Ultraviolet radiation (UVR) tends to damage key cellular machinery. Cells may adapt by developing several defence mechanisms as a response to such damage; otherwise, their destiny is cell death. Since cyanobacteria are primary biotic components and also important biomass producers, any drastic effects caused by UVR may imbalance the entire ecosystem. Cyanobacteria are exposed to UVR in their natural habitats. This exposure can cause oxidative stress which affects cellular morphology and vital processes such as cell growth and differentiation, pigmentation, photosynthesis, nitrogen metabolism, and enzyme activity, as well as alterations in the native structure of biomolecules such as proteins and DNA. The high resilience and several mitigation strategies adopted by a cyanobacterial community in the face of UV stress are attributed to the activation of several photo/dark repair mechanisms, avoidance, scavenging, screening, antioxidant systems, and the biosynthesis of UV photoprotectants, such as mycosporine-like amino acids (MAAs), scytonemin (Scy), carotenoids, and polyamines. This knowledge can be used to develop new strategies for protecting other organisms from the harmful effects of UVR. The review critically reports the latest updates on various resilience and defence mechanisms employed by cyanobacteria to withstand UV-stressed environments. In addition, recent developments in the field of the molecular biology of UV-absorbing compounds such as mycosporine-like amino acids and scytonemin and the possible role of programmed cell death, signal perception, and transduction under UVR stress are discussed.

Phycobiliproteins (PBPs) are accessory light-harvesting pigment complexes found in cyanobacteria, red algae, and certain types of cryptophytes. The unique spectral features (strong absorbance and fluorescence), proteinaceous nature, and some imperative properties such as the anti-oxidative, hepato-protective, anti-inflammatory, and anti-aging activity of PBPs allow their use in biomedical industries. However, basic research and technological innovations are required to explore their potential in biomedical applications. The techniques responsible for therapeutic effects need to be standardized for medical application purposes. This review focuses on the current status of PBPs, their structure, functions, methods of preparation, and applications. Additionally, the stability, bioavailability, and safety issues of PBPs, along with their use in therapeutics, are discussed.

The combustion of fossil fuels constitutes a significant catalyst for climate change, resulting in the annual release of about two billion tonnes of carbon dioxide (CO₂). The increase in CO₂ emission is directly linked to a heightened occurrence of natural calamities and health-related issues. The substitution of fossil fuels with renewable energy sources is a fundamental approach to reduce the negative impacts caused by consumption of these nonrenewable energy resources. The utilisation of biological methodologies to produce environmentally friendly energy from renewable sources holds significant potential for the sustainable production of fuel. However, the cultivation of first- and second-generation biofuel crops presents a challenge, since they compete for limited cropland, hence constraining their overall viability. In contrast, photosynthetic microorganisms such as algae and cyanobacteria exhibit significant potential as third-generation biofuel catalysts, devoid of the limitations associated with contemporary biofuels. Cyanobacteria, a type of photosynthetic prokaryotes, exhibit significant potential for the direct conversion of carbon dioxide (CO₂) into biofuels, chemicals, and various other valuable compounds. There has been a growing interest in the concept of utilising biological processes to convert carbon dioxide into fuels and chemicals. The introduction of a limited number of heterologous genes has the potential to confer upon cyanobacteria the capability to convert particular central metabolites into a diverse range of end products. The progress in the field of synthetic biology and genetic manipulation has enabled the manipulation of cyanobacteria to synthesise compounds that are not generally produced by these organisms in their natural environment. This study focuses on recent papers that employ various methodologies to engineer cyanobacteria for the purpose of producing high-value compounds, such as biofuels.

A field experiment was conducted during 2006 and 2007 rainy season on a silty loam soil at Pusa, Bihar to study the effect of inorganic fertilizer in combination with organic sources, viz. vermicompost, poultry manure, FYM and green manuring under four dates of transplanting (5, 15, 25 July and 4 August) on rice ( Oryza sativa L.). Rice Rajendra Suwasani recorded significantly higher values of yield attributes (panicles/m2, panicle length, grains/ panicle, panicle weight, 1000-grains weight), yields and nutrient accumulation under integrated source of nutrients than inorganic fertilizer alone. Maximum grain yield (4.12 t/ha) was with 75% recommended dose of nitrogen (RDN) + 25% N from dhaincha ( Sesbania aculata L.) and it was 14.8 and 26.1% higher over 100 and 75% RDN, respectively. There was significant reduction in yield attributes, yields and nutrient uptake due to delayed trans- planting. Transplanting on 5 July recorded 13.6 and 25.3% higher grain yield than transplanting on 25 July and 4 August, respectively.

Ultraviolet (UV) radiation reaching the Earth’s surface is a major societal concern, and therefore, there is a significant consumer demand for cosmetics formulated to mitigate the harmful effects of UV radiation. Synthetic sunscreens being formulated to block UV penetration include inorganic metal oxide particles and organic filters. Lately, organic UV-absorbing compounds are manufactured from non-renewable petrochemicals and, as a result, there is a need to develop a sustainable manufacturing process for efficient, high-level production of a naturally occurring group of UV-absorbing compounds, namely mycosporine-like amino acids (MAAs), for use as a sunscreen additive to skincare products. Currently, the commercial production of MAAs for use in sunscreens is not a viable proposition due to the low yield and the lack of fermentation technology associated with native MAA-producing organisms. This review summarizes the biochemical properties of MAAs, the biosynthetic gene clusters and transcriptional regulations, the associated carbon-flux-driving processes, and the host selection and biosynthetic strategies, with the aim to expand our understanding on engineering suitable cyanobacteria for cost-effective production of natural sunscreens in future practices.