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.

Regardless of their growth locations and species diversity, plants have endophytic bacterial communities. Bilberry (Vaccinium myrtillus L.) is valuable for human health because of its antioxidant properties, and the plant has adapted to stressful growing conditions in forests. Here, we aimed to describe the composition of the community of endophytic microorganisms in bilberry leaves and to determine whether the diversity of endophytic bacteria varies depending on the geographical location of the plants. In this study, we evaluated the significance of endophytes in the host plant and the potential use of such bacteria. Twenty-five culturable bacterial isolates were identified in V. myrtillus leaves based on 16S rRNA gene sequencing and phylogenetic analysis. For the first time, we report upon the diversity of endophytic communities coexisting in bilberry leaves in different geographical locations of the Nordic-Baltic region. Under harsh conditions, the bilberry plants had a greater diversity of bacteria. The bacterial families Bacillaceae, Paenibacillaceae and Micrococcaceae were the most common endophytes in leaves of bilberry. Strains of Staphylococcaceae, Lactobacillaceae, Pseudomonaceae, Corynebacteriaceae and Planococcaceae were identified in samples from Finland and Norway. Plant growth-promoting genes (acdS and AcPho) and/or enzymatic activity were identified in many isolates.

Our previous research has indicated that bioactive protein hydrolysates derived from porcine by-products possess the potential to be utilized in the production of functional additives and food supplements. The objective of this investigation was to assess the antioxidant and antimicrobial characteristics and amino acid changes in hydrolysates of lyophilized meat of bovine livers and hearts. The relevant enzymes, papain and pepsin, were used to hydrolyze the meat by-products over periods of 3, 6, and 24 h. The antimicrobial properties of all enzymatically digested samples were assessed against Listeria monocytogenes, Bacillus cereus, Salmonella enterica subsp. enterica Serovar Typhimurium. Bacillus cereus, and Escherichia coli, S. aureus subsp. aureus. The assessment of antiradical activity involved the quantification of DPPH• and ABTS•+ absorbance in bovine by-product hydrolysates. The hydrolysates were subjected to amino acid analysis using AccQ Tag technology, which was performed by Waters Corporation in Milford, MA, USA. The bacteria L. monocytogenes had the highest antibacterial activity (inhibition zone) (20.00 ± 0.20 mm) and less against E. coli (10.00 ± 0.10 mm) of bovine heart hydrolysates and were prepared for 24 h with papain. The highest values of ABTS•+ (98.1 ± 0.30%) and of DPPH• scavenging activity (92.56 ± 0.56%) of cationic radicals were evaluated in the bovine liver hydrolysates after the effect of papain for 24 h. Longer hydrolysis time influenced the decrease in free hydrophobic amino acids (Ala, Val, Ile, Leu, Tyr, Phe, Pro, Met). The results confirmed the potential use of bovine liver and heart hydrolysates as functional or biologically active materials.

Plant microbiota contributes to nutrient absorption, and the production of hormones and vitamins, and plays a crucial role in responding to environmental stress. We hypothesized that Vaccinium spp. harbour a unique microbiota that enables them to coexist in extreme environments such as saline, nutrient-poor, and waterlogged conditions. Upon examining Bacillus spp. endophytes isolated from blueberries, cranberries and lingonberries in vitro, we identified B. halotolerans (Bil-LT1_1, Bil-LT1_2) and B. velezensis (Cran-LT1_8, Ling-NOR4_15) strains that inhibit the growth of five pathogenic fungi and five foodborne bacteria. Whole-genome sequencing provided insights into genome organization and plasticity, helping identify mobile elements and genes potentially acquired through horizontal gene transfer. Functional annotation identified genes associated with plant colonization, stress tolerance, biocontrol activity, and plant growth promotion. Comparative genomic analyses revealed key biosynthetic gene clusters (BGCs) responsible for producing antifungal metabolites, including lipopeptides and polyketides. Genes supporting plant nutrition, growth, and environmental adaptation were present also in these strains. Notably, isolated endophytes exhibited particularly high levels of genomic plasticity, likely due to horizontal gene transfer involving gene ontology (GO) pathways related to survival in polymicrobial and foreign environments.