Abstract
BackgroundHalomonas sp. ZM3 was isolated from Zelazny Most post-flotation mineral waste repository (Poland), which is highly contaminated with heavy metals and various organic compounds. Mobile DNA of the strain (i.e. plasmids and transposons) were analyzed in order to identify genetic information enabling adaptation of the bacterium to the harsh environmental conditions.ResultsThe analysis revealed that ZM3 carries plasmid pZM3H1 (31,370 bp), whose replication system may be considered as an archetype of a novel subgroup of IncU-like replicons. pZM3H1 is a narrow host range, mobilizable plasmid (encodes a relaxase of the MOBV family) containing mercury resistance operon (mer) and czcD genes (mediate resistance to zinc and cobalt), which are part of a large truncated Tn3 family transposon. Further analysis demonstrated that the phenotypes determined by the pZM3H1 resistance cassette are highly dependent on the host strain. In another strand of the study, the trap plasmid pMAT1 was employed to identify functional transposable elements of Halomonas sp. ZM3. Using the sacB positive selection strategy two insertion sequences were identified: ISHsp1 - representing IS5 group of IS5 family and ISHsp2 - a distinct member of the IS630 family.ConclusionsThis study provides the first detailed description of mobile DNA in a member of the family Halomonadaceae. The identified IncU plasmid pZM3H1 confers resistance phenotypes enabling adaptation of the host strain to the Zelazny Most environment. The extended comparative analysis has shed light on the distribution of related IncU plasmids among bacteria, which, in many cases, reflects the frequency and direction of horizontal gene transfer events. Our results also identify plasmid-encoded modules, which may form the basis of novel shuttle vectors, specific for this group of halophilic bacteria.
Highlights
Physiological characterization of the strain ZM3 A comparative analysis of the partial 16S rDNA sequence (1409 bp) of strain ZM3 revealed a high level of similarity to the corresponding sequences of several environmental isolates of Halomonas spp. (98.87%) and Halomonas variabilis DSM 3051T (97.89%) isolated from the Great Salt Lake (Utah, USA) [43]
ZM3 that have enabled its adaptation to the extreme environment of Zelazny Most, a complex physiological characterization of the strain was performed, including analyses of (i) temperature, pH and salinity tolerance, (ii) siderophore production, (iii) resistance to heavy metal ions, and (iv) polycyclic aromatic hydrocarbons (PAH) utilization ability
The obtained results revealed that strain ZM3 can grow in Lysogeny broth (LB) medium at temperatures ranging from 15 to 37°C, but within a relatively narrow pH range of between 6 and 8
Summary
ZM3 was isolated from Zelazny Most post-flotation mineral waste repository (Poland), which is highly contaminated with heavy metals and various organic compounds. The Zelazny Most surface waste management system is the largest mineral waste repository in Europe and one of the largest in the world. It is located in the LubinGlogow Copper District in southwest Poland and covers an area of 13.94 km. Polymetallic organic-rich copper ore is currently mined underground in this area. This ore is characterized by its neutral or slightly alkaline pH (of up to 8.5) and its high salinity. The annual deposition of flotation tailings varies from 20 to 26 million tons [1]
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