Diketopiperazines as Cross-Communication <i>Quorum</i>-<i>Sensing</i> Signals between Cronobacter sakazakii and Bacillus cereus

Herein, we reveal a second <i>quorum-sensing</i> system produced by Cronobacter sakazakii. A cyclo­(l-Pro–l-Leu) diketopiperazine, detected in pure and mixed cultures of C. sakazakii and Bacillus cereus explains the coexistence of both in the same industrial environments. The molecule was identified by gas chromatography–mass spectrometry (GC–MS), ¹H, and ¹³C NMR, including 2D NMR (correlation spectroscopy, heteronuclear multiple bond correlation, and heteronuclear single quantum correlation), and the absolute configuration was compared with that of four synthetic standards produced by solid phase peptide synthesis using a chiral column on a GC–flame ionization detection. This article provides a new method to determine the absolute configuration of cyclo­(Pro–Leu) diketopiperazine replacing the joint use of ¹H NMR and Marfey’s method

Additional Vinyl Ketones and Their Pyranyl Ketones in Gonyleptid Harvestmen (Arachnida: Opiliones) Suggest These Metabolites Are Widespread in This Family

Four species of gonyleptid harvestmen, <i>Acanthogonyleptes pulcher</i>,<i> Gonyleptes saprophilus</i> (Gonyleptinae), <i>Sodreana barbiellini</i>, and <i>Sodreana leprevosti</i> (Sodreaninae), were examined by GC-MS and ¹H NMR. All of these species release vinyl ketones, and three of them produce the corresponding pyranyl ketones, which are presumed hetero-Diels–Alder (HDA) dimers. The vinyl ketones 5-methyl-1-hexen-3-one, <i>rac</i>-4-methyl-1-hexen-3-one, and (<i>S</i>)-4-methyl-1-hexen-3-one were synthesized. Natural 4-methyl-1-hexen-3-one is present as a single stereoisomer and has the <i>R</i>-configuration. Vinyl ketone dimers (HDA dimers) were also observed in the scent gland exudate and characterized by HRMS, ¹³C NMR, and ¹H NMR chemical shifts of the pyranyl moiety

Simultaneous Multienzymatic Screening with Fluorogenic Probes

<div><p>The simultaneous screening of multiple enzyme activities in a single assay has numerous advantages over the traditional format, since it decreases sampling errors, allows savings in reagents and consumables and reduces the time and labor required to conduct the assays. In the present study, a direct and sensitive assay for the simultaneous detection of epoxide hydrolase and esterase (or lipase) activities was developed. Signal overlap is avoided by synthesizing fluorogenic probes with enzyme-specific alkyl linkers, connected to different fluorophores (resorfurin and umbelliferone), which exhibit emission spectra at different wavelengths. The simultaneous assays were conducted in microplate format with the fluorogenic probes monitored in the same well that uses microorganisms as enzyme source. Our results show that the fluorescent signal from each of the probes used here can be discriminated, allowing multiple enzyme activity detection and quantitation.</p></div

Classification and Identification of Petroleum Microorganisms by MALDI-TOF Mass Spectrometry

<div><p>Indigenous bacteria isolated from a crude oil sample from a deep water reservoir in the Pampo Sul Oilfield (Campos Basin-RJ, Brazil) were previously classified as strains of B. pumilus. However, their enzymatic activities with fluorogenic probes and rates of petroleum biodegradation were completely different. Some of the bacteria depleted n-alkanes, whereas others did not. Aromatic compounds reported to be recalcitrant were also biodegraded by some of these Bacillus strains, revealing their outstanding ability to deplete petroleum. Further classification using matrixassisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) followed by statistical analysis revealed that these strains could be clustered into three different groups, consistent with their enzymatic activity evaluation. A more accurate phylogenetic analysis using gyrB gene sequences confirmed the MALDI-TOF MS classification of three groups of strains and identified them as Bacillus safensis, B. cereus and B. thuringiensis.</p></div