Seasonal Variation in Airborne Microbial Concentrations and Diversity at Landfill, Urban and Rural Sites

University of Kuopio, Department of Environmental Sciences, KUOPIO, Finland.
CLEAN - Soil Air Water (Impact Factor: 1.95). 07/2008; 36(7):556 - 563. DOI: 10.1002/clen.200700179


Microbes are present everywhere in outdoor air. However, the general characterization of outdoor air mycobiota and bacterial flora is incomplete. In this study, seasonal variations in outdoor air microbial concentrations and differences between a landfill, urban and rural sites were compared. Samples were collected monthly for a period of one year. Airborne dust samples were collected onto polyvinyl chloride filters. Filter samples were analyzed for ergosterol, and 14 species or assay groups of fungi and for the bacterial genus Streptomyces by using quantitative PCR. Viable bacteria and fungi were collected with a cascade impactor twice each month from the three sampling sites. The concentrations in the different sampling sites varied depending on the species. The concentrations of Penicillium and Aspergillus species were significantly higher in the waste center compared with the other sites, while the concentration of Cladosporium spp. was highest in the rural area. The highest concentrations of Streptomyces and Cladosporium species were observed in warmer weather periods. Similar observations were made for ergosterol. Group and species seasonal variation was less distinct for Penicillium and Aspergillus. According to the present results, both season and environment are determinants of microbial communities in outdoor air.

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    • "Indeed, it has been previously estimated that the biological fraction can be up to 25% of the total particulate mass (Jones and Harrison, 2004). In a study of Kaarakainen et al. (2008), the highest seasonal concentrations of microbial material in PM 10 have been measured during autumn and summer in southern Finland. "
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    ABSTRACT: The chemical and microbial composition of urban air particulate matter (PM) displays seasonal variation that may affect its harmfulness on human health. We studied the in vitro inflammatory and cellular metabolic activity/cytotoxicity of urban air particulate samples collected in four size-ranges (PM10–2.5, PM2.5–1, PM1–0.2, PM0.2) during four seasons in relatively clean urban environment in Helsinki, Finland. The composition of the same samples were analyzed, including ions, elements, PAH compounds and endotoxins. In addition, microbial contribution on the detected responses was studied by inhibiting the endotoxin-induced responses with Polymyxin B both in the PM samples and by two different bacterial strains representing Gram-positive and -negative bacteria. Macrophage cell line (RAW 264.7) was exposed to the size segregated particulate samples as well as to microbe samples for 24 h and markers of inflammation and cytotoxicity were analyzed. The toxicological responses were dependent on the dose as well as size range of the particles, PM10–2.5 being the most potent and smaller size ranges having significantly smaller responses. Samples collected during spring and autumn had in most cases the highest inflammatory activity. Soil components and other non-exhaust particulate emissions from road traffic correlated with inflammatory responses in coarse particles. Instead, PAH-compounds and K+ had negative associations with the particle-induced inflammatory responses in fine particles, suggesting the role of incomplete biomass combustion. Endotoxin content was the highest in PM10–2.5 samples and correspondingly, the largest decrease in the responses by Polymyxin B was seen with the very same samples. We found also that inhibitory effect of Polymyxin B was not completely specific for Gram-negative bacteria. Thus, in addition to endotoxin, also other microbial components may have a significant effect on the toxicological responses by ambient particulate matter.
    07/2015; 40(2):375-387. DOI:10.1016/j.etap.2015.06.023
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    • "s in outdoor air are at their lowest in winter ( Reponen et al . , 1992 ) . This view is also partly supported by culture - independent studies measuring both viable and non - viable microbes which showed lowest concentrations of Streptomyces spp . and C . cladosporioides in outdoor air in winter , but not for the Penicillium / Aspergillus group ( Kaarakainen et al . , 2008 ) . Moreover , other culture - independent studies have shown that the microbial content of the outdoor air can vary greatly even on a day - to - day basis as the aerosols are transported with the air currents ( Fierer et al . , 2008 ; Fahlgren et al . , 2010 ) ."
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    ABSTRACT: The respirable particles in both outdoor and indoor air contain several different components that are considered to have adverse health effects; e.g., polycyclic aromatic hydrocarbons (PAHs), various metals and microbial species. In this study, size segregated particle samples were collected for chemical, microbial and toxicological analyses from the indoor and outdoor air during each season of the year. The indoor sampling was carried out in a new, detached house with a novel sampling approach. The inorganic species accounted for 8–43% of the total respirable particles. The highest fine particle metal concentrations, both outdoors and indoors, were observed during summer, when the air quality was affected by wildfire smoke plumes, while in coarse particles the total metal concentrations were the highest during the spring, due to the high contribution from mineral dust. The PAH concentrations were 1.3 to 4.8 times higher in outdoor than in indoor air, and they were clearly the highest during winter, most probably due to residential heating, which is a major PAH source. PAHs with four rings had the largest contribution to the total PAHs. Microbial DNA was observed in all size classes, but the highest concentrations were measured in the coarse (PM 2.5–10) fraction. The microbial concentrations were higher in the indoor air samples during winter, while in the outdoor ones during summer.
    Aerosol and Air Quality Research 07/2013; 13(4):1212-1230. DOI:10.4209/aaqr.2012.11.0300 · 2.09 Impact Factor
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    • "This underscores that species-specific properties, and the characteristics of the airborne bacterial community are highly relevant to atmospheric processes. Knowledge of bacteria in the atmosphere has traditionally been based on cultivation-dependent techniques (Di Giorgio et al. 1996; Fang et al. 2007; Kaarakainen et al. 2008; Kellogg and Griffin 2006; Shaffer and Lighthart 1996), leaving uncertainty about the representativeness of these species in the natural environment, since many bacterial strains cannot grow on nutrient-rich agar plates (Staley and Konopka 1985; Simu et al. 2005). This uncertainty has recently been reduced by using cultivation-independent sampling techniques and identification of the 16S rRNA gene. "
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    ABSTRACT: The atmosphere is host to an omnipresent bacterial community that may influence fundamental atmospheric processes such as cloud formation and precipitation onset. Knowledge of this bacterial com-munity is scarce, particularly in air masses relevant to cloud formation. Using a light aircraft, we sampled above the atmospheric boundary layer—that is, at heights at which cloud condensation occurs—over coastal areas of Sweden and Denmark in summer 2009. Enumeration indicated total bacterial numbers of 4 9 10 1 to 1.8 9 10 3 m -3 air and colony-forming units of 0–6 bacteria m -3 air. 16S rRNA gene libraries constructed from samples collected above the Baltic Sea coast revealed a highly diverse bacterial commu-nity dominated by species belonging to the genera Sphingomonas and Pseudomonas. Bacterial species known to carry ice-nucleating proteins were found in several samples. Modeled back trajectories suggested the potential sources of the sampled bacteria to be diverse geographic regions, including both marine and terrestrial environments in the northern hemisphere. Several samples contained 16S rRNA genes from plant chloroplasts, confirming a terrestrial contribu-tion to these samples. Interestingly, the airborne bacterial community displayed an apparent seasonal succession that we tentatively ascribe to in situ succession in the atmosphere.
    Aerobiologia 12/2012; 28(4):481-498. DOI:10.1007/s10453-012-9250-6 · 1.38 Impact Factor
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