Growth Properties Of Schizophyllum Commune Isolated From Deep Subseafloor Sediments And Its Degradation Capacity On Phenanthrene And Fluoranthene

Schizophyllum commune is global distributed fungal species and inhabited in various extreme environments,except in the Antarctic and subseafloor habitats.Four S.commune strains have been isolated from the deep sediment samples in...mbsf(meters below seafloor)respectively during IODP Expedition 337 in our laboratory.In this study,we mainly focus on the growth properties of these strains and their biodegradation and utilization capacities of phenanthrene and fluoranthene by application of a comparative analysis with the strains isolated from plants and marine habitats.The purpose of this research is to unveil the survival mechanism of fungi and their possible roles in the biogeochemical cycle of carbon in the deep subseafloor biosphere.The main results are described in the followings:Four of the S.commune strains collected from the subseafloor sediments showed common growth properties,with optimal temperature 30?,pH7,salinity 2.92%,Cu2+0.064 mg/L,carbon source of sodium lignin sulfonate and nitrogen source of yeast powder.These strains grow better under anaerobic than aerobic conditions.Taken together,the growth properties of the strains isolated from the subseafloor sediments are closely like the strain CFCC 7252 isolated from terrene and far away from the strain MCCC 3A002333 isolated from marine.All the strains isolated from the subseafloor sediments can grow in the media containing either phenanthrene or fluoranthene at concentration as high as 200 mg/L with growth inhibition rate less than 50%.The result indicated that these strains may have the potential in degrading and utilizing both phenanthrene and fluoranthene.Phenanthrene or fluoranthene can be used as unique carbon source for S.commune growth.Except strain 24R-3-F01 grows better at 75 mg/L of phenanthrene,the optimal concentration of phenanthrene or fluoranthene for all the other strains are 50 mg/L.Different strains of S.commune showed different degradation capacity against phenanthrene or fluoranthene.Strain 15R-5-F01,CFCC 7252 and MCCC 3A002333 exhibited higher degradation of the compounds than strain 6R-2-F01,20R-7-F01 and 24R-3-F01 under aerobic condition.Moreover,at anaerobic condition,79.81%phenanthrene and 84.42%fluoranthene were degraded by strain 15R-5-F01 at 10d after treatment.Data of enzymatic activities showed that the degradation of phenanthrene and fluoranthene by the test strains of S.commune was dependent on the production of manganese peroxidase(MnP),lignin peroxidase(LiP)and laeese.Moreover,production time and activities of these enzymes varied among the test strains and culture conditions.The strains isolated from the subseafloor sediments showed higher enzymatic activity under anaerobic than aerobic conditions.The degraded metabolites of phenanthrene or fluoranthene by the test strains did not show inhibition against seed germination of wheat and soybeans.However,the degraded products exhibited growth inhibition on the length of embryo roots up to 50%,which was significantly less than the treatment by phenanthrene or fluoranthene at 50 mg/L.Similarly,the degraded products also showed less toxic effects on the growth of Escherichia coli and Staphylococcus aureus.All these results suggest that the S.commune has the ability to degrade phenanthrene and fluoranthene.Data of GC/MS indicated that the major intermediate compounds of phenanthrene degraded by S.commune were Isophthalaldehyde under aerobic condition,and phenol,phthalates under anaerobic condition.Meanwhile,the major intermediate compounds of fluoranthene degraded by S.commune were phthalates,three hydroxyl cyclohexene under aerobic condition,and 1,2-diphenyl ethylene under anaerobic condition.To be concluded,S.commune,which was isolated from deep sediments below the seafloor not only has similar growth properties to the species inhabited in terrane and marine,but also show special survival abilities to adapt the anaerobic environments.Moreover,the species grows well when phenanthrene or fluoranthene of PAHs was used as sole carbon source in the media.All these results suggest that fungi may play important roles in the biogeochemical cycle of carbon in the subseafloor biosphere.