Date Published: August 4, 2016
Publisher: Public Library of Science
Author(s): Daniela Janek, Alexander Zipperer, Andreas Kulik, Bernhard Krismer, Andreas Peschel, Gongyi Zhang.
The human nasal microbiota is highly variable and dynamic often enclosing major pathogens such as Staphylococcus aureus. The potential roles of bacteriocins or other mechanisms allowing certain bacterial clones to prevail in this nutrient-poor habitat have hardly been studied. Of 89 nasal Staphylococcus isolates, unexpectedly, the vast majority (84%) was found to produce antimicrobial substances in particular under habitat-specific stress conditions, such as iron limitation or exposure to hydrogen peroxide. Activity spectra were generally narrow but highly variable with activities against certain nasal members of the Actinobacteria, Proteobacteria, Firmicutes, or several groups of bacteria. Staphylococcus species and many other Firmicutes were insusceptible to most of the compounds. A representative bacteriocin was identified as a nukacin-related peptide whose inactivation reduced the capacity of the producer Staphylococcus epidermidis IVK45 to limit growth of other nasal bacteria. Of note, the bacteriocin genes were found on mobile genetic elements exhibiting signs of extensive horizontal gene transfer and rearrangements. Thus, continuously evolving bacteriocins appear to govern bacterial competition in the human nose and specific bacteriocins may become important agents for eradication of notorious opportunistic pathogens from human microbiota.
The microbiomes of human body surfaces contribute to health and wellbeing in multiple ways [1, 2]. At the same time, they represent major reservoirs for many human bacterial pathogens such as Staphylococcus aureus and members of the Enterococcaceae, Streptococcaceae, and Enterobacteriaceae. The composition of microbiota is highly variable between different human individuals and it changes over time . Environmentally exposed microbiomes such as those of the human skin and airways are much more variable than those of the gut . Changing environmental stressors, climate, personal hygiene, and contact to other persons contribute to the dynamic alteration of skin and airway microbiota [3, 5–7].
Bacteriocins have been described in many bacterial species, but their ecological significance has remained unclear [27, 40]. Specifically, we are lacking insights into the frequency, diversity, regulation, and activity spectra of bacterial antimicrobial molecules in a given microbial niche. It is obvious that bacteriocins can augment bacterial fitness when producing strains reside in a complex microbiota such as those of human body surfaces. The poor availability of nutrients in the nose , compared to other human body surfaces, such as those of the gastrointestinal tract , may cause a particularly high competitive pressure and may be a reason why we found an unexpectedly high frequency and diversity of bacteriocins in nasal bacteria.