Probiotic starters are a biological product based on lactic acid bacteria. Their metabolic characteristics determine the properties of the final products. This study evaluated the bacterial composition of a starter culture at various time intervals during the fermentation of a probiotic dairy product. The starter consisted of Streptococcus salivarius ssp. thermophiles, Lactobacillus delbrueckii ssp. bulgaricus, Bifidobacterium bifidum, Bifidobactreium animalis ssp. lactis, Bifidobacterium longum, Lactobacillus acidophilus, and Lacticaseibacillus casei. Pasteurized milk served as the object of fermentation. The starter culture was activated in sterilized skimmed milk. Sampling occurred throughout the entire fermentation process (0, 3, 6, 9, 12, 15, and 18 h). To determine the microbiome of the substrates, the authors used the next-generation high-throughput sequencing that targeted V3 of 16S rRNA gene. The fermentation resulted in a decrease in Bifidobacterium and an increase in Lactobacillus, which peaked (97.5%) after 15 h of fermentation. Each sampling showed that the count of Streptococcus went down. Eventually, Lactobacillus replaced all other genera, including Bifidobacterium, probably, as a result of pH going down during fermentation. The optimal values for the proliferation of Lactobacillus (pH = 4.2–4.4), which were registered after 18 h, turned out to be too low for the productive growth of Bifidobacterium. The research demonstrated the changes in the bacterial composition of the dairy base during fermentation. The high-throughput sequencing proved to be an efficient tool in controlling probiotic fermentation processes.

The study is devoted to the analysis of the prevalence of antibiotic resistance genes in cultures of E. coli isolated from the gut of the piglets with diarrhea. With the use of high-throughput sequencing, it was possible to identify 26 antibiotic resistance genes. They belonged to 7 groups of antibiotics: aminoglycosides, beta-lactam antibiotics, quinolones, sulfonamides, tetracyclines, diaminopyrimidine, phenicols. The relative abundance of the QnrD gene was maximal in the studied sample of E. coli isolates (50%). For other sequences of antibiotic resistance genes, the percentage ratio of each separate group of genes did not exceed 10%. The largest number of gene variants was characteristic of the class of genes resistant to beta-lactam antibiotics (AmpC1_Ecoli, OXA-10, OXA-14, OXA-16, Penicillin_Binding_Protein_Ecoli, TEM-143, TEM-166, TEM-215 and TEM-76, TEM- 95).

The aim of the study was to analyze the gut microbiome of swine during the fattening period, aimed at identify-ing antibiotic resistance genes. High-throughput sequencing allowed a total of 119 636 readings, bioinformatic re-search of which revealed 17 antibiotic resistance genes belonging to 4 classes of antibiotics: tetracyclines (81%), beta-lactam antibiotics (11%), erythromycins (7%) and aminoglycosides (1%). Among the 5 detected tetracycline resistance genes, the gene Tet(W) dominated, the percentage of which was 73% of the number of all tetracycline antibiotic resistance genes. Erythromycin resistance genes included ermB, ErmG and ErmF with the overwhelming majority of the latter (88%). Among the beta-lactam antibiotic resistance genes, cfxA4 (18%), cfxA5 (10%), cfxA6 (42%) and ACI1 (30%) were identified. The presence of resistance genes to aminoglycosides (Aph3-III, Ant6-Ia, Ant6-Ib, Sat4A and aadA1-pm) was found. The most common genes were Aph3-III (58%), and the least – aadA1-pm (3%). The results of the study indicate the wide presence of antibiotic resistance genes in the gut microbiome of swine. The spread of these genes may pose a threat in the future not only for agriculture, but also for the public healthcare.

The article presents the assessment of the presence and relative amount of antibiotic resistance genes of bacteria in the gut microbiome of piglets in the early neonatal period. The genes for beta-lactam antibiotics (penicillins, cephalosporins, carbapenems, monobactams) have become the dominant majority of the antibiotic resistance genes present in both healthy and sick piglets. Tetracycline resistance genes were also found in the samples of healthy and sick animals. Healthy animals had the aminoglycoside resistance gene Aph3-III (relative content - 81.15%). The quinolone antibiotic resistance genes QnrB5 and QnrB19 were present in both healthy and sick animals, and the gene QnrD was identified only in the piglets with diarrhea (relative content - 10.27%). The same relative abundance of the sulfonamide resistance gene SulII (relative content - 82%) was demonstrated in both healthy and sick piglets, while the gene SulIII was found only in the animals with diarrhea (relative content - 13.44%). The results show a wide spread of antibiotic resistance genes in the population of healthy piglets and piglets with diarrhea, and this requires special attention from pig breeding farms in order to minimize further migration of antibiotic resistance genes.

The most stable reference gene in Lactobacillus plantarum was identified. It was found that the expression of the rpoD gene was most stable with the addition of fucoidan and inulin. The level of expression of the usp gene in L. plantarum bacteria increased by 4 times when fucoidan was added compared to the control sample, but when inulin was added to the culture medium, the expression of this gene decreased by 12 times compared to the control sample. The expression of the opuA gene with the addition of fucoidan increased by 6 times compared to the control sample, and with the addition of inulin decreased by 3 times compared to the control sample. The level of expression of the ATP gene in L. plantarum bacteria with the addition of fucoidan increased by 9 times in comparison with control sample. The expression of the lactate dehydrogenase (ldh) gene with the addition of fucoidan increased by 2 times compared with the control sample, whereas with the addition of inulin it decreased by 18 times compared to control sample. The expression level of the gacT gene with the addition of fucoidan decreased by more than 50 times compared to the control sample, and with the addition of inulin decreased by 12 times compared to the control sample. There were no significant changes in the expression of the GroEL and hsp1 genes. Thus, based on gene expression data, it can be assumed that when fucoidan is added to the culture medium, catabolic processes in L. plantarum bacteria are activated. It was found that the addition of inulin to the culture medium does not lead to an increase in the expression of catabolism genes in L. plantarum.