Due to the enormous complexity of soil bacterial communities, functional gene markers, like the alkB
gene coding for the bacterial alkane monooxygenase, might be more suitable to monitor specific
ecosystem functions, i.e. alkane degradation, compared to phylogenetic gene markers which include
species not providing the respective service. However, the routine application of such functional fingerprints
needs careful method development and evaluation. This study aimed at identifying a reliable,
highly resolving fingerprinting method to monitor alkane degrading communities in soil. Therefore, we
(i) evaluated various available terminal restriction fragment length polymorphism (T-RFLP) protocols for
the alkB gene, (ii) comparatively analyzed the same soil communities targeting either a functional (alkB)
or a phylogenetic marker gene (16S rRNA gene) in the T-RFLP, and (iii) judged on the applicability of
diversity indices to follow diversity changes in the degrader community during alkane input. In silico
restriction of 83 alkB gene sequences from public databases identified HpyCH4V as the enzyme yielding
the highest T-RF richness for alkB. Analyzing DNA extracts from microcosms of two different agricultural
soils (sandy and silty, amended with either maize or pea litter as alkane source) revealed a higher
sensitivity of the alkB T-RFLP compared to 16S rRNA gene T-RFLP for following spatiotemporal changes in
the alkane degrader community. As expected, the diversity indices based on either phylogenetic or
functional fingerprinting profiles deviated significantly, but both resulted in lower richness estimates
compared to an alkane degrading enrichment culture obtained from the same soil samples. The latter
indicated that alkane degradation is a very common capability of soil bacteria. However, as the two
fingerprinting methods monitor different kinds of diversity, they might provide complementary answers
(i.e. phylogenetic and functional) to the same research questions, i.e. which is the robustness of an
ecosystem function in a given system.