Impacts of pH and temperature on soil bacterial 3-hydroxy fatty acids: Development of novel terrestrial proxies. (April 2016)

• Record Type: Journal Article
• Authors: Wang, Canfa; Bendle, James; Yang, Yi; Yang, Huan; Sun, Huiling; Huang, Junhua; Xie, Shucheng
• Is Part Of: Organic geochemistry. Volume 94(2016:May)
• Page Start: 21
• Page End: 31
• Publication Date: 2016-04
• Subjects: Proxy -- 3-Hydroxy fatty acids -- Soil -- Temperature -- Soil pH -- Palaeoclimate; Organic geochemistry -- Periodicals; Biogeochemistry -- Periodicals; Géochimie organique -- Périodiques; 553.205
• DOI: 10.1016/j.orggeochem.2016.01.010
• Languages: English
• ISSNs: 0146-6380

Abstract

Highlights: Distributions of 3-hydroxy fatty acids in soils from an altitudinal transect. Novel terrestrial 3-hydroxy fatty acid based proxies proposed for pH and MAAT. 3-Hydroxy fatty acids preserved in several palaeoclimate archives. Abstract: Gram-negative bacterial 3-hydroxy fatty acids (3-OH-FAs) biomarkers are widespread in a variety of environments including both marine and terrestrial sediments (including speleothems). In this study we analysed the hydroxylated membrane lipids of 26 soil samples from an altitudinal transect of Shennongjia Mountain in central China to study the environmental factors controlling the relative distribution of 3-OH-FAs. Our results show that both the ratio of the summed iso and anteiso to the total amount of normal 3-OH-FAs (RIAN), and the ratio of summed iso and anteiso to the total amount of all 3-OH-FAs (Branched Index) were primarily related to the pH of soil ( R 2 = 0.70 and 0.70, respectively). Additionally, the anteiso to normal 3-hydroxy fatty acids ratio of the C15 and C17 homologues (RAN15 and RAN17 ) shows a significant negative correlation with mean annual air temperature (MAAT) ( R 2 = 0.51 and 0.48, respectively). When comparing the 3-OH-FA based indices with established glycerol dialkyl glycerol tetraether (GDGT) based indices from the same soil samples, the RIAN and Branched Index show strong linear correlations with the cyclisation ratio of branched tetraethers (CBT) ( R 2 = 0.77 and 0.74, respectively), and the RAN15 and RAN17 show negative correlations with the MBT/CBT-MAAT (MBT, methylation index of branched tetraethers) ( R 2 = 0.61 and 0.36, respectively). Our new field-based correlations demonstrate the physiological response of Gram-negative bacterial cell membranes to the external environment and suggest that 3-hydroxy fatty acids can be applied in palaeoenvironmental studies to estimate past MAAT and soil pH.