A Moonlighting Enolase from Lactobacillus gasseri does not Require Enzymatic Activity to Inhibit Neisseria gonorrhoeae Adherence to Epithelial Cells

Genomic and transcriptomic analysis of Ligilactobacillus salivarius IBB3154-in search of new promoters for vaccine construction

IMPORTANCE

The genome of the strain Ligilactobacillus salivarius IBB3154 was sequenced, and transcriptome analysis was carried out at two different temperatures, allowing the determination of gene expression levels in response to environmental changes (temperature). Genes with higher expression at 42°C were identified. The use of a reporter gene (β- glucuronidase) did not confirm the transcriptomic results; it was found that the promoters of the genes sasA1 and sasA2 were active in the presence of bile salts. This opens up new opportunities for the overexpression of genes of other bacterial species in Ligilactobacillus cells in the intestinal environment.

Proteomic characterization of extracellular vesicles derived from lactic acid bacteria

Lactobacillus species confer health benefits by their metabolites, secreted molecules, and population numbers. Extracellular vesicles (EVs) are nano-sized particles released from cells and mediate intercellular communications. EVs-encapsulated cargos are a crucial key to decide involved biological function. However, little is known about the composition of EVs, leaving mechanisms by which Lactobacillus-derived EVs affect recipient cells remaining unresolved. This study examined the composition of EV proteins from Lactobacillus species by using liquid chromatography coupled with tandem mass spectrometry, including L. plantarum, L. fermentum, and L. gasseri. The major proteins of EVs are associated with biological processes such as catalytic activity, gluco-neogenesis, cell wall organization, and glycolytic processes. Motif enrichment analysis revealed that EVs from L. plantarum and L. fermentum contained proteins with serine-rich motif. This is the first study to report the composition and comparison of EV proteins from Lactobacillus species, providing important information of EVs in functional food products development.

GAPDH Released from Lactobacillus johnsonii MG Enhances Barrier Function by Upregulating Genes Associated with Tight Junctions

Extracellular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has multiple interactions with various gut epithelial components. For instance, GAPDH in Lactobacillus johnsonii MG cells interacts with junctional adhesion molecule-2 (JAM-2) in Caco-2 cells and enhances tight junctions. However, the specificity of GAPDH toward JAM-2 and its role in the tight junctions in Caco-2 cells remain unclear. In the present study, we assessed the effect of GAPDH on tight junction regeneration and explored the GAPDH peptide fragments required for interaction with JAM-2. GAPDH was specifically bound to JAM-2 and rescued H₂O₂-damaged tight junctions in Caco-2 cells, with various genes being upregulated in the tight junctions. To understand the specific amino acid sequence of GAPDH that interacts with JAM-2, peptides interacting with JAM-2 and L. johnsonii MG cells were purified using HPLC and predicted using TOF-MS analysis. Two peptides, namely ¹¹GRIGRLAF¹⁸ at the N-terminus and ³²³SFTCQMVRTLLKFATL³³⁸ at the C-terminus, displayed good interactions and docking with JAM-2. In contrast, the long peptide ⁵²DSTHGTFNHEVSATDDSIVVDGKKYRVYAEPQAQNIPW⁸⁹ was predicted to bind to the bacterial cell surface. Overall, we revealed a novel role of GAPDH purified from L. johnsonii MG in promoting the regeneration of damaged tight junctions and identified the specific sequences of GAPDH involved in JAM-2 binding and MG cell interaction.

Moonlighting proteins: beacon of hope in era of drug resistance in bacteria

Moonlighting proteins (MLPs) are ubiquitous and provide a unique advantage to bacteria performing multiple functions using the same genomic content. Targeting MLPs can be considered as a futuristic approach in fighting drug resistance problem. This review follows the MLP trail from its inception to the present-day state, describing a few bacterial MLPs, viz., glyceraldehyde 3'-phosphate dehydrogenase, phosphoglucose isomerase glutamate racemase (GR), and DNA gyrase. Here, we carve out that targeting MLPs are the beacon of hope in an era of increasing drug resistance in bacteria. Evolutionary stability, structure-functional relationships, protein diversity, possible drug targets, and identification of new drugs against bacterial MLP are given due consideration. Before the final curtain calls, we provide a comprehensive list of small molecules that inhibit the biochemical activity of MLPs, which can aid the development of novel molecules to target MLPs for therapeutic applications.

Lactobacilli extracellular vesicles: potential postbiotics to support the vaginal microbiota homeostasis

Background

Lactobacillus species dominate the vaginal microflora performing a first-line defense against vaginal infections. Extracellular vesicles (EVs) released by lactobacilli are considered mediators of their beneficial effects affecting cellular communication, homeostasis, microbial balance, and host immune system pathways. Up to now, very little is known about the role played by Lactobacillus EVs in the vaginal microenvironment, and mechanisms of action remain poorly understood.

Results

Here, we hypothesized that EVs can mediate lactobacilli beneficial effects to the host by modulating the vaginal microbiota colonization. We recovered and characterized EVs produced by two vaginal strains, namely Lactobacillus crispatus BC5 and Lactobacillus gasseri BC12. EVs were isolated by ultracentrifugation and physically characterized by Nanoparticle Tracking Analysis (NTA) and Dynamic Light Scattering (DLS). EVs protein and nucleic acids (DNA and RNA) content was also evaluated. We explored the role of EVs on bacterial adhesion and colonization, using a cervical cell line (HeLa) as an in vitro model. Specifically, we evaluated the effect of EVs on the adhesion of both vaginal beneficial lactobacilli and opportunistic pathogens (i.e., Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, and Enterococcus faecalis). We demonstrated that EVs from L. crispatus BC5 and L. gasseri BC12 significantly enhanced the cellular adhesion of all tested lactobacilli, reaching the maximum stimulation effect on strains belonging to L. crispatus species (335% and 269% of average adhesion, respectively). At the same time, EVs reduced the adhesion of all tested pathogens, being EVs from L. gasseri BC12 the most efficient.

Conclusions

Our observations suggest for the first time that EVs released by symbiotic Lactobacillus strains favor healthy vaginal homeostasis by supporting the colonization of beneficial species and preventing pathogens attachment. This study reinforces the concept of EVs as valid postbiotics and opens the perspective of developing postbiotics from vaginal strains to maintain microbiota homeostasis and promote women’s health.

Multiple Proteins of Lacticaseibacillus rhamnosus GG Are Involved in the Protection of Keratinocytes From the Toxic Effects of Staphylococcus aureus

We have previously shown that lysates of Lacticaseibacillus rhamnosus GG confer protection to human keratinocytes against Staphylococcus aureus. L. rhamnosus GG inhibits the growth of S. aureus as well as competitively excludes and displaces the pathogen from keratinocytes. In this study, we have specifically investigated the anti-adhesive action. We have tested the hypothesis that this activity is due to quenching of S. aureus binding sites on keratinocytes by molecules within the Lacticaseibacillus lysate. Trypsinisation or heat treatment removed the protective effect of the lysate suggesting the involvement of proteins as effector molecules. Column separation of the lysate and analysis of discrete fractions in adhesion assays identified a fraction of moderate hydrophobicity that possessed all anti-adhesive functions. Immunoblotting demonstrated that this fraction contained the pilus protein, SpaC. Recombinant SpaC inhibited staphylococcal adhesion to keratinocytes in a dose-dependent manner and improved keratinocyte viability following challenge with viable S. aureus. However, SpaC did not confer the full anti-adhesive effects of the LGG lysate and excluded but did not displace S. aureus from keratinocytes. Further purification produced four protein-containing peaks (F1–F4). Of these, F4, which had the greatest column retention time, was the most efficacious in anti-staphylococcal adhesion and keratinocyte viability assays. Identification of proteins by mass spectrometry showed F4 to contain several known “moonlighting proteins”—i.e., with additional activities to the canonical function, including enolase, Triosephosphate isomerase (TPI), Glyceraldehyde 3 phosphate dehydrogenase (G3P) and Elongation factor TU (EF-Tu). Of these, only enolase and TPI inhibited S. aureus adhesion and protected keratinocytes viability in a dose-dependent manner. These data suggest that inhibition of staphylococcal binding by the L. rhamnosus GG lysate is mediated by SpaC and specific moonlight proteins.

Bioprospecting of Ribosomally Synthesized and Post-translationally Modified Peptides Through Genome Characterization of a Novel Probiotic Lactiplantibacillus plantarum UTNGt21A Strain: A Promising Natural Antimicrobials Factory

The present work describes the genome sequencing and characterization of a novel Lactiplantibacillus plantarum strain assigned UTNGt21A isolated from wild Solanum quitoense (L.) fruits. In silico analysis has led to identifying a wide range of biosynthetic gene clusters (BGCs) and metabolic compounds. The genome had a total of 3,558,611 bp with GC of 43.96%, harboring 3,449 protein-coding genes, among which 3,209 were assigned by the EggNOG database, and 240 hypothetical proteins have no match in the BLASTN database. It also contains 68 tRNAs, 1 23S rRNA, 1 16S rRNA, 6 5S rRNA, and 1 tmRNA. In addition, no acquired resistance genes nor virulence and pathogenic factors were predicted, indicating that UTNGt21A is a safe strain. Three areas of interest (AOI) consisting of multiple genes encoding for bacteriocins and ABC transporters were predicted with BAGEL4, while eight secondary metabolite regions were predicted with the antiSMASH web tool. GutSMASH analysis predicted one metabolic gene cluster (MGC) type pyruvate to acetate-formate, a primary metabolite region essential for anaerobe growth. Several lanthipeptides and non-ribosomal peptide synthetase (NRPS) clusters were detected in the UTNGt21A but not the reference genomes, suggesting that their genome diversity might be linked to its niche-specific lineage and adaptation to a specific environment. Moreover, the application of a targeted genome mining tool (RiPPMiner) uncovered a diverse arsenal of important antimicrobial molecules such as lanthipeptides. Furthermore, in vitro analysis indicated that the crude extract (CE) of UTNGt21A exerted a wide spectrum of inhibition against several pathogens. The results indicated that the possible peptide-protein extract (PC) from UTNGt21A induces morphological and ultrastructural changes of Salmonella enterica subsp. enterica ATCC51741, compatible with its inhibitory potential. Genome characterization is the basis for further in vitro and in vivo studies to explore their use as antimicrobial producers or probiotic strains.

Identification of Biomarkers for Systemic Distribution of Nanovesicles From Lactobacillus johnsonii N6.2

The ability of bacterial extracellular vesicles (EV) to transport biological molecules has increased the research to determine their potential as therapeutic agents. In this study, Lactobacillus johnsonii N6.2-derived nanovesicles (NV) were characterized to identify components that may serve as biomarkers in host-microbe interactions. Comparative proteomic and lipidomic analyses of L. johnsonii N6.2 NV and cell membrane (CM) were performed. The lipidomic profiles indicated that both fractions contained similar lipids, however, significant differences were observed in several classes. LC-MS/MS proteomic analysis indicated that NV contained several unique and differentially expressed proteins when compared to the CM. Analysis of Gene Ontology (GO) terms, based on cellular component, showed significant enrichment of proteins in the cytoplasm/intracellular space category for the NV fraction. Based on these results, the proteins T285_RS00825 (named Sdp), Eno3 and LexA were selected for studies of localization and as potential biomarkers for host-microbe interactions. Immunogold staining, followed by scanning and transmission electron microscopy (SEM and TEM, respectively), revealed that Sdp was preferentially localized along the cell wall/membrane, and on NV-like structures surrounding the bacteria. These results were confirmed using immunofluorescence staining in Caco-2 cells incubated with NV. Consequently, we evaluated the potential for NV surface-exposed proteins to generate an immune response in the host. Plasma from individuals administered L. johnsonii N6.2 showed that IgA and IgG antibodies were generated against NV and Sdp domains in vivo. Altogether, these results show that L. johnsonii N6.2 NV have the potential to mediate host interactions through immune modulation.

Identification and characterization of a moonlighting protein-enolase for surface display in Streptococcus thermophilus

Background

Streptococcus thermophilus is an important food starter and receiving more attention to serve as cell factories for production of high-valued metabolites. However, the low yields of intracellular or extracellular expression of biotechnological and biomedical proteins limit its practical applications.

Results

Here, an enolase EnoM was identified from S. thermophilus CGMCC7.179 with about 94% identities to the surface-located enolases from other Streptococcus spp. strains. The EnoM was used as an anchor to achieve surface display in S. thermophilus using GFP as a reporter. After respectively mixing the GFP-EnoM fusion protein or GFP with S. thermophilus cells in vitro, the relative fluorescence units (RFU) of the S. thermophilus cells with GFP-EnoM was 80-folds higher than that with purified GFP. The sharp decrease in the RFU of sodium dodecyl sulfate (SDS) pretreated cells compared to those of non-pretreated cells demonstrated that the membrane proteins were the binding ligand of EnoM. Furthermore, an engineered β-galactosidase (β-Gal) was also successfully displayed on the cell surface of S. thermophilus CGMCC7.179 and the relative activity of the immobilized β-Gal remained up to 64% after reused 8 times. Finally, we also demonstrated that EnoM could be used as an anchor for surface display in L. casei, L. bulgaricus, L. lactis and Leuconostoc lactis.

Conclusion

To our knowledge, EnoM from S. thermophilus was firstly identified as an anchor and successfully achieved surface display in LAB. The EnoM-based surface display system provided a novel strategy for the enzyme immobilization.

Lactobacillus crispatus and its enolase and glutamine synthetase influence interactions between Neisseria gonorrhoeae and human epithelial cells

Neisseria gonorrhoeae, an obligatory human pathogen causes the sexually transmitted disease gonorrhea, which remains a global health problem. N. gonorrhoeae primarily infects the mucosa of the genitourinary tract, which in women, is colonized by natural microbiota, dominated by Lactobacillus spp., that protect human cells against pathogens. In this study, we demonstrated that precolonization of human epithelial cells with Lactobacillus crispatus, one of the most prevalent bacteria in the female urogenital tract, or preincubation with the L. crispatus enolase or glutamine synthetase impairs the adhesion and invasiveness of N. gonorrhoeae toward epithelial cells, two crucial steps in gonococcal pathogenesis. Furthermore, decreased expression of genes encoding the proinflam-matory cytokines, TNFα and CCL20, which are secreted as a consequence of N. gonorrhoeae infection, was observed in N. gonorrhoeae-infected epithelial cells that had been preco-lonized with L. crispatus or preincubated with enolase and glutamine synthetase. Thus, our results indicate that the protection of human cells against N. gonorrhoeae infection is a complex process and that L. crispatus and its proteins enolase and glutamine synthetase can have a potential role in protecting epithelial cells against gonococcal infection. Therefore, these results are important since disturbances of the micro-biota or of its proteins can result in dysbiosis, which is associated with increased susceptibility of epithelium to pathogens.

Extracellular vesicles from symbiotic vaginal lactobacilli inhibit HIV-1 infection of human tissues

The vaginal microbiota, dominated by Lactobacillus spp., plays a key role in preventing HIV-1 transmission. Here, we investigate whether the anti-HIV effect of lactobacilli is mediated by extracellular vesicles (EVs) released by these bacteria. Human cervico-vaginal and tonsillar tissues ex vivo, and cell lines were infected with HIV-1 and treated with EVs released by lactobacilli isolated from vaginas of healthy women. EVs released by L. crispatus BC3 and L. gasseri BC12 protect tissues ex vivo and isolated cells from HIV-1 infection. This protection is associated with a decrease of viral attachment to target cells and viral entry due to diminished exposure of Env that mediates virus-cell interactions. Inhibition of HIV-1 infection is associated with the presence in EVs of several proteins and metabolites. Our findings demonstrate that the protective effect of Lactobacillus against HIV-1 is, in part, mediated by EVs released by these symbiotic bacteria. If confirmed in vivo, this finding may lead to new strategies to prevent male-to-female sexual HIV-1 transmission.

Lactobacillus associates with vaginal protection from HIV-1 infection. Here, the authors show that lactobacilli extracellular vesicles contain bacterial proteins and metabolites that inhibit HIV-1 infection in T cells and in human cervico-vaginal and tonsillar tissues ex vivo via altering viral Env proteins.

Selective Inhibition of Neisseria gonorrhoeae by a Dithiazoline in Mixed Infections with Lactobacillus gasseri

The Gram-negative human pathogen Neisseria gonorrhoeae has progressively developed resistance to antibiotic monotherapies, and recent failures of dual-drug therapy have heightened concerns that strains resistant to all available antibiotics will begin circulating globally. Targeting bacterial cell wall assembly has historically been effective at treating infections with N. gonorrhoeae, but as the effectiveness of β-lactams (including cephalosporins) is challenged by increasing resistance, research has expanded into compounds that target the numerous other enzymes with roles in peptidoglycan metabolism. One example is the dithiazoline compound JNJ-853346 (DTZ), which inhibits the activity of an Escherichia coli serine protease l,d-carboxypeptidase (LdcA). Recently, the characterization of an LdcA homolog in N. gonorrhoeae revealed localization and activity differences from the characterized E. coli LdcA, prompting us to explore the effectiveness of DTZ against N. gonorrhoeae We found that DTZ is effective at inhibiting N. gonorrhoeae in all growth phases, unlike the specific stationary-phase inhibition seen in E. coli Surprisingly, DTZ does not inhibit gonococcal LdcA enzyme activity, and DTZ sensitivity is not significantly decreased in ldcA mutants. While effective against numerous N. gonorrhoeae strains, including recent multidrug-resistant isolates, DTZ is much less effective at inhibiting growth of the commensal species Lactobacillus gasseri DTZ treatment during coinfections of epithelial cells resulted in significant lowering of gonococcal burden and interleukin-8 secretion without significantly impacting recovery of viable L. gasseri This selective toxicity presents a possible pathway for the use of DTZ as an effective antigonococcal agent at concentrations that do not impact vaginal commensals.

Enolase, a plasminogen receptor isolated from salivary gland transcriptome of the ixodid tick Haemaphysalis flava

Enolase, a multifunctional protein, is shown to act as a plasminogen receptor that contributes to fibrinolysis, which plays an important role in preventing the formation of blood clots during tick feeding. The study of enolase genes provides opportunities to develop a potential antigen target for tick control. So far, enolase has been identified in only a few species of ticks. Knowledge of the exact mechanisms of plasminogen activation and fibrinolysis by enolase as a plasminogen receptor is limited. Here, we cloned the enolase full-length complementary DNA (cDNA) from the salivary glands of Haemaphysalis flava, expressed it, and analyzed the function of the recombinant H. flava enolase. The enolase cDNA was 1988 bp in length and encoded 433 amino acid residues. It contained two domains and some highly conserved functional motifs including an assumed membrane re-association region "AAVPSGASTGI." The enolase exhibited 83.3 % amino acid similarity to that of the putative enolase of Ixodes ricinus, and 85 % to that of Ornithodoros moubata enolase. After eukaryotic expression in insect cells, Western blot analysis showed that the mouse antiserum against the hexahistidine-tagged recombinant enolase protein recognized a band of approximately 48 kDa. The recombinant enolase bound human plasminogen in a dose-dependent manner and enhanced plasminogen activation in the presence of host tissue plasminogen activator (t-PA), most probably to promote fibrinolysis and maintain blood flow at the host-tick interface. Real-time quantitative polymerase chain reaction (qPCR) analysis showed that the expression level of enolase in salivary glands was significantly higher than in other tested tissues. Although the enolase was expressed in all developmental stages, it had the highest expression in the rapid blood feeding period of ticks. These findings indicate that the enolase might play an important role in blood feeding of H. flava.