Multi-omics Evidences For Nonionic Surfactants Influence Phenanthrene Biodegradation By Sphingomonas Sp.GY2B

The content of polycyclic aromatic hydrocarbons(PAHs)increases dramatically in environment as the demand and consumption of fossil fuels increase with the develpment of industry.Contamination of environments with PAHs is posing ongoing detrimental to human health and natural ecosystems due to their potential toxic,mutagenic,and carcinogenic properties,so selecting appropriate remediation method to decontaminate the PAHs-polluted sites is urgent.Surfactant,due to its ability to enhance the solubility of PAHs and increase their bioavailability,has been used for improving PAHs biodegradation and thus developed into surfactant-enhanced bioremediation technique.Researchers conducted numerous studies to explore the effects of surfactants on PAHs biodegradation;however,these impacts(stimulative,negligible or inhibitive)have been controversial in the past years.To gain a clear insight into the influencing mechanisms,nonionic surfactants were selected to systematically investigate their effects on cell characteristics and subsequent phenanthrene degradation ability of Sphingomonas sp.GY2 B,the underlying mechanisms were also studied by the multi-omics(i.e.proteomics,genomics and transcriptomics).The main results of this research are as follows:(1)Three nonionic surfactants(Tween80,TritonX-100 and Brij30)were selected to systematically investigate their effects on cell surface properties(membrane permeability,functional groups and elements),cell vitality as well as subsequent phenanthrene degradation ability of Sphingomonas sp.GY2 B.Results showed that biodegradation of phenanthrene was stimulated by Tween80,slightly inhibited by TritonX-100 and severely inhibited by Brij30,respectively.Positive effect of Tween80 may arise from its role as the additional carbon source for GY2 B to increase bacterial growth and activity,as demonstrated by the increasing viable cells in Tween80 amended degradation systems determined by flow cytometry.Although TritonX-100 could inhibit bacterial growth and disrupt cell membrane,its toxic impacts on microbial cells were weaker than Brij30,which may result in its weaker inhibitive extent.(2)Comparative proteomic approaches were used to investigate protein expressions of Sphingomonas sp.GY2 B during phenanthrene biodegradation in the presence and absence of Tween80.A total of 23 up-regulated and 19 down-regulated proteins were detected upon Tween80 treatment.Addition of Tween80 could regulate ion transport(e.g.H+)in cell membrane to provide driving force(ATP)for the transmembrane transport of phenanthrene thus increasing its uptake and biodegradation by GY2 B.Moreover,the addition of Tween80 probably increased GY2 B vitality and growth by inducing the expression of peptidylprolyl isomerase to stabilize cell membrane,increasing the abundances of proteins involved in intracellular metabolic pathways(e.g.TCA cycle,purine/pyrimidine metabolism,biosynthesis of amine acids,glycolysis,pentose phosphate pathway),as well as decreasing the abundances of translation/transcription-related proteins and cysteine desulfurase,thereby facilitating phenanthrene biodegradation.(3)The genome of Sphingomonas sp.GY2 B was sequenced by Illumina Hiseq2000 sequencing platform,which generated a total data amount of 776 Mb.The reads were assembled into 16 scaffolds including 22 contigs,and the genome sequence was determined to 4,994,934 bp with a GC content of 65.16 %.According to the analysis of genome component,we found that GY2 B contained 5,048 genes(total length: 452,678 bp,average length: 882 bp),289 tandem repeat sequences,187 minisatellite and 12 microsatellite DNA,56 tRNA and 6 rRNA genes.Based on the GO functions and KEGG pathways databases analysis,39 essential genes encoding enzymes required for PAHs degradation(i.e.naphthalene,fluorene,anthracene,phenanthrene,pyrene,and benzo(a)anthracene),such as catechol 1,2-dioxygenase.In particular,6 of those genes involved in phenanthrene degradation process.In addition,there were 43 genes related to other organic pollutants(i.e.dioxin,xylene,nitrotoluene,ethylbenzene,toluene and atrazine)degradation.Several genes responsible for glycolysis,tricarboxylic acid(TCA)cycle,oxidative phosphorylation,pentose phosphate pathway were also observed in the genome of GY2 B.(4)Transcriptome analysis were conducted to observe the gene expressions of GY2 B during phenanthrene biodegradation in the presence and absence of Tween80,basing on RNAsequencing technologies(RNA-seq).A number of genes were regulated in the presence of Tween80 to promote the degrading ability of GY2B: addition of Tween80 could increase the expression of genes related to H+ transport in plasma membrane to provide driving force(ATP)for accelerating the transmembrane transport of phenanthrene thus increasing its uptake by GY2B;addition of Tween80 promoted the intracellular biodegradation of phenanthrene by stimulating expression of genes encoding protocatechuate 4,5-dioxygenase and phenanthrene 9,10-monooxygenase,increasing the expression of genes involved in TCA cycle and its closely related metabolic process(i.e.carbohydrate,fatty acid and amino acid metabolism and oxidative phosphorylation),this also facilitated the production of energy for cellular process;the presence of Tween80 probably increased GY2 B vitality and growth via inducing the expression of genes associated with ABC transporters and protein transport,regulating the genes involved in other biological processes(e.g.transcription,translation,synthesis of secondary metabolites and response to oxidative stress),thereby contributing to the increased biodegradation of phenanthrene by GY2 B.