| 1. |
- Amin, H., et al.
(författare)
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Indoor Airborne Microbiome and Endotoxin: Meteorological Events and Occupant Characteristics Are Important Determinants
- 2023
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 57:32, s. 11750-11766
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Tidskriftsartikel (refereegranskat)abstract
- Minimal research exists onthe factors influencing the indoorbacterial community. Despite their proposed importance for health,here we report environmental factors influencing the composition ofthe indoor bacterial communities. Airborne bacteria and endotoxin may affect asthma andallergies.However, there is limited understanding of the environmental determinantsthat influence them. This study investigated the airborne microbiomesin the homes of 1038 participants from five cities in Northern Europe:Aarhus, Bergen, Reykjavik, Tartu, and Uppsala. Airborne dust particleswere sampled with electrostatic dust fall collectors (EDCs) from theparticipants' bedrooms. The dust washed from the EDCs'clothes was used to extract DNA and endotoxin. The DNA extracts wereused for quantitative polymerase chain (qPCR) measurement and 16SrRNA gene sequencing, while endotoxin was measured using the kineticchromogenic limulus amoebocyte lysate (LAL) assay. The results showedthat households in Tartu and Aarhus had a higher bacterial load anddiversity than those in Bergen and Reykjavik, possibly due to elevatedconcentrations of outdoor bacterial taxa associated with low precipitationand high wind speeds. Bergen-Tartu had the highest difference (ANOSIM R = 0.203) in & beta; diversity. Multivariate regressionmodels showed that & alpha; diversity indices and bacterial and endotoxinloads were positively associated with the occupants' age, numberof occupants, cleaning frequency, presence of dogs, and age of thehouse. Further studies are needed to understand how meteorologicalfactors influence the indoor bacterial community in light of climatechange.
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| 2. |
- Ling, M. L., et al.
(författare)
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Effects of Ice Nucleation Protein Repeat Number and Oligomerization Level on Ice Nucleation Activity
- 2018
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Ingår i: Journal of Geophysical Research: Atmospheres. - 2169-8996. ; 123:3, s. 1802-1810
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Tidskriftsartikel (refereegranskat)abstract
- Ice nucleation active bacteria have attracted particular attention due to their unique ability to produce specific ice nucleation proteins (INpros), which are the most efficient ice nuclei known as they induce nucleation at temperatures close to 0°C. Our model bacterium Pseudomonas syringae strain R10.79 produced INpros containing 67 tandem repeats, forming the proposed ice-binding surface. To understand the role of the INpro repeats as well as the role of intermolecular interactions between INpros for their ice nucleation behavior, we produced a truncated version of the protein with only 16 tandem repeats (INpro16R). The purified INpro16R produced oligomers of varying sizes. Immersion freezing ice nucleation behavior of purified INpro16R was characterized by droplet-freezing assays and in the Leipzig Aerosol Cloud Interaction Simulator. Predominant INpro16R oligomers introduced into Leipzig Aerosol Cloud Interaction Simulator as single particles with diameters of 50 nm or 70 nm were ice nucleation active at temperatures of -26°C and -24°C, respectively. These are much lower temperatures compared to that of intact INpros (-12°C). The data clearly indicated that the number of repeats determines the ice nucleation temperature. In addition, ice nucleation between -9°C and -10°C, comparable to the activity of intact INpro, was caused by higher-order INpro16R oligomers. This supported previous observations that INpro oligomerization increases the ice-binding surface, thereby affecting ice nucleation activity. In conclusion, both repeat number and oligomerization contribute in a seemingly independent manner to the nucleation mechanism of INpros.
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