Search for biogenic ice nucleation activity (INA) - a study on Snomax, pollen, moulds and mushrooms

Abstract

The ice nucleation of atmospheric biological particles and the contribution to ice cloud formation is a topic of growing interest, but only partly understood. In our studies we present the results of ice nucleation measurements in the oil immersion mode [1] of a representative spectrum of different species. Different pollen species show impressive differences in their INA, ranging from quite active (e.g. birch) to nearly inactive (e.g. ragweed). Furthermore, the INA is caused by rather robust macromolecules in the range of 100-300 kDa [2]. Also the dependence of INA on environmental stresses has been investigated. In the past a few species of Fusarii and lichen [3,4] have shown INA nearly as high as the bacterial ice nucleation proteins, which are the most active ice nuclei known. Other investigated species, however, showed no INA [5]. We searched for INA among abundant moulds and edible mushrooms, most of which have not been investigated before. However, all species except for the INA-positive Fusarium avenaceum showed no or only a slight increase in nuleation temperature in comparison to pure water. Consequently it seems that the ability to express highly-efficient ice nuclei is limited to a small number of fungal species.