## 1 Introduction  
The design of stable winter wheat yields is determined by the use of proven cultivation methods and technologies under specific soil and climate conditions [1, 2, 3]. Intensive farming systems contribute to a reduction in soil fertility, which can result in environmental degradation as well as a drop in the quantity and quality of crop yields [4, 5, 6]. An alternative to conventional production resources used to support crop production may be biological preparations serving as biofertilisers and biopesticides. These are intended to protect plants against pathogens, influence soil fertility and shape the growth and development of plants [7, 8, 9, 10, 11]. An important group of biological preparations are those containing plant-growth-promoting rhizobacteria (PGPR), which comprise bacterial strains of _Azoarcus_, _Azospirillum_, _Azotobacter_, _Artlrobacter_, _Bacillus_, _Clostridium_, _Enterobacter_, _Gluconacetobacter_, _Pseudomonas_ and _Serratia_[12]. The rhizosphere bacteria are supportive of the recovery of nutrients from the soil and are important for soil fertility [9, 13, 14, 15, 16]. Bacteria of the genus _Bacillus_ are widely distributed in nature. Most of them are species that are safe for humans, animals and plants. Due to the above-mentioned characteristics of the bacteria _Bacillus_ sp., they are used for the production of commercial preparations in the form of insecticides or biostimulants and are involved in supporting plant production [17; 18; 19; 20]. _Bacillus_ sp. _bacteria_ (_B. subtilis_, _B. cereus_, _B. thuringiensis_, _B. pumilus_, _B. megaterium_, etc.) have evolved mechanisms to stimulate plant growth by increasing the availability of the nutrients: N, P, potassium (K) and iron (Fe). Moreover, _Bacillus_ strains are capable of fixing molecular nitrogen [19; 21; 22; 23]. _Bacillus subtilis_ is a saprophyte which decomposes organic compounds of plant origin. This bacterium produces peptide antibiotics, e.g., polymycin B and subtilis, amino acids, polysaccharide inulin and enzymes, e.g., amylase and protease [24; 25; 26; 27; 28]. It also forms siderophores (bacillobactin) which are capable of binding iron ions by binding all available forms of iron into chelates and sharing them with plants. The protein of these bacteria also contains hydrophobin BsIA, which reduces surface tension, thus increasing the wetting of the surface on which the bacteria are located, leading to an improvement in moisture within the root system and covering it with an additional protective film (which is particularly important during dry periods) [29; 30; 31]. It also stabilises soil colloids [32]. The bacterium _Bacillus subtilis_ reduces the number of pathogenic fungi and bacteria in the soil, thus contributing to improved phytosanitary status in crops. [33; 34]. _Bacillus subtilis_ can also solubilise P in the soil, contribute to nitrogen fixation and produce siderophores which inhibit the growth of pathogens. _Bacillus subtilis_ increases stress tolerance in its plant hosts by inducing the expression of stress response genes, phytohormones and stress-related metabolites [20; 35]. _Bacillus megaterium_ bacteria are described as soil microorganisms with a natural ability to produce acids or enzymes as metabolites, making them capable of dissolving phosphorus [36; 37]. _Paneibacillus azotofkanus_ was initially classified as _Bacillus azotofkanus_ and then reclassified as belonging to the genus _Paneibacillus_[38]. _Paneibacillus_ presents the nifH gene encoding the Fe nitrogenase protein, an enzyme responsible for nitrogen fixation [39]; it has been suggested as a potential biofertifier for certain crops, e.g., maize or wheat [40; 41; 42; 43]. What is more, _Paneibacillus_ are well known as effective plant growth promoters in many crops, e.g., maize, wheat, or sorghum [39; 44]. _Paneibacillus azotofixanus_ is a nitrogen-fixing bacterium often found in the soil and rhizospheres of various plants [45; 46; 47; 48; 49].