We present a comprehensive update on the studies of atmospheric aging processes for airborne bioaerosols under various laboratory-controlled conditions. We reviewed changes in physical, chemical, and ...biological properties of aerosolized biological organisms suspended in air under different simulated environmental parameters or open air factors (OAFs). These changes were scrutinized by measuring viability, inactivation, infectivity, DNA damage, qPCR signal, fluorescence spectral profile and intensity, or/and Raman spectral features. The OAFs considered here are the solar or ultra-violet (UV) radiation, heat or temperature, ozone (O3), free radicals, pollutants, relative humidity, and volatile organic compounds. Most times, especially in actual environmental conditions, far more than one of these factors were involved in the aging processes under various mixed conditions with different levels of individual factors and procedures applied. It is extremely challenging to quantitatively describe these changes of airborne bioaerosols under various combined influences of multiple OAFs. To date, there is not yet sufficient knowledge to enable us to quantitatively express relationships among viability, PCR signals, and spectral features for the atmospheric aging processes, except for some simple changes under particular conditions. Therefore, more comprehensive studies are strongly encouraged to be carried out to address those challenges in the field.
•Review on the atmospheric aging processes of bioaerosol particles.•Studies about the aging effects of various open air factors.•Solar radiation, relative humidity, ozone or free radicals, volatile organic compounds (VOC), second organic aerosols (SOA).•Focusing on the influences of laboratory-controlled conditions.•Changes of viability, fluorescence, and Raman signatures.
Intestinal microbial metabolites have been increasingly recognized as important regulators of enteric viral infection. However, very little information is available about which specific ...microbiota-derived metabolites are crucial for swine enteric coronavirus (SECoV) infection in vivo. Using swine acute diarrhea syndrome (SADS)-CoV as a model, we were able to identify a greatly altered bile acid (BA) profile in the small intestine of infected piglets by untargeted metabolomic analysis. Using a newly established ex vivo model-the stem cell-derived porcine intestinal enteroid (PIE) culture-we demonstrated that certain BAs, cholic acid (CA) in particular, enhance SADS-CoV replication by acting on PIEs at the early phase of infection. We ruled out the possibility that CA exerts an augmenting effect on viral replication through classic farnesoid X receptor or Takeda G protein-coupled receptor 5 signaling, innate immune suppression or viral attachment. BA induced multiple cellular responses including rapid changes in caveolae-mediated endocytosis, endosomal acidification and dynamics of the endosomal/lysosomal system that are critical for SADS-CoV replication. Thus, our findings shed light on how SECoVs exploit microbiome-derived metabolite BAs to swiftly establish viral infection and accelerate replication within the intestinal microenvironment.
We integrated a rigid optical trap into a tunable pulsed cavity ringdown spectroscopy (OT-CRDS) system to characterize the extinction of single airborne particles in the UV spectral region (306-315 ...nm). Single solid particles from a multi-walled carbon nanotube (MWCNT), Bermuda grass smut spore, carbon microsphere, and blackened polyethylene microsphere were trapped in air based on the photophoretic force. The improved OT-CRDS system was highly sensitive and able to resolve extinctions of single particles from different materials and sizes at a given wavelength. Further, we successfully manipulated the number of particles, e.g., 1, 2 or more particles, in the trap and measured their distinguishable extinctions using the OT-CRDS. We also show that the particle size and extinction have a good linear correlation from the measurements of 24 single MWCNT particles. Material- and wavelength-dependent extinctions of the four types of airborne particles were also characterized. Results reveal that single airborne particles regardless of their differences in material and size, due to their heterogeneous morphology, have individual-particle dependent extinctions and that dependence can be resolved and characterized using the OT-CRDS technique.
The study of physical and chemical properties of a microscopic object, such as a single particle, is made possible using optical trapping (OT) technology combined with other measuring techniques. ...Here we show a universal optical trap combined with Raman spectroscopy (RS) and microscopy imaging for single-particle studies. The universal optical trap is constructed using two counter-propagating hollow beams and is able to stably levitate single particles of a wide range of properties, such as transparent or absorbing materials, organic (polymers, bioaerosols, etc.) or inorganic constituents (carbon, silica, glass, etc.), and spherical or irregularly shaped morphologies. Both physical and chemical properties and their temporal evolution of the trapped particle can be characterized simultaneously using the integrated OT-RS and imaging system. We created three sample cases to demonstrate the analytical merits of the system: (I) a single particle with no change, (II) partially degraded over the measuring period, and (III) one part from the fragmentized single particle. The particles' chemical compositions, crystalline states, etc. are inferred from their Raman spectra, while their physical properties (sizes, shapes, morphologies, etc.) are revealed by images. This integrated OT-RS system provides a new approach to concurrently characterize and monitor physical and chemical properties of single micrometer-sized objects optically trapped in air.
Display omitted
•A universal optical trap for trapping a wide variety of particles in air.•Integrated OT-RS system for concurrent measurements of physical and chemical properties.•Three test cases to demonstrate the analytical merits of the integrated OT-RS system.•A new method to study the physical and chemical evolutions of single particles in air.
Photophoretic trapping-Raman spectroscopy (PTRS) is a new technique for measuring Raman spectra of particles that are held in air using photophoretic forces. It was initially demonstrated with Raman ...spectra of strongly-absorbing carbon nanoparticles (Pan et al. 44 (Opt Express 2012)). In the present paper we report the first demonstration of the use of PTRS to measure Raman spectra of absorbing and weakly-absorbing bioaerosol particles (pollens and spores). Raman spectra of three pollens and one smut spore in a size range of 6.2–41.8µm illuminated at 488nm are shown. Quality spectra were obtained in the Raman shift range of 1600–3400cm−1 in this exploratory study. Distinguishable Raman scattering signals with one or a few clear Raman peaks for all four aerosol particles were observed within the wavenumber region 2940–3030cm−1. Peaks in this region are consistent with previous reports of Raman peaks in the 1600–3400cm−1 range for pollens and spores excited at 514nm measured by a conventional Raman spectrometer. Noise in the spectra, the fluorescence background, and the weak Raman signals in most of the 1600–3400cm−1 region make some of the spectral features barely discernable or not discernable for these bioaerosols except the strong signal within 2940–3030cm−1. Up to five bands are identified in the three pollens and only two bands appear in the fungal spore, but this may be because the fungal spore is so much smaller than any of the pollens. The fungal spore signal relative to the air-nitrogen Raman band is approximately 10 times smaller than that ratio for the pollens. The five bands are tentatively assigned to the CH2 symmetric stretch at 2948cm−1, CH2 Fermi resonance stretch at 2970cm−1, CH3 symmetric stretch at 2990cm−1, CH3 out-of-plane end asymmetric stretch at 3010cm−1, and unsaturated =CH stretch at 3028cm−1. The two dominant bands of the up-to-five Raman bands in the 2940–3030cm−1 region have a consistent band spacing of 25cm−1 in all four aerosols. Finally we discuss improvements to the PTRS that should provide a system which can trap a higher fraction of particle types and obtain Raman spectra over a larger range (e.g., 200–3600cm−1) than those achieved here.
•Photophoretic trapping-Raman spectroscopy (PTRS).•Raman spectra of a single pollen/spore trapped in air.•PTRS spectra of three pollens and one fungal spore.•Up to five Raman bands in the Raman shift region of 2940–3030cm−1.
The combination of optical trapping with Raman spectroscopy provides a powerful method for the study, characterization, and identification of biological micro-particles. In essence, optical trapping ...helps to overcome the limitation imposed by the relative inefficiency of the Raman scattering process. This allows Raman spectroscopy to be applied to individual biological particles in air and in liquid, providing the potential for particle identification with high specificity, longitudinal studies of changes in particle composition, and characterization of the heterogeneity of individual particles in a population. In this review, we introduce the techniques used to integrate Raman spectroscopy with optical trapping in order to study individual biological particles in liquid and air. We then provide an overview of some of the most promising applications of this technique, highlighting the unique types of measurements enabled by the combination of Raman spectroscopy with optical trapping. Finally, we present a brief discussion of future research directions in the field.
Swine acute diarrhea syndrome coronavirus (SADS‐CoV) is a newly discovered alphacoronavirus with zoonotic potential that causes diarrhea and vomiting mainly in piglets. Having emerged suddenly in ...2017, the prevailing opinion is that the virus originated from HKU2, an alphacoronavirus whose primary host is bats, and at some unknown point achieved interspecies transmission via some intermediate. Here, we further explore the evolutionary history and possible cross‐species transmission event for SADS‐CoV. Coevolutionary analysis demonstrated that HKU2 may have achieved host switch via SADS‐related (SADSr)‐CoV, which was isolated from the genus Rhinolophus in 2017. SADS‐CoV, HKU2, and SADSr‐CoV share similar codon usage patterns and showed a lower tendency to use CpG, which may reflect a method of immune escape. The analyses of virus‐host coevolution and recombination support SADSr‐CoV is the direct source of SADS‐CoV that may have undergone recombination events during its formation. Structure‐based spike glycoprotein variance analysis revealed a more nuanced evolutionary pathway to receptor recognition for host switch. We did not find a possible positive selection site, and the dN/dS of the S gene was only 0.29, which indicates that the current SADS‐CoV is slowly evolving. These results provide new insights that may help predict future cross‐species transmission, and possibly surveil future zoonotic outbreaks and associated public health emergencies.
Single particles trapped in an optical trap may experience temperature elevation, yet direct measurement of temperature and its distribution inside the optical trap of several to hundreds of microns ...in size remains a big challenge. We introduce a method that can measure the temperature inside a universal optical trap (UOT) using Raman spectroscopy of single trapped particles of high thermal conductivity. We measured temperature and temperature distributions inside the UOT using Raman shifts of single-walled carbon nanotubes (SWCNTs) and micron-sized diamonds (MSDs), which are heated by trapping laser beams directly or indirectly, depending on the location of the particle in the trap. We show that the temperature at the center of the UOT is much lower than the temperature along the hollow beams that form a hollow, cage-shaped UOT. In the range of the trapping laser power of 200–2950 mW, the surface temperature of particles trapped at the center of a UOT changes from 322 K to 830 K, correspondingly. This result gives a heating rate as a high thermal-absorbing particle trapped in the center of the UOT with 18.3 ± 0.4 °C/100 mW. In addition, the temperature gradient outside the UOT was also characterized by trapping SWCNT particles outside the UOT. Results show that when a light-absorbing particle is trapped for the study of material property, phase transitions, surface equilibrium process, chemical reactions, etc., this method can be used to measure temperature distribution and its variations in the trap and its surroundings.
Graphical Abstract
This is a visual representation of the abstract.
Outbreaks of severe diarrhea in neonatal piglets in Guangdong, China, in 2017 resulted in the isolation and discovery of a novel swine enteric alphacoronavirus (SeACoV) derived from the species
(Y. ...Pan, X. Tian, P. Qin, B. Wang, et al., Vet Microbiol 211:15-21, 2017). SeACoV was later referred to as swine acute diarrhea syndrome CoV (SADS-CoV) by another group (P. Zhou, H. Fan, T. Lan, X.-L. Yang, et al., Nature 556:255-258, 2018). The present study was set up to investigate the potential species barriers of SADS-CoV
and
We first demonstrated that SADS-CoV possesses a broad species tropism and is able to infect cell lines from diverse species, including bats, mice, rats, gerbils, hamsters, pigs, chickens, nonhuman primates, and humans. Trypsin contributes to but is not essential for SADS-CoV propagation
Furthermore, C57BL/6J mice were inoculated with the virus via oral or intraperitoneal routes. Although the mice exhibited only subclinical infection, they supported viral replication and prolonged infection in the spleen. SADS-CoV nonstructural proteins and double-stranded RNA were detected in splenocytes of the marginal zone on the edge of lymphatic follicles, indicating active replication of SADS-CoV in the mouse model. We identified that splenic dendritic cells (DCs) are the major targets of virus infection by immunofluorescence and flow cytometry approaches. Finally, we demonstrated that SADS-CoV does not utilize known CoV receptors for cellular entry. The ability of SADS-CoV to replicate in various cells lines from a broad range of species and the unexpected tropism for murine DCs provide important insights into the biology of this bat-origin CoV, highlighting its possible ability to cross interspecies barriers.
Infections with bat-origin coronaviruses (CoVs) (severe acute respiratory syndrome CoV SARS-CoV and Middle East respiratory syndrome CoV MERS-CoV) have caused severe illness in humans after "host jump" events. Recently, a novel bat-HKU2-like CoV named swine acute diarrhea syndrome CoV (SADS-CoV) has emerged in southern China, causing lethal diarrhea in newborn piglets. It is important to assess the species barriers of SADS-CoV infection since the animal hosts (other than pigs and bats) and zoonotic potential are still unknown. An
susceptibility study revealed a broad species tropism of SADS-CoV, including various rodent and human cell lines. We established a mouse model of SADS-CoV infection, identifying its active replication in splenic dendritic cells, which suggests that SADS-CoV has the potential to infect rodents. These findings highlight the potential cross-species transmissibility of SADS-CoV, although further surveillance in other animal populations is needed to fully understand the ecology of this bat-HKU2-origin CoV.
PDF
