Bacteriohopanepolyols in tropical soils and sediments from the Congo River catchment area

Abstract

a b s t r a c tThe Congo River basin drains the second largest area of tropical rainforest in the world, including a large proportion of pristine wetlands. We present the bacteriohopanepolyol (BHP) inventory of a suite of tropical soils and, from comparison with published data, propose some initial ideas on BHP distribution controls. Strong taxonomic controls on BHP production are evident in wetland sediments. Dominant within the suite were 35-aminobacteriohopane-31,32,33,34-tetrol (aminotetrol) and 35-aminobacterio hopane-30,31,32,33,34-pentol (aminopentol), indicating aerobic methanotrophy. A narrow range and low mean relative abundance of 30-(5 0 -adenosyl)hopane (adenosylhopane) and related compounds, collectively termed ''soil marker" BHPs, were observed in Congo soils (mean 17%, range 7.9-36% of total BHPs, n = 22) compared with literature data from temperate surface soils and Arctic surface soils (mean 36%, range 0-66% of total BHPs, n = 28) suggesting a greater rate of conversion of these BHP precursors to other structures.

Methanotroph‐derived bacteriohopanepolyol signatures as a function of temperature related growth, survival, cell death and preservation in the geological record

“…The aminopentol isomer (I'; Fig. 1C) detected at 408C has been described previously (van Winden et al, 2012) and found in environmental settings where aminopentol is abundant relative to other BHPs Wagner et al, 2014;Spencer-Jones et al, 2015). Additionally at 408C, which was dominated by a Methylobacter sp.…”

The Bacteriohopanepolyol Inventory of Novel Aerobic Methane Oxidising Bacteria Reveals New Biomarker Signatures of Aerobic Methanotrophy in Marine Systems

“…The near-absence of soil-marker BHPs in AMV (Table 2) may still point towards in-situ marine production of aminopentol. However, the relative abundance of soil-markers in terrestrial settings has recently been found to be strongly influenced by environmental factors; higher temperatures and low pH (in peatlands) can both strongly reduce the relative proportion of soil marker BHPs as a proportion of total BHPs [40,110,111]. Aminopentol was found in NZS sediments that also contained soil marker BHPs (Table 2).…”

“…For example, only limited depletion in 13 C, with values between -25‰ and -40‰, have been reported for hopanoids with an inferred methanotrophic origin from modern peat bogs [37,38] as well as other ancient lignite deposits [39]. Also, BHPs in Congo deep sea fan sediments, originating from low-latitude wetlands [40], had higher 13 C values than expected (i.e., C 30 hopanol ~ -41‰; [14]). In marine CH 4 seep carbonates from the Gulf of Mexico, BHPs, hopanoic acids, and 4-methylated sterols of aerobic methanotrophs were found with similar δ 13 C values as the CH 4 source [41].…”

Understanding terrestrial organic carbon export : a time-series approach

“…Congolaise soils is indirectly supported by the high concentrations and 13 C composition of aminobacteriohopanepolyls in soils of this region (Talbot et al, 2014;Spencer-Jones et al, 2015). Therefore, in addition to higher CBT values, increased incorporation of GDGTs from swamp-forest soils during high discharge should lead to elevated GDGT-0/cren ratios, as is observed (Figure 5.4D).…”