The human bile salt sodium deoxycholate induces metabolic and cell envelope changes in Salmonella Typhi leading to bile resistance

Introduction. Salmonella enterica serovar Typhi (S. Typhi) is the etiological agent of typhoid fever. To establish an infection in the human host, this pathogen must survive the presence of bile salts in the gut and gallbladder. Hypothesis. S. Typhi uses multiple genetic elements to resist the presence of human bile. Aims. To determine the genetic elements that S. Typhi utilizes to tolerate the human bile salt sodium deoxycholate. Methodology. A collection of S. Typhi mutant strains was evaluated for their ability to growth in the presence of sodium deoxycholate and ox-bile. Additionally, transcriptomic and proteomic responses elicited by sodium deoxycholate on S. Typhi cultures were also analysed. Results. Multiple transcriptional factors and some of their dependent genes involved in central metabolism, as well as in cell envelope, are required for deoxycholate resistance. Conclusion. These findings suggest that metabolic adaptation to bile is focused on enhancing energy production to sustain synthesis of cell envelope components exposed to damage by bile salts.

Structural and Dynamic Determinants of Molecular Recognition in Bile Acid-Binding Proteins

Disorders in bile acid transport and metabolism have been related to a number of metabolic disease states, atherosclerosis, type-II diabetes, and cancer. Bile acid-binding proteins (BABPs), a subfamily of intracellular lipid-binding proteins (iLBPs), have a key role in the cellular trafficking and metabolic targeting of bile salts. Within the family of iLBPs, BABPs exhibit unique binding properties including positive binding cooperativity and site-selectivity, which in different tissues and organisms appears to be tailored to the local bile salt pool. Structural and biophysical studies of the past two decades have shed light on the mechanism of bile salt binding at the atomic level, providing us with a mechanistic picture of ligand entry and release, and the communication between the binding sites. In this review, we discuss the emerging view of bile salt recognition in intestinal- and liver-BABPs, with examples from both mammalian and non-mammalian species. The structural and dynamic determinants of the BABP-bile–salt interaction reviewed herein set the basis for the design and development of drug candidates targeting the transcellular traffic of bile salts in enterocytes and hepatocytes.

Ilexsaponin A1 Ameliorates Diet-Induced Nonalcoholic Fatty Liver Disease by Regulating Bile Acid Metabolism in Mice

Bile acid (BA) metabolism is an attractive therapeutic target in nonalcoholic fatty liver disease (NAFLD). We aimed to investigate the effect of ilexsaponin A1 (IsA), a major bioactive ingredient of Ilex, on high-fat diet (HFD)-induced NAFLD in mice with a focus on BA homeostasis. Male C57BL/6J mice were fed an HFD to induce NAFLD and were treated with IsA (120 mg/kg) for 8 weeks. The results showed that administration of IsA significantly decreased serum total cholesterol (TC), attenuated liver steatosis, and decreased total hepatic BA levels in HFD-induced NAFLD mice. IsA-treated mice showed increased BA synthesis in the alternative pathway by upregulating the gene expression levels of sterol 27-hydroxylase (CYP27A1) and cholesterol 7b-hydroxylase (CYP7B1). IsA treatment accelerated efflux and decreased uptake of BA in liver by increasing hepatic farnesoid X receptor (FXR) and bile salt export pump (BSEP) expression, and reducing Na+-taurocholic acid cotransporting polypeptide (NTCP) expression. Alterations in the gut microbiota and increased bile salt hydrolase (BSH) activity might be related to enhanced fecal BA excretion in IsA-treated mice. This study demonstrates that consumption of IsA may prevent HFD-induced NAFLD and exert cholesterol-lowering effects, possibly by regulating the gut microbiota and BA metabolism.

PROBIOTIC CHARACTERIZATION OF BACILLUS SUBTILIS STRAIN ISOLATED FROM INFANT FECAL MATTER REVEALED BY 16S rRNA GENE AND PHYLOGENETIC ANALYSIS

Objective: The rationale of our study was to isolate and identify the putative probiotic strain from infant fecal matter exhibiting a broad range of antimicrobial activity and to analyze the effect of different culturing conditions on its probiotic properties and the production of antimicrobial metabolites. Methods: In the present study, bacterial strains were screened for probiotic properties and antimicrobial activity from infant fecal matter (6 months–2 years). The effect of varying culture conditions such as tolerance to acid, bile salt, phenol, NaCl, pH, incubation period, and temperature along with autoaggregation assay, hydrophobicity, and hemolysis was studied. The characterization of the potent strain was studied by morphological, biochemical, and 16S rRNA gene sequencing along the phylogenetic affiliation of the strain was studied. Results: Two putative probiotic bacteria (DAM and IFM) were isolated, identified, characterized, and predicted at pH 2.0, 3.0, and 4.0, the isolate IFM had 50%, 60%, and 70% survivability, while isolate DAM had 55%, 63%, and 75% survivability, respectively. At a bile salt concentration of 0.5%, both isolates had a 75% survival rate. The isolates exhibited a high percentage of hydrophobicity and autoaggregation. The isolates also had non-hemolytic activity and were susceptible to many clinical tested antibiotics (tetracycline, erythromycin, ampicillin, gentamycin, penicillin, etc.). The isolate showed antimicrobial activity against enteric pathogens such as Staphylococcus aureus, Escherichia coli, and Shigella dysenteriae. The accession number of Bacillus subtilis MT279753 and MK453362 was submitted to NCBI. Conclusion: The result revealed that isolates have potent probiotic properties and possess a direct influence on the production of antimicrobial metabolites. These parameters can be modified for the improvement of the potentiality of the isolates.

Molecular identification and technological properties of yeasts isolated from spontaneously fermented cassava waste pulp

The aim of this work was to report on molecular identification and technological properties of the yeast flora isolated from spontaneously fermented cassava waste pulp. This was done with a view of obtaining yeast strains that could be used as a starter culture for the fermentation of cassava waste pulp. Molecular identification was based on the nucleotide sequence of the ITS region of the genomic DNA of the yeast isolates while the technological properties evaluated include linamarase (U/mL), gelatinase, and haemolytic activity; growth at pH 2.5 and tolerance to 2 % bile salt. All the representative five isolated yeasts were identified as Geotrichum silvicola KLP04 – KLP08. The isolates exhibited linamarase activity ranging between 3.3 and 4.2 with strain KLP04 having the highest value and strain KLP05 the least. None of the isolates demonstrated gelatinase and haemolytic activity except strain KLP08 which was partially haemolytic. All the examined yeasts exhibited good growth at pH 2.5, with strain KLP08 having the highest viable counts of 4.1 log10cfu/ml and strain KLP04 the least value of 3.5 log10cfu/ml after 72 h of growth. All the identified yeasts showed strain-specific tolerance to 2% bile salt with strain KLP04 having the highest viable count of 4.3 log10cfu/ml and strain KLP08 the least value of 2.2 log10cfu/ml at the end of 72 h of incubation. Based on all the examined technological properties, Candida silvicola KLP04 strain had the highest potential to be considered for starter culture for the fermentation of cassava waste pulp.

Screening of Bacterial Isolates with Probiotic Potential of Tiger Nut Drink, Ogi and Palm Wine

Probiotics are live microorganisms that are very beneficial to human health when consumed in a sufficient amount. Screening and fingerprinting of isolates with probiotic potentials from indigenous food products were evaluated. Fresh palm wine, Ogi and Tiger nut drinks were bought from retailers in Obio-Akpor and Port Harcourt Local Government Area, Rivers State. These samples on getting to the lab in sterile containers were analysed using standard microbiological techniques for the enumeration and isolation of bacterial isolates. Identification of isolates relied on the biochemical and genomic techniques using standard methods. The probiotics were screened based on their ability to tolerate ethanol, bile salt, low pH, high salt concentration, lactose utilization and the production of biogenic amine. Antimicrobial susceptibility of the bacterial isolates (probiotics) was carried out using the Kirby-Bauer disc diffusion. Forty-two bacterial isolates which belonged to the genera: Lactobacillus sp, Pediococcus sp, Enterococcus sp and Streptococcus sp were identified. Genomic characterization of isolates showed that isolate NO2 has 83.4% pairwise identity with Bacillus firmus strain T1, Isolate NP2 has 86.5% pairwise identity with Bacillus cereus strain PKID1, NT8 has 80.3% pairwise identity with Bacillus cereus strain PV-G21. Results of screened probiotics showed that out of the forty-two bacterial isolates, only fifteen were non-spore producers and that they were tolerant to ethanol, low pH, NaCl and bile salt at all concentrations. Results of lactose utilization showed that only twelve out of the fifteen bacterial isolates utilized lactose. Results of biogenic amine production showed that only five out of fifteen bacterial isolates produced biogenic amine. The antibiotic susceptibility pattern of the screened bacterial isolates showed that they exhibited resistance to Pefloxacin, Gentamycin, Ampiclox, Amoxicillin, Rocephin, Ciprofloxacin; Streptomycin, Sceptrin and Erythromycin. They were highly resistant to Gentamycin and Zinnacef. Bacillus firmus strain T1, Bacillus cereus strain PKID1 and Bacillus cereus strain PV-G21 were identified as bacterial probiotics. Consumption of palm wine, Ogi and tiger nut drinks is highly recommended due to the availability of probiotics.