Evidence for surfactant production by the haloarchaeon Haloferax sp. MSNC14 in hydrocarbon-containing media

Abstract

The potential for surfactant production by the extreme halophilic archaeon Haloferax sp. MSNC14 in the presence of individual hydrocarbon substrates was studied. This strain was selected for its ability to grow on different types of hydrocarbons at high NaCl concentrations. Linear (n-heptadecane or C17) and isoprenoid (pristane) alkanes, a polyaromatic hydrocarbon (phenanthrene) and ammonium acetate (highly water-soluble control compound) were used as growth substrates. The adherence potential was demonstrated by the ability of the cells to adhere to liquid or solid hydrocarbons. The biosurfactant production was indicated by the reduction of the surface tension (ST) and by the emulsification activity (EA) of cell-free supernatants. Growth on acetate was accompanied by a low EA (lower than 0.1) and a high ST (~70 mN/m), whereas an important EA (up to 0.68 ± 0.08) and a reduction of ST (down to 32 ± 2.3 mN/m) were observed during growth on the different hydrocarbons. Both ST and EA varied with the growth phase. The adhesion to hydrocarbons was higher when cells were grown on C17 (by 60-70 %) and pristane (by 30-50 %) than on phenanthrene (~25 %). The results demonstrated that strain MNSC14 was able to increase the bioavailability of insoluble hydrocarbons, thus facilitating their uptake and their biodegradation even at high salt concentration.

Halophiles and their enzymes: negativity put to good use

“…Strains from the Persian Gulf coast capable of both hydrocarbon utilization and volatilization of toxic mercury were recently reported [47]. A Haloferax strain was found to produce surfactants that enhanced hydrocarbon degradation [48]. Additionally, an Arhodomonas strain was reported to have the capability to degrade aromatic compounds, including benzene and toluene [49].…”

Diversity and Niche of Archaea in Bioremediation

“…Haloferax st. MSNC 14 also grew on phenanthrene while the other three isolates could not [ 18 ]. Later research found that Haloferax st. MSNC 14 produced surfactants during growth on n -heptadecane, pristane, and phenanthrene, but not during growth on acetate [ 31 ]. Thus, it was able to increase the bioavailability of low-solubility hydrocarbons during their degradation [ 31 ].…”

“…Later research found that Haloferax st. MSNC 14 produced surfactants during growth on n -heptadecane, pristane, and phenanthrene, but not during growth on acetate [ 31 ]. Thus, it was able to increase the bioavailability of low-solubility hydrocarbons during their degradation [ 31 ]. Four strains were also isolated from soil and water in a hypersaline coastal area of the Arabian Gulf ( Haloferax st. HA-1, Haloferax st. HA-2, Halobacterium st. HA-3, and Halococcus st. HA-4) with a multitude of alkane and aromatic degradation abilities [ 16 ].…”

Environmental microbiology as a mosaic of explored ecosystems and issues

“…The degradation of unsaturated and saturated alkanes by different types of sulfatereducing microorganisms (Grossi et al 2011;Hakil et al 2014), including a hyperthermophilic archaeon widespread in petroleum reservoirs (Khelifi et al 2010a(Khelifi et al , b, 2014, has been documented. The diversity of hydrocarbonoclastic microorganisms adapted to high salinity (Tapilatu et al 2010a) or high hydrostatic pressure (Tapilatu et al 2010b) and some original strategies to use hydrocarbons under such harsh environmental conditions (Grossi et al 2010;Silva et al 2010;Djeridi et al 2013) were also highlighted. Clearly, the capacity of extremophiles to grow on hydrocarbons still remains underestimated and undoubtedly deserves further attention for many ecological, geochemical, environmental, and biotechnological reasons.…”