Isolation of Adherent Polycyclic Aromatic Hydrocarbon (PAH)-Degrading Bacteria Using PAH-Sorbing Carriers

Abstract

Two different procedures were compared to isolate polycyclic aromatic hydrocarbon (PAH)-utilizing bacteria from PAH-contaminated soil and sludge samples, i.e., (i) shaken enrichment cultures in liquid mineral medium in which PAHs were supplied as crystals and (ii) a new method in which PAH degraders were enriched on and recovered from hydrophobic membranes containing sorbed PAHs. Both techniques were successful, but selected from the same source different bacterial strains able to grow on PAHs as the sole source of carbon and energy. The liquid enrichment mainly selected for Sphingomonas spp., whereas the membrane method exclusively led to the selection of Mycobacterium spp. Furthermore, in separate membrane enrichment set-ups with different membrane types, three repetitive extragenic palindromic PCR-related Mycobacterium strains were recovered. The new Mycobacterium isolates were strongly hydrophobic and displayed the capacity to adhere strongly to different surfaces. One strain, Mycobacterium sp. LB501T, displayed an unusual combination of high adhesion efficiency and an extremely high negative charge. This strain may represent a new bacterial species as suggested by 16S rRNA gene sequence analysis. These results indicate that the provision of hydrophobic sorbents containing sorbed PAHs in the enrichment procedure discriminated in favor of certain bacterial characteristics. The new isolation method is appropriate to select for adherent PAH-degrading bacteria, which might be useful to biodegrade sorbed PAHs in soils and sludge.

Physiology and transcriptome of the polycyclic aromatic hydrocarbon-degrading Sphingomonas sp. LH128 after long-term starvation

“…A GFP-labelled variant of Sphingomonas sp. LH128 (Bastiaens et al, 2000;Wouters et al, 2010) was used. Based on its 16S rRNA gene sequence (accession number KC599553), strain LH128 is phylogenetically most closely related to Sphingomonas subarctica, which belongs to the Novosphingobium branch of the genus Sphingomonas (Takeuchi et al, 2001).…”

“…One of the important bacterial genera implicated in the biodegradation of PAHs is Sphingomonas. Members of the genus Sphingomonas are strictly aerobic, Gram-negative, rod shaped and chemoheterotrophic bacteria that are widely distributed in soil, water and sediments (Bastiaens et al, 2000;Leys et al, 2004). They have been isolated as aerobic organic xenobiotic-and PAH-degraders and, recently, their association with actual PAH biodegradation in soil has been shown by nucleic acid-and lipid-based stable-isotope probing (Johnsen et al, 2002;Jones et al, 2011).…”

Application of Chemically Accelerated Biotreatment to Reduce Risk in Oil-Impacted Soils

“…As a consequence of its longer aliphatic groups and resultant greater hydrophobicity, TBP is more resistant to solubilization than TBP; for example, we observed that the former tended to form persistent globules in the culture media, whereas the latter did not. It is, however, difficult to attribute these observations to the effects of solubility alone, since the same adaptations (e.g., lipid-rich outer cell layers, production of biosurfactants) which confer the capability to take up HMW PAHs upon bacteria such as Mycobacterium (3,12) and Sphingomonas (3) would be expected to have the same effect on TBP. It is therefore possible that the increased removal of some PAHs which was occasionally seen with TBP (Table 2), as well as the high mineralization of phenanthrene supported by both alkylphosphates in the MGP soil (Fig.…”

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“…These isolated strains, PHPY and SK, are proposed to be new members of Sphingomonadaceae and Rhodobacteraceae, respectively. Several reports have shown the important role of bacteria in Sphingomonadaceae for PAH degradation in soils 16,31,32 , mangrove sediments 33 , and deep subsurface sediments 34 . This study, in accordance with previous reports 35 , also found that sphingomonads with PAH degradation ability can be isolated from seawater, indicating that sphingomonads are found in a wide variety of environments and might play a key role in the degradation of PAHs in various environments, including the marine environment.…”