Abstract
Altered intestinal microbiota is associated with systemic and intestinal diseases, such as inflammatory bowel disease (IBD). Dysbiotic microbiota with enhanced proinflammatory capacity is characterized by depletion of anaerobic commensals, increased proportion of facultatively anaerobic bacteria, as well as reduced diversity and stability. In this study, we developed a high-throughput in vitro screening assay to isolate intestinal commensal bacteria with anti-inflammatory capacity from a healthy fecal microbiota transplantation donor. Freshly isolated gut bacteria were screened for their capacity to attenuate Escherichia coli lipopolysaccharide (LPS)-induced interleukin 8 (IL-8) release from HT-29 cells. The screen yielded a number of Bacteroides and Parabacteroides isolates, which were identified as P. distasonis, B. caccae, B. intestinalis, B. uniformis, B. fragilis, B. vulgatus and B. ovatus using whole genome sequencing. We observed that a cell-cell contact with the epithelium was not necessary to alleviate in vitro inflammation as spent culture media from the isolates were also effective and the anti-inflammatory action did not correlate with the enterocyte adherence capacity of the isolates. The anti-inflammatory isolates also exerted enterocyte monolayer reinforcing action and lacked essential genes to synthetize hexa-acylated, proinflammatory lipid A, part of LPS. Yet, the anti-inflammatory effector molecules remain to be identified. The Bacteroides strains isolated and characterized in this study have potential to be used as so-called next-generation probiotics.
Highlights
The human intestine harbors a complex bacterial ecosystem of which 90% of the species belong to the phyla Firmicutes and Bacteroidetes [1,2,3]
Bacteria from fecal material of a pre-screened, healthy FMT donor was cultivated on GAM (Gifu anaerobic medium), reinforced clostridial medium (RCM) and Brucella agar under anaerobic conditions and 600 bacterial isolates were picked during 72 hours of incubation (Figure 1)
We focused our further studies on the Parabacteroides and Bacteroides isolates, which formed a major part of the bacterial isolates and are associated with the restoration of mucosal microbiota after FMT [20,21]
Summary
The human intestine harbors a complex bacterial ecosystem of which 90% of the species belong to the phyla Firmicutes and Bacteroidetes [1,2,3]. Most individuals carry approximately 200 different bacterial species with varying abundance in their gastrointestinal tract but only around 30% of the species, the so-called common core microbiota, are shared between subjects [4,5]. Dysbiotic, unbalanced intestinal microbiota composition with enhanced proinflammatory capacity is characterized by reduced species richness and diversity as well as reduced microbial stability [7]. Nutrients 2020, 12, 935 abundance of health-associated, short-chain fatty acid-producing Firmicutes and proinflammatory, lipopolysaccharide-(LPS-)containing pathobionts, such as gamma-Proteobacteria, have been linked to dysbiosis [8]. Several studies have shown that IBD patients have decreased abundance of mucosal or fecal Bacteroides in comparison to healthy subjects [10,11,12]
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