**2. Materials and Methods**

Biomimetic syntheses in the presence of bacteria were carried out by precipitation at 37 ◦C from solutions that simulated the composition of human urine and its inorganic components, where the content corresponded to their minimum or maximum values (Table 1). The volume of the solution after mixing of initial components in accordance with Figure 2 was 500 mL. The content of calcium cations in solutions ranged from 5 to 7.7 mmol/L, which is due to the fact that in small volumes of solution (0.2 L) and with a limited time to carry out the synthesis (1–2 days) the formation of a crystalline precipitate at lower calcium concentrations does not occur. To accelerate the crystallization of calcium and magnesium phosphates, oxalate ions (in the form of ammonium oxalate) were also added to the initial solution in a low concentration (0.1 mmol/L). Also, experiments in the so-called "oxalate system" containing only calcium ions and oxalate ions were conducted (calcium oxalate supersaturation is equal to 7, which corresponds to the physiological values of urine), since calcium oxalate does not crystallize in the system simulating the composition of urine. Ovalbumin was added to the experiments at a concentration of 10 mmol/L [22]. Syntheses were carried out by precipitation in an aqueous solution or in solutions of protein-containing nutrient media, the Müller Hinton Broth (MHB) nutrient medium or the Meat-Peptone Broth (MPB), which were prepared according to standard techniques [23,24]. In addition, bacteria associated with inflammatory processes and present in significant quantities both in the environment and in the human body were added to each of the protein media and to the model media in an amount of 106 particles per liter: *Escherichia coli* («e»), *Klebsiella pneumoniae* («kl»), *Pseudomonas aeruginosa* («ps»), and *Staphylococcus aureus* («s»). The following bacterial American Type Culture Collection (ATCC) strains were used in the experiments: 25922 («e»), 70060325922 («kl»), 27853 («ps»), and 29213 («s»). The pH of the solutions varied between 5.77–7.26 (minimum concentrations of inorganic components) and 6.10–8.07 (maximum concentrations of inorganic components). The acidity of the initial solutions was adjusted using aqueous solutions of HCl and NaOH. The crystallization start time (clouding of the solution) and phase composition of the obtained precipitates were recorded during experiments. Clouding of the solution was recorded visually. The precipitate obtained a day later was filtered, washed with distilled water, and dried at room temperature; at least three iterations were performed for each experiment.


**Table 1.** Elemental composition (mmol/L) of model solutions and urine.

**Figure 2.** The scheme of the synthesis experiment in system which simulated the composition of urine by inorganic components.

The phase composition of precipitate products was determined by means of powder X-ray diffraction method (PXRD). The measurements were performed using a Rigaku «MiniFlex II» powder diffractometer (CuKα radiation, λ = 1.54178 Å; 30 kV/15 mA; Bragg–Brentano geometry; PSD D-Tex Ultra detector). X-ray diffraction patterns were collected at room temperature in the range of 3–60 ◦2θ with a step of 0.02 ◦2θ. Phase identification was carried out using the ICDD PDF-2 Database (release 2016). The unit cell parameters were refined by the Pawley method using TOPAS 4.2 software [26]. The background was modeled using a Chebychev polynomial of 12th order. The peak profile was described using the fundamental parameters approach.
