Regulation of lactose-phosphoenolpyruvate-dependent phosphotransferase system and beta-D-phosphogalactoside galactohydrolase activities in Lactobacillus casei.

The lactose-phosphoenolpyruvate-dependent phosphotransferase system (lac-PTS) and beta-D-phosphogalactoside galactohydrolase (P-beta-gal) mediate the metabolism of lactose by Lactobacillus casei. Starved cells of L. casei contained a high intracellular concentration of phosphoenolpyruvate, and this endogenous energy reserve facilitated characterization of phosphotransferase system activities in physiologically intact cells. Data obtained from transport studies with whole cells and from in vitro phosphotransferase system assays with permeabilized cells revealed that the lac-PTS had a high affinity for beta-galactosides (e.g., lactose, lactulose, lactobionic acid, and arabinosyl-beta-D-galactoside). lac-PTS and P-beta-gal activities were determined in wild-type strains and strains defective in the glucose-phosphoenolpyruvate-dependent phosphotransferase system after growth on various sugars and in the presence of potential inducers. We found that (i) the lac genes (i.e., the genes coding for the lac-PTS proteins and P-beta-gal) were induced by metabolizable and non-metabolizable beta-galactosides (presumably acting as their phosphorylated derivatives), (ii) galactose 6-phosphate was not an inducer in most strains, (iii) the ratio of lac-PTS activity to P-beta-gal activity in a given strain was not constant, and (iv) inhibition of lac gene expression during growth on glucose was a consequence of glucose-phosphoenolpyruvate-dependent phosphotransferase system-mediated inducer exclusion, repressive effects of a functional glucose-phosphoenolpyruvate-dependent phosphotransferase system and glucose-derived metabolites. The expression of the lac-PTS structural genes and the expression of the P-beta-gal gene are independently regulated and may be subject to both positive control and negative control.     

Inhibition of food-borne pathogenic bacteria by bacteriocins from Lactobacillus gasseri

Seventy-three strains of the Lactobacillus acidophilus group and a Lact. reuteri isolated from human faeces were examined for production of antimicrobial agents against 16 strains of six species of food-borne enteric pathogenic bacteria. Several strains of Lact. gasseri showed wide inhibitory activity against the tested bacteria. Gassericin A produced by Lact. gasseri LA39 was one of the most widely active bacteriocins. It was bactericidal without causing cell lysis.     

Lactic acid bacteria isolated from canine faeces

AIMS: Lactic acid bacteria (LAB) were isolated and sequenced from the faeces of healthy dogs. Five of these strains were selected and further characterized to clarify the potential of these strains as probiotics for canine. METHODS AND RESULTS: LAB were found in 67% (14/21) of the canine faeces samples when plated on Lactobacilli Selective Media without acetic acid. Out of 13 species identified with partial 16S rRNA gene sequencing, Lactobacillus fermentum LAB8, L. mucosae LAB12, L. rhamnosus LAB11, L. salivarius LAB9 and Weissella confusa LAB10 were selected as candidate probiotic strains based on their frequency, quantity in faeces, growth density, acid tolerance and antimicrobial activity. The minimal inhibitory concentration values of these isolates were determined for 14 antibiotics. L. salivarius LAB9, W. confusa LAB10 and L. mucosae LAB12 were viable in pH 2 for 4 h (mLBS), indicating tolerance to acidity and thus the potential to survive in gastrointestinal tract of the canine. The LAB8-LAB12 strains showed antimicrobial activity against Micrococcus luteus A1 NCIMB86166. CONCLUSIONS: Thirteen different LAB species were found from the faecal microbiota of the healthy canines. Five acid tolerant and antimicrobially active LAB strains with the capacity to grow to high densities both aerobically and anaerobically were chosen to serve as candidate probiotics. SIGNIFICANCE AND IMPACT OF THE STUDY: The selected LAB strains are among the first host-specific LAB with antimicrobial activity isolated from canines that could serve as potential probiotics for canine use.     

Lactic acid bacteria fermentation of human milk oligosaccharide components, human milk oligosaccharides and galactooligosaccharides

Human milk contains about 7% lactose and 1% human milk oligosaccharides (HMOs) consisting of lactose with linked fucose, N-acetylglucosamine and sialic acid. In infant formula, galactooligosaccharides (GOSs) are added to replace HMOs. This study investigated the ability of six strains of lactic acid bacteria (LAB), Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus reuteri, Streptococcus thermophilus and Leuconostoc mesenteroides subsp. cremoris, to digest HMO components, defined HMOs, and GOSs. All strains grew on lactose and glucose. N-acetylglucosamine utilization varied between strains and was maximal in L. plantarum; fucose utilization was low or absent in all strains. Both hetero- and homofermentative LAB utilized N-acetylglucosamine via the Embden-Meyerhof pathway. Lactobacillus acidophilus and L. plantarum were the most versatile in hydrolysing pNP analogues and the only strains releasing mono- and disaccharides from defined HMOs. Whole cells of all six LAB hydrolysed oNP-galactoside and pNP-galactoside indicating β-galactosidase activity. High β-galactosidase activity of L. reuteri, L. fermentum, S. thermophilus and L. mesenteroides subsp. cremoris whole cells correlated to lactose and GOS hydrolysis. Hydrolysis of lactose and GOSs by heterologously expressed β-galactosidases confirmed that LAB β-galactosidases are involved in GOS digestion. In summary, the strains of LAB used were not capable of utilizing complex HMOs but metabolized HMO components and GOSs.     

Probiotic properties of vaginal lactic acid bacteria to prevent metritis in cattle

AIMS: The isolation of bovine vaginal lactic acid bacteria (LAB) and the screening of their beneficial properties to select those that could be used as probiotics in the prevention of bovine metritis were performed. METHODS AND RESULTS: Out of 76 Lactobacillus sp. and seven Streptococcus sp. strains, a small number showed high- and medium hydrophobicity when the microbial adhesion to hydrocarbons method (MATH) was applied. In the agar plate diffusion test, a large number of strains inhibited vaginal bovine Escherichia coli 99/14 and human E. coli. This inhibition was due to acid. Only a few strains inhibited Actinomyces pyogenes 96/393, a pathogen isolated from bovine metritis. This inhibition remained after neutralization. The taxonomic identification of the selected strains was carried out by an amplified ribosomal DNA restriction analysis (ARDRA). Most of the strains were identified as Lactobacillus fermentum, a few as Lactobacillus gasseri and one as Lactobacillus rhamnosus. CONCLUSIONS: Bovine vaginal lactobacilli strains have differential surface properties. The strains selected are capable of inhibiting specific metritis pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results can be applied for future studies to design a probiotic product to prevent metritis in dairy postpartum cows.     

Antimicrobial potential of four Lactobacillus strains isolated from breast milk

AIMS: The antimicrobial potential of four lactobacilli (Lactobacillus salivarius CECT5713, Lactobacillus gasseri CECT5714, L. gasseri CECT5715 and Lactobacillus fermentum CECT5716), isolated from fresh human breast milk, was evaluated in this study and compared with Lactobacillus coryniformis CECT5711, a reuterin-producing strain isolated from an artisan goat's cheese. METHODS AND RESULTS: Agar diffusion tests, competitive adhesion assays and mucin expression assays were carried out in order to value the antibacterial properties of the lactobacilli strains. The antibacterial capability of the strains was tested in vivo by using a murine infection model with Salmonella choleraesuis. The results revealed that all the strains studied, displayed antibacterial properties against pathogenic bacteria. However, the antibacterial potential varied among the lactobacilli tested and, in fact, L. salivarius CECT5713 showed not only the best in vitro antibacterial activity, but also the highest protective effect against a Salmonella strain in the murine infection model. CONCLUSION: The four breast-milk lactobacilli, and particularly L. salivarius CECT5713, possess potent antibacterial activities that result in a higher protection against S. choleraesuis CECT4155 in a mouse infection model. SIGNIFICANCE AND IMPACT OF THE STUDY: These results suggest that lactobacilli from breast milk could contribute to an anti-infective protection in neonates and would be excellent candidates for the development of infant probiotic products.     

Lactic acid bacteria (LAB) bind to human B- or H-antigens expressed on intestinal mucosa

Twenty lactobacilli isolated from human feces were studied for binding to the human blood type B-antigen [Galalpha1-3 (Fucalpha1-2) Gal-] and H-antigen (Fucalpha1-2Gal-] expressed sugar chains in human intestinal mucosa. We found two strains, L. gasseri OLL2755 and L. gasseri OLL2877 that firmly adhere to human B-antigen, and we found L. gasseri OLL2827 bound to the H-antigen.     

Screening of Lactobacillus spp. and Pediococcus spp. for glycosidase activities that are important in oenology

AIMS: To assess glycosidase activities from a range of Lactobacillus and Pediococcus species and characterize these activities under conditions pertinent to the wine industry. METHODS AND RESULTS: Lactic acid bacteria were cultured in MRS broth supplemented with apple juice before being harvested, washed and assayed for glycosidase activity using p-nitrophenol-linked substrates. All strains exhibited a detectable capacity for the hydrolysis of the beta- and alpha-d-glucopyranosides. The magnitude of these activities and their response to the physico-chemical parameters investigated varied in a strain-dependent manner. The use of an assay buffer with a pH below 4 generally resulted in a reduced hydrolysis of both substrates while temperature optima ranged between 35 and 45 degrees C. The effect of the inclusion of ethanol in the assay buffer (up to 12%, v/v) ranged from near complete inhibition to increases in activity approaching 80%. With the clear exception of a single strain, glucose and fructose (0.1-20 g l(-1)) acted as inhibitors. An assessment of glycosidase activity during simultaneous exposure to glucose and ethanol at a pH of 3.5 suggested that ethanol decreased loss of activity under these wine-like conditions. CONCLUSIONS: Lactobacillus spp. and Pediococcus spp. possess varying degrees of beta- and alpha-d-glucopyranosidase activities, which in turn are influenced differently by exposure to ethanol and/or sugars, temperature and pH. Several strains appeared suited for further evaluation under winemaking conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: This work highlights the fact that strains of Lactobacillus and Pediococcus have the potential to influence the glycoside composition of wine. Tailoring of wine may therefore be possible through selective application of strains or enzymatic extracts thereof.     

Species-specific oligonucleotide probes for the detection and identification of Lactobacillus isolated from mouse faeces

AIMS: To develop species-specific monitoring techniques for rapid detection and identification of Lactobacillus isolated from mouse faeces. METHODS AND RESULTS: The specificity of oligonucleotide probes was evaluated by dot blot hybridization to 16S rDNA and 23S rDNA amplified by PCR from 12 Lactobacillus type strains and 100 strains of Lactobacillus isolated from mouse faeces. Oligonucleotide probes specific for each Lactobacillus species hybridized only with targeted rDNA. The Lactobacillus strains isolated from mouse faeces were identified mainly as Lactobacillus intestinalis, L. johnsonii, L. murinus and L. reuteri using species-specific probes. 16S rDNA of eight unidentified isolates were sequenced and two new probes were designed. Four of eight strains of unhybridized Lactobacillus were identified as L. johnsonii/gasseri group, and the remaining four strains as L. vaginalis. CONCLUSIONS: The species-specific probe set of L. intestinalis, L. johnsonii, L. murinus, L. reuteri and L. vaginalis in this study was efficient for rapid identification of Lactobacillus isolated from mouse faeces. SIGNIFICANCE AND IMPACT OF THE STUDY: The oligonucleotide probe set for Lactobacillus species harboured in the mouse intestine, can be used for rapid identification of lactobacilli and monitoring of the faecal Lactobacillus community.     

Probiotic properties of human lactobacilli strains to be used in the gastrointestinal tract

AIMS: The study of two human strains of Lactobacillus to be used as probiotics in the gastrointestinal tract. METHODS AND RESULTS: The Lactobacillus acidophilus UO 001 and Lact. gasseri UO 002, were resistant to the gastrointestinal conditions (pH 2 and 3, presence of pepsin, pancreatin or bile salts), the resistance was enhanced in the presence of skimmed milk. Additionally, adhered to Caco-2 cells through glycoproteins in Lact. gasseri and carbohydrates in the case of Lact. acidophilus. These strains are able to inhibit the growth of certain enteropathogens: Salmonella, Listeria and Campylobacter without interfering with the normal microbiota of the gastrointestinal tract, as stated by using the mixed culture and the spot agar test. Finally, strongly adherent Lact. gasseri were found to inhibit the attachment of Escherichia coli O111 to intestinal Caco-2 cells under the condition of exclusion. CONCLUSIONS: These results indicate that the two strains of Lactobacillus from human origin present important properties for survival in, and colonization of, the gastrointestinal tract, that give them potential probiotic. SIGNIFICANCE AND IMPACT OF THE STUDY: Two strains of Lactobacillus isolated from human vagina of healthy premenopausal women could be promising candidates to be used in the preparation of probiotic products and for their use as health-promoting bacteria.     

Purification and characterization of two phospho-β-galactosidases, LacG1 and LacG2, from Lactobacillus gasseri ATCC33323(T)

Lactobacillus gasseri ATCC33323(T) expresses four enzymes showing phospho-β-galactosidase activity (LacG1, LacG2, Pbg1 and Pbg2). We previously reported the purification and characterization of two phospho-β-galactosidases (Pbg1 and Pbg2) from Lactobacillus gasseri JCM1031 cultured in lactose medium. Here we aimed to characterize LacG1 and LacG2, and classify the four enzymes into 'phospho-β-galactosidase' or 'phospho-β-glucosidase.' LacG1 and recombinant LacG2 (rLacG2), from Lb. gasseri ATCC33323(T), were purified to homogeneity using column chromatography. Kinetic experiments were performed using sugar substrates, o-nitrophenyl-β-D-galactopyranoside 6-phosphate (ONPGal-6P) and o-nitrophenyl-β-D-glucopyranoside 6-phosphate (ONPGlc-6P), synthesized in our laboratory. LacG1 and rLacG2 exhibited high k(cat)/K(m) values for ONPGal-6P as compared with Pbg1 and Pbg2. The V(max) values for ONPGal-6P were higher than phospho-β-galactosidases previously purified and characterized from several lactic acid bacteria. A phylogenetic tree analysis showed that LacG1 and LacG2 belong to the phospho-β-galactosidase cluster and Pbg1 and Pbg2 belong to the phospho-β-glucosidase cluster. Our data suggest two phospho-β-galactosidase, LacG1 and LacG2, are the primary enzymes for lactose utilization in Lb. gasseri ATCC33323(T). We propose a reclassification of Pbg1 and Pbg2 as phospho-β-glucosidase.     

Hydrolysis of whey proteins by Lactobacillus acidophilus, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus grown in a chemically defined medium

AIMS: To evaluate the ability of themophilic lactic acid bacteria (LAB) to hydrolyse the whey proteins beta-lactoglobulin (BLG) and alpha-lactalbumin (ALA) in a chemically defined medium (CDM). METHODS AND RESULTS: The ability of three LAB strains to hydrolyse BLG and ALA was studied in a CDM supplemented with these proteins or whey protein concentrate (WPC). Protein hydrolysis was determined by Tricine/SDS-PAGE and RP-HPLC. Maximum BLG (21%) and ALA (26%) degradation by LAB was observed using WPC. Under starving conditions, BLG degradation was greater for Lactobacillus delbrueckii ssp. bulgaricus CRL 454 than for Lactobacillus acidophilus CRL 636 and Streptococcus thermophilus CRL 804. All three strains showed different peptide profiles and were not able to hydrolyse ALA under starvation. CONCLUSIONS: The assayed LAB strains were able to degrade BLG during growth in a CDM and under starving conditions. The different peptide profiles obtained indicate distinct protease specificities. SIGNIFICANCE AND IMPACT OF THE STUDY: These strains could be used as adjunct cultures to increase BLG digestibility in whey-based or whey-containing foods. To our knowledge, this is the first report on the ability of a Lact. acidophilus strain to degrade BLG.     

Isolation and characterization of anti-Salmonella lactic acid bacteria from the porcine gastrointestinal tract

AIMS: To identify lactic acid bacteria (LAB) of porcine intestinal origin with anti-Salmonella activity. METHODS AND RESULTS: Samples were obtained from pig faeces and caeca and screened for the presence of anti-Salmonella LAB. The 11 most promising isolates were identified as belonging to the genera Lactobacillus and Pediococcus. The LAB exhibited large variation in their ability to survive in simulated gastric juice at pH 1.85. While Lactobacillus johnsonii species survived at levels of 80% for up to 30 min, Lactobacillus pentosus species declined to <0.001% in that time. All isolates tolerated porcine bile at a concentration of 0.3% (w/v), with some isolates capable of growth in the presence of up to 5% (w/v) bile. The ability of the LAB isolates to prevent Salmonella invasion of intestinal epithelial HT-29 cells varied, with reductions of between 30% (Lact. pentosus) and 80% (Lactobacillus murinus spp.) observed. CONCLUSIONS: LAB of porcine origin were observed to survive simulated passage through the GIT and inhibit growth of Salmonella and its invasion of the intestinal epithelium. SIGNIFICANCE AND IMPACT OF THE STUDY: The data demonstrate that some porcine intestinal LAB isolates may offer potential as probiotics for the reduction of Salmonella carriage in pigs.     

Characterization of bacteriocin-like inhibitory substances (BLIS) from sourdough lactic acid bacteria and evaluation of their in vitro and in situ activity

AIMS: To identify and characterize bacteriocion-producing lactic acid bacteria (LAB) in sourdoughs and to compare in vitro and in situ bacteriocin activity of sourdough- and nonsourdough LAB. METHODS AND RESULTS: Production of antimicrobial compounds by 437 Lactobacillus strains isolated from 70 sourdoughs was investigated. Five strains (Lactobacillus pentosus 2MF8 and 8CF, Lb. plantarum 4DE and 3DM and Lactobacillus spp. CS1) were found to produce distinct bacteriocin-like inhibitory substances (BLIS). BLIS-producing Lactococcus lactis isolated from raw barley showed a wider inhibitory spectrum than sourdough LAB, but they did not inhibit all strains of the key sourdough bacterium Lb. sanfranciscensis. Antimicrobial production by Lb. pentosus 2MF8 and Lc. lactis M30 was also demonstrated in situ. CONCLUSIONS: BLIS production by sourdough LAB appears to occur at a low frequency, showing limited inhibitory spectrum when compared with BLIS-producing Lc. lactis. Nevertheless, they are active BLIS producers under sourdough and bread-making conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The activity of BLIS has been demonstrated in situ. It may influence the complex sourdough microflora and support the implantation and stability of selected insensitive bacteria, such as Lb. sanfranciscensis, useful to confer good characteristics to the dough.     

Partial characterization of bacteriocins produced by human Lactococcus lactis and Pediococccus acidilactici isolates

AIMS: The aim of this study was to isolate bacteriocin-producing lactic acid bacteria (LAB) from human intestine. METHODS AND RESULTS: A total of 111 LAB were isolated from human adult stool and screened for their bacteriocin production. Neutralized cell-free supernatants from Lactococcus lactis subsp. lactis MM19 and Pediococcus acidilactici MM33 showed antimicrobial activity. The antimicrobials in the supernatant from a culture of L. lactis inhibited Enterococcus faecium, various species of Lactobacillus and Staphylococcus aureus; while those in the supernatant from a culture of P. acidilactici inhibited Enterococcus spp., some lactobacilli and various serotypes of Listeria monocytogenes. The antimicrobial metabolites were heat-stable and were active over a pH range of 2-10. The antimicrobial activities of the supernatants of both bacteria were inhibited by many proteases but not by catalase. The plate overlay assay allowed an approximation of size between 3.5 and 6 kDa for both antimicrobial substances. CONCLUSIONS: As the antagonistic factor(s) produced by L. lactis MM19 and P. acidilactici MM33 were sensitive to proteolytic enzymes, it could be hypothesized that bacteriocins were involved in the inhibitory activities. Inhibition spectrum and biochemical analysis showed that these bacteria produced two distinct bacteriocins. SIGNIFICANCE AND IMPACT OF THE STUDY: We are the first to isolate bacteriocin-producing strains of Pediococcus and Lactococcus from human intestine. These strains might be useful for control of enteric pathogens.     

Strong immunostimulatory activity of AT-oligodeoxynucleotide requires a six-base loop with a self-stabilized 5'-C...G-3' stem structure

Lactobacillus gasseri OLL2716 has recently been discovered as a probiotic that suppresses the growth of Helicobacter pylori and reduces gastric mucosal inflammation in humans. This has resulted in the development of a new type of probiotic yoghurt 'LG21' in Japan. In our previous study, we found an immunostimulatory AT5ACL oligodeoxynucleotide (AT-ODN) containing a unique core sequence (5'-ATTTTTAC-3') in L. gasseri JCM1131(T). Interestingly, although the AT-ODN does not contain any CpG sequences, it exerts mitogenic activity in B cells and augments Th-1-type immune responses via Toll-like receptor 9. These findings prompted us to identify strong immunostimulatory non-CpG AT-ODNs that contain the 5'-ATTTTTAC-3' motif in the genomic sequence of L. gasseri OLL2716. We identified 280 kinds of AT-ODNs in the L. gasseri OLL2716 genome. Mitogenicity and NF-kappaB gene reporting assays showed that 13 of the 280 AT-ODNs were strongly immunostimulatory when in the TLR9 transfectant. Of these, AT-ODNs LGAT-145 and LGAT-243 were the most potent. With respect to the induction of Th-1-type cytokines, LGAT-243 had the greatest activity and was more potent than the swine prototype, ODN D25. We further found that a six-base secondary loop structure containing a self-stabilized 5'-C...G-3' stem sequence is important for potent immunostimulatory activity. These results show for the first time that AT-ODNs with a specific loop and stem structure are important factors for immunostimulatory activity. Finally, we found that novel strong immunostimulatory non-CpG AT-ODNs exist in the genome of probiotic lactic acid bacteria.     

Group-specific comparison of four lactobacilli isolated from human sources using differential blast analysis

Lactic acid bacteria (LAB) have been used in fermentation processes for centuries. More recent applications including the use of LAB as probiotics have significantly increased industrial interest. Here we present a comparative genomic analysis of four completely sequenced Lactobacillus strains, isolated from the human gastrointestinal tract, versus 25 lactic acid bacterial genomes present in the public database at the time of analysis. Lactobacillus acidophilus NCFM, Lactobacillus johnsonii NCC533, Lactobacillus gasseri ATCC33323, and Lactobacillus plantarum WCFS1are all considered probiotic and widely used in industrial applications. Using Differential Blast Analysis (DBA), each genome was compared to the respective remaining three other Lactobacillus and 25 other LAB genomes. DBA highlighted strain-specific genes that were not represented in any other LAB used in this analysis and also identified group-specific genes shared within lactobacilli. Initial comparative analyses highlighted a significant number of genes involved in cell adhesion, stress responses, DNA repair and modification, and metabolic capabilities. Furthermore, the range of the recently identified potential autonomous units (PAUs) was broadened significantly, indicating the possibility of distinct families within this genetic element. Based on in silico results obtained for the model organism L. acidophilus NCFM, DBA proved to be a valuable tool to identify new key genetic regions for functional genomics and also suggested re-classification of previously annotated genes.     

Identification of bacteria with beta-galactosidase activity in faeces from lactase non-persistent subjects

Previous studies suggest that, besides the maldigestion of lactose in the small intestine, the colonic processing of lactose might play a role in lactose intolerance. beta-Galactosidase is the bacterial enzyme which catalyzes the first step of lactose fermentation in the colon. We propose a practical method to differentiate and identify bacteria with beta-galactosidase activity in faeces which combines a colony-lift filter assay with X-gal (5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside) as substrate for differentiation and the fluorescent in situ hybridization technique for identification. The method was applied to faeces from lactase non-persistent subjects. After 28 subjects had undergone one glucose and two lactose challenges, consistent intolerant (n=5) and tolerant (n=7) groups were defined according to their symptom scores. Of the 28 faecal samples, 80.6% (mean, SD: 12.1, range: 47.8-100%) of the total cultured bacteria were found to possess beta-galactosidase activity, which indicates that the bacterial beta-galactosidase is abundant in the colon. The tolerant and intolerant groups did not differ in the percentage or composition of the bacteria with beta-galactosidase activity or beta-galactosidase activity in faeces. Results suggest that the percentage or composition of the bacteria with beta-galactosidase activity in faeces do not play a role in lactose intolerance.     

β-Galactosidase and 6-phospho-β-galactosidase activities in strains of the Lactobacillus acidophilus complex

β-Galactosidase (β-gal) and 6-phospho-β-galactosidase (P-β-gal) activities were measured in a total of 34 strains from Lactobacillus acidophilus, Lactobacillus crispatus, Lactobacillus amylovorus, Lactobacillus gasseri and Lactobacillus johnsonii. The Lact. gasseri strains have P-β-gal but little or no β-gal activities. The strains from other species have β-gal but only very little P-β-gal activities.     

Anti-proliferative effect of two lactic acid bacteria strains of human origin on the growth of a myeloma cell line

AIMS: Twenty lactic acid bacteria strains were isolated from human faeces and tested by MTT assay for stimulation or inhibition of the proliferation of Vero and myeloma cells. METHODS AND RESULTS: None of the strains significantly affected the proliferation of Vero cells. However, two isolates (HN1 and HA8) showed a strong inhibition of myeloma cell proliferation (16.7 and 5.0%, respectively) by MTT assay. CONCLUSION: Both strains have an anti-proliferative effect on a tumoral cell line. SIGNIFICANCE AND IMPACT OF THE STUDY: The beneficial effect of LAB cancer therapy has been linked to their ability for immunomodulation.