Adaptive laboratory evolution of cadmium tolerance in Synechocystis sp. PCC 6803

Abstract

BackgroundCadmium has been a significant threat to environment and human health due to its high toxicity and wide application in fossil-fuel burning and battery industry. Cyanobacteria are one of the most dominant prokaryotes, and the previous studies suggested that they could be valuable in removing Cd2+ from waste water. However, currently, the tolerance to cadmium is very low in cyanobacteria. To further engineer cyanobacteria for the environmental application, it is thus necessary to determine the mechanism that they respond to high concentration of cadmium.ResultsIn this study, a robust strain of Synechocystis PCC 6803 (named ALE-9.0) tolerant to CdSO4 with a concentration up to 9.0 µM was successfully isolated via adaptive laboratory evolution over 802-day continuous passages under cadmium stress. Whole-genome re-sequencing was then performed and nine mutations were identified for the evolved strain compared to the wild-type strain. Among these mutations, a large fragment deletion in slr0454 encoding a cation or drug efflux system protein was found to contribute directly to the resistance to Cd2+ stress. In addition, five other mutations were also demonstrated related to the improved Cd2+ tolerance in ALE-9.0. Moreover, the evolved ALE-9.0 strain was found to obtain cross tolerance to some other heavy metals like zinc and cobalt as well as higher resistance to high light.ConclusionsThe work here identified six genes and their mutations related to Cd2+ tolerance in Synechocystis PCC 6803, and demonstrated the feasibility of adaptive laboratory evolution in tolerance modifications. This work also provided valuable information regarding the cadmium tolerance mechanism in Synechocystis PCC 6803, and useful insights for cyanobacterial robustness and tolerance engineering.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1205-x) contains supplementary material, which is available to authorized users.

Evolutionary Engineering of Cyanobacteria to Enhance the Production of α-Farnesene from CO2

“…PCC 6803 strain by culturing it in a medium containing 9 μM cadmium sulphate (CdSO 4 ) over 800 days to identify high cadmium tolerant strains that can be used for wastewater treatment. 18 Phototrophic sesquiterpene compounds, such as β-caryophyllene 19 (0.32 ng/L), α-bisabolene 20 (0.6 mg/L), amorpha-4,11-diene 7 (19.8 mg/L), and farnesene 8 (4.6 mg/L), have been successfully produced in metabolically engineered cyanobacterial strains. Metabolic engineering of Synechococcus elongatus PCC 7942 with overexpressed MEP pathway genes (dxs, idi, and ispA) and synthetic FS gene has resulted in the production of 4.6 mg/L α-farnesene (a precursor of squalene or biodiesel) from CO 2 (Figure 1).…”

“…Another study obtained an evolved Synechocystis sp. PCC 6803 strain by culturing it in a medium containing 9 μM cadmium sulphate (CdSO 4 ) over 800 days to identify high cadmium tolerant strains that can be used for wastewater treatment …”

Genomic and Transcriptomic Investigation of the Physiological Response of the Methylotroph Bacillus methanolicus to 5-Aminovalerate

“…For microorganisms amenable to gene deletion or gene replacement, reverse engineering of the identified mutations into the parental strain to identify causal mutations among the candidates identified by genome sequencing is the strategy of choice (Hennig et al, 2020;Walter et al, 2020). Due to the lack of genome editing tools for B. methanolicus, we opted to analyze strains overexpressing the mutant genes identified by genome sequencing (Figures 6A-D) in a similar manner as used, e.g., for validating improved cadmium tolerance observed in ALE of a cyanobacterium (Xu et al, 2018). Concerning the analysis of the AVA6 intergenic mutation (Supplementary Table 3), it is possible to further investigate this SNP without the use of genome editing.…”

Adaptive laboratory evolution triggers pathogen-dependent broad-spectrum antimicrobial potency inStreptomyces

“…Many attempts have been made by researchers to develop methods to stimulate the production of new chemical molecules (Mutka et al 2006;Gottelt et al 2010;Scherlach et al2010;Laureti 2011;Baltz et al 2011;Garbeva et al 2011). One of these methods includes adaptive laboratory evolution that has been successfully used to augment the production of antimicrobial molecules (Goers et al 2014;Charusanti et al 2012;Stergiopoulos et al 2013;Blum et al, 2016;Chunxiao et al 2018). The adaptive laboratory evolution is a phenomenon in which a parent strain is serially passed against a certain selection pressure for few generations to promote adaptation to a new prevailing niche.…”