Food Science

Among endosymbiotic bacterial lineages, few are as intensely studied as Rickettsiales , which include the causative agents of spotted fever, typhus, and anaplasmosis. However, an important subgroup called “ Candidatus Midichloriaceae” receives little attention despite accounting for a third of the diversity of Rickettsiales and harboring a wide range of bacteria with unique features, like the ability to infect mitochondria.

Amycolatopsis coloradensis ATCC 53629 is the producer of the glycopeptide antibiotic avoparcin. While setting up the production of the avoparcin complex, in view of its use as analytical standard, we uncovered the production of a to-date not described ristosamynil-avoparcin. Ristosamynil-avoparcin is produced together with α- and β-avoparcin (overall indicated as the avoparcin complex). Selection of one high producer morphological variant within the A. coloradensis population, together with the use of a new fermentation medium, allowed to increase productivity of the avoparcin complex up to 9 g/L in flask fermentations. The selected high producer displayed a non-spore forming phenotype. All the selected phenotypes, as well as the original unselected population, displayed invariably the ability to produce a complex rich in ristosamynil-avoparcin. This suggested that the original strain deposited was not conforming to the description or that long term storage of the lyovials has selected mutants from the original population.

HighlightsA portable system based on real-time fluorescence analysis was developed for field detection of Candidatus Liberibacter asiaticus within 40 min from sample to answer.A smartphone-assisted device was designed for easy operation, reliable nucleic acid amplification, and highly sensitive fluorescence detection, with sensitivity comparable to that of a commercial instrument.A novel homemade 3D printed box was used for in-field reagent storage, and it could maintain low temperature (<4°C) for about 8 hours without power supply.This fully integrated system is stable, easy to use, inexpensive, and has great application prospects in resource-limited areas.Abstract. Candidatus Liberibacter asiaticus (Las) is a main causal agent of huanglongbing (HLB), a destructive disease that has greatly reduced citrus yields and quality. Instruments with high sensitivity and portability are urgently required for on-site testing. In this study, a novel sample-to-answer optical system for on-site detection of Las was developed. Three major functions, including DNA extraction, amplification, and detection, are integrated into a portable case. This system mainly consists of (1) a specially designed 3D printed box for on-site reagent storage that can maintain low temperature (below 4°C) for 7.5 h at ambient temperature (35°C); (2) a custom device, called the IF-Device, for DNA amplification and detection of HLB, with an optimized optical structure, a sensitive signal processing circuit, and a precise temperature control algorithm with an accuracy of ±0.1°C; and (3) a battery-based power supply for the whole system. In a typical test using sodium fluorescein as a standard model, the results showed that the sensitivity of this system (1.0 nM) could easily meet the requirements of fluorescence biosensors. The feasibility of this homemade system was evaluated with samples extracted from infected citrus leaves based on the loop-mediated isothermal amplification (LAMP) method, and the limit of detection (LOD) was approximately 1.0 × 10-4 ng µL-1. The whole detection process for eight samples could be simultaneously accomplished within 40 min, and the results could be displayed on a smartphone in real-time. Moreover, the portable case is anti-interference, low cost, and only 2 kg in weight. Considering its sensitivity, stability, and portability, this highly integrated system possesses promising prospects for in-field detection. Keywords: Field detection, Fluorescence biosensor, Huanglongbing, Isothermal amplification, Sample-to-answer.

Here, we demonstrate how microbial storage metabolism can adjust to a wide range of environmental conditions. Such flexibility generates a selective advantage under fluctuating environmental conditions. It can also explain the different observations reported in PAO literature, including the capacity of “ Ca . Accumulibacter phosphatis” to act like glycogen-accumulating organisms (GAOs). These observations stem from slightly different experimental conditions, and controversy arises only when one assumes that metabolism can operate only in a single mode. Furthermore, we also show how the study of metabolic strategies is possible when combining omics data with functional cofactor assays and modeling. Genomic information can only provide the potential of a microorganism. The environmental context and other complementary approaches are still needed to study and predict the functional expression of such metabolic potential.