Lactobacillus reuteri 100-23 Modulates Urea Hydrolysis in the Murine Stomach

ABSTRACTComparisons ofin vivo(mouse stomach) andin vitro(laboratory culture) transcriptomes ofLactobacillus reuteristrain 100-23 were made by microarray analysis. These comparisons revealed the upregulation of genes associated with acid tolerance, including urease production, in the mouse stomach. Inactivation of theureCgene reduced the acid tolerance of strain 100-23in vitro, and the mutant was outcompeted by the wild type in the gut of ex-Lactobacillus-free mice. Urine analysis showed that stable isotope-labeled urea, administered by gavage, was metabolized to a greater extent inLactobacillus-free mice than animals colonized by strain 100-23. This surprising observation was associated with higher levels of urease activity and fecal-type bacteria in the stomach digesta ofLactobacillus-free mice. Despite the modulation of urea hydrolysis in the stomach, recycling of urea nitrogen in the murine host was not affected since the essential amino acid isoleucine, labeled with a stable isotope, was detected in the livers of bothLactobacillus-free and 100-23-colonized animals. Therefore, our experiments reveal a new and unexpected impact ofLactobacilluscolonization on urea hydrolysis in the murine gut.

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Genes Involved in Galactooligosaccharide Metabolism in Lactobacillus reuteri and Their Ecological Role in the Gastrointestinal Tract

Applied and Environmental Microbiology ◽

10.1128/aem.01788-19 ◽

2019 ◽

Vol 85 (22) ◽

Cited By ~ 3

Author(s):

Monchaya Rattanaprasert ◽

Jan-Peter van Pijkeren ◽

Amanda E. Ramer-Tait ◽

Maria Quintero ◽

Car Reen Kok ◽

...

Keyword(s):

Type Strain ◽

Wild Type Strain ◽

Lactobacillus Reuteri ◽

Selective Advantage ◽

Wild Type ◽

Carbohydrate Source ◽

Content Type ◽

Gnotobiotic Mice

ABSTRACT Strains of Lactobacillus reuteri are commonly used as probiotics due to their demonstrated therapeutic properties. Many strains of L. reuteri also utilize the prebiotic galactooligosaccharide (GOS), providing a basis for formulating synergistic synbiotics that could enhance growth or persistence of this organism in vivo. In this study, in-frame deletion mutants were constructed to characterize the molecular basis of GOS utilization in L. reuteri ATCC PTA-6475. Results suggested that GOS transport relies on a permease encoded by lacS, while a second unidentified protein may function as a galactoside transporter. Two β-galactosidases, encoded by lacA and lacLM, sequentially degrade GOS oligosaccharides and GOS disaccharides, respectively. Inactivation of lacL and lacM resulted in impaired growth in the presence of GOS and lactose. In vitro competition experiments between the wild-type and ΔlacS ΔlacM strains revealed that the GOS-utilizing genes conferred a selective advantage in media with GOS but not glucose. GOS also provided an advantage to the wild-type strain in experiments in gnotobiotic mice but only on a purified, no sucrose diet. Differences in cell numbers between GOS-fed mice and mice that did not receive GOS were small, suggesting that carbohydrates other than GOS were sufficient to support growth. On a complex diet, the ΔlacS ΔlacM strain was outcompeted by the wild-type strain in gnotobiotic mice, suggesting that lacL and lacM are involved in the utilization of alternative dietary carbohydrates. Indeed, the growth of the mutants was impaired in raffinose and stachyose, which are common in plants, demonstrating that α-galactosides may constitute alternate substrates of the GOS pathway. IMPORTANCE This study shows that lac genes in Lactobacillus reuteri encode hydrolases and transporters that are necessary for the metabolism of GOS, as well as α-galactoside substrates. Coculture experiments with the wild-type strain and a gos mutant clearly demonstrated that GOS utilization confers a growth advantage in medium containing GOS as the sole carbohydrate source. However, the wild-type strain also outcompeted the mutant in germfree mice, suggesting that GOS genes in L. reuteri also provide a basis for utilization of other carbohydrates, including α-galactosides, ordinarily present in the diets of humans and other animals. Collectively, our work provides information on the metabolism of L. reuteri in its natural niche in the gut and may provide a basis for the development of synbiotic strategies.

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Draft Genome Sequence of Lactobacillus reuteri CECT8605

Genome Announcements ◽

10.1128/genomea.00297-17 ◽

2017 ◽

Vol 5 (18) ◽

Author(s):

Ana I. Sañudo ◽

Mónica M. Olivares ◽

Oscar Bañuelos

Keyword(s):

Genome Sequence ◽

Genetic Stability ◽

Lactobacillus Reuteri ◽

Draft Genome ◽

Human Consumption ◽

Probiotic Properties ◽

Content Type ◽

General Aspects

ABSTRACT Lactobacillus reuteri CECT8605 has shown potential probiotic properties in both in vitro and in vivo assays. Besides its beneficial characteristics, general aspects concerning genetic stability and safety for human consumption have been studied. Its genome sequence has been a useful tool to support preliminary conclusions based on empirical observations.

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Uptake and Metabolism ofN-Acetylglucosamine and Glucosamine by Streptococcus mutans

Applied and Environmental Microbiology ◽

10.1128/aem.00820-14 ◽

2014 ◽

Vol 80 (16) ◽

pp. 5053-5067 ◽

Cited By ~ 39

Author(s):

Zachary D. Moye ◽

Robert A. Burne ◽

Lin Zeng

Keyword(s):

Streptococcus Mutans ◽

De Novo ◽

Dominant Role ◽

Acid Tolerance ◽

Amino Sugars ◽

Phosphotransferase System ◽

Pathogenic Potential ◽

Content Type

ABSTRACTGlucosamine andN-acetylglucosamine are among the most abundant sugars on the planet, and their introduction into the oral cavity via the diet and host secretions, and through bacterial biosynthesis, provides oral biofilm bacteria with a source of carbon, nitrogen, and energy. In this study, we demonstrated that the dental caries pathogenStreptococcus mutanspossesses an inducible system for the metabolism ofN-acetylglucosamine and glucosamine. These amino sugars are transported by the phosphoenolpyruvate:sugar phosphotransferase system (PTS), with the glucose/mannose enzyme II permease encoded bymanLMNplaying a dominant role. Additionally, a previously uncharacterized gene product encoded downstream of themanLMNoperon, ManO, was shown to influence the efficiency of uptake and growth onN-acetylglucosamine and, to a lesser extent, glucosamine. A transcriptional regulator, designated NagR, was able to bind the promoter regionsin vitro, and repress the expressionin vivo, of thenagAandnagBgenes, encodingN-acetylglucosamine-6-phosphate deacetylase and glucosamine-6-phosphate deaminase, respectively. The binding activity of NagR could be inhibited by glucosamine-6-phosphatein vitro. Importantly, in contrast to the case with certain otherFirmicutes, the gene forde novosynthesis of glucosamine-6-phosphate inS. mutans,glmS, was also shown to be regulated by NagR, and NagR could bind theglmSpromoter regionin vitro. Finally, metabolism of these amino sugars byS. mutansresulted in the production of significant quantities of ammonia, which can neutralize cytoplasmic pH and increase acid tolerance, thus contributing to enhanced persistence and pathogenic potential.

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Exploiting Prophage-Mediated Lysis for Biotherapeutic Release byLactobacillus reuteri

Applied and Environmental Microbiology ◽

10.1128/aem.02335-18 ◽

2019 ◽

Vol 85 (10) ◽

Cited By ~ 3

Author(s):

Laura M. Alexander ◽

Jee-Hwan Oh ◽

Donald S. Stapleton ◽

Kathryn L. Schueler ◽

Mark P. Keller ◽

...

Keyword(s):

Recombinant Protein ◽

Secretory Pathway ◽

Lactobacillus Reuteri ◽

Gastrointestinal Transit ◽

Biologically Active ◽

Content Type ◽

Extracellular Milieu ◽

Therapeutic Molecules

ABSTRACTLactobacillus reuterihas the potential to be developed as a microbial therapeutic delivery platform because of an established safety profile, health-promoting properties, and available genome editing tools. Here, we show thatL. reuteriVPL1014 exhibits a low mutation rate compared to other Gram-positive bacteria, which we expect will contribute to the stability of genetically modified strains. VPL1014 encodes two biologically active prophages, which are induced during gastrointestinal transit. We hypothesized that intracellularly accumulated recombinant protein can be released following bacteriophage-mediated lysis. To test this, we engineered VPL1014 to accumulate leptin, our model protein, inside the cell.In vitroprophage induction of recombinant VPL1014 released leptin into the extracellular milieu, which corresponded to bacteriophage production. We also employed a plasmid system that does not require antibiotic in the growth medium for plasmid maintenance. Collectively, these data provide new avenues to exploit native prophages to deliver therapeutic molecules.IMPORTANCELactic acid bacteria (LAB) have been explored as potential biotherapeutic vehicles for the past 20 years. To secrete a therapeutic in the extracellular milieu, one typically relies on the bacterial secretion pathway, i.e., the Sec pathway. Overexpression of a secreted protein can overload the secretory pathway and impact the organism’s fitness, and optimization of the signal peptide is also required to maximize the efficiency of the release of mature protein. Here, we describe a previously unexplored approach to release therapeutics from the probioticLactobacillus reuteri. We demonstrate that an intracellularly accumulated recombinant protein is released following prophage activation. Since we recently demonstrated that prophages are activated during gastrointestinal transit, we propose that this method will provide a straightforward and efficient approach to deliver therapeuticsin vivo.

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Xylitol enhances synthesis of propionate in the colon via cross-feeding of gut microbiota

Microbiome ◽

10.1186/s40168-021-01029-6 ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Shasha Xiang ◽

Kun Ye ◽

Mian Li ◽

Jian Ying ◽

Huanhuan Wang ◽

...

Keyword(s):

Gut Microbiome ◽

Lactobacillus Reuteri ◽

Carbon Sources ◽

Short Chain Fatty Acids ◽

Microbial Composition ◽

Key Enzymes ◽

Rrna Sequencing ◽

Phosphate Acetyltransferase

Abstract Background Xylitol, a white or transparent polyol or sugar alcohol, is digestible by colonic microorganisms and promotes the proliferation of beneficial bacteria and the production of short-chain fatty acids (SCFAs), but the mechanism underlying these effects remains unknown. We studied mice fed with 0%, 2% (2.17 g/kg/day), or 5% (5.42 g/kg/day) (weight/weight) xylitol in their chow for 3 months. In addition to the in vivo digestion experiments in mice, 3% (weight/volume) (0.27 g/kg/day for a human being) xylitol was added to a colon simulation system (CDMN) for 7 days. We performed 16S rRNA sequencing, beneficial metabolism biomarker quantification, metabolome, and metatranscriptome analyses to investigate the prebiotic mechanism of xylitol. The representative bacteria related to xylitol digestion were selected for single cultivation and co-culture of two and three bacteria to explore the microbial digestion and utilization of xylitol in media with glucose, xylitol, mixed carbon sources, or no-carbon sources. Besides, the mechanisms underlying the shift in the microbial composition and SCFAs were explored in molecular contexts. Results In both in vivo and in vitro experiments, we found that xylitol did not significantly influence the structure of the gut microbiome. However, it increased all SCFAs, especially propionate in the lumen and butyrate in the mucosa, with a shift in its corresponding bacteria in vitro. Cross-feeding, a relationship in which one organism consumes metabolites excreted by the other, was observed among Lactobacillus reuteri, Bacteroides fragilis, and Escherichia coli in the utilization of xylitol. At the molecular level, we revealed that xylitol dehydrogenase (EC 1.1.1.14), xylulokinase (EC 2.7.1.17), and xylulose phosphate isomerase (EC 5.1.3.1) were key enzymes in xylitol metabolism and were present in Bacteroides and Lachnospiraceae. Therefore, they are considered keystone bacteria in xylitol digestion. Also, xylitol affected the metabolic pathway of propionate, significantly promoting the transcription of phosphate acetyltransferase (EC 2.3.1.8) in Bifidobacterium and increasing the production of propionate. Conclusions Our results revealed that those key enzymes for xylitol digestion from different bacteria can together support the growth of micro-ecology, but they also enhanced the concentration of propionate, which lowered pH to restrict relative amounts of Escherichia and Staphylococcus. Based on the cross-feeding and competition among those bacteria, xylitol can dynamically balance proportions of the gut microbiome to promote enzymes related to xylitol metabolism and SCFAs.

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Exogenous Alginate Protects Staphylococcus aureus from Killing by Pseudomonas aeruginosa

Journal of Bacteriology ◽

10.1128/jb.00559-19 ◽

2019 ◽

Vol 202 (8) ◽

Cited By ~ 2

Author(s):

Courtney E. Price ◽

Dustin G. Brown ◽

Dominique H. Limoli ◽

Vanessa V. Phelan ◽

George A. O’Toole

Keyword(s):

Staphylococcus Aureus ◽

Pseudomonas Aeruginosa ◽

Physical Space ◽

Late Time ◽

Protective Effects ◽

Content Type ◽

Alginate Production ◽

The Impact

ABSTRACT Cystic fibrosis (CF) patients chronically infected with both Pseudomonas aeruginosa and Staphylococcus aureus have worse health outcomes than patients who are monoinfected with either P. aeruginosa or S. aureus. We showed previously that mucoid strains of P. aeruginosa can coexist with S. aureus in vitro due to the transcriptional downregulation of several toxic exoproducts typically produced by P. aeruginosa, including siderophores, rhamnolipids, and HQNO (2-heptyl-4-hydroxyquinoline N-oxide). Here, we demonstrate that exogenous alginate protects S. aureus from P. aeruginosa in both planktonic and biofilm coculture models under a variety of nutritional conditions. S. aureus protection in the presence of exogenous alginate is due to the transcriptional downregulation of pvdA, a gene required for the production of the iron-scavenging siderophore pyoverdine as well as the downregulation of the PQS (Pseudomonas quinolone signal) (2-heptyl-3,4-dihydroxyquinoline) quorum sensing system. The impact of exogenous alginate is independent of endogenous alginate production. We further demonstrate that coculture of mucoid P. aeruginosa with nonmucoid P. aeruginosa strains can mitigate the killing of S. aureus by the nonmucoid strain of P. aeruginosa, indicating that the mechanism that we describe here may function in vivo in the context of mixed infections. Finally, we investigated a panel of mucoid clinical isolates that retain the ability to kill S. aureus at late time points and show that each strain has a unique expression profile, indicating that mucoid isolates can overcome the S. aureus-protective effects of mucoidy in a strain-specific manner. IMPORTANCE CF patients are chronically infected by polymicrobial communities. The two dominant bacterial pathogens that infect the lungs of CF patients are P. aeruginosa and S. aureus, with ∼30% of patients coinfected by both species. Such coinfected individuals have worse outcomes than monoinfected patients, and both species persist within the same physical space. A variety of host and environmental factors have been demonstrated to promote P. aeruginosa-S. aureus coexistence, despite evidence that P. aeruginosa kills S. aureus when these organisms are cocultured in vitro. Thus, a better understanding of P. aeruginosa-S. aureus interactions, particularly mechanisms by which these microorganisms are able to coexist in proximal physical space, will lead to better-informed treatments for chronic polymicrobial infections.

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In Vitro Synergy and In Vivo Activity of Tigecycline-Ciprofloxacin Combination Therapy against Vibrio vulnificus Sepsis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00310-19 ◽

2019 ◽

Vol 63 (10) ◽

Author(s):

Seong Eun Kim ◽

Hee Kyung Kim ◽

Su-Mi Choi ◽

Yohan Yu ◽

Uh Jin Kim ◽

...

Keyword(s):

Survival Rate ◽

Mortality Rate ◽

Combination Therapy ◽

Combination Treatment ◽

Vibrio Vulnificus ◽

Antibiotic Regimen ◽

Content Type ◽

Time Kill

ABSTRACT The mortality rate associated with Vibrio vulnificus sepsis remains high. An in vitro time-kill assay revealed synergism between tigecycline and ciprofloxacin. The survival rate was significantly higher in mice treated with tigecycline plus ciprofloxacin than in mice treated with cefotaxime plus minocycline. Thus, combination treatment with tigecycline-ciprofloxacin may be an effective novel antibiotic regimen for V. vulnificus sepsis.

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ZN148 Is a Modular Synthetic Metallo-β-Lactamase Inhibitor That Reverses Carbapenem Resistance in Gram-Negative Pathogens In Vivo

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02415-19 ◽

2020 ◽

Vol 64 (6) ◽

Cited By ~ 3

Author(s):

Ørjan Samuelsen ◽

Ove Alexander Høgmoen Åstrand ◽

Christopher Fröhlich ◽

Adam Heikal ◽

Susann Skagseth ◽

...

Keyword(s):

Active Site ◽

Therapeutic Potential ◽

Treatment Options ◽

Carbapenem Resistance ◽

Functional Space ◽

Bactericidal Effect ◽

Gram Negative ◽

Content Type

ABSTRACT Carbapenem-resistant Gram-negative pathogens are a critical public health threat and there is an urgent need for new treatments. Carbapenemases (β-lactamases able to inactivate carbapenems) have been identified in both serine β-lactamase (SBL) and metallo-β-lactamase (MBL) families. The recent introduction of SBL carbapenemase inhibitors has provided alternative therapeutic options. Unfortunately, there are no approved inhibitors of MBL-mediated carbapenem-resistance and treatment options for infections caused by MBL-producing Gram-negatives are limited. Here, we present ZN148, a zinc-chelating MBL-inhibitor capable of restoring the bactericidal effect of meropenem and in vitro clinical susceptibility to carbapenems in >98% of a large international collection of MBL-producing clinical Enterobacterales strains (n = 234). Moreover, ZN148 was able to potentiate the effect of meropenem against NDM-1-producing Klebsiella pneumoniae in a murine neutropenic peritonitis model. ZN148 showed no inhibition of the human zinc-containing enzyme glyoxylase II at 500 μM, and no acute toxicity was observed in an in vivo mouse model with cumulative dosages up to 128 mg/kg. Biochemical analysis showed a time-dependent inhibition of MBLs by ZN148 and removal of zinc ions from the active site. Addition of exogenous zinc after ZN148 exposure only restored MBL activity by ∼30%, suggesting an irreversible mechanism of inhibition. Mass-spectrometry and molecular modeling indicated potential oxidation of the active site Cys221 residue. Overall, these results demonstrate the therapeutic potential of a ZN148-carbapenem combination against MBL-producing Gram-negative pathogens and that ZN148 is a highly promising MBL inhibitor that is capable of operating in a functional space not presently filled by any clinically approved compound.

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Arsenic Directly Binds to and Activates the Yeast AP-1-Like Transcription Factor Yap8

Molecular and Cellular Biology ◽

10.1128/mcb.00842-15 ◽

2015 ◽

Vol 36 (6) ◽

pp. 913-922 ◽

Cited By ~ 17

Author(s):

Nallani Vijay Kumar ◽

Jianbo Yang ◽

Jitesh K. Pillai ◽

Swati Rawat ◽

Carlos Solano ◽

...

Keyword(s):

Transcription Factor ◽

Transcriptional Activation ◽

Transcriptional Response ◽

Transcriptional Regulator ◽

Yeast Protein ◽

Content Type ◽

Arsenic Tolerance ◽

Arsenic Sensing

The AP-1-like transcription factor Yap8 is critical for arsenic tolerance in the yeastSaccharomyces cerevisiae. However, the mechanism by which Yap8 senses the presence of arsenic and activates transcription of detoxification genes is unknown. Here we demonstrate that Yap8 directly binds to trivalent arsenite [As(III)]in vitroandin vivoand that approximately one As(III) molecule is bound per molecule of Yap8. As(III) is coordinated by three sulfur atoms in purified Yap8, and our genetic and biochemical data identify the cysteine residues that form the binding site as Cys132, Cys137, and Cys274. As(III) binding by Yap8 does not require an additional yeast protein, and Yap8 is regulated neither at the level of localization nor at the level of DNA binding. Instead, our data are consistent with a model in which a DNA-bound form of Yap8 acts directly as an As(III) sensor. Binding of As(III) to Yap8 triggers a conformational change that in turn brings about a transcriptional response. Thus, As(III) binding to Yap8 acts as a molecular switch that converts inactive Yap8 into an active transcriptional regulator. This is the first report to demonstrate how a eukaryotic protein couples arsenic sensing to transcriptional activation.

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Surface-Engineered Dendrimeric Nanoconjugates for Macrophage-Targeted Delivery of Amphotericin B: Formulation Development andIn VitroandIn VivoEvaluation

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04213-14 ◽

2015 ◽

Vol 59 (5) ◽

pp. 2479-2487 ◽

Cited By ~ 40

Author(s):

Keerti Jain ◽

Ashwni Kumar Verma ◽

Prabhat Ranjan Mishra ◽

Narendra Kumar Jain

Keyword(s):

Drug Release ◽

Amphotericin B ◽

Human Erythrocytes ◽

Antileishmanial Activity ◽

Cell Uptake ◽

Antiparasitic Activity ◽

Content Type ◽

Drug Localization

ABSTRACTThe present study aimed to develop an optimized dendrimeric delivery system for amphotericin B (AmB). Fifth-generation (5.0G) poly(propylene imine) (PPI) dendrimers were synthesized, conjugated with mannose, and characterized by use of various analytical techniques, including Fourier transform infrared spectroscopy (FTIR),1H nuclear magnetic resonance (1H-NMR) spectroscopic analysis, and atomic force microscopy (AFM). Mannose-conjugated 5.0G PPI (MPPI) dendrimers were loaded with AmB and evaluated for drug loading efficiency,in vitrodrug release profile, stability, hemolytic toxicity to human erythrocytes, cytotoxicity to and cell uptake by J774A.1 macrophage cells, antiparasitic activity against intracellularLeishmania donovaniamastigotes,in vivopharmacokinetic and biodistribution profiles, drug localization index, toxicity, and antileishmanial activity. AFM showed the nanometric size of the MPPI dendrimers, with a nearly globular architecture. The conjugate showed a good entrapment efficiency for AmB, along with pH-sensitive drug release. Highly significant reductions in toxicity toward human erythrocytes and macrophage cells, without compromising the antiparasitic activity of AmB, were observed. The dendrimeric formulation of AmB showed a significant enhancement of the parasiticidal activity of AmB toward intramacrophagicL. donovaniamastigotes. In thein vitrocell uptake studies, the formulation showed selectivity toward macrophages, with significant intracellular uptake. Further pharmacokinetic and organ distribution studies elucidated the controlled delivery behavior of the formulation. The drug localization index was found to increase significantly in macrophage-rich organs.In vivostudies showed a biocompatible behavior of MPPIA, with negligible toxicity even at higher doses, and promising antileishmanial activity. From the results, we concluded that surface-engineered dendrimers may serve as optimized delivery vehicles for AmB with enhanced activity and low or negligible toxicity.

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