The most commonly found group utilized mid-chain alkanes, previously reported to be most easily degraded by microorganisms (Atlas, 1981). Shorter chain length alkanes and metabolites resulting from their degradation can be toxic to organisms, while very long-chain

alkanes are rather resistant Cytoskeletal Signaling inhibitor to degradation (Singer & Finnerty, 1984; Vestal et al., 1984; Atlas & Unterman, 2002). The profiling data also revealed that the two groups of alkane degraders showed some intergroup and low intragroup variability through highly similar DGGE profiles and the separation seen in axis 2 of the PCA scatter plot. However, those communities degrading naphthalene exhibited a larger inter- and intragroup (seen through the separation on axis Fulvestrant purchase 1 of the PCR scatter plot) variation in diversity over replicate enrichments, suggesting more stochastic events occurring within these microbial communities. These results suggested a potential

cooperative effect in terms of community-based diesel degradation. In order to investigate the extent to which site isolates could utilize diesel constituents and whether they exhibited any carbon source preference, each isolate was cultured individually on each hydrocarbon. 16S rRNA gene sequence analysis of the site isolates resulted in the recovery of 12 taxa consisting of five Pseudomonas spp., three Psychrobacter spp., two Achromobacter spp., one Rhodococcus sp., and an Acinetobacter sp. (Table 1). All of the genera fell into the phylum Proteobacteria,

with the exception of Rhodoccocus belonging to the Actinobacteria, and have frequently been associated with hydrocarbon degradation (Venkateswaran et al., 1991; Prince, 1993; Cutright & Lee, 1994; Baldi et al., 1999; de Carvalho & da Fonseca, 2005; de Carvalho et al., 2009). OD600 nm measurements showed that all 12 organisms were capable of utilizing some or all of the diesel constituents (Table 2). Although the values were relatively low, they were not unlike those seen in previous studies (Peng et al., 2007; Zeinali et al., 2007; Bouchez-Naitali GBA3 & Vandecasteele, 2008); taking into account that the organisms in the present study were cultured using lower nutrient concentrations, agitation, and temperature in order to better reflect environmental conditions. Overall, the physiological response was variable, ranging from Pseudomonas sp. 3, which was capable of growth on only two and Pseudomonas sp. 1, which could utilize all 10 hydrocarbons. Relatively high growth was observed for six of the isolates (Table 2), including Rhodococcus erythropolis, Psychrobacter sp. 1, Pseudomonas sp. 1, two Achromobacter xylosoxidans, and an Acinetobacter sp., but only in relation to mid-chain length alkanes (C13–C17). Preferential utilization of lower chain length alkanes within a community has been described previously (Richard & Vogel, 1999).