Ozonized biochar filtrate effects on the growth of Pseudomonas putida and cyanobacteria Synechococcus elongatus PCC 7942

Background Biochar ozonization was previously shown to dramatically increase its cation exchange capacity, thus improving its nutrient retention capacity. The potential soil application of ozonized biochar warrants the need for a toxicity study that investigates its effects on microorganisms. Results In the study presented here, we found that the filtrates collected from ozonized pine 400 biochar and ozonized rogue biochar did not have any inhibitory effects on the soil environmental bacteria Pseudomonas putida, even at high dissolved organic carbon (DOC) concentrations of 300 ppm. However, the growth of Synechococcus elongatus PCC 7942 was inhibited by the ozonized biochar filtrates at DOC concentrations greater than 75 ppm. Further tests showed the presence of some potential inhibitory compounds (terephthalic acid and p-toluic acid) in the filtrate of non-ozonized pine 400 biochar; these compounds were greatly reduced upon wet-ozonization of the biochar material. Nutrient detection tests also showed that dry-ozonization of rogue biochar enhanced the availability of nitrate and phosphate in its filtrate, a property that may be desirable for soil application. Conclusion Ozonized biochar substances can support soil environmental bacterium Pseudomonas putida growth, since ozonization detoxifies the potential inhibitory aromatic molecules. Graphical Abstract

Wastewater Substrate Disinfection for Application of Synechococcus Elongatus PCC 7942 Cultivation as Tertiary Treatment

The cultivation of microalgae or/and cyanobacteria in nutrient-rich wastewaters presents a significant opportunity for enhancing sustainability of tertiary wastewater treatment processes via resources/energy recovery/production. However, maintaining a monoculture in wastewater-media constitutes a significant challenge to be addressed, as a plethora of antagonistic and predating microorganisms exist is such media. In this regard, the present work assesses the efficiency of the low-cost wastewater substrate disinfection techniques of filtration, use of NaClO, H2O2 or Fe(VI), in terms of antagonistic or/and predating microbial species growth inhibition in Synechococcus elongatus PCC 7942 cultivations. Nitrates and phosphates removal rates were also experimentally assessed. The results showed that filter thickness has a greater effect on disinfection efficiency than that of filter’s pore size. Furthermore, the disinfection efficiency of Fe(VI), which was produced on-site by electrosynthesis via a Fe0/Fe0 cell, was greater than that of NaClO and H2O2. Filtration at ≤ 1.2 µm pore size coupled with chemical disinfection leads to unhindered S7942 growth and efficient nitrates and phosphates removal rates, at dosages of CT ≥ 270 mg min L−1 for NaClO and CT ≥ 157 mg min L−1 for Fe(VI). The coagulation action of Fe(III) species that result from Fe(VI) reduction and the oxidation action of Fe(VI) can assist in turbidity, organic compounds and phosphorous removal from wastewater-media. Moreover, the residual iron species can assist in S7942 harvesting and may enhance photosynthesis rate. Thus, the utilization of wastewaters for S7942 cultivation as tertiary treatment seems a promising and novel alternative to common nutrient removal processes that can reduce environmental footprint and operational costs of wastewater treatment plants.

Overexpression of Cu/Zn Superoxide Dismutase (Cu/Zn SOD) in Synechococcus elongatus PCC 7942 for Enhanced Azo Dye Removal through Hydrogen Peroxide Accumulation

Discharge of recalcitrant azo dyes to the environment poses a serious threat to environmental health. However certain microorganisms in nature have developed their survival strategies by degrading these toxic dyes. Cyanobacteria are one such prokaryotic, photosynthetic group of microorganisms that degrade various xenobiotic compounds, due to their capability to produce various reactive oxygen species (ROS), and particularly the hydrogen peroxide (H2O2) when released in their milieu. The accumulation of H2O2 is the result of the dismutation of superoxide radicals by the enzyme superoxide dismutase (SOD). In this study, we have genetically modified the cyanobacterium Synechococcus elongatus PCC 7942 by integrating Cu/Zn SOD gene (sodC) from Synechococcus sp. PCC 9311 to its neutral site through homologous recombination. The overexpression of sodC in the derivative strain was driven using a strong constitutive promoter of the psbA gene. The derivative strain resulted in constitutive production of sodC, which was induced further during dye-treated growth. The genetically engineered Synechococcus elongatus PCC 7942 (MS-sodC+) over-accumulated H2O2 during azo dye treatment with a higher dye removal rate than the wild-type strain (WS-sodC−). Therefore, enhanced H2O2 accumulation through SODs overexpression in cyanobacteria may serve as a valuable bioremediation tool.

https://ecotoxbrasil.org.br/revista/28/ecotoxicology-and-environmental-contamination/

Glyphosate is an active ingredient used in herbicide formulations worldwide. However, besides glyphosate, these formulations have other components to facilitate glyphosate absorption by plants. These include the surfactants such as polyoxyethylene amine (POEA) present in the Roundup Transorb® (RT) formulation. Glyphosate formulations are potentially more toxic to non-target organisms than the pure active ingredient. In this work, we evaluated the toxicity (72 h) of pure glyphosate and RT for the cyanobacterium Synechococcus elongatus, based on biomass growth and cell viability. The formulation proved more toxic than pure glyphosate for both parameters analysed, with an IC50 (Inhibition concentration mean) based on biomass measured by optical density (750 nm) that was sixty times lower. Cell viability was not as sensitive as the biomass because, of the few cells left in the culture, most were viable. This indicates that there is a variation in tolerance between the cyanobacteria present in the inoculum. Thus, cell viability may underestimate the results of glyphosate and RT toxicity and be useful only in low concentrations of exposure

Requirement of Cyanobacteria Synechococcus elongatus for the biomass and lipid production

Synechococcus elongatus is unicellularCyanobacteria having fast growth and can conduct photosynthesis process in its cells.This research purposed to evaluate the potential of Synechococcus elongatus as an candidate of biodiesel feedstocks by evaluating its biomass and lipid content in appropriate nutrients. The study was conducted at Asian Institute of Technology, Thailand. The Factorial Completely Randomized Design was used as experimental design in this study. The species was grown in BG II medium which was added by different doses of NaNO3 and KHPO4. Cultivation was conducted for seven days for several parameters, namely appropriate dose of nutrients, specific growth rate, biomass, and lipid content. This study resulted the optimal dose of nitrate from NaNO3 and phosphate from KHPO4 for good growth of Synechococcus elongatus which were 289.11 mg/L of NO3- and 22.26 mg/L of HPO4.This species grew well in BG-II medium added optimal nutrients at specific growth rate of 0.34µg/day. The optimal lipid productivity of Synechococcus elongatus was achieved at day 6th of cultivation which its dried biomass was 0.21±0.03 g/L and total lipid was 1.89±0.28%. Based on the results, Synechococcus elongatus cultivated in BG-II medium was potential tobe biodiesel source with its fast growth and lipid content in its cell.

Engineering natural competence into the fast-growing cyanobacterium Synechococcus elongatus UTEX 2973

Natural transformation is the process by which bacteria actively take up and integrate extracellular DNA into their genomes. In cyanobacteria, natural transformation has only been experimentally demonstrated in a handful of species. Although, cyanobacteria are important model systems for studying photosynthesis and circadian cycling, natural transformation in cyanobacteria has not been characterized to the degree that the process has been studied in other gram-negative bacteria. Two cyanobacterial species that are 99.8% genetically identical provide a unique opportunity to better understand the nuances of natural transformation in cyanobacteria: Synechococcus elongatus PCC 7942 and Synechococcus elongatus UTEX 2973 (hereafter Synechococcus 7942 and Synechococcus 2973 respectively). Synechococcus 7942 is a naturally transformable model system, while Synechococcus 2973 is a recently discovered species that is not naturally competent. Taking only 1.5 hours to replicate, Synechococcus 2973 is the fastest growing cyanobacterial species known, and thus is a strong candidate for serving as a model organism. However, the organism’s inability to undergo natural transformation has prevented it from becoming a widely used model system. By substituting polymorphic alleles from Synechococcus 7942 for native Synechococcus 2973 alleles, natural transformation was introduced into Synechococcus 2973. Two genetic loci were found to be involved in differential natural competence between the two organisms: transformation pilus component pilN and circadian transcriptional master regulator rpaA . By using targeting genome editing and enrichment outgrowth, a strain that was both naturally transformable and fast-growing was created. This new Synechococcus 2973-T strain will serve as a valuable resource to the cyanobacterial research community. Importance Certain bacterial species have the ability to take up naked extracellular DNA and integrate it into their genomes. This process is known as natural transformation and is widely considered to play a major role in bacterial evolution. Because of the ease of introducing new genes into naturally transformable organisms, this capacity is also highly valued in the laboratory. Cyanobacteria are photosynthetic and can therefore serve as model systems for some important aspects of plant physiology. Here, we describe the creation of a modified cyanobacterial strain ( Synechococcus 2973-T) that is capable of undergoing natural transformation and has a replication time that is on par with the fastest-growing cyanobacterium that has been discovered to date. This new cyanobacterium has the potential to serve as a new model organism for the cyanobacterial research community and will allow experiments to be completed in a fraction of the time that it took to complete previous assays.