High susceptibility of MDR and XDR Gram-negative pathogens to biphenyl-diacetylene-based difluoromethyl-allo-threonyl-hydroxamate LpxC inhibitors.

OBJECTIVES: Inhibitors of uridine diphosphate-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC, which catalyses the first, irreversible step in lipid A biosynthesis) are a promising new class of antibiotics against Gram-negative bacteria. The objectives of the present study were to: (i) compare the antibiotic activities of three LpxC inhibitors (LPC-058, LPC-011 and LPC-087) and the reference inhibitor CHIR-090 against Gram-negative bacilli (including MDR and XDR isolates); and (ii) investigate the effect of combining these inhibitors with conventional antibiotics. METHODS: MICs were determined for 369 clinical isolates (234 Enterobacteriaceae and 135 non-fermentative Gram-negative bacilli). Time-kill assays with LPC-058 were performed on four MDR/XDR strains, including Escherichia coli producing CTX-M-15 ESBL and Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii producing KPC-2, VIM-1 and OXA-23 carbapenemases, respectively. RESULTS: LPC-058 was the most potent antibiotic and displayed the broadest spectrum of antimicrobial activity, with MIC90 values for Enterobacteriaceae, P. aeruginosa, Burkholderia cepacia and A. baumannii of 0.12, 0.5, 1 and 1 mg/L, respectively. LPC-058 was bactericidal at 1× or 2× MIC against CTX-M-15, KPC-2 and VIM-1 carbapenemase-producing strains and bacteriostatic at ≤4× MIC against OXA-23 carbapenemase-producing A. baumannii. Combinations of LPC-058 with β-lactams, amikacin and ciprofloxacin were synergistic against these strains, albeit in a species-dependent manner. LPC-058's high efficacy was attributed to the presence of the difluoromethyl-allo-threonyl head group and a linear biphenyl-diacetylene tail group. CONCLUSIONS: These in vitro data highlight the therapeutic potential of the new LpxC inhibitor LPC-058 against MDR/XDR strains and set the stage for subsequent in vivo studies.

Rational design of a (S)-selective-Transaminase for asymmetric synthesis of (1S)-1-(1,1'-biphenyl 2-yl)ethanamine

Amine transaminases offer an environmentally sustainable synthesis route for the production ofpure chiral amines. However, their catalytic efficiency towards bulky ketone substrates isgreatly limited by steric hindrance and therefore presents a great challenge for industrialsynthetic applications. Hereby we report an example of rational transaminase enzyme design tohelp alleviate these challenges. Starting from the Vibrio fluvialis amine transaminase that has nodetectable catalytic activity towards the bulky aromatic ketone 2-acetylbiphenyl, we employed arational design strategy combining in silico and in vitro studies to engineer the transaminaseenzyme with a minimal number of mutations, achieving an high catalytic activity and highenantioselectivity. We found that by introducing two mutations W57G/R415A detectableenzyme activity was achieved. The rationally designed best variant,W57F/R88H/V153S/K163F/I259M/R415A/V422A, showed an improvement in reaction rateby > 1716-fold towards the bulky ketone under study, producing the corresponding enantiomericpure (S)-amine (ee value of > 99%). 

Potential adverse health effects of persistent organic pollutants on sea turtles: Evidences from a cross-sectional study on Cape Verde loggerhead sea turtles

[EN] The Cape Verde nesting population of loggerhead sea turtles (Caretta caretta) is the third largest population of this species in the world. For conservation purposes, it is essential to determine how these reptiles respond to different types of anthropogenic contaminants. We evaluated the presence of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) in the plasma of adult nesting loggerheads from Boa Vista Island, Cape Verde, and studied the effects of the contaminants on the health status of the turtles using hematological and biochemical parameters. All turtles had detectable levels of non-dioxin like PCBs, whereas dioxin-like congeners (DL-PCBs) were detected in only 30% of the turtles.

On the reactivity of naphthalene and biphenyl dianions: tying up loose ends concerning an SN2-ET dichotomy in alkylation reactions

Naphthalene and biphenyl dianions are interesting compounds that can be obtained by double reduction of the corresponding arenes in solution with certain alkali metals. These dianions are highly reactive and rather elusive species with very high laying and highly delocalized electrons. They share many aspects of the reactivity of the alkali metal they originated from and consequently behave primarily as strong electron transfer (ET) reagents. We report here kinetic evidence for a different type of reactivity in their alkylation reactions with alkyl fluorides. By using cyclopropylmethyl fluoride (c-C3H5CH2F) as a very fast radical probe, we were able to settle that this alkylation does not involve the classical electron transfer reaction followed by radical coupling between diffusing radicals, but supports the alternative SN2 concerted mechanism, discerning thus this mechanistic SN2-ET dichotomy.

Development of measurement and modeling techniques to quantify atmospheric deposition of persistent, bioaccumulative and toxic chemicals in the Great Lakes

Measurement and modeling techniques were developed to improve over-water gaseous air-water exchange measurements for persistent bioaccumulative and toxic chemicals (PBTs). Analytical methods were applied to atmospheric measurements of hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Additionally, the sampling and analytical methods are well suited to study semivolatile organic compounds (SOCs) in air with applications related to secondary organic aerosol formation, urban, and indoor air quality. A novel gas-phase cleanup method is described for use with thermal desorption methods for analysis of atmospheric SOCs using multicapillary denuders. The cleanup selectively removed hydrogen-bonding chemicals from samples, including much of the background matrix of oxidized organic compounds in ambient air, and thereby improved precision and method detection limits for nonpolar analytes. A model is presented that predicts gas collection efficiency and particle collection artifact for SOCs in multicapillary denuders using polydimethylsiloxane (PDMS) sorbent. An approach is presented to estimate the equilibrium PDMS-gas partition coefficient (Kpdms) from an Abraham solvation parameter model for any SOC. A high flow rate (300 L min-1) multicapillary denuder was designed for measurement of trace atmospheric SOCs. Overall method precision and detection limits were determined using field duplicates and compared to the conventional high-volume sampler method. The high-flow denuder is an alternative to high-volume or passive samplers when separation of gas and particle-associated SOCs upstream of a filter and short sample collection time are advantageous. A Lagrangian internal boundary layer transport exchange (IBLTE) Model is described. The model predicts the near-surface variation in several quantities with fetch in coastal, offshore flow: 1) modification in potential temperature and gas mixing ratio, 2) surface fluxes of sensible heat, water vapor, and trace gases using the NOAA COARE Bulk Algorithm and Gas Transfer Model, 3) vertical gradients in potential temperature and mixing ratio. The model was applied to interpret micrometeorological measurements of air-water exchange flux of HCB and several PCB congeners in Lake Superior. The IBLTE Model can be applied to any scalar, including water vapor, carbon dioxide, dimethyl sulfide, and other scalar quantities of interest with respect to hydrology, climate, and ecosystem science.

Bioremediation of polychlorinated biphenyls (PCBs) polluted marine sediments: a study of the effectiveness of bioaugmentation and biostimulation via microbial electrochemical technologies and polyhydroxyalkanoates

Polychlorinated biphenyls (PCBs) are chemicals largely employed in the industry, banned at the end of the last century yet still persistent in the environment. Bioremediation, namely exploiting bacteria to reduce PCBs’ toxicity, is receiving attention as a promising approach to remediate polluted site in situ. Natural bioremediation is constrained by several factors as the low amount of the required growth substrates (e.g. electron donors, oxygen) and the scarcity of bacteria able to metabolize PCBs. In this regard, use of biodegradable polymers or applied potentials have been demonstrated effective in priming bioremediation of freshwater environments (e.g. river sediments) polluted by chlorinated solvents or PCBs. Yet, little is known regarding the application in marine sediments, where the abundance of anaerobic competitors (i.e. sulfate reducing bacteria) and the different sediment’s features might affect the bioremediation. In this study, polyhydroxyalkanoates (PHAs) and Microbial Electrochemical Technologies (METs) were applied for the first time to prime bioremediation of PCBs polluted marine sediments. The influence of PHAs was studied on the main anaerobic metabolisms and on the microbial community of the heavily polluted sediments coming from the Pialassa della Baiona, a micro-tidal coastal lagoon in Ravenna, and from Mar Piccolo, the marine basin aside Taranto. The impact of METs was deepened by monitoring the physical-chemical parameters and the main anaerobic metabolisms of the sediments coming from Ravenna. The effectiveness of biostimulating with PHAs depended on the features of the treated site, possibly due to the availability of the amendments and to the competition of the indigenous microbial communities. The bioelectrochemical stimulation inhibited the bioremediation process. In both cases, the presence of an inoculated bacterial community was required to perform bioremediation. The collected results led to a comprehensive analysis of the available literature, questioning what could be the further approaches for an effective in situ bioremediation.

A New Species Of Pseudopaludicola Miranda-ribeiro, 1926 (anura: Leptodactylidae: Leiuperinae) From Northwestern State Of São Paulo, Brazil.

A new species of Pseudopaludicola is described from human-altered areas originally covered by Semideciduous Forest in northwestern state of São Paulo, southeastern Brazil. Morphologically, the new species differs from four species belonging to the P. pusilla group by the absence of either T-shaped terminal phalanges or toe tips expanded, and from all other congeners except P. canga and P. facureae by possessing an areolate vocal sac, with dark reticulation. The higher duration (300-700 ms) of each single, pulsed note (9-36 nonconcatenated pulses) that compose the call in the new species distinguishes it from all other 14 species of Pseudopaludicola with calls already described (10-290 ms). Absence of harmonics also differ the advertisement call of the new species from the call of its sister species P. facureae, even though these two species presented unexpected low genetic distances. Although we could not identify any single morphological character distinguishing the new species from P. facureae, a PCA and DFA performed using 12 morphometric variables evidenced significant size differences between these two species. 

A new species of Neotropical freshwater stingray of the genus Potamotrygon Garman, 1877 from the Río Madrede Díos, Peru (Chondrichthyes: Potamotrygonidae)

Potamotrygon tatianae sp. nov., is described from Río Madre de Díos, Peru, upper Rio Madeira basin. The new species is distinguished from all congeners by a unique combination of characters, including its dorsal color pattern formed by a relatively slender, highly convoluted, beige to dark brown vermicular pattern, a single row of dorsal tail spines, and a relatively longer tail posterior to caudal stings. Potamotrygon tatianae sp. nov., occurs sympatrically with other species of Potamotrygon (P. falkneri, P. orbignyi and P. motoro). From the similar species P. falkneri, P. tatianae sp. nov., is further distinguished by the absence of circular, reniform, and oval spots, by its proportionally much longer tail, by having dorsal tail spines in one irregular row, and by features of the ventral lateral-line canal, dermal denticles and neurocranium. From P. orbignyi, the new species is distinct by lacking a reticulate pattern on dorsal disc and by the presence of two angular cartilages. From P. motoro, P. tatianae sp. nov., is further separated by the lack of ocelli formed by strong black concentric rings, by the more flattened aspect of its head and disc, and by having smaller and more numerous teeth. The discovery of a new species that so closely resembles a congeneric form in color pattern, a feature highly variable within the latter, highlights the importance of examining large series of individuals and of detailed morphological analyses in revealing the potentially highly cryptic nature of the diversity within the family.

Trichomycterus dali: a new highly troglomorphic catfish (Silurifomes: Trichomycteridae) from Serra da Bodoquena, Mato Grosso do Sul State, Central Brazil

Trichomycterus dali, new species, is described from flooded limestone caves in Serra da Bodoquena karst area, State of Mato Grosso do Sul, Central Brazil. The new species is diagnosed by a unique character in the genus, the presence of conspicuous, ridge-like adipose folds lining dorsally throughout the body. Trichomycterus dali can be further distinguished readily from epigean congeners by the reduction of eyes and skin pigmentation (except for T. gorgona), and from remaining congeners (i.e., all hypogean plus T. gorgona) by the total loss of eyes, not visible externally (except for T. sandovali and T. spelaeus). Other diagnostic features includes very long barbels, especially the nasal (99.3-143.5% HL) and the maxillary (97.0-131.3% HL), pectoral-fin ray count reaching I,9 and a unique cranial fontanel with a conspicuous constriction on the meeting point of supraoccipital and the two frontal bones. The troglobitic status of the species is suggested by the presence of troglomorphisms on an advanced degree, especially the reduction of skin pigmentation, the total loss of eyes and the enlarged barbels. In addition, the presence of a well developed adipose fold in adults may indicate a distinctive adaptation acquired by neoteny to withstand the food scarce conditions of its hypogean habitat.

Ituglanis mambai, a new subterranean catfish from a karst area of Central Brazil, rio Tocantins basin (Siluriformes: Trichomycteridae)

Ituglanis mambai, new species, is described from a cave in the Mambaí karst area, State of Goiás, Central Brazil. The new species distinguishes from epigean and cave congeners by the combination of the following characteristics: posterior supraoccipital fontanel absent; pectoral-fin rays usually i,7; six pleural ribs; total vertebrae 37-38 behind Weberian apparatus; shorter predorsal length (65.1-70.8% SL); shorter caudal peduncle length (8.4-11.9% SL); shorter dorsal-fin base length (7.7-11.3% SL); wider interobital width (29.2-36.5% HL); larger mouth width (43.4-64.0% HL); intermediate between epigean and other cave Ituglanis species as regards to both eyes (diameter varying from 0.5 to1.0 mm in adults, 7.8-10.1 % HL) and pigmentation, composed by irregular light brown spots along the body. The latter indicate the troglobitic status for I. mambai. In addition, this species has the maxillae with a discrete medial-posterior projection; fronto-lacrimal one half-length of the maxillae and pointed backwards; posterior process of palatine half its length, with a tenuous medial concavity; 14 dorsal and 12 ventral procurrent rays. In the natural habitat, I. mambai displayed cryptobiotic habits, trying to hide in the graveled bottom or under boulders when disturbed, apparently showing a negative response to light. It was observed a preference to slow-moving waters. Recent flood marks were observed in the stream conduit in March/April 2007 (end of the rainy season) when less individuals were observed on 300 m of the subterranean stream compared to September 2004 (end of the dry season).

Potamotrygon boesemani (Chondrichthyes: Myliobatiformes: Potamotrygonidae), a new species of Neotropical freshwater stingray from Surinam

Potamotrygon boesemani, new species, is described from the Corantijn river drainage in Surinam. The species has a diagnostic dorsal color pattern formed by deep orange to red ocellated spots of irregular form, encircled by relatively broad black rings. Potamotrygon boesemani is distinguished from other ocellated congeners (P. motoro, P. henlei and P. leopoldi) by the more intensely colored ocelli, which are usually yellow in the latter species. From P. motoro it is also distinguished by the darker dorsal background coloration, by the broader black contour of the dorsal ocelli, and by the irregular form of the ocelli as compared to the more rounded shape in the latter species. From P. henlei and P. leopoldi, it is distinguished by the lack of ocelli on tail. From the tentatively identified specimen of P. ocellata, which also has dark orange ocelli, the irregular contour of the ocelli in the new species is also distinctive. The teeth are relatively smaller and in greater number than in P. motoro and P. ocellata, with up to 45 rows in the upper jaw.