Environmental Engineering Reference
In-Depth Information
Figure 5 (continued)
(a) glycerol dibiphytanyl glycerol tetraether (GDGT)-0 membrane lipid ubiquitous for Archaea,
and 2,6,10,15,19-pentamethylicosane (PMI) of methanogenic Archaea (µg.g
−
1
TOC). (b) Di-
ether membrane lipids (µg.g
−
1
TOC) ubiquitous in Archaea (i.e. archaeol), plus markers for
methanogens of the orders Methanosarcinales and Methanococcales (i.e.
sn
-2-hydroxyarchaeol
and
sn
-3-hydroxyarchaeol). (c) 4α-methyl-5α-cholest-8(14)-en-3β-ol (µg.g
−
1
TOC) derived
from group I aerobic methane oxidizing bacteria (Methylococcaceae). (d) Chlorobactene (mg.g
−
1
TOC) indicative of fossil obligate photolithotrophic green sulfur bacteria derived from the an-
cient euxinic chemocline. (e) DNA of the two recovered phylotypes of GSB (µg.g
−
1
TOC). (f)
Ratio (Log
10
) of phylotype AL-GSB 1 (µg.g
−
1
TOC) to chlorobactene (mg.g
−
1
TOC). Note that
the partial 16S rDNA sequences of the fossil phylotype AL-GSB 1 and the phylotype AL-GSB
1 recovered from the extant chemocline of Ace Lake are identical. (g) Abundance of phylotypes
AL-GSB 1 and 2 as % of total DNA. Dashed horizontal lines indicate sediments layers deposited
at times when Ace Lake was a freshwater lacustrine basin (Unit III), a stratified, sulfidic fjord
including an unknown substantial period in which Ace Lake became isolated from the ocean
(Unit II), and the present day saline, sulfidic, methane saturated, stratified lacustrine basin with
sulfate-depleted bottom waters (Unit I). Calendar years (BP) of selected sediment layers are
denoted left of Fig. 5a.
layers as well as the ratio of chlorobactene or chlorobactane between both
sediment layers are listed in Table 1.
Table 1.
Concentration of intact chlorobactene and its hydrogenated form, chlorobactane, in
two selected sediment layers.
Sediment
Chlorobactene
Chlorobactane
(mg.g
−
1
(mg.g
−
1
(cm)
TOC)
TOC)
37-39
258
40
85-87
5
10
ratio
52
4
Extant and Ancient 16S rDNA of GSB.
PCR amplified partial 16S rDNA
of GSB recovered from the extant water column and the Holocene sediments
were separated based on variations in the nucleotide positions on DGGE (Fig.
6). Sequences of GSB were not recovered from the oxygenated mixolimnion
or the deepest analyzed water layer (21.5
22 m). Separation of the GSB am-
plicons of the chemocline and the water layers below the anoxyphotic zone
(14.2
−
18.7 m) resulted in one DGGE band with identical melting position to
the position marker (PM, Fig. 6). The PM represented 16S rDNA of GSB ampli-
fied from a sediment sample (5
−
7 cm) of Ace Lake. The same DGGE band was
found in all analyzed sediment layers except for the sediments of freshwater
Unit III (Fig. 6). The amplification of 16S rDNA of GSB resulted in a unique
−
