Purification of Antilisterial Peptide (Subtilosin A) from Novel Bacillus tequilensis FR9 and Demonstrate Their Pathogen Invasion Protection Ability Using Human Carcinoma Cell Line

Unveiling the synergistic potency of chlorhexidine and azithromycin in combined action

The growing challenge of antibiotic resistance necessitates novel approaches for combating bacterial infections. This study explores the distinctive synergy between chlorhexidine, an antiseptic and disinfectant agent, and azithromycin, a macrolide antibiotic, in their impact on bacterial growth and virulence factors using Escherichia coli strain Crooks (ATCC 8739) as a model. Our findings reveal that the chlorhexidine and azithromycin combination demonstrates enhanced anti-bacterial effects compared to individual treatments. Intriguingly, the combination induced oxidative stress, decreased flagellin expression, impaired bacterial motility, and enhanced bacterial autoaggregation. Notably, the combined treatment also demonstrated a substantial reduction in bacterial adherence to colon epithelial cells and downregulated NF-κB in the epithelial cells. In conclusion, these results shed light on the potential of the chlorhexidine and azithromycin synergy as a compelling strategy to address the rising challenge of antibiotic resistance and may pave the way for innovative therapeutic interventions in tackling bacterial infections.

Isolation and characterization of lactic acid bacteria producing a potent anti-listerial bacteriocin-like inhibitory substance (BLIS) from chhurpi, a fermented milk product

Nowadays, the bacteriocin industries have seen significant growth, supplanting chemical preservatives in its ability to improve the shelf-life and safety of food. The increasing customer desire to use natural preservatives has fueled advancing bacteriocin research. The objective of this study was to identify lactic acid bacteria (LAB) that produce bacteriocin-like inhibitory substance (BLIS) and have strong anti-listerial activity. We have identified and analyzed a LAB obtained from chhurpi samples, a popular milk-derived product in the Himalayan regions of India and Nepal. The strain was studied and identified based on its morphological, biochemical, and physiological characteristics. Furthermore, the molecular 16s-rDNA analysis suggests that the strain was Lactococcus sp. RGUAM1 (98.2% similar to Lactococcus lactis subsp. hordniae NBRC 100931T). The isolated strain can produce a potent BLIS, which has shown efficacy against three gram-positive bacteria responsible for food spoilage, such as Listeria monocytogenes (MTCC 657), Staphylococcus aureus subsp. aureus (MTCC 87), Lactobacillus plantarum (MTCC 1407), Lactobacillus paraplantarum (MTCC 12904). The scanning electron microscope (SEM) image illustrates that the crude cell-free supernatant (CFS) disrupts the cell envelope, leading to the release of cellular contents and the clustering of cells. In addition, this BLIS can easily withstand a wide range of pH (2-12), temperature (up to 100 °C for 15 min), bile salt (0.3% W/V), salinity (4% W/V), and enzyme activity of 1600 AU/ml against Listeria monocytogenes. Our research offers a robust framework and valuable insights into bio-preservation and its potential applications in diverse food products.

Tracing probiotic producing bacterial species from gut of buffalo (Bubalus bubalis), South-East-Asia

Abstract Due to extensive application of antibiotics as growth promoters in animal feed, antimicrobial resistance has been increased. To overcome this challenge, rumen microbiologists search for new probiotics to improve the rate of livestock production. The present study was aimed to isolate and evaluate breed-specific lactic acid bacteria (LAB) as potential animal probiotics. The current study was conducted during 10 months from July 2020 to April 2021, in which a total of n=12 strains were isolated from different samples including milk, rumen, and feces of Nilli Ravi Buffaloes. These isolates were evaluated for their antimicrobial potential against common animal pathogens (Bacillus spp., E. coli, Staphylococcus aureus, Salmonella spp., Listeria spp.). All the isolates were identified using 16S rRNA gene sequencing and the phylogenetic analyses inferred that these strains showed close relations to the species of various genera; Enterococcus lactis, Pediococcus pentosaceus, Bacillus subtilis Weissella cibaria, Weissella soli, Bacillus tequilensis, Weissella bombi, Bacillus licheniformis, Lactococcus lactis, Bacillus megaterium, Lactobacillus ruminis, and Lactococcus lactis. NMCC-Ru2 has exhibited the enormous potential of antimicrobial activity, 28 mm, for Salmonella typhimurium;23 mm for Listeria monocytogenes 21 mm for E.coil. Highest resistance was seen in NMCC-Ru2 agasint test antbiotic, like 25.5 mm for Tetracycline. Overall results revesl that the probiotic profile of isolates was achieved using standard criteria, particularly with animal probiotic properties

Probiotic potential of gluten degrading Bacillus tequilensis AJG23 isolated from Indian traditional cereal-fermented foods as determined by Multiple Attribute Decision-Making analysis

The present study reported the characterization of gluten hydrolyzing strains of Bacillus sp. from fermented cereal dough. The strains were characterized for probiotic as well as technological attributes. A total of 45 presumptive gluten degrading isolates were obtained on gliadin agar plate assay. Based on hemolytic and antibiotic susceptibility pattern, only six isolates were considered safe which also indicated gliadinase activity on zymography. All the six strains were able to resist the pH 2.0, 0.25% bile and also possessed ability to adhere to the organic solvents and mucin. The cell free supernatant of five strains exhibited antimicrobial activities against Gram-positive and Gram-negative pathogens. A more than 50% survival of the isolated strains was obtained at a salt concentration of 2%, phenol concentration of 0.1% and temperature upto 45 °C. All the strains exhibited antioxidant activities and biofilm forming ability. Furthermore, the ranking of strains based on probiotic as well as other functional attributes was determined using multidimensional Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). A matrix of multidimensional indicators was prepared using alternatives and criteria, the analysis indicated the strain Bacillus tequilensis AJG23 as the potential probiotic candidate based on all screening criteria. Further work still needs to be done about the protective role of the potential strain against gluten sensitivity using in vitro models.

Characterization of Bacillus spp. isolated from the intestines of Rhynchocypris lagowskii as a potential probiotic and their effects on fish pathogens

Probiotics sourced from fish intestinal microbiota have a merit over other bacterial sources due to colonization ability and effective time. This study aimed to evaluate the bacilli isolated from the Rhynchocypris lagowskii intestines and their validity as a probiotic. Three isolates were selected (LSG 2-5, LSG 3-7, and LSG 3-8) and defined by morphological and 16S rRNA analysis as Bacillus velezensis, Bacillus aryabhattai, and Bacillus mojavensis, respectively. Results showed the strain tolerant abilities to gastrointestinal fluid, bile salt, pH, and temperature expotures. Additionally, all bacterial strains showed anti-pathogenic activity against at least four strains out of six tested pathogen strains (Staphylococcus aureus, Aeromonas hydrophila, Escherichia coli, Aeromonas veronii, Edwardsiella, and Aeromonas sobria). The bacterial strains also showed a high percentage of co-aggregation activity, more than 70%, with Aer. hydrophile, Staph. epidermidis, and Klebsiella aerogenes. At the same time, the results of competition, rejection, and substitution activity with Aer. hydrophila and Aer. veronii indicated the ability of the isolated strains to reduce the adhesion of pathogens to mucin. All strains showed safety properties, non-hemolytic, and sensitivity characteristics for most of tested antibiotics. In vivo test after injecting these strains into fish at various concentrations showed no side effects in the internal or external organs of fish compared to controls, proving that this is safe for these fish. Furthermore, the three strains produced lipase, amylase, and protease enzymes. The strains also showed bile salt hydrolase activity and biofilm formation, allowing them to tolerate stressful conditions. Conclusion: Based on these strains characteristics and features, they could be considered a promising candidate probiotic and can be used as an anti-pathogenic, especially in aquaculture.

Identification and Characterization of a Bacteriocin from the Newly Isolated Bacillus subtilis HD15 with Inhibitory Effects against Bacillus cereus

Natural antimicrobial substances are needed as alternatives to synthetic antimicrobials to protect against foodborne pathogens. In this study, a bacteriocin-producing bacterium, Bacillus subtilis HD15, was isolated from doenjang, a traditional Korean fermented soybean paste. We sequenced the complete genome of B. subtilis HD15. This genome size was 4,173,431 bp with a G + C content of of 43.58%, 4,305 genes, and 4,222 protein-coding genes with predicted functions, including a subtilosin A gene cluster. The bacteriocin was purified by ammonium sulfate precipitation, Diethylaminoethanol-Sepharose chromatography, and Sephacryl gel filtration, with 12.4-fold purification and 26.2% yield, respectively. The purified protein had a molecular weight of 3.6 kDa. The N-terminal amino acid sequence showed the highest similarity to Bacillus subtilis 168 subtilosin A (78%) but only 68% similarity to B. tequilensis subtilosin proteins, indicating that the antimicrobial substance isolated from B. subtilis HD15 is a novel bacteriocin related to subtilosin A. The purified protein from B. subtilis HD15 exhibited high antimicrobial activity against Listeria monocytogenes and Bacillus cereus. It showed stable activity in the range 0-70°C and pH 2-10 and was completely inhibited by protease, proteinase K, and pronase E treatment, suggesting that it is a proteinaceous substance. These findings support the potential industrial applications of the novel bacteriocin purified from B. subtilis HD15.

Purification and characterization of bacteriocin produced by a strain of Lacticaseibacillus rhamnosus ZFM216

The recent surge in demand for natural preservatives has ushered in a new era of research into novel bacteriocins capable of effectively combating food-borne infections. In this study, the bacteriocin from Lacticaseibacillus rhamnosus ZFM216, which has a molecular mass of 11851.9 Da, was purified using macroporous resin, gel chromatography, and reversed-phase high performance liquid chromatography. This bacteriocin could inhibit both Gram-positive and Gram-negative bacteria. It had a strong inhibitory effect on Staphylococcus aureus D48 with minimum inhibitory concentration values of 1.75 μM. Bacteriocin ZFM216 was heat stable and showed pH stability under weakly acidic conditions. It was sensitive to pepsin, proteinase K and trypsin. Electron microscopy results showed that when treated with bacteriocin ZFM216, S. aureus D48 was severely deformed, the cell structure was obviously changed, and the intracellular electrolyte leaked to the outside of the cell. Bacteriocin ZFM216 caused the ATP level of the indicator to decrease, the conductivity to sharply increase, and the transmembrane potential difference (ΔΨ) to instantaneously decrease. This research formed the basis for further development and utilization of bacteriocin ZFM216 which has potential in the food industry.

Antioxidant and Antibacterial Effects of Potential Probiotics Isolated from Korean Fermented Foods

A total of sixteen bacterial strains were isolated and identified from the fourteen types of Korean fermented foods that were evaluated for their in vitro probiotic potentials. The results showed the highest survivability for Bacillus sp. compared to Lactobacillus sp. in simulated gastric pH, and it was found to be maximum for B. inaquosorum KNUAS016 (8.25 ± 0.08 log10 CFU/mL) and minimum for L. sakei KNUAS019 (0.8 ± 0.02 log10 CFU/mL) at 3 h of incubation. Furthermore, B. inaquosorum KNUAS016 and L. brevis KNUAS017 also had the highest survival rates of 6.86 ± 0.02 and 5.37 ± 0.01 log10 CFU/mL, respectively, in a simulated intestinal fluid condition at 4 h of incubation. The percentage of autoaggregation at 6 h for L. sakei KNUAS019 (66.55 ± 0.33%), B. tequilensis KNUAS015 (64.56 ± 0.14%), and B. inaquosorum KNUAS016 (61.63 ± 0.19%) was >60%, whereas it was lower for L. brevis KNUAS017 (29.98 ± 0.09%). Additionally, B. subtilis KNUAS003 showed higher coaggregation at 63.84 ± 0.19% while B. proteolyticus KNUAS001 found at 30.02 ± 0.33%. Among them, Lactobacillus sp. showed the best non-hemolytic activity. The highest DPPH and ABTS radical scavenging activity was observed in L. sakei KNUAS019 (58.25% and 71.88%). The cell-free supernatant of Lactobacillus sp. considerably inhibited pathogenic growth, while the cell-free supernatant of Bacillus sp. was moderately inhibited when incubated for 24 h. However, the overall results found that B. subtilis KNUAS003, B. proteolyticus KNUAS012, L. brevis KNUAS017, L. graminis KNUAS018, and L. sakei KNUAS019 were recognized as potential probiotics through different functional and toxicity assessments.

A Biofloc-Based Aquaculture System Bio-augmented with Probiotic Bacteria Bacillus tequilensis AP BFT3 Improves Culture Environment, Production Performances, and Proteomic Changes in Penaeus vannamei

Experiments were conducted to evaluate the probiotic effect of bio-augmented Bacillus tequilensis AP BFT3 on improving production, immune response, and proteomic changes of Penaeus vannamei reared in a biofloc system. Penaeus vannamei larvae (PL13) were stocked in 100-L tanks at a rate of 100 no per tank to study the effect of B. tequilensis AP BFT3 with and without biofloc (BFT-PRO and PRO). Control tanks devoid of probiotic strain were maintained in a clear water system. The growth and survival considerably increased in probiotic added biofloc reared shrimp than probiotic added clear water reared ones and control. Water quality significantly improved in probiotic added (PRO) and biofloc-probiotics (BFT-PRO) system than control. Microbiological investigations indicate increased heterotrophic bacterial load in BFT-PRO compared to the PRO and control. The quality of the isolated microbes was analyzed in terms of enzyme production, and an abundance of enzyme-producing bacterial population was observed in BFT-PRO shrimp. Immune-related genes were significantly upregulated in BFT-PRO shrimp, followed by the PRO and control. The proteomic data (2D gel electrophoresis and MALDI-TOF) of muscle tissue from the experimental animals identified 11 differentially expressed proteins. The Daxx OS and Lit v 1 tropomyosin was found upregulated in BFT-PRO shrimps. Downregulation of Na⁺/K⁺ATPase was observed in biofloc with probiotic-supplied groups. The findings revealed that the BFT system's efficacy could be improved through the addition of probiotics. The addition of B. tequilensis AP BFT3 as a probiotic in biofloc induced the expression of essential proteins, reducing contracting diseases during culture.

Probiotic Bacillus subtilis LF11 Protects Intestinal Epithelium Against Salmonella Infection

Enteric diseases caused by Salmonella are prevalent in poultry farming. With the forbiddance of antibiotics in feedstuff industry, Bacillus subtilis (B. subtilis) preparation as antibiotic alternatives against Salmonella infection has gained increasing attention recently. However, the protection modes of B. subtilis against Salmonella infection in broilers are strain-specific. In this study, probiotic B. subtilis LF11 significantly reduced diarrhea and mortality of broilers caused by Salmonella braenderup (S. braenderup) in spite of no inhibition effect on it in vitro. Here, the intestinal epithelial cells NCM460 were incubated to explore the protection of B. subtilis LF11 on intestinal epithelium against Salmonella. The results revealed that B. subtilis LF11 showed obvious exclusion activity with the decrease of adhesion and invasion of S. braenderup to NCM460 cells, accordingly with the increase of NCM460 cell survival compared with S. braenderup challenge alone. Meanwhile, RT-PCR and Western blot proved that the gene transcription and expression levels of four tight junction proteins in NCM 460 cells were upregulated, which was further confirmed by immunofluorescence observation. Besides, B. subtilis LF11 downregulated the gene transcription levels of the proinflammatory cytokines IL-6, IL-8, and TNF-α induced by S. braenderup H9812. ELISA analysis also verified that B. subtilis LF11 reduced the IL-8 production significantly. In general, B. subtilis LF11 has the ability to protect the intestinal epithelium against Salmonella infection by reducing the Salmonella adhesion and invasion, enhancing the intestinal barrier and attenuating the enterocyte inflammatory responses, and has the potential as probiotics to prevent enteric diseases in broilers.

Screening of Antimicrobial Activities and Lipopeptide Production of Endophytic Bacteria Isolated from Vetiver Roots

The exploration of certain microbial resources such as beneficial endophytic microorganisms is considered a promising strategy for the discovery of new antimicrobial compounds for the pharmaceutical industries and agriculture. Thirty-one endophytic bacterial strains affiliated with Bacillus, Janthinobacterium, Yokenella, Enterobacter, Pseudomonas, Serratia, and Microbacterium were previously isolated from vetiver (Chrysopogon zizanioides (L.) Roberty) roots. These endophytes showed antifungal activity against Fusarium graminearum and could be a source of antimicrobial metabolites. In this study, in particular, using high-throughput screening, we analyzed their antagonistic activities and those of their cell-free culture supernatants against three species of Fusarium plant pathogens, a bacterial strain of Escherichia coli, and a yeast strain of Saccharomyces cerevisiae, as well as their capacity to produce lipopeptides. The results showed that the culture supernatants of four strains close to B. subtilis species exhibited antimicrobial activities against Fusarium species and E. coli. Using mass spectrometry analyses, we identified two groups of lipopeptides (surfactins and plipastatins) in their culture supernatants. Whole-genome sequencing confirmed that these bacteria possess NRPS gene clusters for surfactin and plipastatin. In vitro tests confirmed the inhibitory effect of plipastatin alone or in combination with surfactin against the three Fusarium species.

Antimicrobial Bacillus: Metabolites and Their Mode of Action

The agricultural industry utilizes antibiotic growth promoters to promote livestock growth and health. However, the World Health Organization has raised concerns over the ongoing spread of antibiotic resistance transmission in the populace, leading to its subsequent ban in several countries, especially in the European Union. These restrictions have translated into an increase in pathogenic outbreaks in the agricultural industry, highlighting the need for an economically viable, non-toxic, and renewable alternative to antibiotics in livestock. Probiotics inhibit pathogen growth, promote a beneficial microbiota, regulate the immune response of its host, enhance feed conversion to nutrients, and form biofilms that block further infection. Commonly used lactic acid bacteria probiotics are vulnerable to the harsh conditions of the upper gastrointestinal system, leading to novel research using spore-forming bacteria from the genus Bacillus. However, the exact mechanisms behind Bacillus probiotics remain unexplored. This review tackles this issue, by reporting antimicrobial compounds produced from Bacillus strains, their proposed mechanisms of action, and any gaps in the mechanism studies of these compounds. Lastly, this paper explores omics approaches to clarify the mechanisms behind Bacillus probiotics.

Selection of Bacteriocinogenic Bacillus spp. from Traditional Fermented Korean Food Products with Additional Beneficial Properties

Two Bacillus spp. isolated from kimchi, Bacillus tequilensis ST816CD and Bacillus subtilis ST830CD, were characterized for their antimicrobial properties and safety. The proteinaceous nature of their inhibitory metabolites was confirmed after exposure to proteolytic enzymes, resulting in partial loss of the antimicrobial effect. This indicated that different non-proteinaceous antimicrobial substances may also be produced by these strains. This hypothesis was later confirmed when genes associated with the production of surfactants were detected in their DNA. The expressed antimicrobial metabolites were not affected by treatment at different temperatures and pH levels, including exposure to selected chemicals. Their strong adherence to susceptible pathogens was not significantly affected by different temperatures, chemicals, or pH values. Both Bacillus strains showed inhibitory activity against clinical and food-associated pathogens, including Listeria monocytogenes ATCC 15313, and some Staphylococcus species. Several genes associated with the production of antimicrobial metabolites were detected, but key virulence and beneficial genes were not present in these strains. Even though only B. tequilensis ST816CD displayed γ-hemolysin production, both selected strains were found to produce gelatinase and biogenic amines, which are considered as either potential virulence- or health-related factors. Moreover, the strains were susceptible to a variety of antibiotics except for the penicillin G [1 IU/disc] resistance of B. tequilensis ST816CD. Both strains showed proteolytic activity. Additionally, both strains showed low hydrophobicity based on bacterial adherence measured by hydrocarbons (n-hexadecane).

Purification, characterization, and mode of action of Paracin 54, a novel bacteriocin against Staphylococci

Staphylococci belong to conditionally pathogenic bacteria, and the pathogenicity of Staphylococcus aureus is the strongest among them. Enterotoxin produced by it can contaminate food and cause food poisoning. Bacteriocin is a kind of polypeptide with antibacterial activity synthesized by some bacteria during metabolism. In this study, we report on purification, characterization, and mode of action of the bacteriocin named Paracin 54, produced by Lactobacillus paracasei ZFM54. Paracin 54 was purified by precipitation with 80% ammonium sulfate, strong cation-exchange chromatography, G-25 gel column, and reversed-phase high-performance liquid chromatography (HPLC). The molecular weight of Paracin 54 (5718.1843 Da) was determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Paracin 54 showed broad-spectrum inhibitory activity. It had a strong inhibitory effect on Staphylococci with minimum inhibitory concentration values of 3.00-4.50 μg/mL. Paracin 54 was heat-stable and active only in acidic pH range (2-6). After treatment with proteases, the activity was lost. The results of mode of action showed Paracin 54 damaged the cell membrane and cell wall of Staphylococcus aureus, and then the cytoplasm leaked out, leading to death of the bacteria. These properties make Paracin 54 a promising candidate to prevent the growth of spoilage bacteria and control food poisoning caused by Staphylococci. KEY POINTS: • Paracin 54 was purified from Lactobacillus paracasei ZFM54 with good biochemical characteristics. • Paracin 54 had a strong effect against Staphylococci, making it a promising preservative to prevent the growth of Staphylococci in food. • The mode of action of Paracin 54 on Staphylococcus aureus was revealed.

Probiotic Potential of Bacillus Strains Isolated from an Acidic Fermented Food Idli

Present study is intended to assess the probiotic properties of Bacillus spp. isolated from idli batter, a traditional fermented food of Southern India and Sri Lanka. A total of 32 isolates were screened for potential pathogenic behaviour through haemolysis assay, DNase activity and antibiotics sensitivity. Two of the isolates were found to be potentially safe and identified as Bacillus spp. These strains were characterized for in vitro probiotic attributes and antioxidant activity. Both the strains showed strong acid and bile tolerance, transit tolerance, lysozyme tolerance, cell surface hydrophobicity, auto-aggregation, co-aggregation, biofilm formation potential and adhesion to human colon adenocarcinoma (HT 29) cell line demonstrating potential probiotic ability. These strains also exhibited considerable cholesterol binding, thermostability, β-galactosidase production, proteolytic, amylolytic and lipolytic activity. Cell-free supernatant inhibited the biofilm formation by Pseudomonas aeruginosa (KT266804) to 90%. Intact cells showed significant DPPH (41%), hydroxyl (31%), radical scavenging activity and lipid peroxidation inhibition (20.38%), while cell-free extracts exhibited significant superoxide anion radical scavenging activity (16.25%). Results revealed that isolates could be potential probiotic candidate after further assessment of in vivo probiotic properties and safety evaluation and could be utilised as starter cultures in functional foods.

In vitro Assessment of the Safety and Potential Probiotic Characteristics of Three Bacillus Strains Isolated From the Intestine of Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂)

Probiotics serving as an alternative to the criticized antibiotics mainly focus on improving animal's growth and health. After realizing the dangers posed by diseases that have led to lots of economic losses, aquaculture scientists have sought the usage of probiotics. However, most probiotics are ineffective in eliciting aquatic animals' preferred effects, since they are from non-fish sources. Again, there are even a few marine aquatic probiotics. Given this, a study was conducted to investigate the probiotic potential of the bacteria species isolated from the digestive tract of hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). Based on the morphological, biochemical, 16S rRNA sequencing analysis and evolutionary relationships, the isolated species were identified as Bacillus tequilensis GPSAK2 (MW548630), Bacillus velezensis GPSAK4 (MW548635), and Bacillus subtilis GPSAK9 (MW548634), which were designated as GPSAK2, GPSAK4, and GPSAK9 strains, respectively. Their probiotic potentials including their ability to tolerate high bile salt concentration, low pH, high temperatures, adhesion ability (auto-aggregation and cell-surface hydrophobicity), antimicrobial activity and biosafety test, compatibility test, hemolytic activity, and antibiotic susceptibility test were evaluated. While GPSAK2 and GPSAK9 strains were γ-hemolytic, that of GPSAK4 was α-hemolytic. All the isolates were resistant to low pH (1) and higher bile salt concentration (0.5%), showed higher viability ability after higher temperature exposure (80, 90, and 100°C), as well as higher cell-surface percentage hydrophobicity and auto-aggregation. All isolates exhibited positive compatibility with each other, signifying their ability to be used as multispecies. The three strains were susceptible to ampicillin (except GPSAK9, which was resistant), penicillin, kanamycin, ceftriaxone, chloramphenicol, erythromycin, clindamycin, furazolidone (except GPSAK2 and GPSAK9, which were moderately susceptible and resistant, respectively), polymyxin B, vancomycin (except GPSAK9, which was resistant), sulfamethoxazole (except GPSAK9, which was moderately susceptible), amikacin, minocycline, ofloxacin, norfloxacin, doxycycline, neomycin, gentamicin, tetracycline, carbenicillin, midecamycin (except GPSAK9, which was moderately susceptible), ciprofloxacin, piperacillin, and cefoperazone. All isolates demonstrated good antimicrobial activity against four pathogens, viz. Streptococcus agalactiae, Streptococcus iniae, Vibrio harveyi, and Vibrio alginolyticus. The results collectively suggest that Bacillus strains GPSAK2, GPSAK4, and GPSAK9 could serve as potential probiotic candidates that can be used to improve the growth and health status of aquatic animals, especially grouper.

Identification of Bile Salt Hydrolase and Bile Salt Resistance in a Probiotic Bacterium Lactobacillus gasseri JCM1131T

Lactobacillus gasseri is one of the most likely probiotic candidates among many Lactobacillus species. Although bile salt resistance has been defined as an important criterion for selection of probiotic candidates since it allows probiotic bacteria to survive in the gut, both its capability and its related enzyme, bile salt hydrolase (BSH), in L. gasseri is still largely unknown. Here, we report that the well-known probiotic bacterium L. gasseri JCM1131^T possesses BSH activity and bile salt resistance capability. Indeed, this strain apparently showed BSH activity on the plate assay and highly tolerated the primary bile salts and even taurine-conjugated secondary bile salt. We further isolated a putative BSH enzyme (LagBSH) from strain JCM1131^T and characterized the enzymatic function. The purified LagBSH protein exhibited quite high deconjugation activity for taurocholic acid and taurochenodeoxycholic acid. The lagBSH gene was constitutively expressed in strain JCM1131^T, suggesting that LagBSH likely contributes to bile salt resistance of the strain and may be associated with survival capability of strain JCM1131^T within the human intestine by bile detoxification. Thus, this study first demonstrated the bile salt resistance and its responsible enzyme (BSH) activity in strain JCM1131^T, which further supports the importance of the typical lactic acid bacterium as probiotics.

In vitro validation studies for adhesion factor and adhesion efficiency of probiotic Bacillus licheniformis MCC 2514 and Bifidobacterium breve NCIM 5671 on HT-29 cell lines

Probiotic bacterial adhesion to the epithelial cell is a composite process and in vivo adhesion studies can be strengthened with the improved in vitro models for preliminary screening of potentially adherent strains. With this rationale, the study aimed is the first report to demonstrate the colonizing efficiency of probiotic Bacillus licheniformis MCC 2514 in comparison to Bifidobacterium breve NCIM 5671on HT-29 cell line. B. licheniformis (54.28 ± 0.99%) and Bif. breve (70.23 ± 0.85%) adhered in a higher percentage on fibronectin and mucin, respectively. However, the adhesion was higher for B. licheniformis when compared to Bif. breve. In adhesion score, B. licheniformis obtained about 138.85 ± 12.32, whereas Bif. breve got the score of 43.05 ± 9.12. The same trend continued in the adhesion percentage study, where B. licheniformis adhered 75.5 ± 5.2%, higher than Bif. breve which adhered 32.66 ± 3.2%. In invasion assay, both the bacteria significantly decreased the colonization of the pathogen Kocuria rhizophila ATCC 9341 about 97.32 ± 0.81% in the competitive assay, 97.87 ± 0.73% in exclusion assay and 82.19 ± 2.51% in displacement assay. The cytotoxicity effects of the test bacterial strains against HT-29 cell line through MTT assay determined no viability loss in the treated cells. Therefore, the data obtained from the in vitro studies showed that both B. licheniformis and Bif. breve had shown significantly good invasion on pathogen and adhesion capacity on HT-29 cell line.

Probiotic characterization of bacterial strains from fermented South Indian tomato pickle and country chicken intestine having antioxidative and antiproliferative activities

AIM

The present study aims to evaluate the potential antioxidant and antiproliferative properties of probiotic bacterial isolates Weissella cibaria p3B, Bacillus subtilis CS, and Bacillus tequilensis CL, isolated from South Indian fermented tomato pickle (homemade) and gut content of indigenous country chicken.

METHODS AND RESULTS

The bacterial isolates exhibited antimicrobial activity against food-borne, human pathogenic bacteria, along with better survival under different bile and acidic conditions, hydrophobicity towards several hydrocarbons, and adherence to intestinal epithelial cells (INT-407 cells). Also, the intact cell (IC) mixture of the three species showed better DPPH, ABTS, and Fe²⁺ chelating activity as compared to the individual IC or cell extract (CE) activity. Among the three bacterial species, W. cibaria p3B revealed maximum antiproliferative activity against HeLa and Caco-2 cancer cells, all of which were nontoxic to INT-407 cells. Apart from being non-hemolytic, the bacterial isolates did not display any necrotic inhibition in HeLa and Caco-2 cells. The cell free supernatant (CFS) of the three bacterial isolates were tested for the production of antimicrobial peptides or bacteriocins. It found that the CFS of bacterial isolates was stable at various temperature, pH and sensitive to proteolytic enzymes confirms protenoius in nature of the antimicrobil peptides or bacteriocins.

CONCLUSION

The bacterial isolates showed promising antimicrobial, antioxidant as well as antiproliferative activities with better survival ability at different pH and bile concentrations. The three bacterial isolates were able to produce potential antimicrobial peptides or bacteriocins.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results indicate better compatibility of our bacterial isolates against synthetic drugs to avoid adverse side effects and can be processed as dietary supplements against food and human pathogens. They can also provide antioxidative and antiproliferative benefits to humans and animals.

Surfactin Like Broad Spectrum Antimicrobial Lipopeptide Co-produced With Sublancin From Bacillus subtilis Strain A52: Dual Reservoir of Bioactives

An antimicrobial substance producing strain designated as A52 was isolated from a marine sediment sample and identified as Bacillus sp., based on 16S rRNA gene sequence analysis. The ANI and dDDH analysis of the genome sequence displayed high identity with two strains of B. subtilis sub sp. subtilis. Strain A52 yielded two antimicrobial peptides (AMPs) that differed in activity spectrum. MALDI mass spectrometry analysis of HPLC purified fractions revealed mass of peptides as 3881.6 and 1061.9 Da. The antiSMASH analysis of genome sequence unraveled presence of identical biosynthetic cluster involved in production of sublancin from B. subtilis sub sp. subtilis strain 168, which yielded peptide with identical mass. The low molecular weight peptide is found to be a cyclic lipopeptide containing C₁₆ β-hydroxy fatty acid that resembled surfactin-like group of biosurfactants. However, it differed in fatty acid composition and antimicrobial spectrum in comparison to other surfactins produced by strains of B. subtilis. It exhibited broad spectrum antibacterial activity, inhibited growth of pathogenic strains of Candida and filamentous fungi. Further, it exhibited hemolytic activity, but did not show phytotoxic effect in seed germination experiment. The emulgel formulation of surfactin-like lipopeptide showed antimicrobial activity in vitro and did not show any irritation effects in animal studies using BALB/c mice. Moreover, surfactin-like lipopeptide displayed synergistic activity with fluconazole against Candida, indicating its potential for external therapeutic applications.

Tannin-Tolerant and Extracellular Tannase Producing Bacillus Isolated from Traditional Fermented Tea Leaves and Their Probiotic Functional Properties

A total of 117 Bacillus strains were isolated from Miang, a culture relevant fermented tea of northern Thailand. These strains were collected from 16 sampling sites in north Thailand. In this collection 95 isolates were tannin-tolerant Bacillus capable of growth on nutrient agar supplemented with 0.5% (w/v) total tannins from tea leaves extract (TE). The strains were also positive for pectinase, xylanase and amylase activity, while 91 and 86 isolates were positive for cellulase and β-mannanase, respectively. Only 21 isolates producing extracellular tannase were selected for further characterization. Identification by 16S rRNA gene sequence analysis revealed that more than 50% (11 of 21 isolates) were Bacillustequilensis, whereas the remaining were B. siamensis (3), B. megaterium (3), B. aryabhattai (3) and B. toyonensis (1). B. tequilensis K34.2 produced the highest extracellular tannase activity of 0.60 U/mL after cultivation at 37 °C for 48 h. In addition, all 21 isolates were resistant to 0.3% (w/v) bile salt, sensitive to gentamicin, erythromycin, vancomycin and kanamycin and also tolerant to acidic condition. Cell hydrophobicity varied from 9.4 to 80.4% and neutralized culture supernatants of some Bacillus isolates showed bacteriocin producing potentiality against Samonella enterica serovar Typhimurium TISTR 292. All tested probiotic properties indicated that B. tequilensis K19.3, B. tequilensis K34.2 and B. siamensis K19.1 had high probiotic potential. This is the first report describing tannin-tolerant Bacillus and their extracellular tannase producing capability in Miang, a traditional fermented tea of Thailand.

High Throughput Identification of Antimicrobial Peptides from Fish Gastrointestinal Microbiota

Antimicrobial peptides (AMPs) are a group of small peptides, which are secreted by almost all creatures in nature. They have been explored in therapeutic and agricultural aspects as they are toxic to many bacteria. A considerable amount of work has been conducted in analyzing 16S and metagenomics of the gastrointestinal (GI) microbiome of grass carp (Ctenopharyngodon idellus). However, these datasets are still untapped resources. In this present study, a homologous search was performed to predict AMPs from our newly generated metagenome of grass carp. We identified five AMPs with high similarities to previously reported bacterial toxins, such as lantibiotic and class II bacteriocins. In addition, we observed that the top abundant genus in the GI microbiota of the grass carp was generally consistent with the putative AMP-producing strains, which are mainly from Lactobacillales. Furthermore, we constructed the phylogenetic relationship of these putative AMP-producing bacteria existing in the GI of grass carp and some popular commercial probiotics (commonly used for microecologics), demonstrating that they are closely related. Thus, these strains have the potential to be developed into novel microecologics. In a word, we provide a high-throughput way to discover AMPs from fish GI microbiota, which can be developed as alternative pathogen antagonists (toxins) for microecologics or probiotic supplements.

Bacillus As Potential Probiotics: Status, Concerns, and Future Perspectives

Spore-forming bacilli are being explored for the production and preservation of food for many centuries. The inherent ability of production of large number of secretory proteins, enzymes, antimicrobial compounds, vitamins, and carotenoids specifies the importance of bacilli in food chain. Additionally, Bacillus spp. are gaining interest in human health related functional food research coupled with their enhanced tolerance and survivability under hostile environment of gastrointestinal tract. Besides, bacilli are more stable during processing and storage of food and pharmaceutical preparations, making them more suitable candidate for health promoting formulations. Further, Bacillus strains also possess biotherapeutic potential which is connected with their ability to interact with the internal milieu of the host by producing variety of antimicrobial peptides and small extracellular effector molecules. Nonetheless, with proposed scientific evidences, commercial probiotic supplements, and functional foods comprising of Bacillus spp. had not gained much credential in general population, since the debate over probiotic vs pathogen tag of Bacillus in the research and production terrains is confusing consumers. Hence, it’s important to clearly understand the phenotypic and genotypic characteristics of selective beneficial Bacillus spp. and their substantiation with those having GRAS status, to reach a consensus over the same. This review highlights the probiotic candidature of spore forming Bacillus spp. and presents an overview of the proposed health benefits, including application in food and pharmaceutical industry. Moreover, the growing need to evaluate the safety of individual Bacillus strains as well as species on a case by case basis and necessity of more profound analysis for the selection and identification of Bacillus probiotic candidates are also taken into consideration.

Characterization of Bile Salt Hydrolase from Lactobacillus gasseri FR4 and Demonstration of Its Substrate Specificity and Inhibitory Mechanism Using Molecular Docking Analysis

Probiotic bacteria are beneficial to the health of poultry animals, thus are used as alternative candidates for antibiotics used as growth promoters (AGPs). However, they also reduce the body weight gain due to innate bile salt hydrolase (BSH) activity. Hence, the addition of a suitable BSH inhibitor along with the probiotic feed can decrease the BSH activity. In this study, a BSH gene (981 bp) encoding 326-amino acids was identified from the genome of Lactobacillus gasseri FR4 (LgBSH). The LgBSH-encoding gene was cloned and purified using an Escherichia coli BL21 (DE3) expression system, and its molecular weight (37 kDa) was confirmed by SDS-PAGE and a Western blot analysis. LgBSH exhibited greater hydrolysis toward glyco-conjugated bile salts compared to tauro-conjugated bile salts. LgBSH displayed optimal activity at 52°C at a pH of 5.5, and activity was further increased by several reducing agents (DTT), surfactants (Triton X-100 and Tween 80), and organic solvents (isopropanol, butanol, and acetone). Riboflavin and penicillin V, respectively, inhibited LgBSH activity by 98.31 and 97.84%. A homology model of LgBSH was predicted using EfBSH (4WL3) as a template. Molecular docking analysis revealed that the glycocholic acid had lowest binding energy of -8.46 kcal/mol; on the other hand, inhibitors, i.e., riboflavin and penicillin V, had relatively higher binding energies of -6.25 and -7.38 kcal/mol, respectively. Our results suggest that L. gasseri FR4 along with riboflavin might be a potential alternative to AGPs for poultry animals.