Deserts represent one of the most inhospitable environments on Earth characterized by extreme daily variations in temperature, limited availability of nitrogen and water, high salinity levels, and other challenging conditions. Within these arid zones, cyanobacteria emerge as a crucial group of organisms capable of actively thriving. They form complex communities known as biocrusts, which not only ensure their own survival, but also significantly contribute to the persistence of other organisms within these ecosystems. Cyanobacteria, through their metabolic activities, play a significant role in the establishment and functioning of soil ecosystems. They are capable of generating primary organic matter, fixing molecular nitrogen, and synthesizing metabolites with potent biological activities. To endure the relentless pressures of their environment, desert cyanobacteria have evolved intricate adaptive strategies to enhance their resilience against multiple concurrent stresses. One such mechanism involves the production of secondary metabolites, enabling them to cope with the extreme conditions of drought and salinity. This comprehensive review delves into the ecological significance of desert cyanobacteria in the context of soil improvement. Additionally, the latest advancements in utilizing cyanobacteria to combat desertification and prevent soil degradation are elucidated.

Strain K-11 was isolated from the highly saline brown semi-desert soil of the Astrakhan region. Based on analysis of the 16S rRNA gene sequence, this strain was identified as Streptomyces carpaticus K-11 RCAM04697 (SCPM-O-B-9993). Whole genome sequencing of the strain was performed. Phytotoxicity, antiviral, antioxidant, antifungal, and insecticidal activities of the strain were studied. All extracts and suspensions of S. carpaticus strain RCAM04697 had plant-stimulating activity. Antiviral properties was exhibited as suppression of development and propagation of viral pathogens in laboratory conditions: Tomato mosaic virus (ToMV)—26.3%, Cucumber mosaic virus (CMV)—33.8%, Y-Potato virus (Potato Y potyvirus, PVY)—51.3%, Potato X-virus (PVX) (Potato X potyvirus, PVX)—41.3%. The highest antioxidant activity was shown by a suspension of S. carpaticus strain RCAM04697 (88.8%) and its aqueous-alcoholic (20 : 80) extract (76.0%). The strain inhibited growth of the phytopathogenic fungus Fusarium sporotrichioides to varying degrees. The insecticidal activity against Aphis fabae after 6 h of treatment was 100% in the variants with suspension treatment, water-alcohol (80 : 20, 50 : 50), methanol, and hexane extracts. The metabolites of the S. carpaticus RCAM04697 strain included flavonoids, alkaloids, glycosides, organic acids (isocitric, acetic, fumaric, lactic, pyruvic, and malic), alcohols, aldehydes, hydrocarbons, ethers, sulfur-containing compounds, and other groups of low-molecular weight organic compounds.

The composition of phototrophic organisms has been studied in light chestnut soils (Cambisols), alluvial meadow soils (Fluvisols), brown semidesert soils (Calcisols), sandy soils (Arenosols), and solonchaks (Solonchaks) of Astrakhan oblast. Representatives of the Cyanobacteria phylum constitute 71.3% of the total number of studied soil phototrophs. Overall, 64 species of cyanobacteria have been identified; they belong to 3 classes (Chroococceae, Chamaeciphoneae, and Hormogoneae), 4 orders (Chroococcales, Pleurocapsales, Nostocales, and Oscillatoriales), 9 families, and 19 genera. Most common species include Phormidium faveolarum, Phormidium tenue, Phormidium retzii, Phormidium ambigum, Phormidium inundatum, Phormidium bohneri, Oscillatoria woronchnii, Oscillatoria mucicola, Gloeocapsa magma, Gloeocapsa minuta, Anabaena variabilis, and Plectonema nostocorum. The assessment of similarity of the species composition of cyanobacteria and green algae in the studied soil types using the Jaccard and Sorensen similarity coefficients demonstrates that the maximum similarity coefficient reaches 0.37–0.54 for cyanobacteria and 0.67–0.80 for green algae. The high diversity of cyanobacteria and green algae denotes an important role of phototrophs in the processes of soil formation in the studied soils.

В Астраханском регионе в условиях аридного экстремального климата с полупустынным ландшафтом формируются сообщества почвенных актиномицетов со специфическими свойствами и метаболитами. Метаболиты стрептомицетов представляют собой многокомпонентные комплексы различных по химическому строению природных соединений - антибиотиков, литических ферментов, аминокислот, витаминов, гормонов и др. Цель настоящих исследований - изучить компонентный состав суспензии и экстрактов штамма Streptomyces carpaticus RCAM04697 для создания экологически безопасных средств защиты растений. Штамм S. carpaticus RCAM04697 выделен из бурых полупустынных почв Астраханской области с очень сильной степенью засоления. Штамм S. carpaticus RCAM04697 выращивали при температуре +28 оС и рН = 7 ед. в течение 72 ч при непрерывном перемешивании на шейкере (120 об./мин) на картофельной среде. В работе изучен компонентный состав суспензии и экстрактов (водно-спиртового, метанольного и гексанового) штамма S. carpaticus RCAM04697 методом газовой хромато-масс-спектрометрии. Анализ показал наличие в составе вторичных метаболитов - спиртов, альдегидов, углеводородов, эфиров, сульфатов и других групп низкомолекулярных органических соединений (НОС). При всех вариантах экстракции в составе НОС преобладали спирты и эфиры. Выявленные НОС обладают ценными с сельскохозяйственной точки зрения свойствами: противовирусными, противомикробными и противоопухолевыми (этил 5-(пиридин-4-ил)-1Н-пиразол-3-карбоксилат); бактерицидными, фунгицидными и антисептическими свойствами (1,2-гександиол); инсектоакарицидными (изопропилмиристат). 1-додеканол входит в состав феромонов, половых аттрактантов и сурфактантов для контроля численности насекомых-вредителей. Исследуемый штамм может быть использован в качестве основы для создания средств защиты растений, в качестве противовирусных средств, инсектицидов, акарицидов, фунгицидов, бактерицидов и...

The study of exogenous metabolites of algae-bacterial communities in the laboratory accumulative culture obtained from natural river water was conducted using gas chromatography-mass spectrometry. Exometabolites of the algae-bacterial community (including microalgae and cyanobacteria) in the culture medium were represented by saturated, unsaturated, and aromatic hydrocarbons, carboxylic acids, phenolic, and terpene compounds and their derivatives. Possible biological activities of the discovered exometabolites are considered. The study has demonstrated that an increase in the number of main groups of microorganisms, along with changes in the composition of algae and cyanobacteria, are responsible for the increase in the composition and concentration of metabolites in the microecosystem’s culture medium after one month of cultivation. The presence of octacosane in high concentration (0.0603 mg/L; 23.78% of the total content of low molecular weight organic compounds) by the end of exposure accumulative culture is associated with the strong development of the cyanobacterium Gloeocapsa sp. in the presence of diatom algae of the genus Navicula and green algae of the genera Chlorella and Scenedesmus. Due to the need to comprehend the ecological and biochemical mechanisms of the formation and functioning of algae-bacterial communities, as well as to predict potential paths of transformation and evolution of aquatic ecosystems, the specificity of exometabolite complexes of algae and microorganisms, as well as their allelopathic and other biochemical interactions in freshwater ecosystems, requires further serious study.

The composition of metabolites of cyanobacteria cultures of the Astrakhan region has been studied by thin-layer chromatography, high-performance thin layer chromatography, and high-performance liquid...