Comparison of mechanisms of hexadecane uptake among pure and mixed cultures derived from a bacterial consortium

Members of a bacterial consortium were isolated from an oil-contaminated site in Veracruz, Mexico and identified as Xanthomonas sp., Acinetobacter bouvetii, Shewanella sp. and Defluvibacter lusatiensis. We compared mechanisms of hexadecane (HXD) uptake by pure and mixed cultures based on cell surface hydrophobicity (CSH), biosurfactant production and emulsification capacity. HXD was removed by the pure cultures of A. bouvetii (72 ± 4%), Xanthomonas sp. (46 ± 4%) and D. lusatiensis (40 ± 6%), but not by Shewanella sp. Mixed cultures showed an enhanced HXD removal, particularly with the whole consortium (79 ± 3%) and when Xanthomonas sp. and A. bouvetii were combined (74 ± 7%). A. bouvetii was the only biosurfactant producer. Based on removal abilities, the uptake mechanisms were evaluated for A. bouvetii and the consortium. Our findings indicated that A. bouvetii combined both direct contact and biosurfactant-mediated uptake. For the consortium the two uptake mechanisms took place; however, the emulsification was predominant after 5 days. Differences in the uptake mechanisms by tested cultures suggested that the prevalence of one or another mechanism depends on changes in the CSH, the emulsification extent and associations among strains. Our results contribute to understand the HXD uptake mechanisms by pure and mixed cultures and reveal A. bouvetii as a potential biosurfactant producer.

► Acinetobacter bouvetii was the best degrader and potential biosurfactant producer. ► Acinetobacter bouvetii removed HXD by direct contact and biosurfactant-mediated uptake. ► Biosurfactant-mediated uptake was the predominant mechanism for the consortium.