Ice nucleation active bacteria and their potential role in precipitation

Abstract

Certain bacteria that are commonly found on plants have the capacity to catalyze the freezing of supercooled water at temperatures as warm as −1 • C. This is conferred by a protein in the outer membrane of the bacterial cell. Because of the abundance of these bacteria and the warm temperature at which they function as ice nuclei, they are considered to be among the most active of the naturally-occurring ice nuclei. As plant pathogens, antagonists of plant pathogens and as causal agents of frost damage, these bacteria have wellstudied interactions with plants. Here we propose that these bacteria also play a role in atmospheric processes leading to rain, given that they are readily disseminated into the atmosphere and have been found in clouds at altitudes of several kilometers. That they participate in a sort of biological cycle of precipitation-whereby they are transported into clouds from plant canopies and incite rain thereby causing favorable conditions for their growth on plant surfaces-was proposed about 20 years ago. Today, sufficient evidence and meteorological tools have emerged to re-ignite interest in bioprecipitation and in the ways in which plants play a role as cloud seeders. 88 JOURNAL DE PHYSIQUE IV 2. THE BIOLOGICAL COMPONENT OF AEROSOLS Outside of urban zones, the air over continents contains 3 × 10 9 to 5 × 10 10 particles/m 3. Mineral dusts are abundant in atmospheric aerosols. In polluted regions a major component of these aerosols can be soot. But, anyone afflicted with allergies to pollen knows that there is a biological component to atmospheric aerosols. In fact, up to 25 % of the insoluble part of aerosols can be of biological origin [1]. Pollen is only one of the biological components of aerosols and is only one of the types of particles that plants contribute to the atmosphere. The seemingly abiotic atmosphere that surrounds our planet is a bouillon of biological bits including bacteria; protozoa; spores of fungi, ferns and mosses; virus particles; parts of insects and dust mites; algae and pollen grains. In some cases, these biotic particles are dead debris that are picked up into the air. But often, aerial dissemination is an integral part of the life cycle of organisms, a sort of boulevard to opportunities for species out-crossing and to supplemental food and water resources. At altitudes below about 15 m, there are hundreds to thousands of particles of biological origin per m 3 of air. Over a suburban region the quantity of microorganisms, for example, in the air has been observed to be as high as 7000 culturable propagules of fungi and 1600 cultural bacteria/m 3 [2]. The bulk of the popular interest in aerobiology concerns the presence-in the air we breath-of biological particles with direct negative impacts on human health such as allergens, causal agents of pneumonia and other lung diseases and of septicemias in hospital environments. The Andersen sampler, widely used in studies of aerobiology, was conceived to simulate uptake of particles by the human respiratory system [3]. This...

Atmospheric Processing and Variability of Biological Ice Nucleating Particles in Precipitation at Opme, France

“…Theories and observations indicate that INPs can be responsible for triggering precipitation [24,28]. In particular the most efficient of them, i.e., those acting at the warmest temperatures, should be relatively enriched in precipitating water compared with their relative abundance in aerosols or clouds, respect to other compounds, particles and less efficient INPs [24,59,66]. For investigating the processing, i.e., the specific behavior, of INPs in the atmosphere, we statistically compared our data with others measurements carried out at nearby, at puy de Dôme Mountain Observatory (1465 m a.s.l.…”

Atmospheric ice nucleators active ≥ −12 °C can be quantified on PM<sub>10</sub> filters

“…Living Pseudomonas syringae, for example, change their IN activity within hours, depending on temperature and nutrient status (Nemecek-Marshall et al, 1993). IN active sites in organisms are proteins (Wolber et al, 1986;Morris et al, 2004). These are well preserved when sorbed to mineral surfaces (Kleber et al, 2007).…”

Immersion freezing of ice nucleation active protein complexes

“…Burrows et al (2009) estimated that the mean bacterial concentrations in air over land are > 10 4 cells per m 3 , which is in the range of total ice nuclei (IN) concentrations in the atmosphere (10 2 − 10 5 per m 3 , Murray et al, 2012). Over agriculturally used areas, the number concentration of bacteria can be even higher (10 6 -10 9 bacteria m −3 given in Morris et al, 2004, and references therein), but the exact fraction of INA bacteria among all airborne bacteria remains poorly quantified. However, species belonging to Pseudomonas have often been found dominant among bacteria from fog and cloud water (Fuzzi et al, 1997;Amato et al, 2006;Ahern et al, 2007).…”

“…Besides P. syringae, other ice nucleation active (INA) bacteria species, such as Pseudomonas fluorescens, Pseudomonas viridiflava, Pantoea agglomerans or Xanthomas campestris, have been described. These INA bacteria can induce heterogeneous freezing at temperatures as high as −1 • C (Morris et al, 2004) and are, therefore, among the most efficient ice nuclei (IN) known (e.g., Yankofsky et al, 1981;Levin and Yankofsky, 1983;Möhler et al, 2008). Most of the INA bacterial species typically grow on plant surfaces, where they cause massive frost damage at high subzero temperatures.…”