Dynamics of symbiont-mediated antibiotic production reveal efficient long-term protection for beewolf offspring

Background

Insects have evolved a wide range of mechanisms to defend themselves and their offspring against antagonists. One of these strategies involves the utilization of antimicrobial compounds provided by symbiotic bacteria to protect the host or its nutritional resources from pathogens and parasites. In the symbiosis of the solitary digger wasp, Philanthus triangulum (Hymenoptera, Crabronidae), the bacterial symbiont ‘Candidatus Streptomyces philanthi’ defends the developing larvae against pathogens by producing a mixture of at least nine antimicrobial substances on the cocoon surface. This antibiotic cocktail inhibits the growth of a broad range of detrimental fungi and bacteria, thereby significantly enhancing the offspring’s survival probability.

Results

Here we show that the production of antimicrobial compounds by the beewolf symbionts is confined to the first two weeks after cocoon spinning, leading to a high concentration of piericidins and streptochlorin on the cocoon surface. Expression profiling of housekeeping, sporulation, and antibiotic biosynthesis genes indicates that antibiotic production coincides with morphological differentiation that enables the symbionts to survive the nutrient-limited conditions on the beewolf cocoon. The antibiotic substances remain stable on the cocoon surface for the entire duration of the beewolf’s hibernation period, demonstrating that the compounds are resistant against environmental influences.

Conclusions

The antibiotic production by the beewolf symbionts serves as a reliable protection for the wasp offspring against pathogenic microorganisms during the long and unpredictable developmental phase in the subterranean brood cells. Thus, the beewolf-Streptomyces symbiosis provides one of the rare examples of antibiotics serving as an efficient defense in the natural environment and may aid in devising new strategies for the utilization of antibiotic combination therapies in human medicine against increasingly resistant bacterial and fungal pathogens.

Mutant Allele-Specific Uncoupling of PENETRATION3 Functions Reveals Engagement of the ATP-Binding Cassette Transporter in Distinct Tryptophan Metabolic Pathways

Arabidopsis (Arabidopsis thaliana) penetration (PEN) genes quantitatively contribute to the execution of different forms of plant immunity upon challenge with diverse leaf pathogens. PEN3 encodes a plasma membrane-resident pleiotropic drug resistance-type ATP-binding cassette transporter and is thought to act in a pathogen-inducible and PEN2 myrosinase-dependent metabolic pathway in extracellular defense. This metabolic pathway directs the intracellular biosynthesis and activation of tryptophan-derived indole glucosinolates for subsequent PEN3-mediated efflux across the plasma membrane at pathogen contact sites. However, PEN3 also functions in abiotic stress responses to cadmium and indole-3-butyric acid (IBA)-mediated auxin homeostasis in roots, raising the possibility that PEN3 exports multiple functionally unrelated substrates. Here, we describe the isolation of a pen3 allele, designated pen3-5, that encodes a dysfunctional protein that accumulates in planta like wild-type PEN3. The specific mutation in pen3-5 uncouples PEN3 functions in IBA-stimulated root growth modulation, callose deposition induced with a conserved peptide epitope of bacterial flagellin (flg22), and pathogen-inducible salicylic acid accumulation from PEN3 activity in extracellular defense, indicating the engagement of multiple PEN3 substrates in different PEN3-dependent biological processes. We identified 4-O-β-D-glucosyl-indol-3-yl formamide (4OGlcI3F) as a pathogen-inducible, tryptophan-derived compound that overaccumulates in pen3 leaf tissue and has biosynthesis that is dependent on an intact PEN2 metabolic pathway. We propose that a precursor of 4OGlcI3F is the PEN3 substrate in extracellular pathogen defense. These precursors, the shared indole core present in IBA and 4OGlcI3F, and allele-specific uncoupling of a subset of PEN3 functions suggest that PEN3 transports distinct indole-type metabolites in distinct biological processes.

Comparison of methods employing gas chromatography retention data to determine vapour pressures at 298 K

Validity of five models suggested for expressing the relationship between vapour pressures and GC retention times measured on a non-polar capillary column were tested on a common set of compounds [five homologous series of the type H-(CH2)n-Y, where Y denotes Cl, Br, CHO, OCOCH3 and COOCH3, and n varies from 6 to 14]. Standard methods of statistical analysis, as well as vapour pressure values obtained independently from direct vapour pressure measurements were used as validity criteria. For the 40-compound data set examined, the methods provided vapour pressures agreeing within 9.2-24.7% (average absolute percent error) with direct experimental data.

Alkynyltrifluoroborates as Versatile Tools in Organic Synthesis: A New Route to Spiroketals

[reaction: see text] A simple and efficient two-step approach to spiroketals is described. Key steps include the preparation of functionalized hydroxyl alpha-alkynones by ring-opening reactions of lactones with lithium alkynyltrifluoroborates followed by a palladium-catalyzed hydrogenation/spirocyclization of the prespiroketal intermediate.

The determination of two analogues of 4-(azidomethyl)-1,1'-biphenyl as potential genotoxic impurities in the active pharmaceutical ingredient of several sartans containing a tetrazole group

4'-(azidomethyl)-[1,1'-biphenyl]-2-carbonitrile (GTI-azide-1) and 5-(4'-(azidomethyl)-[1,1'-biphenyl]-2-yl)-1H-tetrazole (GTI-azide-2) are potentially genotoxic impurities that can be present at trace levels in the active pharmaceutical ingredients and drug products of sartans containing a tetrazole group. A method of high-performance liquid chromatography coupled with mass spectrometry, that allows the determination of those genotoxic impurities at sub-ppm level relative to the active pharmaceutical ingredient, was developed. The method utilises a very efficient liquid chromatograph Waters Acquity I-Class coupled with a highly sensitive tandem mass spectrometer Xevo TQ-XS. The separation was achieved on a column Acquity UPLC BEH Shield RP18 1.7 μm employing a linear elution gradient. The mass spectrometer was used with a heated electrospray ionization. The method was found to be sufficient in terms of sensitivity, linearity, precision, accuracy, selectivity and robustness and is easily applicable in the pharmaceutical quality control environment. The method allows for accurate quantification of both impurities GTI-azide-1 and GTI-azide-2 at levels below 1/10^th of the specification limit, which is crucial in the context of pharmaceutical analysis. The limit of quantification was determined to be 0.033 ppm and 0.025 ppm for GTI-azide-1 and GTI-azide-2, respectively.

Separation of structurally related primary aliphatic amines using hydrophilic interaction chromatography with fluorescence detection after postcolumn derivatization with o-phthaldialdehyde/mercaptoethanol

The retention behavior of primary aliphatic amines (homologous series of aliphatic alkyl amines and cycloalkyl amines) and positional isomers of alkylamines in the hydrophilic interaction chromatography mode was studied. The study was carried out on a TSKgel Amide-80 column followed by postcolumn derivatization with fluorescence detection to describe the retention mechanism of tested compounds. The effect of chromatographic conditions including column temperature, acetonitrile content in the mobile phase, mobile phase pH (ranging from 3.5 to 6.8), and salt concentration in the mobile phase was investigated. The final mobile phase consisted of acetonitrile and solution of 20 mM potassium formate pH 3.5 in ratio 80:20 v/v. The analyses were carried out at mobile phase flow rate of 1.0 mL/min and the column temperature of 20°C. The developed method was fully validated in terms of linearity, sensitivity (limit of detection and limit of quantification), accuracy, and precision according to International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines. The proposed new methods were proved to be highly sensitive, simple, and rapid, and were successfully applied to the determinations of isopropylamine, cyclohexylamine, and cyclopropylamine in relevant active pharmaceutical ingredients.

Comprehensive UHPLC-MS screening methods for the analysis of triazolopyrazine precursor and its genotoxic nitroso-derivative in sitagliptin pharmaceutical formulation

A case study on Sitagliptin drug products and Sitagliptin/Metformin drug products concerning contamination with N-nitrosamines was performed using two newly developed analytical methods for determination of N-nitroso-triazolopyrazine (NTTP; 7-nitroso-3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine) and its precursor triazolopyrazine (3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine). The method for determination of triazolopyrazine was previously unpublished, the method for determination of NTTP was published only for analysis of active pharmaceutical ingredient Sitagliptin and not the drug forms. Solving the N-nitrosamine contamination is requested by regulatory authorities all over the world and thus is vital for all pharmaceutical companies. The solution always requires a sensitive analytical method. Both newly developed methods use liquid chromatography coupled with mass spectrometry (single quadrupole analyzer in case of triazolopyrazine and triple quadrupole analyzer in case of NTTP). Separation of triazolopyrazine was achieved on a column Acquity CSH C18 using a mobile phase consisting of aqueous ammonium formate buffered at pH 4.2 and acetonitrile. Detection was performed using positive electrospray and selected ion monitoring at m/z 193. Separation of NTTP was achieved on a column Acquity HSS T3 using a mobile phase consisting of 0.1 % formic acid in water and methanol. Detection was performed using positive electrospray and multiple reaction monitoring at transitions m/z 222.15→42.05 (collision energy 17 eV) and m/z 222.15→192.15 (collision energy 11 eV). Two issues specific to NTTP and triazolopyrazine previously not described in scientific literature were successfully troubleshooted. Spontaneous degradation of Sitagliptin to triazolopyrazine and methyl (R)-3-amino-4-(2,4,5-trifluorophenyl)butanoate was solved by using N,N-dimethylformamide as sample solvent during development of the method for quantitation of triazolopyrazine. A bad peak shape of NTTP due to the presence of rotamers of NTTP was successfully troubleshooted by increasing column temperature. Both methods were used during an optimization study of manufacturing of Sitagliptin and Sitagliptin/Metformin drug products. The goal of the study was to decrease NTTP content in the final drug product under the strict legislative limit set by Federal Drug Agency. The efficacy of several solutions was proven, but could not be fully disclosed due to Intellectual Property Protection policy of Zentiva. Instead, a brief review of recently published strategies to cope with N-nitrosamine contamination is presented.