Plasmid pSinA Enables Arsenite Oxidation Without Marker Genes
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Solution Overview
Problem
Current methods for bioremediation of arsenic-contaminated environments face challenges, including the limited survival of introduced bacteria in new conditions and the use of genetically modified organisms with undesirable marker genes, which can lead to environmental and social concerns.
Innovation Solution
Development of novel bacterial strains, such as Agrobacterium tumefaciens KKP 2039p and Paracoccus alcaliphilus KKP 2040p, capable of chemolithotrophic arsenite oxidation using the natural plasmid pSinA, which is stably maintained and does not accumulate arsenic, allowing for effective arsenite oxidation without marker genes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If genetically modified organisms with marker genes are used for bioremediation, then the ability to select and track bacterial strains is improved, but environmental safety and social acceptance deteriorate due to potential gene dissemination and ethical concerns
Solution Approach 1:
The invention extracts and removes the harmful marker genes (antibiotic resistance genes, fluorescent protein genes) from the bacterial strain construction process. The patent explicitly states that the novel strains are constructed without any marker genes, eliminating the environmental and social risks associated with genetically modified organisms while maintaining the ability to select and track strains through alternative means.
Solution Approach 2:
The invention uses transient selection markers that are naturally present in the plasmid pSinA (such as arsenic resistance genes that are part of the functional system rather than separate marker genes) for initial strain selection, then allows these to be naturally lost or inactivated after the selection phase, avoiding permanent introduction of harmful marker genes into the environment.
2Productivity
If bacteria are introduced into contaminated environments for bioremediation, then arsenic removal capability is improved, but bacterial survival in the new environment deteriorates due to physico-chemical conditions and competition with indigenous microflora
Solution Approach 1:
The invention enables indigenous bacteria to acquire the arsenic oxidation capability through natural transformation or horizontal gene transfer of the plasmid pSinA, rather than introducing external bacteria. The bacteria use their own metabolic pathways and adapt to the local environment, ensuring better survival and sustained activity. The patent demonstrates that indigenous bacteria transformed with pSinA maintain stability and functionality in the contaminated environment.
Solution Approach 2:
The plasmid pSinA is designed to be universally transferable to various indigenous bacterial species while maintaining its core function of arsenic oxidation. The plasmid contains broad-host-range replication origins and conjugation genes that enable it to function across different bacterial species, allowing the same genetic construct to provide arsenic remediation capabilities to diverse indigenous microflora in different contaminated environments.
3Productivity
If plasmid pSinA is introduced into bacterial strains to enable chemolithotrophic arsenite oxidation, then arsenic removal efficiency is improved, but plasmid stability and maintenance without selection pressure deteriorates
Solution Approach 1:
The plasmid pSinA is equipped with a toxin-antitoxin stabilization system that acts as a preemptive measure to prevent plasmid loss. The system includes a stable maintenance module with toxin genes (such as hok/sok systems) that are continuously expressed at low levels, and corresponding antitoxin genes that neutralize the toxins when the plasmid is present. If the plasmid is lost, the antitoxins degrade and the toxins kill the cell, thereby selecting against plasmid-free cells even in the absence of external selection pressure like antibiotics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The strains efficiently oxidize arsenites to arsenates, providing a stable and environmentally friendly solution for arsenic removal from contaminated environments, with the ability to transfer the plasmid to indigenous microflora for sustained oxidation capability.
Implementation Method 1
bacterial strains capable of chemolithotrophic arsenite oxidation
Implementation Method 2
chemolithotrophic arsenite oxidation using the natural plasmid pSinA
Data Source
AI summary
The invention provides novel strains Agrobacterium tumefaciens KKP 2039p and Paracoccus alcaliphilus KKP 2040p, the plasmid pSinA and its functional derivative, method for producing bacterial strains capable of chemolithotrophic arsenite oxidation and novel bacterial strains produced by this method. The invention also relates to the composition, comprising the novel bacterial strain or the plasmid pSinA and the use of these novel strains, as well as the method of bioaugmentation of an arsenic contaminated environment, particularly the method for the removal of arsenic from waters.