Carbon Dioxide Levels have a Significant Effect on Allergenic Fungal Spores

Airborne allergens commonly include pollen<!–[if supportFields]> XE “pollen” <![endif]–><!–[if supportFields]><![endif]–> and fungal spores. These allergens aggravate allergy and asthma symptoms. In light of global warming, pollen has increased because CO2 levels have increased. However, the effect of CO2concentrations on fungal spore production has not been significantly investigated. Wolf et al. (2010) investigate whether there is a clear relationship between CO2 levels and fungal spore production. The fungi under study are Alternaria alternata<!–[if supportFields]> XE “Alternaria alternata” <![endif]–><!–[if supportFields]><![endif]–> and Cladosporum phlei<!–[if supportFields]> XE “Cladosporum phlei” <![endif]–><!–[if supportFields]><![endif]–>. A. alternata spores are sensitized by 11.9% of the asthmatic global population. On a more local scale, they are sensitized by 28.2% of asthmatic people residing in Portland, Oregon. People diagnosed with severe asthma are more likely to be sensitized to A. alternata. C. pheli does not produce allergenic spores. However, other Cladosporumspecies do produce them. These fungi, of course, do not grow alone. They grow on plants, either on live or dead tissue. The plant for this experiment was the perennial C3<!–[if supportFields]>XE “C3plants”<![endif]–><!–[if supportFields]><![endif]–> monocot timothy grass (Phleum pratense<!–[if supportFields]> XE “Phleum pratense” <![endif]–><!–[if supportFields]><![endif]–>).—Daniella Barraza
 Wolf, J., O’Neill, N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–>., Rogers, C., Muilenberg, M., Lewis, Z., Halvorsen, 2010. Elevated Atmospheric Carbon Dioxide Concentrations Amplify Alternaria alternata<!–[if supportFields]> XE “Alternaria alternata” <![endif]–><!–[if supportFields]><![endif]–> Sporulation and Total Antigen Production. Environmental Health Perspectives 118, 1223–1228.

Wolf et al. grew the fungi and timothy grass separately. The authors’ main focus was to study the indirect effect CO2 has on production of fungal spores through the host species, timothy grass. Timothy grass was grown in two chambers at different CO2 concentrations: 300, 400, 500, and 600 µmol/mol. These concentrations correspond to preindustrial levels at the beginning of the 19th century, current ambient levels, and projected levels in 2025 and 2040, respectively. Each chamber maintained two different CO2concentration levels at different times. These levels were replicated four times. Each chamber contained ten pots with a single timothy plant. The controlled variables in the chamber were temperature and photosynthetically active radiation (PAR) supplied by high-pressure sodium and metal halide lamps. Temperature was changed gradually from the lowest at night, 20 °C, to the highest in the afternoon, 30 °C. PAR was also changed gradually in conjunction with temperature and lasted 14 hours. After 60 days, the timothy grass was stripped of the leaves. Ten leaves from each plant were analyzed for total area, mass, and nitrogen<!–[if supportFields]>XE “nitrogen”<![endif]–><!–[if supportFields]><![endif]–> and carbon concentrations. The rest were then inoculated by recently prepared fungal inocula and then placed in a sterilized media bottle. After one week, the spores were dislodged from the leaves and counted. For A. alternata spores, the antigen protein was extracted.
The ratio of C to N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> in the ten leaves was significantly higher in timothy grass grown at the highest CO2 concentrations, 500 and 600 µmol/mol. Leaf mass was significantly higher at 600 µmol/mol. There was no significant change in area. A. alternata spores produced per gram of leaf showed a positive and significant relationship with C to N ratio. However, the antigen produced per spore was negatively correlated with C to N ratio. In other words, in the two highest CO2 concentrations, the number of spores produced tripled, and as a result, the antigen produced was doubled. This doubling occurred because there more spores were produced rather than an increase of production of antigen per spore. The decrease in antigens can be attributed to the decreasing nitrogen in the timothy grass. There was no relationship between the size of the spores and the C to N ratio. For C. phlei, the production of spores also increased with the C to N ratio, but the C. phlei spore production did not reach the quantity that A. alternata produced.
There are still lots of unknowns but the relationship between global warming and allergenic fungal spores such as the effects of increasing temperatures and the more significant role that nitrogen<!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> has in spore production. This study showed that increased levels of CO2 will increase allergenic fungal spores through their relationship with a host plant. This will decidedly have an effect on allergy and asthma symptoms.

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