2025 Issue №2

For the first time, a find of an incomplete tooth (a fragment of the crown) belonging to a Cretaceous shark of the genus Ptychodus has been discovered in the Kaliningrad Region, with­in boulder-pebble material along the seashore near Zelenogradsk. Previously, the geogra­phically closest remains of Ptychodus were known from Upper Cretaceous reworked deposits in Lithuania. The morphological features of the studied tooth suggest that it is a symphyseal tooth and may be classified as Ptychodus cf. latissimus Agassiz, 1835. This new find expands our knowledge of the distribution of Ptychodus during the Cretaceous period and enhances our understanding of the diversity of fossils found within the erratic boulders of the region.

The aim of this study was to investigate the effects of selenium nanoparticles on the key cultivation parameters and phytostimulatory properties of Lactococcus lactis IMB B-7352. Cultivation of L. lactis IMB B-7352 was carried out in MRS medium supplemented with nanoselenium at concentrations of 0.25, 0.5, 0.75, and 1.0 mg/L (based on selenium content). The antagonistic activity of L. lactis IMB B-7352 against cultures of phytopathogenic bacteria was assessed using the agar block method. It was found that nanoselenium at a concentration of 0.75 mg/L exhibited optimal stimulatory activity in terms of biomass accumulation by L. lactis IMB B-7352. Examination of the antagonistic activity of L. lactis IMB B-7352 revealed that the inhibition zones against Xanthomonas campestris B-4102 and Agrobacterium tume­faciens B-8833 measured 55.0 mm and 20.0 mm, respectively. The addition of nanoselenium to the MRS medium did not result in statistically significant differences in the inhibition zones of phytopathogenic bacteria. A stimulatory effect of L. lactis IMB B-7352, cultivated on MRS medium supplemented with nanoselenium, was demonstrated on the growth parameters of wheat and pea plants. It was established that nanoselenium concentrations of 0.25—0.5 mg/L in the MRS medium are optimal for promoting plant growth. For the first time, the effectiveness of nanoselenium supplementation in the cultivation medium for Lactococcus species used for plant growth stimulation has been demonstrated. The experiments conducted are promising for the development of microbial preparations for crop production.