Distinct effects of mucin on phage-host interactions in model systems of beneficial and pathogenic bacteria

Phage-host interactions that occur in host-associated microbiomes are influenced by a plethora of environmental factors. Mucins are glycoproteins representing the largest proportion of mucus, found in the animal digestive tract and on the surface of certain organs, serving as the first line of defense against toxins and pathogens. Previous studies have shown that lytic phages have an important influence on the microbial composition in mucosal areas. Our study expands this knowledge to interactions between previously untested lytic phages targeting probiotic and pathogenic bacteria, as well as temperate phages targeting probiotic bacteria. These interactions could be important in shaping the microbial communities and host well-being. This study demonstrates that mucins enhance the adherence of Vibrio anguillarum lytic phages and Bacillus subtilis lytic and temperate phages, as well as B. subtilis and V. anguillarum cells to solid surfaces. Our results also show that mucins positively affect the attachment of B. subtilis cells even in the presence of phages. At the same time, this positive effect was not observed in the case of V. anguillarum. This suggests that mucin may shield certain bacteria from phage infections. Our findings also demonstrate that mucin differently influences metabolic activity of the two tested bacterial species, with strong positive effects on V. anguillarum. but not on B. subtilis. The work supports previous findings that phages efficiently adhere to mucus (Barr et al., 2013), extending them to include new beneficial and pathogenic bacterial species. It also reveals that mucins have different effects on phage-host interactions in different phage-host systems, which may have implications for phage therapies or probiotic treatment strategies.