S3QELs protect against diet‐induced intestinal barrier dysfunction

The underlying causes of aging remain elusive, but may include decreased intestinal homeostasis followed by disruption of the intestinal barrier, which can be mimicked by nutrient‐rich diets. S3QELs are small‐molecule suppressors of site III_Qo electron leak; they suppress superoxide generation at complex III of the mitochondrial electron transport chain without inhibiting oxidative phosphorylation. Here we show that feeding different S3QELs to Drosophila on a high‐nutrient diet protects against greater intestinal permeability, greater enterocyte apoptotic cell number, and shorter median lifespan. Hif‐1α knockdown in enterocytes also protects, and blunts any further protection by S3QELs. Feeding S3QELs to mice on a high‐fat diet also protects against the diet‐induced increase in intestinal permeability. Our results demonstrate by inference of S3QEL use that superoxide produced by complex III in enterocytes contributes to diet‐induced intestinal barrier disruption in both flies and mice.     

Biosynthesis of Yersiniabactin, a complex polyketide-nonribosomal peptide, using Escherichia coli as a heterologous host

The medicinal value associated with complex polyketide and nonribosomal peptide natural products has prompted biosynthetic schemes dependent upon heterologous microbial hosts. Here we report the successful biosynthesis of yersiniabactin (Ybt), a model polyketide-nonribosomal peptide hybrid natural product, using Escherichia coli as a heterologous host. After introducing the biochemical pathway for Ybt into E. coli, biosynthesis was initially monitored qualitatively by mass spectrometry. Next, production of Ybt was quantified in a high-cell-density fermentation environment with titers reaching 67 +/- 21 (mean +/- standard deviation) mg/liter and a volumetric productivity of 1.1 +/- 0.3 mg/liter-h. This success has implications for basic and applied studies on Ybt biosynthesis and also, more generally, for future production of polyketide, nonribosomal peptide, and mixed polyketide-nonribosomal peptide natural products using E. coli.     

Topography, substratum and benthic macrofaunal relationships on a tropical mesophotic shelf margin, central Great Barrier Reef, Australia

Habitats and ecological communities occurring in the mesophotic region of the central Great Barrier Reef (GBR), Australia, were investigated using autonomous underwater vehicle (AUV) from 51 to 145 m. High-resolution multibeam bathymetry of the outer-shelf at Hydrographers Passage in the central GBR revealed submerged linear reefs with tops at 50, 55, 80, 90, 100 and 130 m separated by flat, sandy inter-reefal areas punctuated by limestone pinnacles. Cluster analysis of AUV images yielded five distinct site groups based on their benthic macrofauna, with rugosity and the presence of limestone reef identified as the most significant abiotic factors explaining the distribution of macrofaunal communities. Reef-associated macrofaunal communities occurred in three distinct depth zones: (1) a shallow (<60 m) community dominated by photosynthetic taxa, notably scleractinian corals, zooxanthellate octocorals and photosynthetic sponges; (2) a transitional community (60–75 m) comprising both zooxanthellate taxa and azooxanthellate taxa (notably gorgonians and antipatharians); and (3) an entirely azooxanthellate community (>75 m). The effects of depth and microhabitat topography on irradiance most likely play a critical role in controlling vertical zonation on reef substrates. The lower depth limits of zooxanthellate corals are significantly shallower than that observed in many other mesophotic coral ecosystems. This may be a result of resuspension of sediments from the sand sheets by strong currents and/or a consequence of cold water upwelling.     

Resistance, germination, and permeability correlates of Bacillus megaterium spores successively divested of integument layers

A variant strain that produced spores lacking exosporium was isolated from a culture of Bacillus megaterium QM-B1551. Two additional spore morphotypes were obtained from the parent and variant strains by chemical removal of the complex of coat and outer membrane. Among the four morphotype spores, heat resistance did not correlate with total water content, wet density, refractive index, or dipicolinate or cation content, but did correlate with the volume ratio of protoplast to protoplast plus cortex. The divestment of integument layers exterior to the cortex had little influence on heat resistance. Moreover, the divestment did not change the response of either the parent or the variant spores to various germination-initiating agents, except for making the spores susceptible to germination by lysozyme. The primary permeability barrier to glucose for the intact parent and variant spores was found to be the outer membrane, whereas the barrier for the divested spores was the inner membrane.     

Dehydration partitioned within core protoplast accounts for heat resistance of bacterial spores

Abstract In Escherichia coli , adenosine 3',5'-cyclic monophosphate (cAMP) is excreted into the growth media. Making use of a phosphodiesterase as scavenger of extracellular cAMP we show that: (i) extracellular cAMP does not interfere with cellular functions; (ii) transient accumulation of cAMP, followed by its rapid excretion, elicits a severe repression of catabolic enzymes.     

Photometric immersion refractometry of bacterial spores

Photometric immersion refractometry was used to determine the average apparent refractive index (n) of five types of dormant Bacillus spores representing a 600-fold range in moist-heat resistance determined as a D100 value. The n of a spore type increased as the molecular size of various immersion solutes decreased. For comparison of the spore types, the n of the entire spore and of the isolated integument was determined by use of bovine serum albumin, which is excluded from permeating into them. The n of the sporoplast (the structures bounded by the outer pericortex membrane) was determined by use of glucose, which was shown to permeate into the spore only as deeply as the pericortex membrane. Among the various spore types, an exponential increase in the heat resistance correlated with the n of the entire spore and of the sporoplast, but not of the isolated perisporoplast integument. Correlation of the n with the solids content of the entire spore provided a method of experimentally obtaining the refractive index increment (dn/dc), which was constant for the various spore types and enables the calculation of solids and water content from an n. Altogether, the results showed that the total water content is distributed unequally within the dormant spore, with less water in the sporoplast than in the perisporoplast integument, and that the sporoplast becomes more refractile and therefore more dehydrated as the heat resistance becomes greater among the various spore types.