Dissimilatory arsenate and sulfate reduction in sediments of two hypersaline, arsenic-rich soda lakes: Mono and Searles Lakes, California.
A radioisotope method was devised to study bacterial respiratory reduction of arsenate in sediments. The following two arsenic-rich soda lakes in California were chosen for comparison on the basis of their different salinities: Mono Lake (approximately 90 g/liter) and Searles Lake (approximately 340 g/liter). Profiles of arsenate reduction and sulfate reduction were constructed for both lakes. Reduction of [73As]arsenate occurred at all depth intervals in the cores from Mono Lake (rate constant [k] = 0.103 to 0.04 h(-1)) and Searles Lake (k = 0.012 to 0.002 h(-1)), and the highest activities occurred in the top sections of each core. In contrast, [35S]sulfate reduction was measurable in Mono Lake (k = 7.6 x10(4) to 3.2 x 10(-6) h(-1)) but not in Searles Lake. Sediment DNA was extracted, PCR amplified, and separated by denaturing gradient gel electrophoresis (DGGE) to obtain phylogenetic markers (i.e., 16S rRNA genes) and a partial functional gene for dissimilatory arsenate reduction (arrA). The amplified arrA gene product showed a similar trend in both lakes; the signal was strongest in surface sediments and decreased to undetectable levels deeper in the sediments. More arrA gene signal was observed in Mono Lake and was detectable at a greater depth, despite the higher arsenate reduction activity observed in Searles Lake. A partial sequence (about 900 bp) was obtained for a clone (SLAS-3) that matched the dominant DGGE band found in deeper parts of the Searles Lake sample (below 3 cm), and this clone was found to be closely related to SLAS-1, a novel extremophilic arsenate respirer previously cultivated from Searles Lake.
Kulp
T R
TR
US Geological Survey, Menlo Park, CA 94025, USA.
Hoeft
S E
SE
Miller
L G
LG
Saltikov
C
C
Murphy
J N
JN
Han
S
S
Lanoil
B
B
Oremland
R S
RS
D001149:Arsenates / Q000032:analysis*; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D017753:Ecosystem; D005618:Fresh Water / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D013431:Sulfates / Q000378:metabolism*; D014871:Water Microbiology
D001149:Arsenates; D013431:Sulfates; C025657:arsenic acid