Airborne microalgal and cyanobacterial diversity and composition during rain events in the southern Baltic Sea region

Deposition of airborne cyanobacteria and microalgae in the human respiratory tract (Baltic Sea coastal zone, Poland)

Scientific research confirms the harmful effects of airborne cyanobacteria and microalgae. However, determining human exposure to these microorganisms remains a challenge. The six-stage Tisch impactor was used to collect bioaerosols from April to September 2020 in the coastal zone of the southern Baltic. The MPPD model was used for estimation of regional, lobar, and generation deposition of microorganisms in human respiratory tract. The mass deposition fraction of cyanobacteria and microalgae in the head region gradually increased with the aerosol size. The maximum deposition fractions in the trachea, bronchial, and the pulmonary region were found for particles between 2.1 and 3.3 μm. The contribution of cyanobacteria and microalgae was the highest in the head region. The majority of microorganisms found in pulmonary region dominated in particles smaller than 2.1 μm. Exposure to the ambient bioaerosols may have an adverse impact on the human health in the region of southern Baltic Sea.

A microfluidic microalgae detection system for cellular physiological response based on an object detection algorithm

The composition of species and the physiological status of microalgal cells serve as significant indicators for monitoring marine environments. Symbiotic with corals, Symbiodiniaceae are more sensitive to the environmental response. However, current methods for evaluating microalgae tend to be population-based indicators that cannot be focused on single-cell level, ignoring potentially heterogeneous cells as well as cell state transitions. In this study, we proposed a microalgal cell detection method based on computer vision and microfluidics, which combined microscopic image processing, microfluidic chip and convolutional neural network to achieve label-free, sheathless, automated and high-throughput microalgae identification and cell state assessment. By optimizing the data import, training process and model architecture, we solved the problem of identifying tiny objects at the micron scale, and the optimized model was able to perform the tasks of cell multi-classification and physiological state assessment with more than 95% mean average precision. We discovered a novel transition state and explored the thermal sensitivity of three clades of Symbiodiniaceae, and discovered the phenomenon of cellular heat shock at high temperatures. The evolution of the physiological state of Symbiodiniaceae cells is very important for directional cell evolution and early warning of coral ecosystem health.

Implications of PM2.5 chemical composition in modulating microbial community dynamics during spring in Seoul

Particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) harbors a diverse microbial community. To assess the ecological dynamics and potential health risks associated with airborne microorganisms, it is crucial to understand the factors influencing microbial communities within PM2.5. This study investigated the influence of abiotic parameters, including air pollutants, PM2.5 chemical composition (water-soluble ions and organics), and meteorological variables, on microbial communities in PM2.5 samples collected in Seoul during the spring season. Results revealed a significant correlation between air pollutants and water-soluble ions of PM2.5 with microbial α-diversity indices. Additionally, air pollutants exerted a dominant effect on the microbial community structure, with stronger correlations observed for fungi than bacteria, whereas meteorological variables including temperature, pressure, wind speed, and humidity exerted a limited influence on fungal α-diversity. Furthermore, the results revealed specific water-soluble ions, such as SO42-, NO3-, and NH4+, as important factors influencing fungal α-diversity, whereas K+ negatively correlated with both microbial α-diversity. Moreover, PM2.5 microbial diversity was affected by organic compounds within PM2.5, with fatty acids exhibited a positive correlation with fungal diversity, while dicarboxylic acids exhibited a negative correlation with it. Furthermore, network analysis revealed direct links between air pollutants and dominant bacterial and fungal genera. The air pollutants exhibited a strong correlation with bacterial genera, such as Arthrospira and Clostridium, and fungal genera, including Aureobasidium and Cladosporium. These results will contribute to our understanding of the ecological dynamics of airborne microorganisms and provide insights into the potential risks associated with PM2.5 exposure.

Study on the concentration, composition, and recovery rate of bacterial bioaerosols after rainfall in Ho Chi Minh City

Aerosolized microorganisms have become an important factor in assessing air quality. To determine the characteristics of bacterial bioaerosols in air and rainwater, as well as calculate the recovery rate of bacteria after rains in Ho Chi Minh City, our study was performed using the SKC Biostage sampler for airborne bacteria and Plate Count Agar (PCA) medium for bacterial concentration. Subsequently, the study determined the bacterial community composition at the phylum and order levels using the 16S rRNA (16S metabarcoding) method. Before the rain, bacterial concentrations in the air ranged from 263.39 ± 21.00 to 277.39 ± 78.99 CFU/m3, and in rainwater 264.89 ± 51.17 to 285.72 ± 28.00 CFU/m3. Following rains, the bacterial concentrations decreased to their lowest levels within the first 1-2 h and gradually increased thereafter, reaching their peak after 9 h for heavy rain and after 12 h for light and moderate rains. The bacterial bioaerosols recovery rate was determined to be 100% for light and moderate rains and 94.6% for heavy rain. The change in bacterial concentration after rainfall showed a positive correlation with temperature (r = 0.85) and CO2 concentration (r = 0.70) and a negative correlation with relative humidity (r =  - 0.79). Bacterial composition analysis revealed that the Actinobacteria, Firmicutes, and Proteobacteria phyla were dominant and characteristic of the humid tropical climate in Vietnam. Notably, Firmicutes were the most prevalent phylum both before and after rains. The increased prevalence of certain bacterial orders, particularly Staphylococcus, could contribute to the spread of pathogens, particularly foodborne pathogens. In addition to rain, relative humidity contributed to reducing bacterial bioaerosols concentration and their recovery rate after the rain.

Temporal variation in the spectrum and concentration of airborne microalgae and cyanobacteria in the urban environments of inland temperate climate

Despite their non-negligible representation among the airborne bioparticles and known allergenicity, autotrophic microorganisms-microalgae and cyanobacteria-are not commonly reported or studied by aerobiological monitoring stations due to the challenging identification in their desiccated and fragmented state. Using a gravimetric method with open plates at the same time as Hirst-type volumetric bioparticle sampler, we were able to cultivate the autotrophic microorganisms and use it as a reference for correct retrospective identification of the microalgae and cyanobacteria captured by the volumetric trap. Only in this way, reliable data on their presence in the air of a given area can be obtained and analysed with regard to their temporal variation and environmental factors. We gained these data for an inland temperate region over 3 years (2018, 2020-2021), identifying the microalgal genera Bracteacoccus, Desmococcus, Geminella, Chlorella, Klebsormidium, and Stichococcus (Chlorophyta) and cyanobacterium Nostoc in the volumetric trap samples and three more in the cultivated samples. The mean annual concentration recorded over 3 years was 19,182 cells*day/m3, with the greatest contribution from the genus Bracteacoccus (57%). Unlike some other bioparticles like pollen grains, autotrophic microorganisms were present in the samples over the course of the whole year, with greatest abundance in February and April. The peak daily concentration reached the highest value (1011 cells/m3) in 2021, while the mean daily concentration during the three analysed years was 56 cells/m3. The analysis of intra-diurnal patterns showed their increased presence in daylight hours, with a peak between 2 and 4 p.m. for most genera, which is especially important due to their potential to trigger allergy symptoms. From the environmental factors, wind speed had a most significant positive association with their concentration, while relative air humidity had a negative influence.

Aerosolization flux, bio-products, and dispersal capacities in the freshwater microalga Limnomonas gaiensis (Chlorophyceae)

Little is known on the spreading capacities of Limnomonas gaiensis across freshwater lakes in Northern Europe. In this study, we show that the species could successfully be aerosolized from water sources by bubble bursting (2-40 particles.cm-3), irrespectively of its density in the water source or of the jet velocity used to simulate wave breaking. The species viability was impacted by both water turbulences and aerosolization. The survival rate of emitted cells was low, strain-specific, and differently impacted by bubble busting processes. The entity "microalga and bionts" could produce ethanol, and actively nucleate ice (principally ≤-18 °C) mediated soluble ice nucleation active proteins, thereby potentially impacting smog and cloud formation. Moreover, smallest strains could better cope with applied stressors. Survival to short-term exposure to temperatures down to -21 °C and freezing events further suggest that L. gaiensis could be air dispersed and contribute to their deposition.

Abundant Cyanobacteria in Autumn Adhering to the Heating, Ventilation, and Air-Conditioning (HVAC) in Shanghai

Cyanobacteria are ever-present, mainly flourishing in aquatic environments and surviving virtually in other habitats. The microbiota of indoor dust on the pre-filter of heating, ventilation, and air-conditioning (HVAC) systems, which reflect indoor microbial contamination and affect human health, has attracted attention. Contemporary studies on cyanobacteria deposited on the pre-filter of HVAC remain scant. By the culture-independent approach of qPCR and high throughput sequencing technologies, our results documented that the cyanobacterial concentrations were highest in autumn, occurred recurrently, and were about 2.60 and 10.57-fold higher than those in winter and summer. We proposed that aquatic and terrestrial cyanobacteria contributed to the pre-filter of HVAC by airborne transportation produced by wave breaks, bubble bursts, and soil surface by wind force, owing to the evidence that cyanobacteria were commonly detected in airborne particulate matters. The cyanobacteria community structure was characterized in Shanghai, where Chroococcidiopsaceae, norank_cyanobacteriales, Nostocaceae, Paraspirulinaceae, and others dominated the dust on the pre-filter of HVAC. Some detected genera, including Nodularia sp., Pseudanabaena sp., and Leptolyngbya sp., potentially produced cyanobacterial toxins, which need further studying to determine their potential threat to human health. The present work shed new insight into cyanobacteria distribution in the specific environment besides aquatic habitats.

The Ability of Airborne Microalgae and Cyanobacteria to Survive and Transfer the Carcinogenic Benzo(a)pyrene in Coastal Regions

Air pollution has been a significant problem threatening human health for years. One commonly reported air pollutant is benzo(a)pyrene, a dangerous compound with carcinogenic properties. Values which exceed normative values for benzo(a)pyrene concentration in the air are often noted in many regions of the world. Studies on the worldwide spread of COVID-19 since 2020, as well as avian flu, measles, and SARS, have proven that viruses and bacteria are more dangerous to human health when they occur in polluted air. Regarding cyanobacteria and microalgae, little is known about their relationship with benzo(a)pyrene. The question is whether these microorganisms can pose a threat when present in poor quality air. We initially assessed whether cyanobacteria and microalgae isolated from the atmosphere are sensitive to changes in PAH concentrations and whether they can accumulate or degrade PAHs. The presence of B(a)P has significantly affected both the quantity of cyanobacteria and microalgae cells as well as their chlorophyll a (chl a) content and their ability to fluorescence. For many cyanobacteria and microalgae, an increase in cell numbers was observed after the addition of B(a)P. Therefore, even slight air pollution with benzo(a)pyrene is likely to facilitate the growth of airborne cyanobacteria and microalgae. The results provided an assessment of the organisms that are most susceptible to cellular stress following exposure to benzo(a)pyrene, as well as the potential consequences for the environment. Additionally, the results indicated that green algae have the greatest potential for degrading PAHs, making their use a promising bioremediation approach. Kirchneriella sp. demonstrated the highest average degradation of B(a)P, with the above-mentioned research indicating it can even degrade up to 80% of B(a)P. The other studied green algae exhibited a lower, yet still significant, B(a)P degradation rate exceeding 50% when compared to cyanobacteria and diatoms.

Freshwater Cyanobacterial Toxins, Cyanopeptides and Neurodegenerative Diseases

Cyanobacteria produce a wide range of structurally diverse cyanotoxins and bioactive cyanopeptides in freshwater, marine, and terrestrial ecosystems. The health significance of these metabolites, which include genotoxic- and neurotoxic agents, is confirmed by continued associations between the occurrence of animal and human acute toxic events and, in the long term, by associations between cyanobacteria and neurodegenerative diseases. Major mechanisms related to the neurotoxicity of cyanobacteria compounds include (1) blocking of key proteins and channels; (2) inhibition of essential enzymes in mammalian cells such as protein phosphatases and phosphoprotein phosphatases as well as new molecular targets such as toll-like receptors 4 and 8. One of the widely discussed implicated mechanisms includes a misincorporation of cyanobacterial non-proteogenic amino acids. Recent research provides evidence that non-proteinogenic amino acid BMAA produced by cyanobacteria have multiple effects on translation process and bypasses the proof-reading ability of the aminoacyl-tRNA-synthetase. Aberrant proteins generated by non-canonical translation may be a factor in neuronal death and neurodegeneration. We hypothesize that the production of cyanopeptides and non-canonical amino acids is a more general mechanism, leading to mistranslation, affecting protein homeostasis, and targeting mitochondria in eukaryotic cells. It can be evolutionarily ancient and initially developed to control phytoplankton communities during algal blooms. Outcompeting gut symbiotic microorganisms may lead to dysbiosis, increased gut permeability, a shift in blood-brain-barrier functionality, and eventually, mitochondrial dysfunction in high-energy demanding neurons. A better understanding of the interaction between cyanopeptides metabolism and the nervous system will be crucial to target or to prevent neurodegenerative diseases.

Cyanobacteria, cyanotoxins and lipopolysaccharides in aerosols from inland freshwater bodies and their effects on human bronchial cells

Components of cyanobacterial water blooms were quantified in aerosols above agitated water surfaces of five freshwater bodies. The thoracic and respirable aerosol fraction (0.1-10 µm) was sampled using a high-volume sampler. Cyanotoxins microcystins were detected by LC-MS/MS at levels 0.3-13.5 ng/mL (water) and < 35-415 fg/m³ (aerosol). Lipopolysaccharides (endotoxins) were quantified by Pyrogene rFC assay at levels < 10-119 EU/mL (water) and 0.13-0.64 EU/m³ (aerosol). Cyanobacterial DNA was detected by qPCR at concentrations corresponding to 10⁴-10⁵ cells eq./mL (water) and 10¹-10³ cells eq./m³ (aerosol). Lipopolysaccharides isolated from bloom samples induced IL-6 and IL-8 cytokine release in human bronchial epithelial cells Beas-2B, while extracted cyanobacterial metabolites induced both pro-inflammatory and cytotoxic effects. Bloom components detected in aerosols and their bioactivities observed in upper respiratory airway epithelial cells together indicate that aerosols formed during cyanobacterial water blooms could induce respiratory irritation and inflammatory injuries, and thus present an inhalation health risk.

Harmful cyanobacterial aerosolization dynamics in the airshed of a eutrophic estuary

In addition to obvious negative effects on water quality in eutrophic aquatic ecosystems, recent work suggests that cyanobacterial harmful algal blooms (CHABs) also impact air quality via emissions carrying cyanobacterial cells and cyanotoxins. However, the environmental controls on CHAB-derived aerosol and its potential public health impacts remain largely unknown. Accordingly, the aims of this study were to 1) investigate the occurrence of microcystins (MC) and putatively toxic cyanobacterial communities in particulate matter ≤ 2.5 μm in diameter (PM_2.5), 2) elucidate environmental conditions promoting their aerosolization, and 3) identify associations between CHABs and PM_2.5 concentrations in the airshed of the Chowan River-Albemarle Sound, an oligohaline, eutrophic estuary in eastern North Carolina, USA. In summer 2020, during peak CHAB season, continuous PM_2.5 samples and interval water samples were collected at two distinctive sites for targeted analyses of cyanobacterial community composition and MC concentration. Supporting air and water quality measurements were made in parallel to contextualize findings and permit statistical analyses of environmental factors driving changes in CHAB-derived aerosol. MC concentrations were low throughout the study, but a CHAB dominated by Dolichospermum occurred from late June to early August. Several aquatic CHAB genera recovered from Chowan River surface water were identified in PM_2.5 during multiple time points, including Anabaena, Aphanizomenon, Dolichospermum, Microcystis, and Pseudanabaena. Cyanobacterial enrichment in PM_2.5 was indistinctive between subspecies, but at one site during the early bloom, we observed the simultaneous enrichment of several cyanobacterial genera in PM_2.5. In association with the CHAB, the median PM_2.5 mass concentration increased to 8.97 μg m^-3 (IQR = 5.15), significantly above the non-bloom background of 5.35 μg m^-3 (IQR = 3.70) (W = 1835, p < 0.001). Results underscore the need for highly resolved temporal measurements to conclusively investigate the role that CHABs play in regional air quality and respiratory health risk.

Quantitative and qualitative variability of airborne cyanobacteria and microalgae and their toxins in the coastal zone of the Baltic Sea

Apart from viruses and bacteria, cyanobacteria and microalgae present in the atmosphere may pose a threat to the health of humans by inducing illnesses and diseases. Yet, they play an important role in the environment, influencing the Earth's radiation budget by absorbing and scattering solar radiation. The present study determined the daily and seasonal qualitative and qualitative variabilities of airborne cyanobacteria and microalgae during both vegetative and non-vegetative seasons in the coastal zone of the Baltic Sea. Samples were collected from January to December 2020 with a Tisch six-stage microbiological impactor which was used as a substitute for the respiratory tract. The stage levels of the impactor represented the respiratory tract and reproduced lung penetration by airborne particles, which allowed us to assess penetration of cyanobacteria and microalgae to the deepest parts of the human respiratory system. A total of 296 samples of cyanobacteria and microalgae were collected during the day and 276 samples during the night. The results showed that cyanobacteria and microalgae were present in the air all year, and their maximum abundance was 1685 cells m^-3 in July. Furthermore, the ability of these microorganisms to produce the toxin microcystin-LR (MC-LR) was confirmed, which has a high potential negative impact on human health. MC-LR has been found in Nostoc sp., Pseudanabaena sp., Leptolyngbya sp., Synechococcus sp., Gloeocapsa sp., Aphanothece sp., and Rivularia sp. maintained at our Culture Collection of Airborne Algae (CCAA), as well as from air samples. The highest concentrations of MC-LR were recorded in airborne Synechococcus sp. CCAA 46 and amounted to as much as 420 fg cell^-1. In turn, the highest mean concentration of 0.95 μg L^-1 for MC-LR was recorded in an air sample taken in May. This research expands the knowledge on cyanobacteria and microalgae present in the atmosphere in the coastal zone of the southern Baltic Sea. We propose these microorganisms be used as indicators for further research on bioaerosols, which are potentially dangerous to human health.