Vertillo Aluisio Gaia, Spitale Ambra, Bonifacio Luca, Privitera Grete Francesca, Stivala Aldo, Stefani Stefania, Santagati Maria
Medical Molecular Microbiology and Antibiotic Resistance Laboratory (MMARLab), Department of Biomedical and Biotechnological Sciences (BIOMETEC), University of Catania, 95123 Catania, Italy.
Microorganisms. 2022 Oct 16;10(10):2042. doi: 10.3390/microorganisms10102042.
24SMBc is an oral probiotic with antimicrobial activity against the otopathogens and . Clinical studies have reinforced its role in reducing the recurrence of upper respiratory tract infections (URTIs) and rebalancing the nasal microbiota. In this study, for the first time, we characterized 24SMBc by whole genome sequencing and annotation; likewise, its antagonistic activity vs. and was evaluated by in vitro co-aggregation and competitive adherence tests. The genome of 24SMBc comprises 2,131,204 bps with 1933 coding sequences (CDS), 44 tRNA, and six rRNA genes and it is categorized in 319 metabolic subsystems. Genome mining by BAGEL and antiSMASH tools predicted three novel biosynthetic gene clusters (BGCs): (i) a Blp class-IIc bacteriocin biosynthetic cluster, identifying two bacteriocins and ; (ii) an ABC-type bacteriocin transporter; and (iii) a Type 3PKS (Polyketide synthase) involved in the mevalonate pathway for the isoprenoid biosynthetic process. Further analyses detected two additional genes for class-IIb bacteriocins and 24 putative adhesins and aggregation factors. Finally, in vitro assays of 24SMBc showed significant anti-adhesion and co-aggregation effects against strains, whereas it did not act as strongly against . In conclusion, we identified a novel - bacteriocin-encoding BGC and two class-IIb bacteriocins involved in the activity against and ; likewise the type 3PKS pathway could have beneficial effects for the host including antimicrobial activity. Furthermore, the presence of adhesins and aggregation factors might be involved in the marked in vitro activity of co-aggregation with pathogens and competitive adherence, showing an additional antibacterial activity not solely related to metabolite production. These findings corroborate the antimicrobial activity of 24SMBc, especially against belonging to different serotypes, and further consolidate the use of this strain in URTIs in clinical settings.
24SMBc是一种对耳病原体具有抗菌活性的口服益生菌。临床研究强化了其在减少上呼吸道感染（URTI）复发和重新平衡鼻腔微生物群方面的作用。在本研究中，我们首次通过全基因组测序和注释对24SMBc进行了表征；同样，通过体外共聚集和竞争黏附试验评估了其对[具体病原体1]和[具体病原体2]的拮抗活性。24SMBc的基因组由2,131,204个碱基对组成，有1933个编码序列（CDS）、44个tRNA和6个rRNA基因，并且被归类到319个代谢子系统中。使用BAGEL和antiSMASH工具进行基因组挖掘预测出三个新的生物合成基因簇（BGC）：（i）一个Blp IIc类细菌素生物合成簇，鉴定出两种细菌素[细菌素1]和[细菌素2]；（ii）一个ABC型细菌素转运体；以及（iii）一个参与类异戊二烯生物合成过程中甲羟戊酸途径的3型聚酮合酶（PKS）。进一步分析检测到另外两个IIb类细菌素基因以及24个假定的黏附素和聚集因子。最后，24SMBc的体外试验显示对[具体病原体1]菌株具有显著的抗黏附和共聚集作用，而对[具体病原体2]的作用则没有那么强。总之，我们鉴定出一个新的编码[具体细菌素名称]的BGC和两个参与对[具体病原体1]和[具体病原体2]活性的IIb类细菌素；同样，3型PKS途径可能对宿主有有益作用，包括抗菌活性。此外，黏附素和聚集因子的存在可能参与了与病原体共聚集和竞争黏附的显著体外活性，显示出一种不仅仅与代谢产物产生相关的额外抗菌活性。这些发现证实了24SMBc的抗菌活性，尤其是对属于不同血清型的[具体病原体1]，并进一步巩固了该菌株在临床环境中用于URTI的应用。
