Parallel Exploitation of Diverse Host Nutrients Enhances Salmonella Virulence

Pathogen access to host nutrients in infected tissues is fundamental for pathogen growth and virulence, disease progression, and infection control. However, our understanding of this crucial process is still rather limited because of experimental and conceptual challenges. Here, we used proteomics, microbial genetics, competitive infections, and computational approaches to obtain a comprehensive overview of Salmonella nutrition and growth in a mouse typhoid fever model. The data revealed that Salmonella accessed an unexpectedly diverse set of at least 31 different host nutrients in infected tissues but the individual nutrients were available in only scarce amounts. Salmonella adapted to this situation by expressing versatile catabolic pathways to simultaneously exploit multiple host nutrients. A genome-scale computational model of Salmonella in vivo metabolism based on these data was fully consistent with independent large-scale experimental data on Salmonella enzyme quantities, and correctly predicted 92% of 738 reported experimental mutant virulence phenotypes, suggesting that our analysis provided a comprehensive overview of host nutrient supply, Salmonella metabolism, and Salmonella growth during infection. Comparison of metabolic networks of other pathogens suggested that complex host/pathogen nutritional interfaces are a common feature underlying many infectious diseases.     

Flagellin/TLR5 signalling activates renal collecting duct cells and facilitates invasion and cellular translocation of uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) colonizing kidneys is the main cause of acute pyelonephritis. TLR5 that senses flagellin was shown to be highly expressed in the bladder and to participate in host defence against flagellated UPEC, although its role in kidneys still remains elusive. Here we show that TLR5 is expressed in renal medullary collecting duct (MCD) cells, which represent a preferential site of UPEC adhesion. Flagellin, like lipopolysaccharide, stimulated the production of the chemoattractant chemokines CXCL1 and CXCL2, and subsequent migration capacity of neutrophils in cultured wild‐type (WT) and Tlr4^?/? MCDs, but not in Tlr5^?/? MCDs. UPEC can translocate across intact MCD layers without altering tight junctions. Strikingly, the invasion capacity and transcellular translocation of the UPEC strain HT7 were significantly lower in Tlr5^?/? than in WT MCDs. The non‐motile HT7ΔfliC mutant lacking flagellin also exhibited much lower translocation capacities than the HT7 isolates. Finally, Tlr5^?/? kidneys exhibited less infiltrating neutrophils than WT kidneys one day after the transurethral inoculation of HT7, and greater delayed renal bacterial loads in the day 4 post‐infected Tlr5^?/? kidneys. Overall, these findings indicate that the epithelial TLR5 participates to renal antibacterial defence, but paradoxically favours the translocation of UPEC across intact MCD cell layers.     

Biochemical and physical properties of remnant-HDL2 and of pre beta 1-HDL produced by hepatic lipase

The hepatic lipase acting on triglyceride-rich high-density lipoprotein2 (HDL2) induces the formation of pre beta 1-HDL, leaving a residual alpha-migrating HDL particle that was named "remnant-HDL2" (Barrans, A., Collet, X., Barbaras, R., Jaspard, B., Manent, J., Vieu, C., Chap, H., and Perret, B. (1994) J. Biol. Chem. 269, 11572-11577.]. In this study, these two product particles generated by hepatic lipase were isolated by density gradient ultracentrifugation. Particles were first characterized in terms of chemical composition, density, and mass. The pre beta 1-HDL obtained in vitro contain one to two molecules of apoA-I, associated with phospholipids, and free and esterified cholesterol. When compared to triglyceride-rich HDL2, remnant-HDL2 have lost on average one molecule of apoA-I, 60% of triacylglycerols, and 15% of phospholipids. The estimated composition is concordant with the hypothesis of the splitting of a substrate particle into one pre beta 1-HDL and one remnant-HDL2. Spectroscopic studies were carried out to monitor changes in lipid fluidity upon lipolysis. The fluorescence anisotropy was measured using (1,6)-diphenyl-hexa-(1,3, 5)-triene as a probe, and the degree of order was calculated from electron spin resonance spectra using the 5-nitroxy-derivative of stearic acid. Both approaches showed a decreased lipid fluidity in remnant-HDL2, as compared to triglyceride-rich HDL2. The immunoreactivity of apoA-I toward several monoclonal antibodies was assayed as a reflection of changes of apoA-I conformation. In remnant-HDL2, as compared to triglyceride-rich HDL2, a lower reactivity was noted with the 2G11 antibody, which interacts in the NH2 terminal part of apoA-I. Finally, remnant-HDL2 was clearly different from HDL3 with respect to all of the parameters studied, demonstrating that hepatic lipase does not promote the direct conversion of HDL2 to HDL3. Thus, hepatic lipase produces remnant-HDL2 particles, which display modifications of apoA-I conformation and of fluidity of the lipid environment. This newly described HDL2 subfraction may play a major role in the reverse cholesterol transport.     

Low-temperature electron transfer in photosystem II: a tyrosyl radical and semiquinone charge pair

The states induced by illumination at 7 K in the oxygen-evolving enzyme (PSII) from Thermosynechococcus elongatus were studied by EPR. In the S(0) and S(1) redox states, two g approximately 2 EPR signals, a split signal and a g = 2.03 signal, respectively, were generated by illumination with visible light. These signals were comparable to those already reported in plant PSII in terms of their g value, shape, and stability at low temperatures. We report that the formation and decay of these signals correlate with EPR signals from the semiquinone of the first quinone electron acceptor, Q(A)(-). The light-induced EPR signals from oxidized side-path electron donors (Cyt b(559), Car, and Chl(Z)) were also measured, and from these and the signals from Q(A)(-), estimates were made of the proportion of centers involved in the formation of the g approximately 2 signals (approximately 50% in S(0) and 40% in S(1)). Comparisons with the signals generated in plant PSII indicated approximately similar yields for the S(0) split signal. A single laser flash at 7 K induced more than 75% of the maximum split and g = 2.03 EPR signal observed by continuous illumination, with no detectable oxidation of side-path donors. The matching electron acceptor side reactions, the high quantum yield, and the relatively large proportion of centers involved support earlier suggestions that the state being monitored is Tyr(Z)(*)Q(A)(-), with the g approximately 2 EPR signals arising from Tyr(Z)(*) interacting magnetically with the Mn complex. The current picture of the photochemical reactions occurring in PSII at low temperatures is reassessed.     

Marketing approval of mogamulizumab: A triumph for glyco-engineering

Therapeutic properties of antibodies strongly depend on the composition of their glycans. Most of the currently approved antibodies are produced in mammalian cell lines, which yield mixtures of different glycoforms that are close to those of humans, but not fully identical. Glyco-engineering is being developed as a method to control the composition of carbohydrates and to enhance the pharmacological properties of mAbs. The recent approval in Japan of mogamulizumab (POTELIGEO^®), the first glyco-engineered antibody to reach the market, is a landmark in the field of therapeutic antibodies. Mogamulizumab is a humanized mAb derived from Kyowa Hakko Kirin’s POTELLIGENT^® technology, which produces antibodies with enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) activity. The approval was granted April 30, 2012 by the Japanese Ministry of Health, Labour and Welfare for patients with relapsed or refractory CCR4-positive adult T-cell leukemia-lymphoma.     

Impact of Urban Pollution from the Hanoi Area on Benthic Diatom Communities Collected from the Red, Nhue and Tolich Rivers (Vietnam)

The effects of urban pollution from Hanoi city on the benthic diatom communities of the Nhue–Tolich river system were studied during the 2003 dry season. Benthic diatoms were allowed to grow on glass slides suspended in the water flow for 4 weeks. To reveal the relationship between water quality and diatom communities, Canonical correspondence analysis (CCA) was used on data concerning relative abundances of diatom species and environmental variables. Two diatom indices, IPS and DAIpo, were applied to evaluate water quality in the three rivers. A total of 291 diatom taxa were found in the Red, Nhue and Tolich Rivers. These were mainly cosmopolitan taxa, with some tropical, subtropical and endemic taxa. The most abundant taxa at the Red site were Aulacoseira granulata, Achnanthidium minutissimum, Encyonema minutum, Navicula recens and other halophilous taxa such as Nitzschia kurzii, Seminavis strigosa, Entomoneis paludosa, Bacillaria paradoxa. Diatom assemblages at the Tolich site consisted mainly of Nitzschia umbonata, Nitzschia palea and Eolimna minima. Diatom density ranged from 660 to 30,000 cells/cm². Environmental variables and diatom assemblage composition at all sites were significantly correlated. Two diatom indices gave similar results and indicate the Tolich River with the lowest values as a highly polluted site.     

The anti-biofilm activity secreted by a marine Pseudoalteromonas strain

Bacterial biofilms occur on all submerged structures in marine environments. The authors previously reported that the marine bacterium Pseudoalteromonas sp. 3J6 secretes antibiofilm activity. Here, it was discovered that another Pseudoalteromonas sp. strain, D41, inhibited the development of strain 3J6 in mixed biofilms. Confocal laser scanning microscope observations revealed that the culture supernatant of strain D41 impaired biofilm formation of strain 3J6 and another marine bacterium. A microtiter plate assay of the antibiofilm activity was set up and validated with culture supernatants of Pseudoalteromonas sp. 3J6. This assay was used to determine the spectra of action of strains D41 and 3J6. Each culture supernatant impaired the biofilm development of 13 marine bacteria out of 18. However, differences in the spectra of action and the physical behaviours of the antibiofilm molecules suggest that the latter are not identical. They nevertheless share the originality of being devoid of antibacterial activity against planktonic bacteria.     

A C-terminal aldehyde insect kinin analog enhances inhibition of weight gain and induces significant mortality in Helicoverpa zea larvae

The first reported examples of C-terminal aldehyde analogs of an insect neuropeptide are described. They are hexapeptide insect kinin analogs Boc-VFFPWG-H and Fmoc-RFFPWG-H. Activity observed for these modified analogs in an in vitro insect diuretic assay confirms that the C-terminal aldehyde group is tolerated by an insect kinin receptor. The two analogs demonstrate greatly enhanced activity over standard C-terminal amide insect kinins in a larval weight gain inhibition assay in the corn earworm Helicoverpa zea. Treatment with Boc-VFFPWG-H led to significant increases in larval mortality at doses of 500pm (45%) and 5nm (67%). Boc-VFFPWG-H represents a lead analog in the development of novel, environmentally friendly pest insect management agents based on the insect kinin class of neuropeptides.     

Hydrolysis of concentrated raw starch: A new very efficient α-amylase from Anoxybacillus flavothermus

A new α-amylase from Anoxybacillus flavothermus (AFA) was found to be effective in hydrolyzing raw starch in production of glucose syrup at temperatures below the starch gelatinization temperature. AFA is very efficient, leading to 77% hydrolysis of a 31% raw starch suspension. The final hydrolysis degree is reached in 2-3 h at starch concentrations lower than 15% and 8-24 h at higher concentrations. AFA is also very efficient in hydrolyzing the crystalline domains in the starch granule. The major A-type crystalline structure is more rapidly degraded than amorphous domains in agreement with the observed preferential hydrolysis of amylopectin. Amylose-lipid complexes are degraded in a second step, yielding amylose fragments which then re-associate into B-type crystalline structures forming the final α-amylase resistant fraction. The mode of action of AFA and the factors limiting complete hydrolysis are discussed in details.     

Retroviral Oligonucleotide Distributions Correlate with Biased Nucleotide Compositions of Retrovirus Sequences,Suggesting a Duplicative Stepwise Molecular Evolution

A computer-assisted analysis was made of 24 complete nucleotide sequences selected from the vertebrate retroviruses to represent the ten viral groups. The conclusions of this analysis extend and strengthen the previously made hypothesis on the Moloney murine leukemia virus: The evolution of the nucleotide sequence appears to have occurred mainly through at least three overlapping levels of duplication: (1) The distributions of overrepresented (3–6)-mers are consistent with the universal rule of a trend toward TG/CT excess and with the persistence of a certain degree of symmetry between the two strands of DNA. This suggests one or several original tandemly repeated sequences and some inverted duplications. (2) The existence of two general core consensuses at the level of these (3–6)-mers supports the hypothesis of a common evolutionary origin of vertebrate retroviruses. Consensuses more specific to certain sequences are compatible with phylogenetic trees established independently. The consensuses could correspond to intermediary evolutionary stages. (3) Most of the (3–6)-mers with a significantly higher than average frequency appear to be internally repeated (with monomeric or oligomeric internal iterations) and seem to be at least partly the cause of the bias observed by other researchers at the level of retroviral nucleotide composition. They suggest a third evolutionary stage by slippage-like stepwise local duplications. Received: 3 January 1996 / Accepted: 27 March 1996