scholarly journals Phototaxis in a wild isolate of the cyanobacterium Synechococcus elongatus

2018 ◽  
Vol 115 (52) ◽  
pp. E12378-E12387 ◽  
Author(s):  
Yiling Yang ◽  
Vinson Lam ◽  
Marie Adomako ◽  
Ryan Simkovsky ◽  
Annik Jakob ◽  
...  
Keyword(s):  
Energy Source ◽  
Metabolic Engineering ◽  
Circadian Rhythms ◽  
Green Light ◽  
Synechococcus Elongatus ◽  
Negative Phototaxis ◽  
Wild Isolate ◽  
Environmental Light ◽  
Light Signals ◽  
Pcc 7942

Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This process, termed “phototaxis,” enables organisms to localize in optimal light environments for improved growth and fitness. Mechanisms of phototaxis have been studied in the coccoid cyanobacterium Synechocystis sp. strain PCC 6803, but the rod-shaped Synechococcus elongatus PCC 7942, studied for circadian rhythms and metabolic engineering, has no phototactic motility. In this study we report a recent environmental isolate of S. elongatus, the strain UTEX 3055, whose genome is 98.5% identical to that of PCC 7942 but which is motile and phototactic. A six-gene operon encoding chemotaxis-like proteins was confirmed to be involved in phototaxis. Environmental light signals are perceived by a cyanobacteriochrome, PixJSe (Synpcc7942_0858), which carries five GAF domains that are responsive to blue/green light and resemble those of PixJ from Synechocystis. Plate-based phototaxis assays indicate that UTEX 3055 uses PixJSe to sense blue and green light. Mutation of conserved functional cysteine residues in different GAF domains indicates that PixJSe controls both positive and negative phototaxis, in contrast to the multiple proteins that are employed for implementing bidirectional phototaxis in Synechocystis.

scholarly journals Metabolic engineering of phosphite metabolism in Synechococcus elongatus PCC 7942 as an effective measure to control biological contaminants in outdoor raceway ponds

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Sandra Isabel González-Morales ◽  
Navid Berenice Pacheco-Gutiérrez ◽  
Carlos A. Ramírez-Rodríguez ◽  
Alethia A. Brito-Bello ◽  
Priscila Estrella-Hernández ◽  
...  
Keyword(s):  
Metabolic Engineering ◽  
Synechococcus Elongatus ◽  
Effective Measure ◽  
Biological Contaminants ◽  
Synechococcus Elongatus Pcc 7942 ◽  
Pcc 7942 ◽  
Raceway Ponds

scholarly journals Metabolic engineering of phosphite metabolism in Synechococcus elongatus PCC 7942 as an effective measure to control biological contaminants in outdoor raceway ponds

2020 ◽  
Author(s):  
Sandra Isabel González-Morales ◽  
Navid Pacheco-Gutiérrez ◽  
Carlos A. Ramírez-Rodríguez ◽  
Alethia A. Brito-Bello ◽  
Priscila Estrella-Hernández ◽  
...  
Keyword(s):  
Metabolic Engineering ◽  
Selectable Marker ◽  
Synechococcus Elongatus ◽  
Irrigation Canal ◽  
Effective Measure ◽  
Cell Factories ◽  
Biological Contaminants ◽  
Phosphorus Source ◽  
Pcc 7942 ◽  
Raceway Ponds

Abstract Background: The use of cyanobacteria and microalgae as cell factories to produce biofuels and added-value bioproducts has received great attention during the last two decades. Important investments have been made by public and private sectors to develop this field. However, it has been a challenge to develop a viable and cost-effective platform for cultivation of cyanobacteria and microalgae under outdoor conditions. Dealing with contamination caused by bacteria, weedy algae/cyanobacteria and other organisms is a major constraint to establish effective cultivation processes.Results: Here we describe the implementation in the cyanobacterium Synechococcus elongatus PCC 7942 of a phosphorus selective nutrition system to control biological contamination during cultivation. The system is based on metabolic engineering of S. elongatus to metabolize phosphite, a phosphorus source not normally metabolized by most organisms, by expressing a bacterial phosphite oxidoreductase (PtxD). Engineered S. elongatus strains expressing PtxD grow at a similar rate on media supplemented with phosphite as the non-transformed control supplemented with phosphate. We show that when grown in media containing phosphite as the sole phosphorus source in glass flasks, the engineered strain was able to grow and outcompete biological contaminants even when the system was intentionally inoculated with natural competitors isolated from an irrigation canal. The PtxD/phosphite system was successfully used for outdoor cultivation of engineered S. elongatus in 100 L cylindrical reactors and 1,000 L raceway ponds, under non-axenic conditions and without the need of sterilizing containers and media. Finally, we also show that the PtxD/phosphite system can be used as selectable marker for S. elongatus PCC 7942 transgenic strains selection, eliminating the need of antibiotic resistance genes. Conclusions: Our results suggest that the PtxD/phosphite system is a stable and sufficiently robust strategy to control biological contaminants without the need of sterilization or other complex aseptic procedures. Our data shows that the PtxD/phosphite system can be used as selectable marker and allows production of the cyanobacterium S. elongatus PCC 7942 in non-axenic outdoor reactors at lower cost, which in principle should be applicable to other cyanobacteria and microalgae engineered to metabolize phosphite.

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