Newcastle University

PhD project Student: Martin P. Cooke

Abstract: Bacteriohopanepolyols (BHPs) are a group of membrane lipids produced by a wide range of bacteria which have a high degree of structural specificity relative to bacterial source. This is the widest study to date into the BHP content of soils from around the world and investigates their  use  as  biomarkers  in  modern  soils  and  modern  and  ancient  sediments  using  reversed phase  HPLC-MSn.  A  total  of  46  different  BHP  structures  were  observed  during  the  study including the tentative identification of 11 novel BHP structures.

Analysis  of  the  BHPs  in  a  series  of  soils  from  North  East  England,  South  West England,  Canada,  Sweden,  Vietnam  and  Southern  Spain has  shown  that  soil  BHP distributions  are  dominated  by  up  to  5  different  BHPs:  bacteriohopane-32,33,34,35-tetrol (BHT),  35-aminobacteriohopane  –  32,33,34-triol  (aminotriol),  30-(5’-adenosyl)hopane (adenosylhopane), bacteriohopanetetrol carbopseudopentose ether (BHT cyclitol ether) and, less frequently, adenosylhopane type-1, although generally more than 20 different BHPs are identified in each soil sample.

Soil  bacterial  population  dynamics  were  investigated  using  existing  knowledge  of  the relationship  between  BHPs  and  their  specific  bacterial  sources  and  has  demonstrated,  for example,  a  decrease  in  the  concentration  of  cyanobacteria  related  BHPs  with  soil  depth  in pasture (Palace Leas) and woodland (Hack Hall farm)environments confirming the validity of  these  BHP  –  bacteria  relationships  to  infer  BHP  producing  bacterial  activity.   Principle Component  Analysis  of  the  different  bacterial  types,  identified  by  source  BHPs,  in  the different  soils  can  clearly  identify  variations  between  the  soils  with,  for  example,  the influence of methanotroph and cyanobacteria derivedBHPs having significant and opposite effects  on  the  separation  of  the  soils.  This  potentially  enables  BHPs  to  be  used  to  identify source locations or environments.

Investigation of seasonal variations at two sites in NE England (Palace Leas and Hack Hall Farm)  has  shown  that  soil  BHP  concentrations  increase  during  the  summer  months  and decline  during  winter  with  no  net  accumulation  indicating  that  the  aerobic  conditions observed in near surface soils result in the rapid diagenesis or metabolism of BHPs.

An investigation of estuary sediments from the Congo Fan, River Rhone and 7 arctic rivers has shown that this rapid degradation of these highly functionalized structures does not occur in  anaerobic  marine  sediments  with  the  aerobic  methane  oxidizing  bacteria  biomarker,  35-aminobacteriohopane-30,31,32,33,34-pentol  (aminopentol)  and  other  complex  BHPs  being identified in Congo  Fan sediments up to 1 million  years old (100 metres below sea floor), thus enabling BHPs to be used as biomarkers in palaeo-environments.

The estuary and fan sediments also contained a suite of BHPs that are ubiquitous in soil but absent in many lacustrine and open marine environments where their concentration decreases proportionally with distance from land. These BHPs;adenosylhopane, adenosylhopane type-1 and their C-2 methylated homologues can thereforebe used as markers for the transport of soil derived organic material (SOM) from terrestrial to marine environments.

These results have opened up a wide range of opportunities for BHPs to be used as bacterial proxies in a variety of environments and ages, accessing a wide range of different proxies for different bacterial populations and processes from a single analysis.

 

PUBLICATIONS

Cooke, M.P., Talbot, H.M., Wagner, T., 2008. Tracking soil organic carbon transport to continental margin sediments using soil-specific hopanoid biomarkers: a case study from the Congo fan area. Organic Geochemistry 39, 958-971.

Cooke, M.P., Talbot, H.M., Farrimond, P., 2008. Bacterial populations recorded in bacteriohopanepolyol distributions in soils from Northern England. Organic Geochemistry 39, 1347-1350.

Cooke, M.P., van Dongen, B.E., Talbot, H.M., Semiletov, I., Shakhova, N., Guo, L., Gustafson, Ö., 2009. Transport of terrestrial organic matter to the Arctic Ocean via the great Arctic rivers. Organic Geochemistry 40, 1151-1159.

Handley L., Talbot, H.M., Cooke, M.P., Anderson, K.E., Wagner, T., 2010. Diverse fully functionalised bacteriohopanepolyol distributions up to 1.2 Ma in sediments from the Congo deep-sea fan. Organic Geochemistry 41, 910-914.

Redshaw,C.H., Cooke, M.P., Talbot, H.M., McGrath, S., Rowland, S.J., 2008. Low Biodegradability of Fluoxetine HCl, Diazepam and their Human Metabolites in Sewage Sludge-Amended Soil. Journal of Soils and Sediments 8, 217-230.

Rethemeyer, J., Schubotz, F., Talbot, H.M., Cooke, M.P., Hinrichs, K.U., Mollenhauer, G., 2010. Distribution of polar membrane lipids in permafrost soils and sediments of a small high Arctic catchment. Organic Geochemistry 41, 1130-1145.

Xu, Y., Cooke, M.P., Talbot, H.M., Simpson, M.E., 2009. Bacteriohopanepolyol Signatures of Bacterial Populations in Western Canadian Soils. Organic Geochemistry 40, 79-86.