Control of fungal phytopathogens is a significant challenge in modern agriculture. The widespread use of chemical fungicides to control these pathogens often leads to environmental and food contamination. An eco-friendly alternative that can help reduce reliance on these chemicals is plant growth–promoting bacteria (PGPB), particularly those of the genus Paenibacillus, which appear to be highly effective. The review aims to summarize the existing knowledge on the potential of Paenibacillus spp. as fungal biocontrol agents, identify knowledge gaps, and answer whether other species of the genus Paenibacillus, in addition to Paenibacillus polymyxa, can also be effective biocontrol agents. Paenibacillus spp. can combat plant phytopathogens through various mechanisms, including the production of lipopeptides (such as fusaricidin, paenimyxin, and pelgipeptin), the induction of systemic resistance (ISR), hydrolytic enzymes (chitinase, cellulase, and glucanase), and volatile organic compounds. These properties enable Paenibacillus strains to suppress the growth of fungi such as Fusarium oxysporum, F. solani, Rhizoctonia solani, Botrytis cinerea, or Colletotrichum gloeosporioides. Notably, several strains of Paenibacillus, including P. polymyxa, P. illinoisensis KJA-424, P. lentimorbus B-30488, and P. elgii JCK1400, have demonstrated efficacy in controlling fungal diseases in plants. Importantly, many formulations with Paenibacillus strains have already been patented, and some are commercially available, but most of them contain only P. polymyxa. Nevertheless, considering the data presented in this review, we believe that other strains from the Paenibacillus genus (besides P. polymyxa) will also be commercialized and used in plant protection in the future. Importantly, there is still limited information regarding their impact on the native microbiota, particularly from the metataxonomic and metagenomic perspectives. Expanding knowledge in this area could enhance the effectiveness of biocontrol agents containing Paenibacillus spp., ensuring safe and sustainable use of biological fungicides.

Heavy metals are among the key environmental contaminants which pose a threat to all the living organisms. Bacteria can help detoxify these elements by a range of mechanisms associated to bacterial metabolic processes. One of them is biotransformation, which consists in change in the oxidative state of an element, often followed by its absorption or precipitation. Pseudomonadota—a vast and diverse bacterial phylum—belong to the best studied microorganisms involved in the process. Our review shows their contribution to the redox-based detoxification of four trace elements: chromium, manganese, mercury, and arsenic. Based on a comprehensive literature survey, we try to assess the importance of individual orders and selected genera in redox transformations; we also identify potential risks associated with the use of Pseudomonadota in bioremediation and suggest the most promising directions for future studies and applications. The review leads to a conclusion that the potential of non-pathogenic rhizobia Hyphomicrobiales is particularly worth further exploration.

Members of the phylum Verrucomicrobiota are abundant yet relatively understudied soil bacteria that play key roles in biogeochemical cycling and plant–microbe interactions. They participate in the carbon (C) and nitrogen (N) cycles through the degradation of complex organic polymers such as cellulose, pectin, and starch – via the production of hydrolytic enzymes (e.g., cellulases, xylanases, chitinases), and through nitrogen transformations including denitrification, ammonification, and nitrogen fixation. Methanotrophic representatives ( Methylacidiphilum , Methylacidimicrobium ) oxidise methane under acidic or thermophilic conditions, thereby contributing to greenhouse gas mitigation. The ecological distribution and activity of Verrucomicrobiota are strongly influenced by nutrient availability, particularly of C, N, phosphorus (P), and potassium (K). Their variable responses to these elements reflect diverse life-history strategies, encompassing both copiotrophic (r-strategist) and oligotrophic (K-strategist) taxa. While Spartobacteria (e.g., Ca. Udaeobacter) are typically oligotrophic, classes such as Opitutia and Verrucomicrobiae exhibit mixed strategies. Beyond nutrient cycling, several members of the phylum function as plant growth-promoting and stress mitigating bacteria. They produce phytohormones (e.g., indole-3-acetic acid) and siderophores, increase the availability of nitrogen and solubilise phosphate. Some taxa exhibit antioxidant activity and can suppress phytopathogens such as Fusarium oxysporum through secondary metabolite production. These traits suggest a significant potential in soil health improvement. Overall, Verrucomicrobiota represent a functionally diverse and ecologically significant bacterial phylum whose metabolic versatility, adaptive life strategies, and plant-associated traits underscore their central role in sustainable agricultural ecosystems.

The order of Cyanidiales comprises seven acido-thermophilic red microalgal species thriving in hot springs of volcanic origin characterized by extremely low pH, moderately high temperatures and the presence of high concentrations of sulphites and heavy metals that are prohibitive for most other organisms. Little is known about the physiological processes underlying the long-term adaptation of these extremophiles to such hostile environments. Here, we investigated the long-term adaptive responses of a red microalga Cyanidioschyzon merolae, a representative of Cyanidiales, to extremely high nickel concentrations. By the comprehensive physiological, microscopic and elemental analyses we dissected the key physiological processes underlying the long-term adaptation of this model extremophile to high Ni exposure. These include: (i) prevention of significant Ni accumulation inside the cells; (ii) activation of the photoprotective response of non-photochemical quenching; (iii) significant changes of the chloroplast ultrastructure associated with the formation of prolamellar bodies and plastoglobuli together with loosening of the thylakoid membranes; (iv) activation of ROS amelioration machinery; and (v) maintaining the efficient respiratory chain functionality. The dynamically regulated processes identified in this study are discussed in the context of the mechanisms driving the remarkable adaptability of C. merolae to extremely high Ni levels exceeding by several orders of magnitude those found in the natural environment of the microalga. The processes identified in this study provide a solid basis for the future investigation of the specific molecular components and pathways involved in the adaptation of Cyanidiales to the extremely high Ni concentrations.

Oilseed rape is one of the most important oilseed crops, requiring high levels of nitrogen fertilization. Excessive nitrogen use, however, leads to numerous negative environmental impacts, spurring the search for sustainable, environmentally friendly alternatives to reduce reliance on mineral nitrogen fertilizers. One promising approach involves plant-growth-promoting bacteria (PGPB), which can support oilseed rape growth and lessen the need for traditional nitrogen fertilizers. This study evaluates a selected microbial consortium comprising bacterial isolates obtained from soil: Pseudomonas sp. G31 and Azotobacter sp. PBC2 (P1A). The applied PGPB significantly increased seed yield (a 27.12% increase) and, in the initial phase of the study, reduced the ammonium nitrogen content in the soil (a 20.18% decrease). Metataxonomic analyses were performed using Next-Generation Sequencing (NGS) technology by Illumina. Although P1A did not significantly affect alpha diversity, it altered the relative abundance of some dominant soil microorganisms. In the BBCH 75 phase, the P1A consortium increased the abundance of bacteria of Firmicutes phylum, including the genera Bacillus and Paenibacillus, which was considered a beneficial change. In summary, the Pseudomonas sp. G31 and Azotobacter sp. PBC2 consortium increased seed yield and was found to be part of the native rhizosphere community of oilseed rape, making it a promising candidate for commercialization.

Lead is a highly toxic metal. It impairs the metabolism of living organisms. Plants show different sensitivity to the action of this element. One of the plants with relatively high lead tolerance is Zea mays, where even in detached leaves treated with Pb²⁺ ions, the photosynthesis rate remains very high compared to other plant species. This study set out to determine the mechanism responsible for the high resistance of maize photosynthetic tissue to the toxic effect of this metal. For this purpose, the cut leaves of Z. mays were incubated in Pb(NO₃)₂ solutions at different concentrations. Regions of lead accumulation in tissues and cells were located using histochemical methods and transmission electron microscopy. The experiments showed a diverse distribution of lead ions in the leaf blade of Z. mays. Most of the accumulated Pb²⁺ ions were observed in the vascular bundle and the bundle sheath, while minimal traces of metal were transferred to the mesophyll. In Pisum sativum leaves, although Pb(NO₃)₂ concentration in the solution was two-fold lower, lead accumulated in all the leaf tissues - mainly in the vascular bundle, epidermis, sclerenchyma, and mesophyll. Thus, bundle sheath cells in maize leaves were able to inhibit the flow of Pb²⁺ ions to the ground tissue. Therefore, the influence of the toxic metal on photosynthesis in mesophyll cells remained minimal. These experiments show that the structure of Z. mays leaf, with a layer of bundle sheath cells (characteristic of C₄ plants), contributes to the protecting photosynthetic tissue against the toxic effect of lead.