Respirable Metals, Bacteria, and Fungi during a Saharan–Sahelian Dust Event in Houston, Texas

Abstract

Although airborne bacteria and fungi can impact human, animal, plant, and ecosystem health, very few studies have investigated the possible impact of their long-range transport in the context of more commonly measured aerosol species, especially those present in an urban environment. We report first-of-kind simultaneous measurements of the elemental and microbial composition of North American respirable airborne particulate matter concurrent with a Saharan−Sahelian dust episode. Comprehensive taxonomic and phylogenetic profiles of microbial communities obtained by 16S/18S/ITS rDNA sequencing identified hundreds of bacteria and fungi, including several cataloged in the World Health Organization's lists of global priority human pathogens along with numerous other animal and plant pathogens and (poly)extremophiles. While elemental analysis sensitively tracked long-range transported Saharan dust and its mixing with locally emitted aerosols, microbial diversity, phylogeny, composition, and abundance did not well correlate with the apportioned African dust mass. Bacterial/fungal diversity, phylogenetic signal, and community turnover were strongly correlated to apportioned sources (especially vehicular emissions and construction activities) and elemental composition (especially calcium). Bacterial communities were substantially more dissimilar from each other across sampling days than were fungal communities. Generalized dissimilarity modeling revealed that daily compositional turnover in both communities was linked to calcium concentrations and aerosols from local vehicles and Saharan dust. Because African dust is known to impact large areas in northern South America, the Caribbean Basin, and the southern United States, the microbiological impacts of such long-range transport should be assessed in these regions.

Microorganisms Isolated from Saharan Dust Intrusions in the Canary Islands and Processes of Mineral Atmospherogenesis

“…In total, 19 out of 23 isolated culturable microorganisms were identified by 16S RNAr sequencing (Table 8). The identified microorganisms belonged to Pseudomonadota, Bacillota and Actinomycetota, being consistent with the dominant phyla in other dust studies [9,65,67]. Pseudomonadota (nmc = 6) was the predominant phylum in sample M2, followed by Bacillota (nmc = 4) and Actinomycetota (nmc = 2).…”

A Highly Homogeneous Airborne Fungal Community Around a Copper Open-Pit Mine Reveals a Poor Contribution by the Local Aerosolization of Particles

“…Mercury, which has been used in old-fashioned gold recovery techniques, is particularly elevated in this area, as reported by the present study and previous surveys [60]. It has probably been accumulated historically by deposition of PM or stream sediments, a mechanism of dispersion for metals and inorganic contaminants [19,29,58]. Although heavy metal contamination is a major stressor that may be contributing to microbial community diversity and distribution, this relationship could not be established in this study.…”

A Highly Homogeneous Airborne Fungal Community around a Copper Open Pit Mine Reveals the Poor Contribution Made by the Local Aerosolization of Particles

“…Mercury, which has been used in old-fashioned gold recovery techniques, is particularly elevated in this area, as reported by the present study and previous surveys [29]. It has probably been accumulated historically by deposition of PM or stream sediments, a mechanism of dispersion for metals and inorganic contaminants [18,28]. Although heavy metal contamination is a major stressor that may be contributing to microbial community diversity and distribution, this relationship could not be established in this study.…”

“…A recent study assessed the influence of the Saharan-Sahelian dust event on respirable metals and microorganisms in Texas, USA, i.e., on a global scale. Although elemental composition could be tracked from African sources, the airborne bacterial and fungal communities correlate with local sources such as vehicular emissions, construction activities, and, notably, calcium content [18]. Here, the influence of the mine on airborne fungal communities could not be established.…”

“…Global scale studies suggest that spatial distribution depends on seasonality, meteorological factors, close environments, emission sources, etc. [15][16][17][18]. Fungal and bacterial diversity in urban areas is lower than in rural zones [19], with higher total cultivable fungi on days with lower particulate matter (PM) pollution [20].…”