Photosynthetic Conversion of CO2 Into Pinene Using Engineered Synechococcus sp. PCC 7002

Determinants of mer Promoter Activity from Pseudomonas aeruginosa

Since the MerR family is known for its special regulatory mechanism, we aimed to explore which factors determine the expression activity of the mer promoter. The Tn501/Tn21 mer promoter contains an abnormally long spacer (19 bp) between the -35 and -10 elements, which is essential for the unique DNA distortion mechanism. To further understand the role of base sequences in the mer promoter spacer, this study systematically engineered a series of mutant derivatives and used luminescent and fluorescent reporter genes to investigate the expression activity of these derivatives. The results reveal that the expression activity of the mer promoter is synergistically modulated by the spacer length (17 bp is optimal) and the region upstream of -10 (especially -13G). The spacing is regulated by MerR transcription factors through symmetrical sequences, and -13G presumably functions through interaction with the RNA polymerase sigma-70 subunit.

The volatilome reveals microcystin concentration, microbial composition, and oxidative stress in a critical Oregon freshwater lake

IMPORTANCE

Harmful algal blooms are among the most significant threats to drinking water safety. Blooms dominated by cyanobacteria can produce potentially harmful toxins and, despite intensive research, toxin production remains unpredictable. We measured gaseous molecules in Upper Klamath Lake, Oregon, over 2 years and used them to predict the presence and concentration of the cyanotoxin, microcystin, and microbial community composition. Subsets of gaseous compounds were identified that are associated with microcystin production during oxidative stress, pointing to ecosystem-level interactions leading to microcystin contamination. Our approach shows potential for gaseous molecules to be harnessed in monitoring critical waterways.

Recent developments in the production and utilization of photosynthetic microorganisms for food applications

The growing use of photosynthetic microorganisms for food and food-related applications is driving related biotechnology research forward. Increasing consumer acceptance, high sustainability, demand of eco-friendly sources for food, and considerable global economic concern are among the main factors to enhance the focus on the novel foods. In the cases of not toxic strains, photosynthetic microorganisms not only provide a source of sustainable nutrients but are also potentially healthy. Several published studies showed that microalgae are sources of accessible protein and fatty acids. More than 400 manuscripts were published per year in the last 4 years. Furthermore, industrial approaches utilizing these microorganisms are resulting in new jobs and services. This is in line with the global strategy for bioeconomy that aims to support sustainable development of bio-based sectors. Despite the recognized potential of the microalgal biomass value chain, significant knowledge gaps still exist especially regarding their optimized production and utilization. This review highlights the potential of microalgae and cyanobacteria for food and food-related applications as well as their market size. The chosen topics also include advanced production as mixed microbial communities, production of high-value biomolecules, photoproduction of terpenoid flavoring compounds, their utilization for sustainable agriculture, application as source of nutrients in space, and a comparison with heterotrophic microorganisms like yeast to better evaluate their advantages over existing nutrient sources. This comprehensive assessment should stimulate further interest in this highly relevant research topic.

Exploring the Potential of the Model Cyanobacteria Synechococcus PCC 7002 and PCC 7942 for the Photoproduction of High-Value Terpenes: A Comparison with Synechocystis PCC 6803

We have performed the first comparative analysis of the potential of two physiologically-diverse model cyanobacteria, Synechococcus PCC 7002 (S.7002) and Synechococcus elongatus PCC 7942 (S.7942), for the photosynthetic production of four chemically-different high-value terpenes: two monoterpenes limonene and pinene, and two sesquiterpenes bisabolene and farnesene. We showed, for the first time, that S.7002 and S.7942 can produce farnesene and bisabolene, respectively. Both cyanobacteria produced farnesene (S.7942 produced more efficiently than S.7002) more efficiently than the other tested terpenes (especially pinene, the weakest produced terpene). S.7002 produced limonene more efficiently than bisabolene, whereas S.7942 produced bisabolene more efficiently than limonene. These findings suggest that S.7942 is better suited to produce sesquiterpenes than monoterpenes. Interestingly, higher levels of terpenes were produced by S.7942 and S.7002 expressing a terpene-synthase gene from both an RSF1010-derived replicating plasmid and a neutral chromosomal site, as compared to either the plasmid alone or the chromosome alone. These results suggest that in both cyanobacteria, the production of terpenes is more limited by the activity of terpene synthases than the abundance of terpene precursors. Finally, higher levels of terpenes were produced by S.7002 growing on urea (a frequent pollutant) as compared to nitrate or ammonium, the standard nitrogen sources for cyanobacteria.

Synthetic biology in marine cyanobacteria: Advances and challenges

The current economic and environmental context requests an accelerating development of sustainable alternatives for the production of various target compounds. Biological processes offer viable solutions and have gained renewed interest in the recent years. For example, photosynthetic chassis organisms are particularly promising for bioprocesses, as they do not require biomass-derived carbon sources and contribute to atmospheric CO2 fixation, therefore supporting climate change mitigation. Marine cyanobacteria are of particular interest for biotechnology applications, thanks to their rich diversity, their robustness to environmental changes, and their metabolic capabilities with potential for therapeutics and chemicals production without requiring freshwater. The additional cyanobacterial properties, such as efficient photosynthesis, are also highly beneficial for biotechnological processes. Due to their capabilities, research efforts have developed several genetic tools for direct metabolic engineering applications. While progress toward a robust genetic toolkit is continuously achieved, further work is still needed to routinely modify these species and unlock their full potential for industrial applications. In contrast to the understudied marine cyanobacteria, genetic engineering and synthetic biology in freshwater cyanobacteria are currently more advanced with a variety of tools already optimized. This mini-review will explore the opportunities provided by marine cyanobacteria for a greener future. A short discussion will cover the advances and challenges regarding genetic engineering and synthetic biology in marine cyanobacteria, followed by a parallel with freshwater cyanobacteria and their current genetic availability to guide the prospect for marine species.

Engineering phototrophic bacteria for the production of terpenoids

With more than 80 000 compounds, terpenoids represent one of the largest classes of secondary metabolites naturally produced by various plants and other organisms. Owing to the tremendous structural diversity, they offer a wide range of properties relevant for biotechnological and pharmaceutical applications. In this context, heterologous terpenoid production in engineered microbial hosts represents an often cost-effective and eco-friendly way to make these valuable compounds industrially available. This review provides an overview of current strategies to employ and engineer oxygenic and anoxygenic phototrophic bacteria as alternative cell factories for sustainable terpenoid production. Besides terpenoid pathway engineering, the effects of different illumination strategies on terpenoid photoproduction are key elements in the latest studies.