Characterization Of A Deep-sea Alkane Degrading Bacterium Acinetobacter Pittii Sw-1 With Genomic And Transcriptomic Analysis

Alkanes,as the main pollutants in petroleum,has brought great impact on the balance of natural ecology due to the hydrophobicity and toxicity.Microbial remediation is widely used in the petroleum polluted environment.In this study,the alkane degradation characteristics and metabolic regulation mechanisms of Acinetobacter pittii sw-1 were studied in combination with genomics and transcriptomics analysis.The n-alkane degradation results showed that A.pittii sw-1 could efficiently utilize long-chain n-alkanes(C₁₈–C₃₆)as the sole carbon source.The degradation rate of C₁₈-C₂₄was more than 80%,while the degradation ability of C₃₂ and C₃₆ was weaker.Adding proper concentration of rhamnolipids could promote the utilization of alkanes by strain sw-1.The optimum p H for strain sw-1 was between 7-8,and it could survive in 3%Na Cl and degrade alkanes at 15?.In addition,strain sw-1 had certain tolerance to most of tested heavy metals.The genome size of strain sw-1 was 4071456 bp,and the G+C content was 38.66%.A total of 3,808 protein coding sequences(CDSs),1 16S rRNAs,1 23S rRNAs,63 tRNAs and4 ncRNAs were identified.A series of alkane degradation related genes were also found in the genome of this strain,including four alkane hydroxylase genes,alk B,alm A,lad A1,lad A2,the corresponding regulatory factors,and the alcohol dehydrogenases and aldehyde dehydrogenase genes.The homologous relationships of four alkane hydroxylases in different strains were compared.Comparative genomic analysis revealed the closely relationship between sw-1 and A.pittii HUMV4683.In addition,strain sw-1 had certain advantages than other alkane-degrading bacteria in lipid metabolism and transport,DNA replication,recombination and repair,transcription,defense mechanism,and mobile elements like prophages and transposons.The expression of alkane degradation related genes in strain sw-1 in C₂₀ as the sole carbon source was investigated byRNA-seq.The results showed that a total of 831 genes were differentially expressed.Among these,the expression levels of 437 genes were up-regulated and 394 genes were down-regulated.A series of genes involved in alkane metabolic pathways were induced,and the transcriptional level of alk B was increased78.28-fold.In addition,the genes involved in the TCA cycle,unsaturated fatty acids,membrane proteins,permeases enzymes,efflux pumps and sulfur transporters biosynthesis were also induced.The RT-qPCR confirmed that the expression of alk B was significantly induced by C₂₀,C₂₄,and C₃₂,and alm A induction by C₂₄ and C₃₂was higher than that with C₂₀,while lad A2 was only induced by C₃₂,and lad A1 was not induced by any of these n-alkanes.In conclusion,based on genomics and transcriptomics analysis,we analyzed the alkane degradation characteristics and metabolic regulation pathway of A.pittii sw-1,which provided basic theoretical guidance for this strain to be applied in alkane pollution remediation.