Light intensity and spectral distribution affect chytrid infection of cyanobacteriaviamodulation of host fitness

Light gradients are an inherent feature in aquatic ecosystems and play a key role in shaping the biology of phytoplankton. Parasitism by chytrid fungi is gaining increasing attention as a major control agent of phytoplankton due to its previously overlooked ubiquity, and profound ecological and evolutionary consequences. Despite this interest, if and how light conditions modulate phytoplankton chytridiomycosis remains poorly studied. We investigated life-history traits of a chytrid parasite,Rhizophydium megarrhizum, under different light intensities and spectral compositions when infecting two closely related planktonic cyanobacteria with different light-harvesting strategies:Planktothrix rubescensandP. agardhii. In general, parasite transmission was highest under light conditions (both intensity and quality) that maximized growth rates for uninfected cyanobacteria. Chytrid encystment on hosts was significantly affected by light intensity and host strain identity. This likely resulted from higher irradiances stimulating the increased discharge of photosynthetic by-products, which drive parasite chemotaxis, and from strain-specific differences at the cell-surface. Comparisons of parasite transmission and host growth rates under different light conditions suggest the potential for epidemic development at higher irradiances, whereas host and parasite could coexist without epidemic outbreaks at lower light levels. These results illustrate the close relationship between parasite transmission and host fitness, which is ultimately modulated by the external environment

On-Site Quantification and Infection Risk Assessment of Airborne SARS-CoV-2 Virus Via a Nanoplasmonic Bioaerosol Sensing System in Healthcare Settings

On-site quantification and early-stage infection risk assessment of airborne severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with high spatiotemporal resolution is a promising approach for mitigating the spread of coronavirus disease 2019 (COVID-19) pandemic and informing life-saving decisions. Here, a condensation (hygroscopic growth)-assisted bioaerosol collection and plasmonic photothermal sensing (CAPS) system for on-site quantitative risk analysis of SARS-CoV-2 virus-laden aerosols is presented. The CAPS system provided rapid thermoplasmonic biosensing results after an aerosol-to-hydrosol sampling process in COVID-19-related environments including a hospital and a nursing home. The detection limit reached 0.25 copies/µL in the complex aerosol background without further purification. More importantly, the CAPS system enabled direct measurement of the SARS-CoV-2 virus exposures with high spatiotemporal resolution. Measurement and feedback of the results to healthcare workers and patients via a QR-code are completed within two hours. Based on a dose-responseµ model, it is used the plasmonic biosensing signal to calculate probabilities of SARS-CoV-2 infection risk and estimate maximum exposure durations to an acceptable risk threshold in different environmental settings

Super-resolution imaging and tracking of protein–protein interactions in sub-diffraction cellular space

Imaging the location and dynamics of individual interacting protein pairs is essential but often difficult because of the fluorescent background from other paired and non-paired molecules, particularly in the sub-diffraction cellular space. Here we develop a new method combining bimolecular fluorescence complementation and photoactivated localization microscopy for super-resolution imaging and single-molecule tracking of specific protein–protein interactions. The method is used to study the interaction of two abundant proteins, MreB and EF-Tu, in Escherichia coli cells. The super-resolution imaging shows interesting distribution and domain sizes of interacting MreB–EF-Tu pairs as a subpopulation of total EF-Tu. The single-molecule tracking of MreB, EF-Tu and MreB–EF-Tu pairs reveals intriguing localization-dependent heterogonous dynamics and provides valuable insights to understanding the roles of MreB–EF-Tu interactions

Detection of nucleic acids as the biomarkers of hazardous agents in bioaerosols

The transmission of hazardous agents via bioaerosols has been long-acknowledged as an important risk, yet it has been poorly studied and understood, due to paltry data, methodological heterogeneity and limitation. Therefore, this thesis mainly chose 2 different kind of hazardous agents: antibiotic resistance genes (ARGs) and human respiratory viruses as examples to attempt to narrow several gaps in bioaerosol research. Antibiotic resistance genes (ARG) have been considered as a global emerging threat to public health systems. As special locations where both antibiotics and ARGs are directly used, biology laboratories are poorly studied but potential important emission sources where not only the environmental stress is strong but also obtaining resistance is much easier comparing to other well studied hot spots including farms, hospitals, wastewater treatment plants and landfills where antibiotics but not ARGs are used or discharged. Therefore, Chapter 2 focused on emission source identification .11 Swiss biology laboratories working on different fields and located in the city center, suburb and rural area were studied to reveal the abundance and diversity of airborne ARGs in them and their surrounding areas with Colony-forming units (CFU) cultivation and quantitative Polymerase Chain Reaction (qPCR). Most biology laboratories did not discharge significant amounts or varieties of ARGs and cultivable bacteria via air. No correlation was found between the number of CFUs and the abundance of 16S rRNA, but two clusters of correlated airborne ARGs, the animal husbandry related cluster, and city and hospital related cluster were identified in this study. Although most biology laboratories may not be the emission sources of a wide variety of airborne ARGs, the ARGs in the animal husbandry related cluster which are abundant in the animal laboratories and aadA1 which is abundant in the laboratories working on other eukaryocytes need to be furtherly studied to make sure if they are potential health risks for the researchers. Another gap in bioaerosol research is methodology standardization. While the pandemic of coronavirus disease 2019 (COVID-19) continues to threaten public health, various primers of reverse transcription quantitative polymerase chain reaction (RT-qPCR) have been swiftly developed. Comparing their performances is very necessary for the optimization and standardization the detection and quantification method to assist the disease control. Furthermore, for developing countries, cheaper alternative molecular methods for SARS-CoV-2 identification can be crucial to prevent the next wave of infections. Therefore, in Chapter 2, we evaluated the 12 primer sets recommended by the World Health Organization (WHO) on testing both clinical patient and environmental samples with the gold standard diagnosis method: TaqMan-based RT-qPCR and a cheaper alternative method: SYBR Green-based RT-qPCR. We found that using suitable primer sets, such as ORF1ab, 2019_nCoV_N1 and 2019_nCoV_N3, the performance of the SYBR Green approach was comparable or even outperformed the TaqMan approach, even when considering the newly dominating or emerging variants, including Delta, Eta, Kappa, Lambda and Mu. ORF1ab and 2019_nCoV_N3 were found to be the best combination for sensitive and reliable SARS-CoV-2 molecular diagnostics due to their high sensitivity, specificity and broad accessibility. Based on the results of Chapter 2, we furtherly collected outdoor airborne particulate matter (PM) samples from November 2019 to April 2020 in Bern, Lugano, and Zurich to study the correlations between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses, between viruses and environmental factors, and between viruses and human behavior changes due to the public health measures against COVID-19. Because similar studies are scarce on air surveillance of the virus in outdoor non-healthcare environments which is also a current gap of the understanding of viral bioaerosols, although virus-laden particles have been commonly detected and studied in the aerosol samples from indoor healthcare settings. Among 14 detected viruses, influenza A, HCoV-NL63, HCoV-HKU1, and HCoV-229E were abundant in air. SARS-CoV-2 and enterovirus were moderately common, while the remaining viruses occurred only in low concentrations. SARS-CoV-2 was detected in PM10 (PM below 10 µm) samples of Bern and Zurich, and PM2.5 (PM below 2.5 µm) samples of Bern which exhibited a concentration positively correlated with the local COVID-19 case number. The concentration was also correlated with the concentration of enterovirus which raised the concern of coinfection. The estimated COVID-19 infection risks of an hour exposure at these two sites were generally low but still cannot be neglected. This study demonstrated the potential functionality of outdoor air surveillance of airborne respiratory viruses, especially at transportation hubs and traffic arteries. However, there is no available detection and quantification method capable of fast, sensitive, specific and convenient onsite measuring for air surveillance and risk alarming. CRISPR diagnostics systems are potential candidates because they are fast and specific. Yet, current CRISPR diagnostics are either moderate sensitive enough or supersensitive, and rely heavily on pre-amplification which hinders their potential for quantification. To overcome this limitation, in Chapter 4, a new ultrasensitive CRISPR-Cas based nucleic acid detection system, named Paired-CRISPR-Cas-Only Identification Relay Origination Technique (POIROT) was developed to enable CRISPR-Cas12 cascade the signal to CRISPR-Cas13 for nucleic acid detection. The system was tested with two different DNA targets: the viral DNA of human monkey pox virus and floR, an antibiotic resistance gene against florfenicol. This system has an impressive low limit of detection (LoD) of 1 copy/μl and a short responding time of 15 minutes. The system has potential for use in both diagnosis and environmental surveillance, and may provide new insights into the forms of DNAs in the environment. While the system has some limitations that need to be addressed, it offers promising potential for the development of high-performance artificial nucleic acid detection methods with CRISPR-Cas, particularly in environmental surveillance. The findings in this thesis have improved the understanding of bioaerosols from several angles, and offered potential choices to narrow the gaps in bioaerosol research, paving the ways for future. These advancements can help scientists, public health planners, policymakers, and regulators to improve the air quality, and protecting the environment, and also provide suggestions and warnings to the public on self-protection, ultimately contributing to creating healthier conditions on our habitable planet together from both sides

Abundance and diversity of antibiotic resistance genes possibly released to ambient air by experiments in biology laboratories

Antibiotic resistance genes (ARG) have been considered as a global emerging threat to public health systems. As special locations where both antibiotics and ARGs are directly used, biology laboratories are poorly studied but potential important emission sources where not only the environmental stress is strong but also obtaining resistance is much easier comparing to other well studied hot spots including farms, hospitals, wastewater treatment plants and landfills where antibiotics but not ARGs are used or discharged. Therefore, in this study, 11 Swiss biology laboratories working on different fields and located in the city center, suburb and rural area were studied to reveal the abundance and diversity of airborne ARGs in them and their surrounding areas with Colony-forming units (CFU) cultivation and quantitative Polymerase Chain Reaction (qPCR). Most biology laboratories did not discharge significant amounts or varieties of ARGs and cultivable bacteria via air. No correlation was found between the number of CFUs and the abundance of 16S rRNA, but two clusters of correlated airborne ARGs, the animal husbandry related cluster, and city and hospital related cluster were identified in this study. Although most biology laboratories may not be the emission sources of a wide variety of airborne ARGs, the ARGs in the animal husbandry related cluster which are abundant in the animal laboratories and aadA1 which is abundant in the laboratories working on other eukaryocytes need to be furtherly studied to make sure if they are potential health risks for the researchers.ISSN:0048-9697ISSN:1879-102

Infection of filamentous phytoplankton by fungal parasites enhances herbivory in pelagic food webs

Chytrid fungal parasites are ubiquitous in aquatic ecosystems and infect a wide array of aquatic organisms, including all phytoplankton groups. In addition to their role as parasites, chytrids serve as food to zooplankton, thereby establishing an alternative trophic link between primary and secondary production in pelagic food webs, the so-called mycoloop. We hypothesized that, in addition to the mycoloop, chytrid infection facilitates grazing of filamentous phytoplankton by rendering it more edible to zooplankton consumers through infection-induced fragmentation. We undertook grazing assays to compare the ability of the key zooplankter Daphnia to graze on a filamentous cyanobacterium in the presence or absence of chytrid infection. A near doubling in mean clearance rates was consistently recorded when Daphnia were fed with infected cultures of the cyanobacterium as compared to uninfected ones. Infected filaments were shorter than noninfected ones, indicating that infection-induced fragmentation undermines resistance of filamentous phytoplankton to grazing. We propose an extended conceptualization of the mycoloop that includes both direct effects (i.e., transfer via grazing of chytrid zoospores) and indirect effects (i.e., trophic upgrading and facilitated grazing on phytoplankton via fragmentation) of chytrid infection on trophic transfer at the base of pelagic food webs

Telocytes reduce oxidative stress by downregulating DUOX2 expression in inflamed lungs of mice

Telocytes (TCs), a novel type of interstitial cells, have been found to participate in tissue protection and repair. In this study, we investigated the antioxidative effects of TCs in inflamed lungs of mice. Acute respiratory distress syndrome (ARDS) mice were used as models of inflamed lungs of mice. Gene sequencing was used to screen the differentially expressed miRNAs in TCs after lipopolysaccharide (LPS) stimulation. AntagomiR-146a-5p-pretreated TCs were first injected into mice, and antioxidant activity of TCs was estimated. TCs, RAW264.7 cells, and MLE-12 cells were collected for the detection of expressions of NOX1–4, DUOX1–2, SOD1–3, GPX1–2, CAT, Nrf2, miR-146a-5p, and miR-21a-3p after LPS stimulation. Silencing miRNAs were delivered to examine the involved signaling pathways. Oxidative stress was examined by measuring malondialdehyde (MDA) levels. We found that microRNA-146a-5p and microRNA-21a-3p were upregulated in TCs after LPS stimulation. ARDS mice that were preinfused with TCs had lower lung tissue injury scores, lung wet-dry ratios, white blood cell counts in alveolar lavage fluid and lower MDA concentrations in lung tissue. However, in antagomiR-146a-5p-pretreated ARDS mice, the infusion of TCs caused no corresponding changes. After LPS stimulation, DUOX2 and MDA concentrations were downregulated in TCs, while DUOX2 was restored by antagomiR-146a-5p in TCs. Dual-luciferase reporter assay confirmed that CREB1 was downregulated by miR-146a-5p, while DUOX2 was downregulated by CREB1, which was confirmed by treating TCs with a specific CREB1 inhibitor. This study demonstrates that LPS stimulation upregulates miR-146a-5p in TCs, which downregulates the CREB1/DUOX2 pathway, resulting in a decrease in oxidative stress in cultured TCs. TCs reduce LPS-induced oxidative stress by decreasing DUOX2 in inflamed lungs of mice