Ice nucleation in a Gram-positive bacterium isolated from precipitation depends on a polyketide synthase and non-ribosomal peptide synthetase

Abstract

Earth’s radiation budget and frequency and intensity of precipitation are influenced by aerosols with ice nucleation activity (INA), i.e., particles that catalyze the formation of ice. Some bacteria, fungi, and pollen are among the most efficient ice nucleators but the molecular basis of INA is poorly understood in most of them. Lysinibacillus parviboronicapiens (Lp) was previously identified as the first Gram-positive bacterium with INA. INA of Lp is associated with a secreted, nanometer-sized, non-proteinaceous macromolecule or particle. Here a combination of comparative genomics, transcriptomics, and a mutant screen showed that INA in Lp depends on a type I iterative polyketide synthase and a non-ribosomal peptide synthetase (PKS-NRPS). Differential filtration in combination with gradient ultracentrifugation revealed that the product of the PKS-NRPS is associated with secreted particles of a density typical of extracellular vesicles and electron microscopy showed that these particles consist in “pearl chain”-like structures not resembling any other known bacterial structures. These findings expand our knowledge of biological INA, may be a model for INA in other organisms for which the molecular basis of INA is unknown, and present another step towards unraveling the role of microbes in atmospheric processes.

Identification of Candidate Ice Nucleation Activity (INA) Genes in Fusarium avenaceum by Combining Phenotypic Characterization with Comparative Genomics and Transcriptomics

“…InaZ and its homologs have been found to catalyze ice formation by affecting the order and dynamics of interfacial water and by removing latent heat [25,26]. The INA of the Gram-positive bacterium Lysinibacillus parviboronicapiens is instead associated with secreted INPs, the production of which depends on a type-I iterative polyketide synthase non-ribosomal peptide synthetase (PKS-NRPS) [27][28][29]. The mechanism by which L. parviboronicapiens INPs induce water to freeze is unknown.…”

“…A recent study found that approximately 16% of 112 Fusarium strains showed an INA above −12 • C. Strains with INA belonged to seven different Fusarium species, with most of these species also including strains without INA [41]. Therefore, it may be possible to identify candidate INA genes in Fusarium using a comparative genomics approach, based on their presence in strains that have INA and absence in strains without INA, as was performed to identify candidate INA genes in L. parviboronicapiens [27][28][29]. Additionally, if INA genes in Fusarium were to be induced under some conditions and suppressed under different ones, candidate INA genes could be identified by comparing gene expression between these conditions.…”

Seasonal Variation of the Atmospheric Bacterial Community in the Greenlandic High Arctic Is Influenced by Weather Events and Local and Distant Sources

“…Alternatively, other than the well known INA microorganisms are present, e.g., Lysinibacillus parviboronicapiens , microalgae or Cyanobacteria (e.g., Microcysti s sp.) ( Tesson and Santl-Temkiv, 2018 ; Failor et al, 2022 ).…”

Isolation and Identification of Ice Nucleation Active Fusarium Strains from Rapid Apple Declined Trees in Korea

“…Fusarium is a genus of cosmopolitan, mycotoxigenic plant pathogens that is also the first discovered and best-studied ice-nucleating fungus (Kunert et al, 2019). Ice nucleation activity (INA) is the ability of foreign particles to catalyse water freezing at temperatures above ~ -38°C, water's freezing temperature on its ultrapure state (Failor et al, 2021;Kunert et al, 2019). Biological particles such as bacteria and fungi have been shown to act as important ice nuclei, causing ice to form at temperatures ranging from −15°C to 0°C (Kunert et al, 2019;Lagzian et al, 2014;Pouleur et al, 1992).…”

“…syringae KACC 21200. In the case of fungi, INA may also be due to proteinaceous compounds produced by them (Failor et al, 2021). High activity has been reported in ice nucleation particles found in F. avenaceum.…”