title: Nascent Genomic Evolution and Allopatric Speciation of Myroides profundi D25 in Its Transition from Land to Ocean.
abstract: A large amount of bacterial biomass is transferred from land to ocean annually. Most transferred bacteria should not survive, but undoubtedly some do. It is unclear what mechanisms these bacteria use in order to survive and even thrive in a new marine environment. Myroides profundi D25(T), a member of the Bacteroidetes phylum, was isolated from deep-sea sediment of the southern Okinawa Trough near the China mainland and had high genomic sequence identity to and synteny with the human opportunistic pathogen Myroides odoratimimus. Phylogenetic and physiological analyses suggested that M. profundi recently transitioned from land to the ocean. This provided an opportunity to explore how a bacterial genome evolved to survive in a novel environment. Changes in the transcriptome were evaluated when both species were cultured under low-salinity conditions and then transferred to high-salinity conditions. Comparative genomic and transcriptomic analyses showed that M. profundi altered transcription regulation in the early stages of survival. In these stages, vertically inherited genes played a key role in the survival of M. profundi. The contribution of M. profundi unique genes, some possibly acquired by horizontal gene transfer (HGT), appeared relatively small, and expression levels of unique genes were diminished under the high-salinity conditions. We postulate that HGT genes might play an important role in longer-term adaptation. These results suggested that some human pathogens might have the ability to survive in and adapt to the marine environment, which may have important implications for public health control in coastal regions.
  
  
  OBJECTIVE
  Horizontal gene transfer (HGT) is considered to be important for bacteria to adapt to a different microhabitat. However, our results showed that vertically inherited genes might play more important roles than HGT genes in the nascent adaptation to the marine environment in the bacterium Myroides profundi, which has recently been transferred from land to ocean. M. profundi unique genes had low expression levels and were less regulated under high-salinity conditions, indicating that the contribution of HGT genes to survival of this bacterium under marine high-salinity conditions was limited. In the early adaptation stages, M. profundi apparently survived and adapted mainly by regulating the expression of inherited core genes. These results may explain in part why human pathogens can easily be detected in marine environments.
authors.affiliation: Marine Biotechnology Research Center, Institute of Marine Science and Technology, Shandong University, Jinan, China State Key Laboratory of Microbial Technology, Shandong University, Jinan, China Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China zhangyz@sdu.edu.cn qinqilong@sdu.edu.cn.
authors.forename: Yu-Zhong
authors.initials: YZ
authors.lastname: Zhang
authors.affiliation: Marine Biotechnology Research Center, Institute of Marine Science and Technology, Shandong University, Jinan, China State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.affiliation: Marine Biotechnology Research Center, Institute of Marine Science and Technology, Shandong University, Jinan, China State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Bin-Bin
authors.initials: BB
authors.lastname: Xie
authors.affiliation: Marine Biotechnology Research Center, Institute of Marine Science and Technology, Shandong University, Jinan, China State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Xiu-Lan
authors.initials: XL
authors.lastname: Chen
authors.affiliation: Marine Biotechnology Research Center, Institute of Marine Science and Technology, Shandong University, Jinan, China State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Qiong-Qiong
authors.initials: QQ
authors.lastname: Yao
authors.affiliation: Marine Biotechnology Research Center, Institute of Marine Science and Technology, Shandong University, Jinan, China State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Xi-Ying
authors.initials: XY
authors.lastname: Zhang
authors.affiliation: Institute for Environmental Genomics, University of Oklahoma, Norman, Oklahoma, USA Department of Botany and Microbiology, University of Oklahoma, Norman, Oklahoma, USA.
authors.forename: Megan L
authors.initials: ML
authors.lastname: Kempher
authors.affiliation: Institute for Environmental Genomics, University of Oklahoma, Norman, Oklahoma, USA Department of Botany and Microbiology, University of Oklahoma, Norman, Oklahoma, USA.
authors.forename: Jizhong
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, Edmond J. Safra Campus, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Aharon
authors.initials: A
authors.lastname: Oren
authors.affiliation: Marine Biotechnology Research Center, Institute of Marine Science and Technology, Shandong University, Jinan, China State Key Laboratory of Microbial Technology, Shandong University, Jinan, China zhangyz@sdu.edu.cn qinqilong@sdu.edu.cn.
authors.forename: Qi-Long
authors.initials: QL
authors.lastname: Qin
mesh_terms: D041963:Bacteroidetes / Q000235:genetics* / Q000254:growth & development* / Q000302:isolation & purification; D002681:China; D003470:Culture Media / Q000737:chemistry; D020869:Gene Expression Profiling; D022761:Gene Transfer, Horizontal; D049810:Genetic Speciation; D016680:Genome, Bacterial; D019015:Geologic Sediments / Q000382:microbiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D054712:Salinity; D017422:Sequence Analysis, DNA
chemical_list: D003470:Culture Media