So much more to mucus: Mammals accommodate a dense community of metabolically active microorganisms in their gut. This is not a passive relationship, and host and microbe have antagonistic as well as mutualistic responses to each other. Using a whole-colon imaging method in mice, Bergstrom et al. looked at the role of colonic mucus in segregating the microbiota from host cells during elimination of feces (see the Perspective by Birchenough and Johansson). Host goblet cells synthesize two forms of mucin that differ in branched chain O-glycosylation and the site of production in the colon. A “thick” mucus in the proximal, ascending colon wraps the microbiota to form fecal pellets. Transit along the distal, descending colon is lubricated by “thin” mucus that transiently links with the thick mucus. Normal mucus encapsulation prevents inflammation and hyperplasia and thus is important for maintenance of a healthy gut. Science , this issue p. 467 ; see also p. 402

Development of novel anti-influenza A virus (IAV) drugs with high efficiency and low toxicity is critical for preparedness against influenza outbreaks. Herein, we investigated the anti-IAV activities and mechanisms of fucoidan in vitro and in vivo. The results showed that a fucoidan KW derived from brown algae Kjellmaniella crassifolia effectively blocked IAV infection in vitro with low toxicity. KW possessed broad anti-IAV spectrum and low tendency of induction of viral resistance, superior to the anti-IAV drug amantadine. KW was capable of inactivating virus particles before infection and blocked some stages after adsorption. KW could bind to viral neuraminidase (NA) and inhibit the activity of NA to block the release of IAV. KW also interfered with the activation of EGFR, PKCα, NF-κB, and Akt, and inhibited both IAV endocytosis and EGFR internalization in IAV-infected cells, suggesting that KW may also inhibit cellular EGFR pathway. Moreover, intranasal administration of KW markedly improved survival and decreased viral titers in IAV-infected mice. Therefore, fucoidan KW has the potential to be developed into a novel nasal drop or spray for prevention and treatment of influenza in the future.