Antibacterial metabolites secreted under glucose-limited environment of the mimicked proximal colon model by lactobacilli abundant in infant feces

Abstract

The most abundance of anti-Salmonella lactic acid bacteria (LAB) was found in feces of naturally born, exclusively breastfed Thai infants. Six strains of Lactobacillus plantarum and one strain of Lactobacillus paracasei were selected and identified. In the co-cultivation assay, L. plantarum subsp. plantarum I62 showed the strongest and broadest antibacterial activity against Escherichia coli, Shigella sonnei, Salmonella Paratyphi A, and Salmonella Typhimurium SA 2093 under the mimicked proximal colon condition, in which glucose and other nutrients were limited. According to GC-MS analysis, the major antibacterial contribution of organic acids secreted by L. plantarum I62 grown in the presence of glucose was dramatically reduced from 95.8 to 41.9 % under glucose-limited niche. The production of low-pK a acids, such as lactic, 1,2-benzenedicarboxylic, and 3-phenyllactic acids, was remarkably dropped. Surprisingly, higher-pK a acids such as 5-chlorobenzimidazole-2-carboxylic, pyroglutamic, palmitic, and oleic acids were enhanced. Moreover, cyclic dipeptides, ketones, alkanes, alcohols, and miscellaneous compounds, which were pH-independent antibacterial metabolites, became dominant. The electron microscopy strongly supported the synergistic attacks of the multiple antibacterial components targeting outer and cytoplasmic membranes leading to severe leakage and cell disruption of Salmonella Typhimurium. This strain poses to be a potential probiotic candidate for effectively controlling and treating human foodborne bacterial infection.

Changes in Microbiota Profiles After Prolonged Frozen Storage of Stool Suspensions

“…This procedure is generally not intended for the extraction of microbial DNA from samples with high microbial mass such as fecal samples. We used this protocol (including a proteinase K pretreatment) to get an estimate of cells able to resist harsh conditions that fecal transplants may face during a freezing period and then, once released in the host intestine by FMT; these include the presence of host antimicrobial proteins and peptides, bacteriocins and antibacterial metabolites of bacterial origin (Ostaff et al, 2013;Kanjan and Hongpattarakere, 2016;Dicks et al, 2018). To the best of our knowledge, no attempts were made to impose stress conditions to fecal transplants and therefore distinguished between live and dead/injured bacteria.…”

An Inducible Operon Is Involved in Inulin Utilization in Lactobacillus plantarum Strains, as Revealed by Comparative Proteogenomics and Metabolic Profiling

“…Additionally, these strains were differentiated from the closest species, L. pentosus and L. paraplantarum, based on the nucleotide sequences of recA and dnaK genes. Seven infant strains (CIF17A2, CIF17A4, CIF17A5, CIF17AN2, CIF17AN8, I08, and I61) (34,35) as well as the marine fish and shrimp intestine strains (A3, MHO2.4, MHO2.5, and MHO2.9) (36, 37) were previously described. The 13 fermented-food isolates were cultured from Thai fermented rice noodles and fish essentially as described previously (38) (kindly provided by A. Nuylert and K. Kanjanasmith).…”

Probiotic Weissella cibaria KY10 derived from digestive tract of healthy shrimp exhibits strong antibacterial effects against Vibrio parahaemolyticus causing AHPND in shrimp

“…The cell‐free supernatant of selected LAB strain was obtained by centrifugation and was then treated as follows: (i) CFS adjusted to pH 6.5–7.0 with 1 M NaOH (NCFS), (ii) NCFS treated with 1 mg/ml proteinase K (Sigma, USA) (NCFSP) and (iii) NCFS treated with 300 units/ml catalase (NCFC). After sterilization using a membrane filter (0.2 μm), the inhibitory activity against Vibrio parahaemolyticus T.11 was assayed using broth microdilution as described by Kanjan and Hongpattarakere (2016).…”

“…The antibacterial activity against Vibrio parahaemolyticus T.11 was determined using agar diffusion assay (Kanjan & Hongpattarakere, 2016). A total of 106 LAB strains were incubated in MRS broth containing 1.5% NaCl for 48 h at 30°C.…”