Hydroxy fatty acids in fresh snow samples from northern Japan: long-range atmospheric transport of Gram-negative bacteria by Asian winter monsoon

Abstract

Hydroxy fatty acids (FAs) in fresh snow from Sapporo, one of the heaviest snowfall regions in the world, have been studied to ascertain the airborne bacterial endotoxin concentrations and their biomass. The presence of beta-hydroxy FAs (C-9-C-28), constituents of the Gram-negative bacterium (GNB), suggests long-range transport of soil microbes. Likewise, the occurrence of alpha- and omega-hydroxy FAs (C-9-C-30 and C-9-C-28, respectively) in snow reveals their contribution from epicuticular waxes and soil microorganisms. Estimated endotoxin and GNB mass can aid in assessing their possible impacts on the diversity and functioning of aquatic and terrestrial ecosystems, as well as lethal effects on pedestrians through dispersal of microbes. Air mass back trajectories together with hydroxy FAs reveal their sources from Siberia, the Russian Far East and northern China by the Asian monsoon. This study highlights the role of fresh snow that reduces the human health risk of GNB and endotoxin by the scavenging from air

Hydroxy fatty acids in snow pit samples from Mount Tateyama in central Japan: Implications for atmospheric transport of microorganisms and plant waxes associated with Asian dust

“…The analytical protocol used for extracting total hydroxy FAs (lipopolysaccharides; LPS bound and free) from the snowmelt water is described in Yamamoto et al [2011] and Tyagi et al [2015b]. In brief, melt snow samples (0.2-0.4 L) were first concentrated using a rotary evaporator under vacuum (<20°C) and then saponified with 1.0 M KOH in methanol at 80°C for 2 h. After the saponification, neutral components were removed by extraction with hexane/methylene chloride (10:1) and the remaining solution was acidified with 6 M HCl to form free carboxylic acids.…”

“…The LPS of GNB contains lipid A (an acylated diglucosamine head) fraction, which is present in the outer cell membrane of bacteria [Pomorska et al, 2007] and β-hydroxy fatty acids (FAs) with C-numbers from 10 to 18. Thus, LPS mass can be estimated by a measurement technique based on a specific LPS molecule such as βhydroxy FAs quantified by GC/MS [Pomorska et al, 2007;Reynolds et al, 2005;Tyagi et al, 2015b]. LPS concentrations can be calculated using the mathematical expression as follows:…”

“…However, among culture-independent techniques, the chemical markerbased approach is considered as a suitable tool for the rapid and comparative analysis of bacterial dry biomass and their endotoxins in a variety of environmental samples. Furthermore, our previous studies showed that atmospheric hydroxy fatty acids (FAs) can be used as chemical markers to trace soil microbes and higher plant metabolites in aerosol and snow samples [Tyagi et al, 2015a[Tyagi et al, , 2015b. These results indicate that higher atmospheric abundances of hydroxy FAs are associated with Asian dust episodes.…”

“…The α-, β-, and ω-isomers of hydroxy FAs (<C 18 ) have been studied in environmental samples such as sediments [Kawamura andIshiwatari, 1981, 1982;Ratledge and Wilkinson, 1988;Wakeham et al, 2003], marine aerosols [Kawamura, 1995;Tyagi et al, 2015a], and snow [Tyagi et al, 2015b] as tracers of microorganisms such as algae, fungi, bacteria, protozoa, and epicuticular waxes of higher plants. β-Hydroxy FAs from C 10 to C 18 have been used as chemical markers for Gram-negative bacteria (GNB) and their lipopolysaccharides (LPS) in previous studies of indoor aerosols Sebastian et al, 2006], dust [Reynolds et al, 2005;Saraf et al, 1997], and snow [Tyagi et al, 2015b].…”

“…The α-, β-, and ω-isomers of hydroxy FAs (<C 18 ) have been studied in environmental samples such as sediments [Kawamura andIshiwatari, 1981, 1982;Ratledge and Wilkinson, 1988;Wakeham et al, 2003], marine aerosols [Kawamura, 1995;Tyagi et al, 2015a], and snow [Tyagi et al, 2015b] as tracers of microorganisms such as algae, fungi, bacteria, protozoa, and epicuticular waxes of higher plants. β-Hydroxy FAs from C 10 to C 18 have been used as chemical markers for Gram-negative bacteria (GNB) and their lipopolysaccharides (LPS) in previous studies of indoor aerosols Sebastian et al, 2006], dust [Reynolds et al, 2005;Saraf et al, 1997], and snow [Tyagi et al, 2015b]. Positional isomers of short-chain αand ω-homologues of hydroxy FAs have been used as potential tracers of soil microorganisms (e.g., bacteria, fungi, yeasts, and protozoa) [Ratledge and Wilkinson, 1988], whereas long-chain αand ω-hydroxy FAs (C 16 to C 32 ) are used as a proxy for microalgae and cyanobacteria , sea grasses [Volkman et al, 1999], and plant waxes [Rogge et al, 1993;Simoneit, 1989].…”