The relevance of nanoscale biological fragments for ice nucleation in clouds

Most studies of the role of biological entities as atmospheric ice-nucleating particles have focused on relatively rare supermicron particles such as bacterial cells, fungal spores and pollen grains. However, it is not clear that there are sufficient numbers of these particles in the atmosphere to strongly influence clouds. Here we show that the ice-nucleating activity of a fungus from the ubiquitous genus Fusarium is related to the presence of nanometre-scale particles which are far more numerous, and therefore potentially far more important for cloud glaciation than whole intact spores or hyphae. In addition, we quantify the ice-nucleating activity of nano-ice nucleating particles (nano-INPs) washed off pollen and also show that nano-INPs are present in a soil sample. Based on these results, we suggest that there is a reservoir of biological nano-INPs present in the environment which may, for example, become aerosolised in association with fertile soil dust particles

Contributions of biogenic material to the atmospheric ice-nucleating particle population in North Western Europe

A minute fraction of atmospheric particles exert a disproportionate effect on the phase of mixed-phase clouds by acting as ice-nucleating particles (INPs). To understand the effects of these particles on weather and climate, both now and into the future, we must first develop a quantitative understanding of the major INP sources worldwide. Previous work has demonstrated that aerosols such as desert dusts are globally important INPs, but the role of biogenic INPs is unclear, with conflicting evidence for their importance. Here, we show that at a temperate site all INPs active above −18 °C at concentrations >0.1 L−1 are destroyed on heating, consistent with these INPs being of biological origin. Furthermore, we show that a global model of desert dust INPs dramatically underestimates the measured INP concentrations, but is consistent with the thermally-stable component. Notably, the heat sensitive INPs are active at temperatures where shallow cloud layers in Northern Europe are frequently observed to glaciate. Hence, we suggest that biogenic material is important for primary ice production in this region. The prevalence of heat sensitive, most likely biogenic, INPs in this region highlights that, as a community, we need to quantify the sources and transport of these particles as well as determine their atmospheric abundance across the globe and at cloud altitudes

A marine biogenic source of atmospheric ice nucleating particles

The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties1,2. The formation of ice in clouds is facilitated by the presence of airborne ice nucleating particles1,2. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice3-11. Sea spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer12-19. Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice nucleating material is likely biogenic and less than ~0.2 μm in size. We find that exudates separated from cells of the marine diatom T. Pseudonana nucleate ice and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol in combination with our measurements suggest that marine organic material may be an important source of ice nucleating particles in remote marine environments such as the Southern Ocean, North Pacific and North Atlantic

The study of atmospheric ice-nucleating particles via microfluidically generated droplets

Ice-nucleating particles (INPs) play a significant role in the climate and hydrological cycle by triggering ice formation in supercooled clouds, thereby causing precipitation and affecting cloud lifetimes and their radiative properties. However, despite their importance, INP often comprise only 1 in 10³–10⁶ ambient particles, making it difficult to ascertain and predict their type, source, and concentration. The typical techniques for quantifying INP concentrations tend to be highly labour-intensive, suffer from poor time resolution, or are limited in sensitivity to low concentrations. Here, we present the application of microfluidic devices to the study of atmospheric INPs via the simple and rapid production of monodisperse droplets and their subsequent freezing on a cold stage. This device offers the potential for the testing of INP concentrations in aqueous samples with high sensitivity and high counting statistics. Various INPs were tested for validation of the platform, including mineral dust and biological species, with results compared to literature values. We also describe a methodology for sampling atmospheric aerosol in a manner that minimises sampling biases and which is compatible with the microfluidic device. We present results for INP concentrations in air sampled during two field campaigns: (1) from a rural location in the UK and (2) during the UK’s annual Bonfire Night festival. These initial results will provide a route for deployment of the microfluidic platform for the study and quantification of INPs in upcoming field campaigns around the globe, while providing a benchmark for future lab-on-a-chip-based INP studies

Multicenter validation of the prognostic value of patient age in patients treated with radical cystectomy.

PURPOSE: Small studies have suggested that older patients have worse outcomes following radical cystectomy (RC) for urothelial carcinoma of the bladder (UCB). We evaluated the association of patient age with clinical outcomes in a large multi-institutional RC series. METHODS: Data were collected from 4,429 patients treated with RC and lymphadenectomy for UCB without neoadjuvant chemotherapy. Age at RC was analyzed both as a continuous and categorical variable. RESULTS: Higher age at RC, analyzed as a continuous or categorical variable, was associated with advanced pathologic stage (P < 0.001), higher tumor grade (P = 0.045), presence of lymphovascular invasion (P = 0.018), and positive soft-tissue surgical margin status (P = 0.004). Elderly patients were less likely to receive postoperative chemotherapy (P < 0.001). In multivariable analyses, higher age was associated with disease recurrence, cancer-specific, and overall mortality (P < 0.001). Patients ≥80 years had a significantly greater risk of cancer-specific mortality than patients <50 years (HR 1.763, P < 0.001). Age minimally improved the accuracy of a base model that included standard pathologic features for prediction of disease recurrence (+0.2-0.3%) and cancer-specific survival (+0.3%). Conversely, age improved the predictive accuracy for overall survival by a sizeable margin (+4.2-4.5%). CONCLUSIONS: This large external validation study confirms that advanced patient age is minimally but significantly associated with worse prognosis after RC. Nevertheless, a large proportion of elderly patients benefitted from RC with curative intent. We need to improve our understanding of the reasons for the worse UCB outcomes in this growing segment of the population and to develop strategies to improve cancer care in the elderly

Ice nucleation active bacteria in precipitation are genetically diverse and nucleate ice by employing different mechanisms.

A growing body of circumstantial evidence suggests that ice nucleation active (Ice(+)) bacteria contribute to the initiation of precipitation by heterologous freezing of super-cooled water in clouds. However, little is known about the concentration of Ice(+) bacteria in precipitation, their genetic and phenotypic diversity, and their relationship to air mass trajectories and precipitation chemistry. In this study, 23 precipitation events were collected over 15 months in Virginia, USA. Air mass trajectories and water chemistry were determined and 33 134 isolates were screened for ice nucleation activity (INA) at -8 °C. Of 1144 isolates that tested positive during initial screening, 593 had confirmed INA at -8 °C in repeated tests. Concentrations of Ice(+) strains in precipitation were found to range from 0 to 13 219 colony forming units per liter, with a mean of 384±147. Most Ice(+) bacteria were identified as members of known and unknown Ice(+) species in the Pseudomonadaceae, Enterobacteriaceae and Xanthomonadaceae families, which nucleate ice employing the well-characterized membrane-bound INA protein. Two Ice(+) strains, however, were identified as Lysinibacillus, a Gram-positive genus not previously known to include Ice(+) bacteria. INA of the Lysinibacillus strains is due to a nanometer-sized molecule that is heat resistant, lysozyme and proteinase resistant, and secreted. Ice(+) bacteria and the INA mechanisms they employ are thus more diverse than expected. We discuss to what extent the concentration of culturable Ice(+) bacteria in precipitation and the identification of a new heat-resistant biological INA mechanism support a role for Ice(+) bacteria in the initiation of precipitation

Ice nucleation by cellulose and its potential contribution to ice formation in clouds

Hiranuma N, Moehler O, Yamashita K, et al. Ice nucleation by cellulose and its potential contribution to ice formation in clouds. Nature Geoscience. 2015;8(4):273-277.Ice particles in the atmosphere influence clouds, precipitation and climate, and often form with help from aerosols that serve as ice-nucleating particles. Biological particles(1), including non-proteinaceous ones(2,3), contribute to the diverse spectrum of ice-nucleating particles(4,5). However, little is known about their atmospheric abundance and ice nucleation efficiency, and their role in clouds and the climate system is poorly constrained(6). One biological particle type, cellulose, has been shown to exist in an airborne form that is prevalent throughout the year even at remote and elevated locations(7,8). Here we report experiments in a cloud simulation chamber(9) to demonstrate that microcrystalline cellulose particles can act as efficient ice-nucleating particles in simulated supercooled clouds. In six immersion mode freezing experiments, we measured the ice nucleation active surface-site densities of aerosolized cellulose across a range of temperatures. Using these active surface-site densities, we developed parameters describing the ice nucleation ability of these particles(10) and applied them to observed atmospheric cellulose and plant debris concentrations in a global aerosol model. We find that ice nucleation by cellulose becomessignificant (>0.1l(-1)) below about -21 degrees C, temperatures relevant to mixed-phase clouds. We conclude that the ability of cellulose to act as ice-nucleating particles requires a revised quantification of their role in cloud formation and precipitation