of hunchback and Krüppel expression. Comparisons with eve functions in other species suggest that the Gb'eve function may represent an intermediate state of the evolution of pair-rule patterning by eve in insects. 相似文献
The tandem conversion process involving nitrile hydratase- and amidase-producing microorganisms has potential for use in the
treatment of acetonitrile-containing wastes. In that process, the acetamide hydrolysis step catalyzed by amidase is very slow
compared with the acetonitrile hydration step catalyzed by nitrile hydratase, and a small amount of acetamide remains in the
resulting solution. This study aimed to improve the efficiency of the acetamide hydrolysis step. An amidase-producing microorganism,
Rhodococcus sp. S13-4, was newly obtained, whose use enabled rapid acetamide degradation. Though residual acetamide was still detected,
it was successfully reduced by the addition of cation/anion mixed ion exchange resin or calcium hydroxide after the acetamide
hydrolysis reaction using Rhodococcus sp. S13-4 cells. This result implies that acetamide hydrolysis and acetamide formation are in equilibrium. The incubation
of Rhodococcus sp. S13-4 cells with high concentrations of ammonium acetate produced acetamide. The purified amidase from Rhodococcus sp. S13-4 revealed the acetamide formation activity (specific activity of 30.6 U/mg protein). This suggests that the amidase-catalyzed
amide formation may cause the remaining of acetamide in the acetonitrile conversion process. 相似文献
Calcification-associated peptide (CAP)-1 is considered to play an important role in calcification of the exoskeleton of the crayfish, Procambarus clarkii. In this study, in order to clarify the molecular mechanism of calcification, we constructed expression systems of recombinant molecules of CAP-1 and its related peptides in Escherichia coli, and verified the structure-activity relationship of these peptides. The inhibitory assay on calcium carbonate precipitation and the calcium-binding assay showed that the C-terminal acidic region was most important for both activities. The CD spectra of these peptides varied depending on calcium concentration and showed that the N-terminal region is associated with the peptide conformation. These results indicate that the C-terminal part of CAP-1 may concentrate calcium ions for nucleation and/or interact with calcium carbonate precipitate to control the growth and that the N-terminal part contribute to maintaining the peptide conformation. 相似文献
Testate amoebae (Protozoa) were studied in spring, summer, and fall from the same microhabitats in a small Sphagnum-dominated peatland in southern Ontario, Canada. A total of 32 sampling stations were established in two wetland plant communities,
19 in an open Ericaceae low-shrub community and 13 in a closed Picea mariana and Larix laricina swamp community. Sphagnum was collected in each station for analysis of testate amoebae and measurement of soil water content parameters and water
table depth in May, August, and October 2001. pH and dissolved oxygen of the groundwater under the Sphagnum were measured also. A total of 52 taxa including the rotifer, Habrotrocha angusticollis, were identified. Soil water content and water table variables emerged as the primary factors separating testate amoebae
between the open bog/fen community and swamp community. Testate amoebae in the open bog/fen community showed a clear separation
between the May sampling period and the August and October sampling periods. Sampling stations in May had much higher water
table and were wetter than those in August and October. Conversely, testate amoebae in the swamp community did not show a
clear difference between sampling periods. Soil moisture and water tables appear to be more constant in the swamp communities.
Biological factors or other microscale environmental factors may need to be considered to explain seasonal changes in testate
amoebae. A greater understanding of relationships between testate amoebae and microenvironmental factors is necessary to track
seasonality in testate amoebae distributions. 相似文献
A generalist predatory mite, Anystis baccarum (L.), was evaluated as a biological control agent against western flower thrips (WFT), Frankliniella occidentalis (Pergande). Laboratory assays showed A. baccarum was able to kill a mean of five WFT adult females or nine WFT larvae in 24 h, out-performing both Neoseiulus cucumeris (Oudemans) and Amblyseius swirskii Athias-Henriot. Next, a greenhouse assay was conducted to assess the performance of A. baccarum on potted chrysanthemums, comparing their efficacy to that provided by N. cucumeris slow-release sachets which represented the commercial standard in Canada. A combined treatment which incorporated both predatory mite species was also included to assess compatibility and potential additive effects of using both species together for WFT management. Introduction of two A. baccarum per pot was as efficacious as 125 N. cucumeris in terms of WFT control; however, despite the lack of significance between the level of WFT control obtained in the single predatory species treatments and the combined treatment, only the combination treatment suppressed WFT populations to levels that were almost unchanged over 8 weeks. There was no significant difference between the number of N. cucumeris recovered from plants in the single-species and the combination treatments, demonstrating the functional compatibility of the two predators. Additionally, WFT feeding damage was significantly lower on the A. baccarum-treated plants than on the untreated control and the N. cucumeris treatment. This study, together with our development of a prototype mass rearing method, shows that A. baccarum could be successfully used as a biocontrol agent for WFT.
In addition to efforts aimed at reducing anthropogenic production of greenhouse gases, geological storage of CO2 is being explored as a strategy to reduce atmospheric greenhouse gas emission and mitigate climate change. Previous studies of the deep subsurface in North America have not fully considered the potential negative effects of CO2 leakage into shallow drinking water aquifers, especially from a microbiological perspective. A test well in the Newark Rift Basin was utilized in two field experiments to investigate patterns of microbial succession following injection of CO2-saturated water into an isolated aquifer interval, simulating a CO2 leakage scenario. A decrease in pH following injection of CO2 saturated aquifer water was accompanied by mobilization of trace elements (e.g. Fe and Mn), and increased bacterial cell concentrations in the recovered water. 16S ribosomal RNA gene sequence libraries from samples collected before and after the test well injection were compared to link variability in geochemistry to changes in aquifer microbiology. Significant changes in microbial composition, compared to background conditions, were found following the test well injections, including a decrease in Proteobacteria, and an increased presence of Firmicutes, Verrucomicrobia and microbial taxa often noted to be associated with iron and sulfate reduction. The concurrence of increased microbial cell concentrations and rapid microbial community succession indicate significant changes in aquifer microbial communities immediately following the experimental CO2 leakage event. Samples collected one year post-injection were similar in cell number to the original background condition and community composition, although not identical, began to revert toward the pre-injection condition, indicating microbial resilience following a leakage disturbance. This study provides a first glimpse into the in situ successional response of microbial communities to CO2 leakage after subsurface injection in the Newark Basin and the potential microbiological impact of CO2 leakage on drinking water resources. 相似文献
Photodynamic therapy (PDT) is a less invasive option for cancer treatment that has evolved through recent developments in nanotechnology. We have designed and synthesized a novel liposome system that includes an indocyanine green (ICG) derivative, ICG-C18, in its bilayer. In addition to its use as an optical imager to visualize blood, lymphatic, and bile flow, ICG has also been used as an optical sensitizer. In the present report, we evaluate the use of our novel liposome system, LP-ICG-C18, in PDT for squamous cell carcinoma in an autologous murine model.
Materials and Methods
An excitation pulse beam (300 μJ/pulse) of a single band (800 nm) was used for sensitization. The cytotoxicity of the photodynamic therapy was evaluated in terms of cellular morphology changes, methyl thiazolyl tetrazolium (MTT) assay results, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) staining. We tested the enhanced permeability and retention effect of LP-ICG-C18 in tumor-bearing C3H/He mice using a near-infrared fluorescence imaging system and fluorescence microscopy. We also examined the antitumor effect of PDT by measuring tumor volume in tumor-bearing mice.
Results
Cell death and apoptosis were only observed in the PDT group receiving LP-ICG-C18. LP-ICG-C18 itself had no cytotoxic activity and showed good biocompatibility. LP-ICG-C18 accumulated on the tumor 24 hours after injection and was retained for approximately 3 weeks. Tumor cell apoptosis following PDT with LP-ICG-C18 was also observed under optical microscopy, MTT assay, and TUNEL staining.
Conclusion
These findings suggest that LP-ICG-C18 may be an effective intervening material in PDT for malignant disease. 相似文献