Characterization and Transcriptome Analysis of a Long-Chain n-Alkane-Degrading Strain Acinetobacter pittii SW-1.

Weina Kong,Cheng Zhao,Liping Wang,Xingwang Gao,Zhuang Han,Fulin Chen,Shiwei Wang,Shuwen Xue,Yu Liu,Qianqian Tian

doi:10.3390/ijerph18126365

Abstract

Strain sw-1, isolated from 7619-m seawater of the Mariana Trench, was identified as Acinetobacter pittii by 16S rRNA gene and whole-genome sequencing. A. pittii sw-1 was able to efficiently utilize long-chain n-alkanes (C18–C36), but not short- and medium-chain n-alkanes (C8–C16). The degradation rate of C20 was 91.25%, followed by C18, C22, C24, C32, and C36 with the degradation rates of 89.30%, 84.03%, 80.29%, 30.29%, and 13.37%, respectively. To investigate the degradation mechanisms of n-alkanes for this strain, the genome and the transcriptome analyses were performed. Four key alkane hydroxylase genes (alkB, almA, ladA1, and ladA2) were identified in the genome. Transcriptomes of strain sw-1 grown in C20 or CH3COONa (NaAc) as the sole carbon source were compared. The transcriptional levels of alkB and almA, respectively, increased 78.28- and 3.51-fold in C20 compared with NaAc, while ladA1 and ladA2 did not show obvious change. The expression levels of other genes involved in the synthesis of unsaturated fatty acids, permeases, membrane proteins, and sulfur metabolism were also upregulated, and they might be involved in n-alkane uptake. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) confirmed that alkB expression was significantly induced by C20, C24, and C32, and almA induction extent by C24 and C32 was higher than that with C20. Furthermore, ladA2 expression was only induced by C32, and ladA1 expression was not induced by any of n-alkanes. In addition, A. pittii sw-1 could grow with 0%–3% NaCl or 8 out of 10 kinds of the tested heavy metals and degrade n-alkanes at 15 °C. Taken together, these results provide comprehensive insights into the degradation of long-chain n-alkanes by Acinetobacter isolated from the deep ocean environment.

Highlights

Species with the values above 95% can be considered as the same species [31], and sw-1 was classified as an A. pittii strain
C20, C24, and C32 (Figure 5). almA was induced 5.03-fold and 3.17-fold in the presence of C24 and C32, respectively, and 1.40-fold in the presence of C20 . ladA2 expression was upregulated 3.56-fold in the presence of C32, while it did not show remarkable change in the presence of C20 and C24 (Figure 5). ladA1 expression was not induced in the presence of any alkane (Figure 5). These results suggested that alkane hydroxylase AlkB could play a predominant role in alkane degradation for A. pittii sw-1
We isolated a LC alkane-degrading bacterium, strain sw-1, from the Mariana Trench, which was identified as A. pittii

Summary

Introduction

The problem of offshore oil leakage during exploitation and transportation has considerably impacted the balance of marine natural ecology and the survival of human beings. Alkanes are the main component of petroleum pollutants. Several microorganisms in nature can degrade alkanes. Bacteria [1,2,3], fungi [4,5], and algae [6,7] have been reported to play roles in the degradation of alkanes. Microbes can transform alkanes into less harmful or non-hazardous substrates that can participate in natural biogeochemical cycles [8], and bioremediation is more economically and environmentally friendly compared with chemical and physical remediation methods.

Methods

Results

Discussion

Conclusion