Deconjugated Bile Salts Produced by Extracellular Bile-Salt Hydrolase-Like Activities from the Probiotic Lactobacillus johnsonii La1 Inhibit Giardia duodenalis In vitro Growth

Giardiasis, currently considered a neglected disease, is caused by the intestinal protozoan parasite Giardia duodenalis and is widely spread in human as well as domestic and wild animals. The lack of appropriate medications and the spread of resistant parasite strains urgently call for the development of novel therapeutic strategies. Host microbiota or certain probiotic strains have the capacity to provide some protection against giardiasis. By combining biological and biochemical approaches, we have been able to decipher a molecular mechanism used by the probiotic strain Lactobacillus johnsonii La1 to prevent Giardia growth in vitro. We provide evidence that the supernatant of this strain contains active principle(s) not directly toxic to Giardia but able to convert non-toxic components of bile into components highly toxic to Giardia. By using bile acid profiling, these components were identified as deconjugated bile-salts. A bacterial bile-salt-hydrolase of commercial origin was able to mimic the properties of the supernatant. Mass spectrometric analysis of the bacterial supernatant identified two of the three bile-salt-hydrolases encoded in the genome of this probiotic strain. These observations document a possible mechanism by which L. johnsonii La1, by secreting, or releasing BSH-like activity(ies) in the vicinity of replicating Giardia in an environment where bile is present and abundant, can fight this parasite. This discovery has both fundamental and applied outcomes to fight giardiasis, based on local delivery of deconjugated bile salts, enzyme deconjugation of bile components, or natural or recombinant probiotic strains that secrete or release such deconjugating activities in a compartment where both bile salts and Giardia are present.

Crassaminicella profunda gen. nov., sp nov., an anaerobic marine bacterium isolated from deep-sea sediments

A novel, anaerobic, chemo-organotrophic bacterium, designated strain Ra1766HT, was isolated from sediments of the Guaymas basin (Gulf of California, Mexico) taken from a depth of 2002 m. Cells were thin, motile, Gram-stain-positive, flexible rods forming terminal endospores. Strain Ra1766H(T) grew at temperatures of 25-45 degrees C (optimum 30 degrees C), pH 6.7-8.1 (optimum 7.5) and in a salinity of 5-60 g l(-1) NaCl (optimum 30 g l(-1)). It was an obligate heterotrophic bacterium fermenting carbohydrates (glucose and mannose) and organic acids (pyruvate and succinate). Casamino acids and amino acids (glutamate, aspartate and glycine) were also fermented. The main end products from glucose fermentation were acetate, butyrate, ethanol, H-2 and CO2. Sulfate, sulfite, thiosulfate, elemental sulfur, fumarate, nitrate, nitrite and Fe(III) were not used as terminal electron acceptors. The predominant cellular fatty acids were C-14 : 0, C-16:1 omega 7, C-16:1 omega 7 DMA and C-16:0. The main polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phospholipids. The G +C content of the genomic DNA was 33.7 molo/o. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Ra1766H(T) was affiliated to cluster XI of the order Clostridia les, phylum Firmicutes. The closest phylogenetic relative of Ra1766H(T) was Geosporobacter subterraneus (94.2% 16S rRNA gene sequence similarity). On the basis of phylogenetic inference and phenotypic properties, strain Ra1766H(T) (=DSM 27501(T)=JCM 19377(T)) is proposed to be the type strain of a novel species of a novel genus, named Crassaminicella pro funda.