The aim of this work was to investigate the most promising natural antimicrobials effective for the growth suppression of Xanthomonas spp. bacteria. The research objects were Xanthomonas spp. strains isolated from tubers and stem of plants growing in Lithuania: Xanthomonas translucens NRCIB X6, X. arboricola NRCIB X7, NRCIB X8, NRCIB X9, and NRCIB X10; the supernatants of lactic acid bacteria Lactococcus lactis strains 140/2, 57, and 768/5, Lactobacillus helveticus strains 14, 148/3, R, and 3, Lb. reuteri 3 and 7, Streptococcus thermophilus 43, Enterococcus faecium 59-30 and 41-2; endophytic bacterial strains Bacillus, Pseudomonas, and Paenibacillus spp.; and essential oils of lavender (Lavandula angustifolia), grapefruit (Citrus paradisi), pine (Pinus sylvestris), thyme (Thymus vulgaris), rosemary (Rosmarinus officinalis), peppermint (Mentha piperita), lemon (Citrus limetta), aqueous extracts of blueberries (Vaccinium myrtillus), and cranberries (Vaccinium vitis-idaea). The antimicrobial activity of tested substances was determined by agar diffusion method. Supernatants of Lb. reuteri strain 7 and Lb. helveticus strains 14, R, 3, and 148/3 were found to have a high antimicrobial activity against Xanthomonas spp. bacteria strains when compared to the positive control—1.0% copper sulfate (diameter of inhibition zones was 28.8 ± 0.7 mm). The diameter of inhibition zones of supernatants ranged from 23.3 ± 0.6 mm to 32.0 ± 0.1 mm. Thyme (2.0%) and lavender (2.0%) essential oils inhibited the growth of Xanthomonas spp. strains. The diameter of the inhibition zones was from 14.7 ± 0.8 mm to 22.8 ± 0.9 mm. The aqueous extracts of blueberries had a weak antimicrobial activity. The diameter of inhibition zones ranged from 11.0 ± 0.2 mm to 13.0 ± 0.2 mm.

Iron compounds can be used in antimicrobial applications by exploiting the toxicity of divalent iron to living organisms due to the Fenton reaction. In this study, the growth inhibitory effects of ferrous sulfate FeSO₄·7H₂O and ferric chloride FeCl₃·6H₂O were observed on Metschnikowia clade and Saccharomyces cerevisiae yeast cells. The relatively high amount of reduced Fe³⁺ to Fe²⁺ in the growth medium determined by Mössbauer spectroscopy may contribute to the antimicrobial activity of ferric chloride. In order to test the reducing ability of sugars in the growth media of yeasts, the reaction of ferric chloride FeCl₃·6H₂O with sugars was investigated. In mixtures of FeCl₃·6H₂O and fructose, approximately two thirds of Fe³⁺ can be reduced to Fe²⁺. When the mixture of FeCl₃·6H₂O and fructose is placed on the surface of aluminum foil, an iron film is formed on the surface of the aluminum due to the reduction by both fructose and aluminum. The relative amount of Fe³⁺ which was reduced to Fe⁰ reached 68%.

Climate-driven warming may enhance the spread of warm-adapted alien cyanobacteria in freshwater ecosystems. This study assessed four nostocalean cyanobacteria from European lakes—native Aphanizomenon gracile and alien Chrysosporum bergii, Raphidiopsis raciborskii, and Sphaerospermopsis aphanizomenoides—to evaluate species identity, toxin production potential, and thermal responses. A polyphasic approach combining phylogenetic analysis, morphology, and toxin screening confirmed the identifications and revealed a saxitoxin-producing A. gracile strain. No toxin genes were detected in the alien taxa. Experimental testing across 15–35 °C demonstrated broader thermal tolerance in the alien species, which maintained positive growth across 20–35 °C but showed limited performance at 15 °C. In contrast, the native Aphanizomenon gracile maintained positive growth at 15 °C, indicating greater adaptation to cooler conditions. Isolate-specific variation at thermal extremes highlighted the importance of ecotype-level traits. Our findings suggest that rising temperatures, combined with strain-level physiological diversity, may increase the risk of alien cyanobacteria establishing and forming blooms in temperate lakes. This study supports the need for monitoring strategies that integrate taxonomy, ecophysiology, and local adaptation to better assess invasion potential under changing environmental conditions.

Application of insecticides for pest control must be minimized due to well-known risks to human health. Application of environmentally friendly means is the best option. For stored product pests’ control, new means are needed alongside a deep understanding of the ecology and behavior of the pests. The present study investigated whether the odor released from wheat grain infected by mold fungus Aspergillus flavus (Eurotiales: Aspergillaceae) influences the behavior of the yellow mealworm (Tenebrio molitor L. (Coleoptera: Tenebrionidae)), a stored product pest of economic importance with worldwide distribution. Analysis of video-recorded behavior and computer data analysis revealed a significant difference in reactions depending on the beetle’s sex. Females were more sensitive to fungus contamination as they discriminated between A. flavus-infected and uninfected wheat grains from the onset of infection, while males discriminated only after a 5-day period. Analysis of single volatile organic compounds (VOCs) revealed the presence of both repellents and attractants. Among those, hexanal was repellent for both males and females, 1-octen-3-ol was repellent for males and indifferent to females, 1-hexanol was attractive to females and repellent (at high concentrations only) to males, and 3-methylbutan-1-ol was attractive to females (at high concentrations only) and indifferent to males. Hexanal, as a potential repellent, was suggested for further testing under grain storage conditions.