Use of isotopic and molecular techniques to link toluene degradation in denitrifying aquifer microcosms to specific microbial populations

Citation
O. Pelz et al., Use of isotopic and molecular techniques to link toluene degradation in denitrifying aquifer microcosms to specific microbial populations, ARCH MICROB, 175(4), 2001, pp. 270-281
Citations number
58
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ARCHIVES OF MICROBIOLOGY
ISSN journal
0302-8933 → ACNP
Volume
175
Issue
4
Year of publication
2001
Pages
270 - 281
Database
ISI
SICI code
0302-8933(200104)175:4<270:UOIAMT>2.0.ZU;2-O
Abstract
Microcosms were inoculated with sediments from both a petroleum-hydrocarbon (PHC)-contaminated aquifer and from a nearby pristine aquifer and incubate d under anoxic denitrifying conditions with [methyl-C-13]toluene. These mic rocosms served as a laboratory model system to evaluate the combination of isotope (C-13-labeling of polar-lipid-derived fatty acids) and molecular te chniques (16S rRNA-targeting gene probes) to identify the toluene-metaboliz ing population. After total depletion of toluene, the following bacterial p hospholipid fatty acids (PLFA) were C-13-enriched: 16:1 omega 7c, 16:1 omeg a 7t, 16:0. cy17:0, and 18. 1 omega 7c. Pure culture experiments demonstrat ed that these compounds were also found in PLFA profiles of PHC-degrading A zoarcus spp. (beta -Proteobacteria) and related species. The origin of the CO2 evolved in the microcosms was determined by measurements of stable carb on isotope ratios. Toluene represented 11% of the total pool of mineralized substrates in the contaminated sediment and 54% in the pristine sediment. The microbial community in the microcosm incubations was characterized by u sing DAPI staining and whole-cell hybridization with specific fluorescently labeled 16S rRNA-targeted oligonucleotide probes. Results revealed that 6% of the DAPI-stained cells in the contaminated sediment and 32% in the pris tine sediment were PHC-degrading Azoarcus spp. In biotic control microcosms (incubated under denitrifying conditions, no toluene added), Azoarcus spp. cells remained at less than 1% of the DAPI-stained cells. The results show that isotope analysis in combination with whole-cell hybridization is a pr omising approach to identify: and to quantify denitrifying toluene degrader s within microbial communities.