Comparative metabolomic analysis of exudates of microcystin-producing and microcystin-free Microcystis aeruginosa strains

Cyanobacterial harmful algal blooms (cHABs) dominated by Microcystis aeruginosa threaten the ecological integrity and beneficial uses of lakes globally. In addition to producing hepatotoxic microcystins (MC), M. aeruginosa exudates (MaE) contain various compounds with demonstrated toxicity to aquatic biota. Previously, we found that the ecotoxicity of MaE differed between MC-producing and MC-free strains at exponential (E-phase) and stationary (S-phase) growth phases. However, the components in these exudates and their specific harmful effects were unclear. In this study, we performed untargeted metabolomics based on liquid chromatography-mass spectrometry to reveal the constituents in MaE of a MC-producing and a MC-free strain at both E-phase and S-phase. A total of 409 metabolites were identified and quantified based on their relative abundance. These compounds included lipids, organoheterocyclic compounds, organic acid, benzenoids and organic oxygen compounds. Multivariate analysis revealed that strains and growth phases significantly influenced the metabolite profile. The MC-producing strain had greater total metabolites abundance than the MC-free strain at S-phase, whereas the MC-free strain released higher concentrations of benzenoids, lipids, organic oxygen, organic nitrogen and organoheterocyclic compounds than the MC-producing strain at E-phase. Total metabolites had higher abundance in S-phase than in E- phase in both strains. Analysis of differential metabolites (DMs) and pathways suggest that lipids metabolism and biosynthesis of secondary metabolites were more tightly coupled to growth phases than to strains. Abundance of some toxic lipids and benzenoids DMs were significantly higher in the MC-free strain than the MC-producing one. This study builds on the understanding of MaE chemicals and their biotoxicity, and adds to evidence that non-MC-producing strains of cyanobacteria may also pose a threat to ecosystem health

Effects of Cyanobacterial Secondary Metabolites on Phytoplankton Community Succession

Allelopathic effects are one of the factors potentially influencing the succession ofphytoplankton communities; however, their influence has often been neglected.This is especially true for cyanobacteria that often outcompete other phytoplanktonspecies and form blooms causing severe problems. Allelopathic effects ofcyanobacteria can play an important role for phytoplankton succession. In thischapter, we introduce the different ways how aquatic organisms are influenced bycyanobacterial allelochemicals; the mechanisms of their interaction from the aspects of chemical intermediates, target reaction, and target signals; and interferingfactors and the ecological consequences of this process.Cyanobacteria produce and excrete a variety of allelopathic compounds thataffect other Cyanophyta, eukaryotic algae, bacteria, zooplankton, higher plants,and fish and mammalian cells. These effects are regulated by various abiotic andbiotic conditions, such as nutrient availability, temperature, and light intensity butalso cell density and growth phase of the source cyanobacterial community. Thebioactive metabolites include cyclic peptides, alkaloids, terpenoids, and otherswhich can have a variety of inhibitory effects on the different target organisms.Ecological consequences such as declines in biodiversity and accumulation oftoxins in the food chain have been shown. However, most of these compoundshave not yet been fully tested regarding their full range of effects on naturalphytoplankton communities. A detailed elucidation of the influence ofcyanobacterial allelochemicals is of key importance for understanding and managingthe succession of natural phytoplankton communities

Inaudible Attack on Smart Speakers with Intentional Electromagnetic Interference

This article demonstrates an inaudible attack on smart speakers using electromagnetic interference (EMI). The EMI induces voltages on the order of a few millivolts on conductors, which are then converted into baseband signals by exploiting the inherent nonlinearity of microphones. The EMI signal is specially preprocessed to minimize the useless harmonics generation at the microphone output signals, which significantly improves the recognition rate as well as nullify the previous countermeasures based on the harmonics detection. The sensitive carrier frequency found by our proposed method can improve the attack distance as well. A measurement-based methodology is applied to locate the sensitive regions for noise coupling without knowing the layout of the printed circuit board (PCB), and the transfer function is also obtained to insure the main coupling location. Our experiments show that in open space, intentional EMI under 2.5 W can inject commands at distances up to 2.5 m on smart speakers

Cyanobacteria blooms induce embryonic heart failure in an endangered fish species

Cyanobacterial blooms drive water-quality and aquatic-ecosystem deterioration in eutrophic lakes worldwide, mainly owing to their harmful, secondary metabolites. The response of fish exposed to these cyanobacterial chemicals, however, remains largely unknown. In this paper, we employed an endangered fish species (Sinocyclocheilus grahami) in Dianchi Lake, China to evaluate the risks of cell-free exudates (MaE) produced by a dominant cyanobacterium (Microcystis aeruginosa) on embryo development, as well as the molecular mechanisms responsible. MaE (3d cultured) caused a reduction of fertilization (35.4%) and hatching (15.5%) rates, and increased mortality rates (≤90.0%) and malformation rate (27.6%), typically accompanied by heart failure. Proteomics analysis revealed that two greatest changed proteins – protein S100A1 (over-expressed 26 times compared with control) and myosin light chain (under-expressed 25 fold) – are closely associated with heart function. Further study revealed that heart failure was due to calcium ion imbalance and malformed cardiac structure. We conclude that harmful secondary metabolites from cyanobacteria may adversely affect embryo development in this endangered fish, and possibly contribute to its disappearance and unsuccessful recovery in Dianchi Lake. Hazardous consequences of substances released by cyanobacteria should raise concerns for managers addressing recovery of this and other imperiled species in affected lakes

High fidelity entanglement of neutral atoms via a Rydberg-mediated single-modulated-pulse controlled-PHASE gate

Neutral atom platform has become an attractive choice to study the science of quantum information and quantum simulation, where intense efforts have been devoted to the entangling processes between individual atoms. For the development of this area, two-qubit controlled-PHASE gate via Rydberg blockade is one of the most essential elements. Recent theoretical studies have suggested the advantages of introducing non-trivial waveform modulation into the gate protocol, which is anticipated to improve its performance towards the next stage. We report our recent experimental results in realizing a two-qubit controlled-PHASE($C_Z$) gate via off-resonant modulated driving(ORMD) embedded in two-photon transition for Rb atoms. It relies upon a single modulated driving pulse with a carefully calculated smooth waveform to gain the appropriate phase accumulations required by the two-qubit gate. Combining this $C_Z$ gate with global microwave pulses, two-atom entanglement is generated with the raw fidelity of 0.945(6). Accounting for state preparation and measurement (SPAM) errors, we extract the entanglement operation fidelity to be 0.980(7). Our work features completing the $C_Z$ gate operation within a single pulse to avoid shelved Rydberg population, thus demonstrate another promising route for realizing high-fidelity two-qubit gate for neutral atom platform.Comment: 4 figure