Feeding on lactic acid bacteria isolated from food extends the lifespan of Caenorhabditis elegans.

Lactic acid bacteria (LAB) contribute to human health, and LAB functionality has been studied using Caenorhabditis elegans as an alternative host. However, many studies have focused on the efficacy of a single strain of LAB, and few reports have compared various LAB strains. In this study, we examined the effects of 15 strains of LAB isolated from vegetables, meat, and fermented foods on nematode longevity and healthy lifespan. To reduce the frequency of laborious survival observations, we performed a lifespan assay on agar plates containing 2'-deoxy-5-fluorouridine (FUdR), which inhibits egg hatching and prevents generation mixing. Four beneficial strains showed significant lifespan extension and increased spontaneous nematode mobility, regardless of treatment with or without FUdR and the frequency of survival observation. These results suggested increased longevity and an extended healthy lifespan, confirming the reliability of our method. The four strains are expected to show anti-ageing effects besides longevity and have effects on age-related degenerative diseases. Our labor-saving method can be used as an alternative to conventional methods and enable simultaneous screening of multiple strains. Future research could explore factors contributing to lifespan regulation by comparing and verifying differential strain effects on lifespan.

Impacts of Bacillus subtilis var. natto on the lifespan and stress resistance of Caenorhabditis elegans.

AIM: Bacillus subtilis var. natto is used in the production of natto, a typical Japanese fermented soybean food. Although the probiotic attributes and health-related effects of B. subtilis var. natto have been reported, the effect on longevity remains unknown. In the present study, the effects of B. subtilis var. natto strains on lifespan extension and the molecular mechanisms governing the prolongevity were examined using Caenorhabditis elegans as a model animal. METHODS AND RESULTS: Synchronized 3-day-old (young adult) worms were fed Escherichia coli OP50 (control) or a subcloned isolate of B. subtilis var. natto Miyagino strain (MI-OMU01) and subjected to lifespan, survival against pathogens and abiotic stress resistance assays. Notably, the lifespan of worms fed MI-OMU01 was significantly longer than that of the animals fed OP50. Moreover, MI-OMU01 increased the resistance of C. elegans to several stressors, including UV irradiation, H2O2, and Cu2+. CONCLUSIONS: Genetic and gene expression analyses using mutant animals suggested that MI-OMU01 extended the lifespan of worms in TIR-1/SARM, p38 MAPK, and insulin/IGF-1 signaling pathway-dependent manners.

Metolazone upregulates mitochondrial chaperones and extends lifespan in Caenorhabditis elegans.

Accumulating studies have argued that the mitochondrial unfolded protein response (UPRmt) is a mitochondrial stress response that promotes longevity in model organisms. In the present study, we screened an off-patent drug library to identify compounds that activate UPRmt using a mitochondrial chaperone hsp-6::GFP reporter system in Caenorhabditis elegans. Metolazone, a diuretic primarily used to treat congestive heart failure and high blood pressure, was identified as a prominent hit as it upregulated hsp-6::GFP and not the endoplasmic reticulum chaperone hsp-4::GFP. Furthermore, metolazone specifically induced the expression of mitochondrial chaperones in the HeLa cell line. Metolazone also extended the lifespan of worms in a atfs-1 and ubl-5-dependent manner. Notably, metolazone failed to increase lifespan in worms with knocked-down nkcc-1. These results suggested that metolazone activates the UPRmt across species and prolongs the lifespan of C. elegans.

Impacts of Endocrine Disruptor di-n-Butyl Phthalate Ester on Microalga Chlorella vulgaris Verified by Approaches of Proteomics and Gene Ontology.

Di-n-butyl phthalate (DBP) is an extensively used plasticizer. Most investigations on DBP have been concentrated on its environmental distribution and toxicity to humans. However, information on the effects of plasticizers on algal species is scarce. This study verified the impacts of endocrine disruptor di-n-butyl phthalate ester on microalga Chlorella vulgaris by approaches of proteomics and gene ontology. The algal acute biotoxicity results showed that the 24h-EC50 of DBP for C. vulgaris was 4.95 mg L-1, which caused a decrease in the chlorophyll a content and an increase in the DBP concentration of C. vulgaris. Proteomic analysis led to the identification of 1257 C. vulgaris proteins. Sixty-one more proteins showed increased expression, compared to proteins with decreased expression. This result illustrates that exposure to DBP generally enhances protein expression in C. vulgaris. GO annotation showed that both acetolactate synthase (ALS) and GDP-L-fucose synthase 2 (GER2) decreased more than 1.5-fold after exposure to DBP. These effects could inhibit both the valine biosynthetic process and the nucleotide-sugar metabolic process in C. vulgaris. The results of this study demonstrate that DBP could inhibit growth and cause significant changes to the biosynthesis-relevant proteins in C. vulgaris.

Diffusely Adherent Escherichia coli Strains Isolated from Healthy Carriers Suppress Cytokine Secretions of Epithelial Cells Stimulated by Inflammatory Substances.

Diarrheagenicity of diffusely adherent Escherichia coli (DAEC) remains controversial. Previously, we found that motile DAEC strains isolated from diarrheal patients induced high levels of interleukin 8 (IL-8) secretion via Toll-like receptor 5 (TLR5). However, DAEC strains from healthy carriers hardly induced IL-8 secretion, irrespective of their possessing flagella. In this study, we demonstrated that SK1144, a DAEC strain from a healthy carrier, suppressed IL-8 and IL-6 secretion from human epithelial cell lines. Suppression of IL-8 in human embryonic kidney (HEK293) cells that were transformed to express TLR5 was observed not only upon inflammatory stimulation by flagellin but also in response to tumor necrosis factor alpha (TNF-α) and phorbol myristate acetate (PMA), despite the fact that the TNF-α- and PMA-induced inflammatory pathways reportedly are not TLR5 mediated. SK1144 neither decreased IL-8 transcript accumulation nor increased intracellular retention of IL-8. No suppression was observed when the bacteria were cultured in Transwell cups above the epithelial cells; however, a nonadherent bacterial mutant (lacking the afimbrial adhesin gene) still inhibited IL-8 secretion. Direct contact between the bacteria and epithelial cells was necessary, but diffuse adhesion was dispensable for the inhibitory effects. Infection in the presence of chloramphenicol did not suppress cytokine release by the epithelial cells, suggesting that suppression depended on effectors synthesized de novo Inflammatory suppression was attenuated with infection by a bacterial mutant deleted for hcp (encoding a component of a type VI secretion system). In conclusion, DAEC strains from healthy carriers impede epithelial cell cytokine secretion, possibly by interfering with translation via the type VI secretion system.

Host Range-Associated Clustering Based on Multilocus Variable-Number Tandem-Repeat Analysis, Phylotypes, and Virulence Genes of Atypical Enteropathogenic Escherichia coli Strains.

Atypical enteropathogenic Escherichia coli (aEPEC) strains (36 Japanese and 50 Bangladeshi) obtained from 649 poultry fecal samples were analyzed by molecular epidemiological methods. Clermont's phylogenetic typing showed that group A was more prevalent (58%, 50/86) than B1 (31%, 27/86). Intimin type ß1, which is prevalent among human diarrheal patients, was predominant in both phylogroups B1 (81%, 22/27) and A (70%, 35/50). However, about 95% of B1-ß1 strains belonged to virulence group I, and 77% of them were Japanese strains, while 17% (6/35) of A-ß1 strains did. Multilocus variable-number tandem-repeat analysis (MLVA) distributed the strains into 52 distinct profiles, with Simpson's index of diversity (D) at 73%. When the data were combined with those of 142 previous strains from different sources, the minimum spanning tree formed five zones for porcine strains, poultry strains (excluding B1-ß1), strains from healthy humans, bovine and human patient strains, and the B1-ß1 poultry strains. Antimicrobial resistance to nalidixic acid was most common (74%) among the isolates. Sixty-eight percent of them demonstrated resistance to ≥3 antimicrobial agents, and most of them (91%) were from Bangladesh. The strains were assigned into two groups by hierarchical clustering. Correlation matrix analysis revealed that the virulence genes were negatively associated with antimicrobial resistance. The present study suggested that poultry, particularly Japanese poultry, could be another reservoir of aEPEC (phylogroup B1, virulence group I, and intimin type ß1); however, poultry strains seem to be apart from patient strains that were closer to bovine strains. Bangladeshi aEPEC may be less virulent for humans but more resistant to antibiotics.IMPORTANCE Atypical enteropathogenic Escherichia coli (aEPEC) is a diarrheagenic type of E. coli, as it possesses the intimin gene (eae) for attachment and effacement on epithelium. Since aEPEC is ubiquitous even in developed countries, we previously used molecular epidemiological methods to discriminate aEPEC as a human pathogen. The present study assessed poultry as another source of human diarrheagenic aEPEC. Poultry could be the source of aEPEC (phylogroup B1, virulence group I, and intimin type ß1) found among patient strains in Japan. However, the minimum spanning tree (MST) suggested that the strains from Japanese poultry were far from Japanese patient strains compared with the distance between bovine and patient strains. Bangladeshi avian strains seemed to be less diarrheagenic but are hazardous as a source of drug resistance genes.

Sesamin extends lifespan through pathways related to dietary restriction in Caenorhabditis elegans.

PURPOSE: Sesamin, a polyphenolic compound found in sesame seeds, has been reported to exert a variety of beneficial health effects. We have previously reported that sesamin increases the lifespan of Caenorhabditis elegans. In this study, we investigated the molecular mechanisms underlying the longevity effect of sesamin in C. elegans. METHODS: Starting from three days of age, Caenorhabditis elegans animals were fed a standard diet alone or supplemented with sesamin. A C. elegans genome array was used to perform a comprehensive expression analysis. Genes that showed differential expression were validated using real-time PCR. Mutant or RNAi-treated animals were fed sesamin, and the lifespan was determined to identify the genes involved in the longevity effects of sesamin. RESULTS: The microarray analysis revealed that endoplasmic reticulum unfolded protein response-related genes, which have been reported to show decreased expression under conditions of SIR-2.1/Sirtuin 1 (SIRT1) overexpression, were downregulated in animals supplemented with sesamin. Sesamin failed to extend the lifespan of sir-2.1 knockdown animals and of sir-2.1 loss-of-function mutants. Sesamin was also ineffective in bec-1 RNAi-treated animals; bec-1 is a key regulator of autophagy, and is necessary for longevity induced by sir-2.1 overexpression. Furthermore, the heterozygotic mutation of daf-15, which encodes the target of rapamycin (TOR)-binding partner Raptor, abolished lifespan extension by sesamin. Moreover, sesamin did not prolong the lifespan of loss-of-function mutants of aak-2, which encodes the AMP-activated protein kinase (AMPK). CONCLUSIONS: Sesamin extends the lifespan of C. elegans through several dietary restriction-related signaling pathways, including processes requiring SIRT1, TOR, and AMPK.

[Major Vehicles and O-Serogroups in Foodborne Enterotoxigenic Escherichia coli Outbreaks in Japan, and Effective Detection Methods of the Pathogen in Food Associated with An Outbreak].

Enterotoxigenic Escherichia coli (ETEC) is a common pathogen in developing countries, and causes foodborne infections through contaminated vegetables and water. ETEC also caused some foodborne infections in developed countries, though the vehicles are often unclear. We analyzed ETEC foodborne outbreaks in Japan based on the National Food Poisoning Statistics. Vegetables and private well water accounted for 50% and 22.2% of vehicles, respectively. The main vehicles were similar to those in developing countries. Serogroups of ETEC were also analyzed, and O6, O25, O27, O148, O153, O159, and O169 were the seven major O-serogroups. We investigated suitable detection methods for the pathogen (O148) in food samples associated with an outbreak of ETEC in Japan in 2011. We show that ETEC O148 could be effectively detected in cut leeks by means of a two-step enrichment and real-time PCR assay targeting heat-stable enterotoxin gene. Our survey of the vehicles and the major O-serogroups of ETEC outbreaks in Japan indicates that ETEC survives in the environment in Japan.

Caenorhabditis elegans homologue of Prox1/Prospero is expressed in the glia and is required for sensory behavior and cold tolerance.

The Caenorhabditis elegans (C. elegans) amphid sensory organ contains only 4 glia-like cells and 24 sensory neurons, providing a simple model for analyzing glia or neuron-glia interactions. To better characterize glial development and function, we carried out RNA interference screening for transcription factors that regulate the expression of an amphid sheath glial cell marker and identified pros-1, which encodes a homeodomain transcription factor homologous to Drosophila prospero/mammalian Prox1, as a positive regulator. The functional PROS-1::EGFP fusion protein was localized in the nuclei of the glia and the excretory cell but not in the amphid sensory neurons. pros-1 deletion mutants exhibited larval lethality, and rescue experiments showed that pros-1 and human Prox1 transgenes were able to rescue the larval lethal phenotype, suggesting that pros-1 is a functional homologue of mammalian Prox1, at least partially. We further found that the structure and functions of sensory neurons, such as the morphology of sensory endings, sensory behavior and sensory-mediated cold tolerance, appeared to be affected by the pros-1 RNAi. Together, our results show that the C. elegans PROS-1 is a transcriptional regulator in the glia but is involved not only in sensory behavior but also in sensory-mediated physiological tolerance.

Influence of oral supplementation with sesamin on longevity of Caenorhabditis elegans and the host defense.

PURPOSE: Nutritional control has been proposed as a potential therapy for slowing the senescence of immune function and decreasing mortality. This study investigated whether sesamin could modify host defense systems and extend the lifespan of the nematode Caenorhabditis elegans. METHODS: Nematodes were fed standard food (the bacterium Escherichia coli strain OP50) supplemented with various doses of sesamin/γ-cyclodextrin inclusion compounds starting from young adulthood. The mean lifespan, muscle function, lipofuscin accumulation, protein carbonyl content, and stress resistance of the worms were examined. Then, C. elegans mutants harboring loss-of-function lesions in longevity- and host defense-related signaling pathways were supplemented with sesamin to identify the genes involved in the longevity effects. RESULTS: Worms supplemented with sesamin displayed higher locomotion and prolongevity and produced offspring at levels similar to unsupplemented control animals. The growth curves of nematodes were similar to those of controls, suggesting that sesamin did not induce prolongevity effects through dietary restriction. Notably, sesamin made the worms more resistant to infection by Legionella pneumophila and more resistant to oxidative stressors such as paraquat and hydrogen peroxide and prolonged the lifespan of a mev-1 mutant that produces abundant superoxide anions. However, the accumulation of protein carbonyls and lipofuscin was similar in sesamin-exposed and control worms, suggesting that sesamin is unlikely to work simply as an antioxidant. Sesamin supplementation failed to extend the lifespan of loss-of-function mutants of daf-2, daf-16, pmk-1, and skn-1. CONCLUSIONS: Sesamin enhances the host defense of C. elegans and increases the average lifespan via activation of both skn-1 (encoding a component of the p38 MAPK pathway) and daf-16 (encoding a component of the IGF-1 pathway).

Campylobacter jejuni infection suppressed Cl⁻ secretion induced by CFTR activation in T-84 cells.

Campylobacter jejuni causes foodborne disease associated with abdominal pain, gastroenteritis, and diarrhea. These symptoms are induced by bacterial adherence and invasion of host epithelial cells. C. jejuni infection can occur with a low infective dose, suggesting that C. jejuni may have evolved strategies to cope with the bacterial clearance system in the gastrointestinal tract. The mucosa layer is the first line of defense against bacteria. Mucus conditions are maintained by water and anion (especially Cl(-)) movement. Cystic fibrosis transmembrane conductance regulator (CFTR) is the main Cl(-) channel transporting Cl(-) to the lumen. Mutations in CFTR result in dehydrated secreted mucus and bacterial accumulation in the lungs, and recent studies suggest that closely related pathogenic bacteria also may survive in the intestine. However, the relationship between C. jejuni infection and CFTR has been little studied. Here, we used an (125)I(-) efflux assay and measurement of short-circuit current to measure Cl(-) secretion in C. jejuni-infected T-84 human intestinal epithelial cells. The basic state of Cl(-) secretion was unchanged by C. jejuni infection, but CFTR activator was observed to induce Cl(-) secretion suppressed in C. jejuni-infected T-84 cells. The suppression of activated Cl(-) secretion was bacterial dose-dependent and duration-dependent. A similar result was observed during infection with other C. jejuni strains. The mechanism of suppression may occur by affecting water movement or mucus condition in the intestinal tract. A failure of mucus barrier function may promote bacterial adhesion or invasion of host intestinal epithelial cells, thereby causing bacterial preservation in the host intestinal tract.

Specific properties of enteropathogenic Escherichia coli isolates from diarrheal patients and comparison to strains from foods and fecal specimens from cattle, swine, and healthy carriers in Osaka City, Japan.

For exhaustive detection of diarrheagenic Escherichia coli, we previously developed a colony-hybridization method using hydrophobic grid-membrane filters in combination with multiplex real-time PCR. To assess the role of domestic animals as the source of atypical enteropathogenic E. coli (aEPEC), a total of 679 samples (333 from foods, fecal samples from 227 domestic animals, and 119 from healthy people) were examined. Combining 48 strains previously isolated from patients and carriers, 159 aEPEC strains were classified by phylogroup, virulence profile, and intimin typing. Phylogroup B1 was significantly more prevalent among aEPEC from patients (50%) and bovine samples (79%) than from healthy carriers (16%) and swine strains (23%), respectively. Intimin type ß1 was predominant in phylogroup B1; B1-ß1 strains comprised 26% of bovine strains and 25% of patient strains. The virulence profile groups Ia and Ib were also observed more frequently among bovine strains than among porcine strains. Similarly, virulence group Ia was detected more frequently among patient strains than strains of healthy carriers. A total of 85 strains belonged to virulence group I, and 63 of these strains (74%) belonged to phylogroup B1. The present study suggests that the etiologically important aEPEC in diarrheal patients could be distinguished from aEPEC strains indigenous to humans based on type, such as B1, Ia, and ß1/γ1, which are shared with bovine strains, while the aEPEC strains in healthy humans are different, and some of these were also present in porcine samples.

Mechanism underlying prolongevity induced by bifidobacteria in Caenorhabditis elegans.

Lactobacilli and bifidobacteria are probiotic bacteria that modify host defense systems and have the ability to extend the lifespan of the nematode Caenorhabditis elegans. Here, we attempted to elucidate the mechanism by which bifidobacteria prolong the lifespan of C. elegans. When the nematode was fed Bifidobacterium infantis (BI) mixed at various ratios with the standard food bacterium Escherichia coli strain OP50 (OP), the mean lifespan of worms was extended in a dose-dependent manner. Worms fed BI displayed higher locomotion and produced more offspring than control worms. The growth curves of nematodes were similar regardless of the amount of BI mixed with OP, suggesting that BI did not induce prolongevity effects through caloric restriction. Notably, feeding worms the cell wall fraction of BI alone was sufficient to promote prolongevity. The accumulation of protein carbonyls and lipofuscin, a biochemical marker of aging, was also lower in worms fed BI; however, the worms displayed similar susceptibility to heat, hydrogen peroxide, and paraquat, an inducer of free radicals, as the control worms. As a result of BI feeding, loss-of-function mutants of daf-16, jnk-1, aak-2, tol-1, and tir-1 exhibited a longer lifespan than OP-fed control worms, but BI failed to extend the lifespan of pmk-1, skn-1, and vhp-1 mutants. As skn-1 induces phase 2 detoxification enzymes, our findings suggest that cell wall components of bifidobacteria increase the average lifespan of C. elegans via activation of skn-1, regulated by the p38 MAPK pathway, but not by general activation of the host defense system via DAF-16.

Development of a method for oral administration of hydrophobic substances to Caenorhabditis elegans: pro-longevity effects of oral supplementation with lipid-soluble antioxidants.

Methods for quantitative oral administration of various substances to Caenorhabditis elegans are needed. Previously, we succeeded in oral administration of hydrophilic substances using liposomes. However, an adequate system for delivery of hydrophobic chemicals was not available. In this study, we developed a method for oral administration of lipid-soluble substances to C. elegans. γ-cyclodextrin (γCD), which delivers hydrophobic chemicals, was used to make micro-particles of inclusion compounds that can be ingested by bacteriophagous nematodes, which do not distinguish these micro-particles from their food bacteria. Successful oral delivery of the hydrophobic fluorescent reagent 3,3'-dioctadecyloxacarbocyanine perchlorate into the intestines of C. elegans was observed. Oral administration of the hydrophobic antioxidants tocotrienol, astaxanthin, or γ-tocopherol, prolonged the nematode lifespan; tocotrienol rendered them resistant to infection with the opportunistic pathogen Legionella pneumophila. In contrast, older conventional delivery methods that involve incorporation of chemicals into the nematode growth medium or pouring chemicals onto the plate produced weaker fluorescence and no longevity effects. Our method efficiently and quantitatively delivers hydrophobic solutes to nematodes, and a minimum effective dose was estimated. In combination with our liposome method, this γCD method expands the usefulness of C. elegans for the discovery of functional food factors and for screening drug candidates.

Caenorhabditis elegans as an alternative model to study senescence of host defense and the prevention by immunonutrition.

Whether nutritional control can retard senescence of immune function and decrease mortality from infectious diseases has not yet been established; the difficulty of establishing a model has made this a challenging topic to investigate. Caenorhabditis elegans has been extensively used as an experimental system for biological studies. Particularly for aging studies, the worm has the advantage of a short and reproducible life span. The organism has also been recognized as an alternative to mammalian models of infection with bacterial pathogens in this decade. Hence we have studied whether the worms could be a model host in the fields of immunosenescence and immunonutrition. Feeding nematodes lactic acid bacteria (LAB) resulted in increases in average life span of the nematodes compared to those fed Escherichia coli strain OP50, a standard food bacteria. The 7-day-old nematodes fed LAN from age 3 days were clearly endurable to subsequent salmonella infection compared with nematodes fed OP50 before the salmonella infection. The worm could be a unique model to study effects of food factors on longevity and host defense, so-called immunonutrition. Then we attempted to establish an immunosenescence model using C. elegans. We focused on the effects of worm age on the Legionella infection and the prevention by immunonutrition. No significant differences in survival were seen between 3-day-old worms fed OP50 and 3-day-old worms infected with virulent Legionella strains. However, when the worms were infected from 7.5 days after hatching, the virulent Legionella strains were obviously nematocidal for the worms' immunosenescence. In contrast, nematodes fed with bifidobacteria prior to Legionella infection were resistant to Legionella. C. elegans could act as a unique alternative host for immunosenescence and resultant opportunistic infection, and immunonutrition researches.

Protective effect of Lactococcus laudensis and Pediococcus parvulus against neuropathy due to amyloid-beta in Caenorhabditis elegans.

In Alzheimer's disease (AD), the amyloid-ß (Aß) protein begins to accumulate in the brain 20 years prior to any dementia symptoms manifestation, in which Aß aggregates in the brain, causing destruction of nerve cells and resulting in memory impairments. Lifestyle and diet appear to inhibit Aß production and amyloid deposition. Therefore, identifying factors that prevent Aß production and administering them before the onset of AD, may be an effective preventive method. Lactic acid bacteria (LAB) exhibit various health effects on the host and are expected to have protective effects on neurological functions via brain-gut correlation. However, the protective effects of LAB against Aß are not well understood. We investigated whether LAB feeding could ameliorate the toxicity of Aß peptide accumulation in transgenic Caenorhabditis elegans expressing the human Aß peptide in neurons or muscle as an AD model. Aß expressed in muscle caused myopathy and worm paralysis, while Aß in neurons disturbed chemotactic activity. Among 14 screened strains, Lactococcus laudensis (LL) and Pediococcus parvulus (PP) prevented the AD worms from losing their chemotaxis behavior and becoming paralyzed by the Aß peptide. Immunostaining and western blotting indicated that Aß peptide was significantly suppressed in worms fed these two strains, and binding of the Aß to vitellogenin was particularly inhibited. Conversely, the mRNA level of the Aß gene did not change between LL- or PP-fed worms and the control. In conclusion, LL and PP alleviate neurotoxicity by inhibiting Aß accumulation; AD model worms can be used to screen efficient LAB for AD prevention.

Prolonged Lifespan, Improved Perception, and Enhanced Host Defense of Caenorhabditis elegans by Lactococcus cremoris subsp. cremoris.

Lactic acid bacteria are beneficial to Caenorhabditis elegans; however, bacteria acting as probiotics in nematodes may not necessarily have probiotic functions in humans. Lactococcus cremoris subsp. cremoris reportedly has probiotic functions in humans. Therefore, we determined whether the strain FC could exert probiotic effects in C. elegans in terms of improving host defenses and extending life span. Live FC successfully extended the life span and enhanced host defense compared to Escherichia coli OP50 (OP50), a standard food source for C. elegans. The FC-fed worms were tolerant to Salmonella enterica subsp. enterica serovar Enteritidis or Staphylococcus aureus infection and had better survival than the OP50-fed control worms. Further, the chemotaxis index, an indicator of perception ability, was more stable and significantly higher in FC-fed worms than in the control worms. The increase in autofluorescence from advanced glycation end products (AGEs) with aging was also ameliorated in FC-fed worms. FC showed beneficial effects in daf-16 and pmk-1 mutants, but not in skn-1 mutants. Since SKN-1 is the C. elegans ortholog of Nrf2, we measured the transcription of heme oxygenase-1 (HO-1), which is regulated by Nrf2, in murine macrophages and found that HO-1 mRNA expression was increased >5 times by inoculation with FC cells. Thus, FC could exert antisenescence effects via the SKN-1/Nrf2 pathway. This study showed for the first time that FC supported perceptive function and suppressed AGEs in nematodes as probiotic bacteria. Therefore, C. elegans can be an alternative model to screen for probiotic bacteria that can be used for antisenescence effects in humans. IMPORTANCE Aging is one of our greatest challenges. The World Health Organization proposed that "active aging" might encourage people to continue to work according to their capacities and preferences as they grow old and would prevent or delay disabilities and chronic diseases that are costly to both individuals and the society, considering that disease prevention is more economical than treatment. Probiotic bacteria, such as lactobacilli, are live microorganisms that exert beneficial effects on human health when ingested in sufficient amounts and can promote longevity. The significance of this study is that it revealed the antisenescence and various beneficial effects of the representative probiotic bacterium Lactococcus cremoris subsp. cremoris strain FC exerted via the SKN-1/Nrf2 pathway in the nematode Caenorhabditis elegans.

Autofluorescence as a noninvasive biomarker of senescence and advanced glycation end products in Caenorhabditis elegans.

To assess the utility of autofluorescence as a noninvasive biomarker of senescence in Caenorhabditis elegans, we measured the autofluorescence of individual nematodes using spectrofluorometry. The fluorescence of each worm increased with age. Animals with lower fluorescence intensity exhibited longer life expectancy. When proteins extracted from worms were incubated with sugars, the fluorescence intensity and the concentration of advanced glycation end products (AGEs) increased over time. Ribose enhanced these changes not only in vitro but also in vivo. The glycation blocker rifampicin suppressed this rise in fluorescence. High-resolution mass spectrometry revealed that vitellogenins accumulated in old worms, and glycated vitellogenins emitted six-fold higher fluorescence than naive vitellogenins. The increase in fluorescence with ageing originates from glycated substances, and therefore could serve as a useful noninvasive biomarker of AGEs. C. elegans can serve as a new model to look for anti-AGE factors and to study the relationship between AGEs and senescence.

Nonpathogenic Cutibacterium acnes Confers Host Resistance against Staphylococcus aureus.

Cutibacterium acnes is a human skin-resident bacterium. Although C. acnes maintains skin health by inhibiting invasion from pathogens like Staphylococcus aureus, it also contributes to several diseases, including acne. Studies suggest that differences in genetic background may explain the diverse phenotypes of C. acnes strains. In this study, we investigated the effects of C. acnes strains on the Caenorhabditis elegans life span and observed that some strains shortened the life span, whereas other strains, such as strain HL110PA4, did not alter it. Next, we assessed the effects of C. acnes HL110PA4 on host resistance against S. aureus. The survival time of C. acnes HL110PA4-fed wild-type animals was significantly longer than that of Escherichia coli OP50 control bacterium-fed worms upon infection with S. aureus. Although the survival times of worms harboring mutations at the daf-16/FoxO and skn-1/Nrf2 loci were similar to those of wild-type worms after S. aureus infection, administration of C. acnes failed to improve survival times of tir-1/SARM1, nsy-1/mitogen-activated protein kinase kinase kinase (MAPKKK), sek-1/mitogen-activated protein kinase kinase (MAPKK), and pmk-1/p38 mitogen-activated protein kinase (MAPK) mutants. These results suggest that the TIR-1 and p38 MAPK pathways are involved in conferring host resistance against S. aureus in a C. acnes-mediated manner. IMPORTANCE Cutibacterium acnes is one of the most common bacterial species residing on the human skin. Although the pathogenic properties of C. acnes, such as its association with acne vulgaris, have been widely described, its beneficial aspects have not been well characterized. Our study classifies C. acnes strains based on its pathogenic potential toward the model host C. elegans and reveals that the life span of C. elegans worms fed on C. acnes was consistent with the clinical association of C. acnes ribotypes with acne or nonacne. Furthermore, nonpathogenic C. acnes confers host resistance against the opportunistic pathogen Staphylococcus aureus. Our study provides insights into the impact of C. acnes on the host immune system and its potential roles in the ecosystem of skin microbiota.

Caenorhabditis elegans as an alternative model host for legionella pneumophila, and protective effects of Bifidobacterium infantis.

The survival times of Caenorhabditis elegans worms infected with Legionella pneumophila from day 7.5 or later after hatching were shorter than those of uninfected worms. However, nematodes fed bifidobacteria prior to Legionella infection were resistant to Legionella. These nematodes may act as a unique alternative host for Legionella research.