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The human milk (HM) microbiome is variable and depends on maternal, perinatal, and cultural–environmental factors. The diversity of the HM microbiome is crucial in the development of the child. The aim of the study was to assess the prevalence of bacteria (using culture-based methods) of Polish women with normal BMI, giving birth on time through vaginal delivery. Methods: The research material consisted of human milk and swabs from the areola and nipple, before and after breastfeeding, derived from Polish women (n = 86). Classic culture methods were used to obtain multiple bacteria. Species identification of the grown colonies was performed using MALDI TOF MS (Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry). Results: 120 species of bacteria were isolated, mainly from the genus Streptococcus and Staphylococcus. Species specific only to human milk were identified (belonging to the following genera: Microbacterium, Shewanella, Psychrobacter, Aeromonas, Serratia, Buttiauxella, Lactobacillus, Bifidobacterium) as well as species specific only to areola and nipple swabs after breastfeeding (Acinetobacter lactucae, Moraxella catarrhalis, Corynebacterium pseudodiphtheriticum, Corynebacterium propinquim). It was confirmed that most species were present in all tested materials collected from one patient. Conclusions: The analysis carried out showed the presence of bacteria in the human milk of Polish women, including strains of lactic acid bacteria. The human milk microbiota may significantly influence the formation of the infant’s intestinal microbiota, including some key genera, i.e., Lactobacillus, Bifidobacterium, and Limosilactobacillus, which were also isolated from the tested samples. The data presented here provide new data on culturable bacterial species isolated from breast milk from Polish women giving birth via vaginal delivery and potential routes of transmission from the neonate’s oral cavity. Full article

The diffusible signal factor (DSF) is a fatty acid signal molecule and is widely conserved in various Gram-negative bacteria. DSF is involved in the regulation of pathogenic virulence in many bacterial pathogens, including Xanthomonas campestris pv. campestris (Xcc). Quorum quenching (QQ) is a potential approach for preventing and controlling DSF-mediated bacterial infections by the degradation of the DSF signal. Acinetobacter lactucae strain QL-1 possesses a superb DSF degradation ability and effectively attenuates Xcc virulence through QQ. However, the QQ mechanisms in strain QL-1 are still unknown. In the present study, whole-genome sequencing and comparative genomics analysis were conducted to identify the molecular mechanisms of QQ in strain QL-1. We found that the fadY gene of QL-1 is an ortholog of XccrpfB, a known DSF degradation gene, suggesting that strain QL-1 is capable of inactivating DSF by QQ enzymes. The results of site-directed mutagenesis indicated that fadY is required for strain QL-1 to degrade DSF. The determination of FadY activity in vitro revealed that the fatty acyl-CoA synthetase FadY had remarkable catalytic activity. Furthermore, the expression of fadY in transformed Xcc strain XC1 was investigated and shown to significantly attenuate bacterial pathogenicity on host plants, such as Chinese cabbage and radish. This is the first report demonstrating a DSF degradation enzyme from A. lactucae. Taken together, these findings shed light on the QQ mechanisms of A. lactucae strain QL-1, and provide useful enzymes and related genes for the biocontrol of infectious diseases caused by DSF-dependent bacterial pathogens. Full article

The bacterial strain KU011TH was isolated from the skin mucus of healthy bighead catfish. The strain is a Gram-negative coccobacillus that is nonmotile, aerobic, catalase positive, oxidase negative, and nonhemolytic. Sequence analyses of the housekeeping genes 16S rRNA, gyrB and rpoB indicate that this strain is a new member of the Acb complex of the genus Acinetobacter and is closely related to Acinetobacter pittii and Acinetobacter lactucae. In addition, the genome relatedness-associated ANIb (<95–96%) and in silico DDH (<70%) values clearly supported the new member of the genus Acinetobacter and the Acb complex. The genome of the strain KU011TH was approximately 3.79 Mbp in size, comprising 3619 predicted genes, and the DNA G+C content was 38.56 mol%. The major cellular fatty acids were C18:1ω9c, C16:0, C16:1, C20:2, C18:2ω6c and C18:1ω9t. The whole-genome sequences and phenotypic, phylogenetic, and chemotaxonomic data clearly support the classification of the strain KU011TH as a new member in the genus Acinetobacter which is closest to A. pittii. Additionally, the new bacterial strain exhibited strong activity against a broad range of freshwater fish pathogens in vitro. Full article