Probiotics: properties, examples, and specific applications

Abstract

Probiotics are beneficial components of the microbiota that have been used for centuries because of the health benefits they confer to the host. Only recently, however, has the contribution of probiotics to modulation of immunological, respiratory, and gastrointestinal functions started to be fully appreciated and scientifically evaluated. Probiotics such as Escherichia coli Nissle 1917 and lactic acid bacteria are currently used to, or have been evaluated for use to, prevent or treat a range of intestinal maladies including inflammatory bowel disease, constipation, and colon cancer. Engineering these natural probiotics to produce immunomodulatory molecules may help to further increase the benefit to the host. In this article, we will discuss some of the mechanisms of action of probiotics as well as advances in the rational design of probiotics.

Figure 1.

Lactococcus lactis. The probiotic L. lactis was engineered to produce different cytokines: interleukin 10 (IL-10), heme oxygenase 1 (HO-1), the Yersinia protein LcrV, TNF-α nanobodies, or trefoil factors. After oral administration, L. lactis secretes these proteins in direct proximity to mucosal surfaces. These proteins can modulate the immune system in different ways to dampen the immune response and establish tolerance to the microbiota in the case of mucosal injury during IBD or cancer treatment.

Figure 2.

Immune modulation by E. coli Nissle 1917. The probiotic E. coli Nissle 1917 modulates the host immune system in multiple ways (summary of data from in vitro and in vivo experiments).

Figure 3.

Fitness factors of E. coli Nissle 1917. The probiotic E. coli Nissle 1917 possesses multiple fitness factors that enable it to colonize the gut and compete with the resident microbiota and pathogenic bacteria.