Biology subjects

Santl-Temkiv, T.

Publications and source records attributed to Santl-Temkiv, T..

4 recordsLinked to original sources

bioRxiv2024

The limited capacity of bioaerosols to serve as cloud-condensation nuclei may restrict their potential to initiate ice formation in mixed-phase clouds

Bioaerosols are gaining prominence due to their ability to nucleate ice in clouds at high subzero temperatures, thereby impacting cloud characteristics, and longevity. Acting first as cloud condensation nuclei (CCN) and second as ice nucleating particles, bioaerosols induce ice formation through immersion freezing. Nevertheless, insights into bioaerosol ability to act as CCN in situ are currently lacking. We simultaneously collected bioaerosols from the condensed and interstitial phase of clouds using size selective inlets during autumn 2020 from the Otlica observatory (Slovenia). With a polarization Raman Lidar, we confirmed the coexistence of ice particles and liquid droplets during one of the three sampling campaigns. Using spectral flow cytometers, the PINGUIN cold-stage setup and MiSeq-facilitated amplicon sequencing to assess bacterial and fungal communities, we found that both bioaerosols and biogenic ice-nucleating particles were significantly more abundant in the interstitial phase compared to the condensed phase, suggesting that they were poor CCN, unable to compete with more hygroscopic particles. Most taxa did not exhibit preferential partitioning, suggesting that surface properties generally did not significantly influence their behaviour as CCN. Our results underline the need to systematically investigate the relation between hygroscopicity and ice-nucleating activity of bioaerosols to understand their in-situ effects on cloud formation. SynopsisThe relationship between the ability of bioaerosols to nucleate cloud droplets and ice particles has not been determined. This study found that bioaerosols are poor cloud condensation nuclei which may impair their ability to nucleate ice and affect cloud formation and climate.

microbiology↗

bioRxiv2023

Micro-PINGUIN: Microtiter plate-based ice nucleation detection in gallium with an infra-red camera

Ice nucleation particles play a crucial role in atmospheric processes e.g., they can trigger ice formation in clouds and thus influence their lifetime and optical properties. The quantification and characterization of these particles require reliable and precise measurement techniques. In this publication, we present a novel droplet freezing instrument to measure immersion freezing of biotic and abiotic ice-nucleating particles within the temperature range of 0 {degrees}C to -25 {degrees}C. Immersion freezing of the samples is investigated using 384-well PCR plates with a sample volume of 30 {micro}l. Nucleation events are detected with high precision using a thermal camera that records the increase in infrared emission due to the latent heat release. To maximize the thermal contact between the PCR plate and the surrounding cooling unit, we use a gallium bath as a mount for the PCR plate. The combination of good thermal connectivity and precise temperature recording enables accurate ({+/-} 0.81 {degrees}C at -10 {degrees}C) and reproducible ({+/-} 0.20 {degrees}C) detection of the nucleation temperatures. For comparison with already existing instruments, the new ice nucleation instrument, "micro-PINGUIN", was characterized using Snomax(R) (hereafter Snomax) and Illite NX suspensions. The results are in agreement with what has been reported in the literature for the already existing instruments. Consequently, the results that will be produced using the micro-PINGUIN are of good quality and can be compared to the results produced by other validated instruments for the study of immersion freezing of various ice nucleating particles. Further, we investigated the reproducibility of experiments using Snomax suspensions and found poor reproducibility when suspensions were prepared freshly even if the same batch of Snomax is used. This could be attributed to substrate heterogeneity, aging effects, and dilution errors. The reproducibility of the measurements is greatly improved for Snomax suspensions that are prepared in advance and stored frozen in aliquots. Thus, we suggest the use of suspensions frozen in aliquots for further reproducibility measurements and intercomparison studies.

microbiology↗

bioRxiv2022

Structure and Protein-Protein Interactions of Ice Nucleation Proteins Drive Their Activity

ABSTRACTMicrobially-produced ice nucleating proteins (INpro) are unique molecular structures with the highest known catalytic efficiency for ice formation. Their critical role in rain formation and frost damage of crops together with their diverse commercial applications warrant an in-depth under-standing of their inherent ice nucleation mechanism. We used the machine-learning based software Al-phaFold to develop the first ab initio structural model of a bacterial INpro which is a novel beta-helix structure consisting of repeated stacks of two beta strands connected by two sharp turns. Using the synchrotron radiation circular dichroism, we validated the {beta}-strand content of the model. Combining functional studies of purified recombinant INpro, electron microscopy and modeling, we further demonstrate that the formation of dimers and higher-order oligomers is key to INpro activity. This work presents a major advance in understanding the molecular foundation for bacterial ice-nucleation activity and the basis for investigating the mechanistic role of INpro-induced ice formation in the atmosphere, and for commercial design and production of ice-nucleating particles for industrial applications.

microbiology↗

bioRxiv2020

The Ice Nucleating Protein InaZ is Activated by Low Temperature

Ice-nucleation active (INA) bacteria can promote the growth of ice more effectively than any other known material. Utilizing specialized ice-nucleating proteins (INPros), they obtain nutrients from plants by inducing frost damage and, when airborne in the atmosphere, they drive ice nucleation within clouds and may affect global precipitation patterns. Despite their evident environmental importance, the molecular mechanisms behind INPro-induced freezing have remained largely elusive. In the present study, we investigated the folding and the structural basis for interactions between water and the ice-nucleating protein InaZ from the INA bacterium Pseudomonas syringae strain R10.79. Using vibrational sum-frequency generation and two-dimensional infrared spectroscopy, we demonstrate that the ice-active repeats of InaZ adopt a {beta}-helical structure in solution and at water surfaces. In this configuration, hydrogen bonding between INPros and water molecules imposes structural ordering on the adjacent water network. The observed order of water increases as the interface is cooled to temperatures close to the melting point of water. Experimental SFG data combined with spectral calculations and molecular-dynamics simulations shows that the INPro reorients at lower temperatures. We suggest that the reorientation can enhance order-inducing water interactions and, thereby, the effectiveness of ice nucleation by InaZ.

biophysics↗