The identification of airborne bacteria has traditionally been performed by retrieval in culture media, but the bacterial diversity in the air is underestimated using this method because many bacteria are not readily cultured. Advances in DNA sequencing technology have produced a broad knowledge of genomics and metagenomics, which can greatly improve our ability to identify and study the diversity of airborne bacteria. However, researchers are facing several challenges, particularly the efficient retrieval of low-density microorganisms from the air and the lack of standardized protocols for sample collection and processing. In this study, we tested three methods for sampling bioaerosols — a Durham-type spore trap (Durham), a seven-day recording volumetric spore trap (HST), and a high-throughput 'Jet' spore and particle sampler (Jet) — and recovered metagenomic DNA for 16S rDNA sequencing. Samples were simultaneously collected with the three devices during one week, and the sequencing libraries were analyzed. A simple and efficient method for collecting bioaerosols and extracting good quality DNA for high-throughput sequencing was standardized. The Durham sampler collected preferentially Cyanobacteria, the HST Actinobacteria, Proteobacteria and Firmicutes, and the Jet mainly Proteobacteria and Firmicutes. The HST sampler collected the largest amount of airborne bacterial diversity. More experiments are necessary to select the right sampler, depending on study objectives, which may require monitoring and collecting specific airborne bacteria.

Copper (Cu) is an essential biocide for wood protection, but fails to protect wood against Cu-tolerant wood-destroying fungi. Recently Cu particles (size range: 1 nm–25 μm) were introduced to the wood preservation market. The new generation of preservatives with Cu-based nanoparticles (Cu-based NPs) is reputedly more efficient against wood-destroying fungi than conventional formulations. Therefore, it has the potential to become one of the largest end uses for wood products worldwide. However, during decomposition of treated wood Cu-based NPs and/or their derivate may accumulate in the mycelium of Cu-tolerant fungi and end up in their spores that are dispersed into the environment. Inhaled Cu-loaded spores can cause harm and could become a potential risk for human health. We collected evidence and discuss the implications of the release of Cu-based NPs by wood-destroying fungi and highlight the exposure pathways and subsequent magnitude of health impact.

A characterization of the physical–chemical composition of the atmospheric PM adsorbed to airborne pollen was performed. Airborne pollen was sampled using a Hirst-type volumetric spore sampler and observed using a Field Emission Electron Probe Microanalyser for PM analysis. A secondary electron image was taken of each pollen grain and EDS spectra were obtained for individually adsorbed particles. All images were analysed and the size parameters of the particles adsorbed to pollen was determined. The measured particles’ equivalent diameter varied between 0.1 and 25.8 μm, mostly in the fine fraction. The dominant particulates identified were Si-rich, Organic-rich, SO-rich, Metals & Oxides and Cl-rich. Significant daily differences were observed in the physical–chemical characteristics of particles adsorbed to the airborne pollen wall. These differences were correlated with weather parameters and atmospheric PM concentration. Airborne pollen has the ability to adsorb fine particles that may enhance its allergenicity.

Faecal indicator bacteria (FIB) are used for the assessment of faecal pollution and possible water quality deterioration. There is growing evidence that FIB used in temperate regions are not adequate and reliable to detect faecal pollution in tropical regions. Hence, this study evaluated the adequacy of FIB, including total coliforms (TC), Escherichia coli (EC), Enterococci (IEC), and Clostridium perfringens (CP) in the high-altitude, tropical country of Ethiopia. In addition to FIB, for microbial source tracking (MST), a ruminant-associated molecular marker was applied at different water types and altitudes, and faecal pollution risk mapping was conducted based on consensus FIB. The performances of the indicators were evaluated at 22 sites from different water types. The results indicate that EC cell enumeration and CP spore determination perform well for faecal contamination monitoring. Most of the sub-basins of Lake Tana were found to be moderately to highly polluted, and the levels of pollution were demonstrated to be higher in the rainy season than in the post-rainy season. Markers associated with ruminants (BacR) were identified in more than three quarters of the sites. A bacterial pollution risk map was developed for sub-basins of Lake Tana, including the un-gauged sub-basins. We demonstrate how bacterial pollution risk mapping can aid in improvements to water quality testing and reduce risk to the general population from stream bacteria.

The objective of this research was to evaluate a soil recovery strategy in soils that were affected by iron mining tailing using herbaceous species inoculated with Acaulospora morrowiae (arbuscular mycorrhizal fungus (AMF)). Tailings were collected on the banks of the Gualaxo do Norte river, one of the places impacted by the Fundão Dam rupture, where tailing layers that were more than one meter were deposited. The experiment was carried out in a greenhouse, using 6 kg pots of non-sterile reject, in a randomized block design in a 4 × 2 factorial scheme, with four cropping systems (Urochloa ruziziensis single crop–RS; and intercropping cultivation: U. ruziziensis with Crotalaria spectabilis–R + C; U. ruziziensis with Guizotia abyssinica–R + G and U. ruziziensis with C. spectabilis and G. abyssinica–R + C + G), with two AMF inoculation conditions (with 200 A. morrowiae spores per pot, and no inoculation), with three replications and 100 days duration. The R + C and R + C + G systems presented the highest shoot dry matter (SDM) yields. Regarding root dry matter production (RDM), a variation of 9.2 g of pot⁻¹ roots was observed between the R + C and R + G systems. Mycorrhizal colonization (MC) was higher in the cultivation system with the three herbaceous species, being the R + C + G system 52% higher than RS system. Spore density did not vary among treatments. Microbial carbon biomass was higher in the RS and R + G treatments when not inoculated. Basal respiration was also higher when not inoculated. Overall, the R + C + G system was more efficient than other systems in the accumulation of elements. The cultivation system with three herbaceous plants proved to be efficient in establishing itself initially in the iron mining tailings, being a viable alternative for the rehabilitation process.

The study of the fungal community composition in house dust is useful to assess the accumulative exposure to fungi in indoor environments. The objective of this research was to characterize the fungal diversity of house dust and its association with the environmental conditions of bedrooms. For this, the dust was collected from 41 bedrooms of children between the ages of 8 and 9 with a family history of asthma, residents of Havana, Cuba. The fungal content of each sample was determined by two methods: plate culture with malt extract agar and by direct microscopy. An ecological analysis was carried out from the fungal diversity detected. To describe the factors associated with the fungi detected, bivariate logistic regression was used. Through direct microscopy, between 10 and 2311 fragments of hyphae and spores corresponding mainly to Cladosporium, Coprinus, Curvularia, Aspergillus/Penicillium, Xylariaceae, and Periconia were identified. Through the culture, 0–208 CFU were quantified, where Aspergillus, Cladosporium, and Penicillium predominated. The culturability evidenced the differences between the quantification determined by both methods. A positive relationship was found between the type of cleaning of the furniture, the presence of trees in front of the bedroom, indoor relative humidity, indoor temperature, the presence of air conditioning, and natural ventilation with specific spore types and genera. The use of two different identification methods allowed to detect a greater fungal diversity in the residences evaluated. Monitoring the exposure to these fungal allergens in childhood can help to prevent sensitization in the allergic child, the development of asthma, and other respiratory diseases.

This study evaluated the effect of crude oil on the intraradical structures and morphospecies of arbuscular mycorrhizal fungi (AMF) and on the aerial and root dry matter of the grass Leersia hexandra Swartz in order to propose indicators of toxicity. An experiment was conducted in a microtunnel for 180 days. The concentrations (g kg⁻¹) of crude oil in the Gleysol were 0.693 (control), 3, 10, 30, 60, 90, 120, 150, and 180. The growth of intraradical hyphae, arbuscules, vesicles, and spores in soil was stimulated by crude oil concentrations of 3, 10, 30 and 60 g, but concentrations of 90, 120, 150, and 180 g kg⁻¹ inhibited it. Eight morphospecies of AMF were identified. The number of spores of Rhizophagus fasciculatus, Rhizophagus intraradices, Funneliformis geosporum, Diversispora eburnea, and Ambispora gerdemannii showed sensitivity to the concentration of crude oil (index values were lower than one). The number of spores of Diversispora sp. was stimulated by exposure to crude oil, with non-toxic values for the eight concentrations. The index based on the aerial dry matter of L. hexandra showed toxicity values lower than one with crude oil concentrations of 60, 90, 120, 150, and 180 g kg⁻¹, but the root dry matter showed non-toxic values with the eight concentrations. We suggest using the number of spores and morphospecies as an index of toxicity of crude oil and recommend using Diversispora sp. and L. hexandra for the phytoremediation of Gleysol contaminated with crude oil in the Mexican humid tropics.

The goal of this study is to clarify the surface-chemical and microphysical variables that influence bacterial spore transport through soil, thereby defining the factors that may affect spore transport velocity. Bacillus cereus spores were continuously monitored in a soil column under saturated conditions with experimental variations in soil grain size (0.359 and 0.718 mm), pH (7.2 and 8.5), and water flow rate (1.3 and 3.0 mL/min). Increasing soil grain size, flow rate, and pH resulted in enhanced spore movement. Spore transport increased 82% when soil grain size was doubled. An increase in effluent flow rate from 1.3 to 3.0 mL/min increased spore movement by 71%. An increase in pH increased spore transport by 53%. The increase in hydrodynamic forces resulting from the larger grain size soil and higher flow rate functioned to overcome the hydrophobic nature of the spore's coat, and the interparticle bonding forces between the spore and soil particles.

Plants establish symbiosis with arbuscular mycorrhizal fungi (AMFs) for nutrient exchange and also for tolerance to contaminants. During February 2019, soil and rhizosphere samples of Laguncularia racemosa (Lr) and Avicennia germinans (Ag) were collected on 4.15 hectares of a mangrove forest established in Histosol affected since 1967 by chronic oil spill in southeastern Mexico. The site was divided into four zones based on the amounts of total hydrocarbons of weathered petroleum (THWPs) accumulated in the soil for half a century. The abundance of intraradical propagules and the colonization structure of the AMFs in the roots of the two mangrove species were compared. The density of phosphate-solubilizing bacteria (PSBs) in soil and rhizosphere samples was also evaluated. The degraded oil stimulated the amount of PSBs in Lr but not in Ag. AMF biodiversity was lower in the Ag root; however, spore abundance was higher. We found abundant spores of Glomus claroideum and Diversispora aurantium in tertiary and quaternary roots of the Ag in soils contaminated with 48462 mg of THWPs. This study provides evidence of the presence and abundance of intraradical propagules in different types of roots, which may be an alternative that contributes to the understanding of oil dissipation and in future applications for the restoration of degraded ecosystems.