AUTHOR=Song Da , Chen Xingjuan , Xu Meiying , Hai Rong , Zhou Aifen , Tian Renmao , Van Nostrand Joy D. , Kempher Megan L. , Guo Jun , Sun Guoping , Zhou Jizhong 

TITLE=Adaptive Evolution of Sphingobium hydrophobicum C1T in Electronic Waste Contaminated River Sediment

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02263

DOI=10.3389/fmicb.2019.02263

ISSN=1664-302X

ABSTRACT=<p>Electronic waste (e-waste) has caused a severe worldwide pollution problem. Despite increasing isolation of degradative microorganisms from e-waste contaminated environments, the mechanisms underlying their adaptive evolution in such habitats remain unclear. Sphingomonads generally have xenobiotic-degrading ability and may play important roles in bioremediation. <italic>Sphingobium hydrophobicum</italic> C1<sup>T</sup>, characterized with superior cell surface hydrophobicity, was recently isolated from e-waste contaminated river sediment. To dissect the mechanisms driving its adaptive evolution, we evaluated its stress resistance, sequenced its genome and performed comparative genomic analysis with 19 other <italic>Sphingobium</italic> strains. Strain C1<sup>T</sup> can feed on several kinds of e-waste-derived xenobiotics, exhibits a great resistance to heavy metals and possesses a high colonization ability. It harbors abundant genes involved in environmental adaptation, some of which are intrinsic prior to experiencing e-waste contamination. The extensive genomic variations between strain C1<sup>T</sup> and other <italic>Sphingobium</italic> strains, numerous C1<sup>T</sup>-unique genes, massive mobile elements and frequent genome rearrangements reflect a high genome plasticity. Positive selection, gene duplication, and especially horizontal gene transfer drive the adaptive evolution of strain C1<sup>T</sup>. Moreover, presence of type IV secretion systems may allow strain C1<sup>T</sup> to be a source of beneficial genes for surrounding microorganisms. This study provides new insights into the adaptive evolution of sphingomonads, and potentially guides bioremediation strategies.</p>