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571.
Anna K. de Regt Yeshi Yin T. Ryan Withers Xin Wang Tania A. Baker Robert T. Sauer Hongwei D. Yu 《Molecular microbiology》2014,93(3):415-425
In Pseudomonas aeruginosa, alginate overproduction, also known as mucoidy, is negatively regulated by the transmembrane protein MucA, which sequesters the alternative sigma factor AlgU. MucA is degraded via a proteolysis pathway that frees AlgU from sequestration, activating alginate biosynthesis. Initiation of this pathway normally requires two signals: peptide sequences in unassembled outer‐membrane proteins (OMPs) activate the AlgW protease, and unassembled lipopolysaccharides bind periplasmic MucB, releasing MucA and facilitating its proteolysis by activated AlgW. To search for novel alginate regulators, we screened a transposon library in the non‐mucoid reference strain PAO1, and identified a mutant that confers mucoidy through overexpression of a protein encoded by the c haperone‐u sher p athway gene cupB5. CupB5‐dependent mucoidy occurs through the AlgU pathway and can be reversed by overexpression of MucA or MucB. In the presence of activating OMP peptides, peptides corresponding to a region of CupB5 needed for mucoidy further stimulated AlgW cleavage of MucA in vitro. Moreover, the CupB5 peptide allowed OMP‐activated AlgW cleavage of MucA in the presence of the MucB inhibitor. These results support a novel mechanism for conversion to mucoidy in which the proteolytic activity of AlgW and its ability to compete with MucB for MucA is mediated by independent peptide signals. 相似文献
572.
Roanne Sutherland Nicolas Meurisse Andrew R. Pugh Christopher M. Ranger Michael E. Reding Jessica L. Kerr Jessica Russell Toni M. Withers 《Agricultural and Forest Entomology》2023,25(3):355-364
- The granulate ambrosia beetle (GAB) Xylosandrus crassiusculus, was first formally detected in New Zealand in 2019. Since then, GAB has subsequently been found infesting numerous tree species in the Auckland region.
- Flight intercept traps baited with ethanol lures were deployed from October 2019 to May 2021 at three sites in the Auckland region to ascertain the phenology of GAB in New Zealand. Two distinct peak flight periods were identified in early and late summer, while a smaller and inconsistent third peak was detected in early autumn. Logistical analysis of GAB captures in the ethanol-lured traps and degree-day (DD) accumulation indicated that 90% of flight activity is completed by 800 DD.
- To assess monitoring tactics, flight intercept traps were baited with three different ethanol lures with varying release rates or ethanol-soaked or non-soaked wood bolts from three species of trees. A lure releasing 2 g ethanol per day was most effective at capturing GAB. Ethanol-soaked bolts were less effective than the lures.
- Xylosandrus crassiusculus represents a significant risk for shrubs and trees native to New Zealand, as well as commercial horticultural and forestry trees. We recommend using ethanol-lured panel traps for monitoring purposes.
573.
Xylanolysis by cocultures of the rumen fungus Neocallimastix frontalis and ruminal bacteria 总被引:4,自引:1,他引:3
The effect of fibrolytic and saccharolytic rumen bacteria on xylanolysis by the rumen fungus Neocallimastix frontalis has been investigated. In cocultivations N. frontalis interacted synergistically with Bacteroides ruminicola, Succinivibrio dextrin-osolvens and Selenomonas ruminantium during xylan utilization. Xylan utilization decreased in cocultures containing Lachnospira multiparus or Streptococcus bovis. Ruminococcus flavefaciens appeared to inhibit fungal growth. 相似文献
574.
Dynamic calibration of mechanically, air- and electromagnetically braked cycle ergometers 总被引:2,自引:0,他引:2
B. F. Maxwell R. T. Withers A. H. Ilsley M. J. Wakim G. F. Woods L. Day 《European journal of applied physiology and occupational physiology》1998,78(4):346-352
In this study we measured the accuracy of the following types of cycle ergometer against the criterion of a dynamic calibration
rig (DCR): 35 friction-braked (Monark), 5 research-grade air-braked (Repco) and 5 electromagnetically braked (2 Siemens, 1
Elema-Schonander, 1 Ergoline, l Warren E. Collins). Monark ergometer power outputs over the range 58.9–353.2 W significantly
(P < 0.001) underestimated those registered by the DCR with mean accuracies of 91.7–97.8%. The least accurate individual reading
for each of the six up-scale (0–353.2 W) power outputs ranged from 81.6␣to␣91.6%; corresponding down-scale (353.2–0 W) accuracies
were 85.1–92.5%. A hysteresis effect was furthermore evident for this ergometer in that up-scale measurements were significantly
(P < 0.05) greater than down-scale ones. In addition, when the oldest [mean (SD): 11.3 (2.3) years old] and newest [1.4 (0.8)
years old] eight ergometers were compared, the latter were significantly (P < 0.05) more accurate over the range 117.7–294.3 W. Apart from the two lowest power outputs of 47␣W (62.2–96.0% accuracy)
and 127 W (88.0–97.7% accuracy), the individual up-scale and down-scale accuracies of the Repco ergometers ranged from 98.0
to 104.2% for power outputs of 272.7–1137.8 W and the means were not significantly different from those of the DCR. There
was also no evidence of hysteresis. Except for the initial power output of 50 W (40 rev/min: 83.8–99.2% accuracy; 60 rev/min:
93.2–122.6% accuracy), the␣individual accuracies of the electromagnetically braked ergometers ranged from 89.3 to 101.4% over
the up-scale range of 100–400 W, and none of the means were significantly different from those of the DCR. The variability
of individual errors for the preceding data emphasises that all cycle ergometers should be validated against the criterion
of a DCR if accurate power outputs are required.
Accepted: 19 February 1998 相似文献
575.
B Withers I A Davies C H Wynn 《Biochemical and biophysical research communications》1968,30(3):227-231