Production Of Volatile Sulfur Compounds Research Articles

Lavandula angustifolia Essential Oil Inhibits the Ability of Fusobacterium nucleatum to Produce Volatile Sulfide Compounds, a Key Components in Oral Malodor.

Oral malodor still constitutes a major challenge worldwide. A strong effort is invested in eliminating volatile sulfur compound-producing oral bacteria through organic natural products such as essential oils. Fusobacterium nucleatum is a known volatile sulfur compound-producing bacteria that inspires oral malodor. The aim of the present study was to test the effect of lavender essential oil on the bacterium's ability to produce volatile sulfide compounds, the principal components of oral malodor. Lavender (Lavandula angustifolia) essential oil was extracted by hydrodistillation and analyzed using GC-MS. The minimal inhibitory concentration (MIC) of lavender essential oil on Fusobacterium nucleatum was determined in a previous trial. Fusobacterium nucleatum was incubated anaerobically in the presence of sub-MIC, MIC, and above MIC concentrations of lavender essential oil, as well as saline and chlorhexidine as negative and positive controls, respectively. Following incubation, volatile sulfur compound levels were measured using GC (Oralchroma), and bacterial cell membrane damage was studied using fluorescence microscopy. Chemical analysis of lavender essential oil yielded five main components, with camphor being the most abundant, accounting for nearly one-third of the total lavender essential oil volume. The MIC (4 µL/mL) of lavender essential oil reduced volatile sulfur compound secretion at a statistically significant level compared to the control (saline). Furthermore, the level of volatile sulfur compound production attributed to 1 MIC of lavender essential oil was in the range of the positive control chlorhexidine with no significant difference. When examining bacterial membrane damage, 2 MIC of lavender essential oil (i.e., 8 µL/mL) demonstrated the same, showing antibacterial membrane damage values comparative to chlorhexidine. Since lavender essential oil was found to be highly effective in hindering volatile sulfur compound production by Fusobacterium nucleatum through the induction of bacterial cell membrane damage, the results suggest that lavender essential oil may be a suitable alternative to conventional chemical-based anti-malodor agents.

Clinical and oral microbiome pattern of halitosis patients with periodontitis and gingivitis.

Halitosis is caused by a bacterial proteolytic process that induces the production of volatile sulfur compounds, odor-causing gases. The aim of this study was to determine the clinical oral hygiene state and oral microbiome pattern of halitosis patients with periodontitis and gingivitis. The oral hygiene state of halitosis patients with periodontitis and gingivitis was assessed using the oral hygiene index simplified (OHI-S), decay missing filled teeth (DMFT), and tongue biofilm. The dorsum of the tongue and subgingival swabs were cultured for bacteria, and bacterial morphology was evaluated using Gram staining. Evaluation of the bacterial genus using the Bergey's systematic bacteriology diagram as a guide. A total of ten patients with periodontitis and gingivitis were included. Our data indicated that the scores of OHI-S and DMFT were different significantly between halitosis patients with periodontitis and gingivitis (both had p<0.001) while tongue biofilm score was not different between groups. On the dorsum of the tongue, periodontitis patients had a significant higher oral microbiome population (85.65x106 CFU/mL) compared to those with gingivitis (0.047x106 CFU/mL) with p=0.002. In contrast, the number of microbiomes in the subgingival had no significant different between periodontitis and gingivitis. On the dorsum of the tongue, six bacterial genera were isolated from periodontitis cases and seven genera were detected from gingivitis patients. On subgingival, 10 and 15 genera were identified from periodontitis and gingivitis, respectively. Fusobacterium, Propionibacterium, Eubacterium and Lactobacillus were the most prevalent among periodontitis cases while Porphyromonas was the most prevalent in gingivitis patients. In conclusion, although OHI-S and DMFT are different between periodontitis and gingivitis, overlapping of bacterial genera was detected between periodontitis and gingivitis cases.

Sulfur metabolism in durian pulps: Factors contributing to the production of volatile sulfur compounds during fruit ripening

Durian (Durio zibethinus L.), an economically important fruit crop in Southeast Asia, is known for its strong sulfuryl aroma resulting from the accumulation of sulfur-containing compounds. However, our understanding of sulfur metabolism in fruit remains limited. In this study, we focused on the functional characterization of durian methionine γ-lyase (DzMGL), the key enzyme in volatile sulfur compound (VSC) production. In addition, to gain a better insight into sulfur metabolism, we profiled metabolites related to this process using various methods and assessed the expression of relevant genes through reverse transcription-quantitative PCR. Our gene and metabolite analyses revealed that sulfur metabolism is activated during ripening. Interestingly, DzMGL exhibited a higher efficiency in using L-cysteine than Arabidopsis MGL. The differential levels of the produced VSCs explained the aroma intensity-related differences between the two commercial Thai cultivars ‘Chanee’ and ‘Monthong’. Furthermore, the cysteine availability-related differences between the two cultivars could contribute to this variation, with ‘Chanee’ containing higher cysteine levels than ‘Monthong’. Our findings indicated that γ-glutamylcysteine was the preferred form of sulfur storage in durian pulps, with a potential recycling process providing intermediates that flux methionine toward ethylene biosynthesis and VSC production. This study provides novel insights into sulfur metabolism in durian fruit.

Evaluation of the antibacterial activity of Elsholtzia ciliate essential oil against halitosis-related Fusobacterium nucleatum and Porphyromonas gingivalis.

The broad-spectrum antimicrobial activity of Elsholtzia ciliate essential oil (ECO) has been previously reported, but its effectiveness against halitosis-causing bacteria such as Fusobacterium nucleatum and Porphyromonas gingivalis is not well understood. In this study, we investigated the bacteriostatic activity of ECO against planktonic cells and biofilms of F. nucleatum and P. gingivalis, as well as its ability to inhibit bacterial metabolism and production of volatile sulfur compounds (VSCs) at sub-lethal concentrations. Our findings revealed that ECO exhibited comparable activities to chlorhexidine against these oral bacteria. Treatment with ECO significantly reduced the production of VSCs, including hydrogen sulfide, dimethyl disulfide, and methanethiol, which are major contributors to bad breath. As the major chemical components of ECO, carvacrol, p-cymene, and phellandrene, were demonstrated in vitro inhibitory effects on F. nucleatum and P. gingivalis, and their combined use showed synergistic and additive effects, suggesting that the overall activity of ECO is derived from the cumulative or synergistic effect of multiple active components. ECO was found to have a destructive effect on the bacterial cell membrane by examining the cell morphology and permeability. Furthermore, the application of ECO induced significant changes in the bacterial composition of saliva-derived biofilm, resulting in the elimination of bacterial species that contribute to halitosis, including Fusobacterium, Porphyromonas, and Prevotella. These results provide experimental evidence for the potential clinical applications of ECOs in the prevention and treatment of halitosis.

Oral Probiotics, Streptococcus salivarius K12 and M18, Suppress the Release of Volatile Sulfur Compounds and a Virulent Protease from Oral Bacteria: An In-Vitro Study.

To evaluate the inhibitory effects of Streptococcus salivarius K12 and M18 strains on the growth of six oral pathogens as well as their release of volatile sulfur compounds (VSCs), and whether these probiotics can inhibit the expression of arginine-specific gingipain A (RgpA), a protease secreted by Porphyromonas gingivalis. After six halitogenic oral pathogens (P. gingivalis, Treponema denticola, Tannerella forsythia, Fusobacterium nucleatum, Parvimonas micra, and Eikenella corrodens) were cultured with or without S. salivarius K12 and M18, the concentration of two VSCs was measured. Moreover, the antimicrobial activity of S. salivarius K12 and M18 against these pathogens and the suppressive effect on RgpA release by P. gingivalis were assessed. In the co-culture of S. salivarius K12 or M18 with oral pathogenic bacteria, the growth of all six oral pathogens was significantly inhibited (p < 0.01). Additionally, S. salivarius K12 and M18 had an inhibitory effect on the production of the halitogenic substances H2S and CH3SH (p < 0.01) as well as the expression of P. gingivalis RgpA. Finally, we demonstrated that the addition of only culture supernatants of the two strains K12/M18 to oral pathogen cultures was sufficient to mimic the effects of K12/M18 co-cultures upon VSCs production and protease expression. S. salivarius K12 and M18 inhibited VSC release by all six of the major oral pathogens that were assayed and reduced the expression of RgpA.

Keterkaitan antara Halitosis dengan Bakteri Penyebab Periodontitis

Halitosis, often known as foul breath, refers to an unpleasant odor that emanates from the mouth cavity when inhaling or talking. Halitosis can have a negative impact on a person's quality of life, including symptoms of depression or anxiety, low self-esteem, embarrassment, prejudice, and social isolation. Bad breath can be caused by both intra oral and extra oral factors. Bacterial growth in the oral cavity is excellent for the production of volatile sulfur compounds (VSC). The posterior dorsum of the tongue, gingival sulcus, periodontal pockets, and gingival embrasures are all places where bacterias can accumulate. Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis, and Treponema dentiocola are known to actively produce VSC through interactions with specific substrates such as cysteine, methionine, tryptophan, arginine, and lysine to produce hydrogen sulfide (H2S) and methylmercaptan (CH3SCH3). However, the presence of VSC does not indicate the presence of periodontitis, as any space in the oral cavity that can cause the retention of bacteria/biofilms can become a site for bacterial decomposition, thereby facilitating the growth of VSC. Tongue cleansing is proven to help reduce the formation of VSC.

Eutrophication levels increase sulfur biotransformation and emissions from sediments of Lake Taihu

Eutrophication can stimulate the emissions of volatile sulfur compounds (VSCs) accompanied by variations in environmental variables in lakes. However, the effects of eutrophication on VSC emissions from lake sediments as well as the underlying mechanisms remain unclear. In this study, depth gradient sediments at different eutrophication levels and seasons were collected from Lake Taihu to investigate the response of sulfur biotransformation in the sediments to eutrophication based on the analysis of environmental variables, microbial activity, abundance and community structure. H2S and CS2 were the main VSCs produced from the lake sediments, with the production rates of 2.3–7.9 and 1.2–3.9 ng g−1 h−1 in August, respectively, which were higher than those in March, mainly due to the increasing activity and abundance of sulfate-reducing bacteria (SRB) at high temperatures. The VSC production rates from the sediments increased with lake eutrophication level. Higher VSC production rates were detected in surface sediments in eutrophic regions but in deep sediments in oligotrophic regions. Sulfuricurvum, Thiobacillus and Sulfuricella were the main sulfur-oxidizing bacteria (SOB) in the sediments, while Desulfatiglans and Desulfobacca were the predominant SRB. Organic matter, Fe3+, NO3−-N and total sulfur had significant influences on the microbial communities in the sediments. Partial least squares path modelling showed that the trophic level index could stimulate VSC emissions from lake sediments by influencing the activities and abundances of SOB and SRB. These findings indicated that sediments contributed substantially to VSC emissions from eutrophic lakes, especially surface sediments, and sediment dredging might be an effective way to mitigate VSC emissions from eutrophic lakes.

The tongue biofilm metatranscriptome identifies metabolic pathways associated with the presence or absence of halitosis

Intra-oral halitosis usually results from the production of volatile sulfur compounds, such as methyl mercaptan and hydrogen sulfide, by the tongue microbiota. There are currently no reports on the microbial gene-expression profiles of the tongue microbiota in halitosis. In this study, we performed RNAseq of tongue coating samples from individuals with and without halitosis. The activity of Streptococcus (including S. parasanguinis), Veillonella (including V. dispar) and Rothia (including R. mucilaginosa) was associated with halitosis-free individuals while Prevotella (including P. shahi), Fusobacterium (including F. nucleatum) and Leptotrichia were associated with halitosis. Interestingly, the metatranscriptome of patients that only had halitosis levels of methyl mercaptan was similar to that of halitosis-free individuals. Finally, gene expression profiles showed a significant over-expression of genes involved in L-cysteine and L-homocysteine synthesis, as well as nitrate reduction genes, in halitosis-free individuals and an over-expression of genes responsible for cysteine degradation into hydrogen sulfide in halitosis patients.

Effects of Bifidobacterium lactis HN019 and Lactobacillus acidophilus NCFM on volatile sulfur compounds produced by oral anaerobes

Halitosis is a term that refers to an unpleasant or foul odor originating from oral cavity, which is mainly caused by volatile sulfur compounds (VSCs) produced by oral anaerobes such as Porphyromonas gingivalis, Fusobacterium nucleatum, Treponema denticola and Prevotella intermedia. General therapies, such as tooth and tongue brushing or usage of bacteriostat can hardly provide a harmless and continuous therapeutic effect on halitosis. Recent evidence has suggested the potential clinical application value of probiotics in the treatment of halitosis. In this study, Bifidobacterium lactis HN019 and Lactobacillus acidophilus NCFM were identified from four kinds of probiotics and the antimicrobial activities against pathogens related to halitosis and inhibitory effects on VSCs were investigated. The results showed that B. lactis HN019 and L. acidophilus NCFM exhibited superior bacteriostatic action against pathogens related to halitosis and showed remarkable inhibitory effect on the production and emission of VSCs. These findings suggest that B. lactis HN019 and L. acidophilus NCFM may serve as promising parts of a successful halitosis manage plan.

In-Depth Analysis of an Obligate Anaerobe Paraclostridium bifermentans Isolated from Uterus of Bubalus bubalis.

Simple SummaryNon-specific uterine infections in bovine (uterine line inflammation) are a significant issue for the dairy industry. These infections are responsible for significant financial losses all over the world. Paraclostridium bifermentans is an obligate anaerobe, gram-positive rod-shaped bacteria belonging to the Clostridia class and the Peptostreptococcaceae family produces endospores. This bacterium has the ability to infiltrate bovine uterine endometrial epithelial cells and cause infection in the endometrium epithelial cells. Our study found that an examination of a buffalo uterus with yellowish purulent discharge reported the presence of pathogenic bacteria Paraclostridium bifermentans, where its genomic characterization, substrate utilization, and antibiotic susceptibility potentiality was studied. This discovery indicates the presence of virulence genes as well as pathogenic features. This is the first report of P. bifermentans from the bovine uterus environment.Chronic non-specific contamination of the reproductive tract in animals is a major issue during early postpartum, natural coitus, or artificial insemination. Uterine infection is one of the major concerns reducing fertility, production loss, and early culling of the animals. Therefore, the aim of this study was to identify any novel bacterium if present in the uterine environment of Bubalus bubalis causing infections. A strictly anaerobic bacterial strain designated as Paraclostridium bifermentans GBRC was isolated and characterized. Bacterium was found to be Gram positive moderate rod with motility. The optimum growth was observed at 40 ± 2 °C. The pathogenic characteristics of the GBRC strain, such as hemolysis, gelatin hydrolysis, and the production of volatile sulfur compounds, were similar to those seen in the epithelial layer invading pathogenic strains. Assembled genome size was 3.6 MB, with 78 contigs, and a G + C content of 28.10%. Furthermore, the whole genome sequence analysis confirmed the presence of genes encoding virulence factors and provided genomic insights on adaptation of the strain in the uterine environment. Based on the phenotypic and genetic differences with phylogenetic relatives, strain GBRC is proposed to represent a first reported species of the genus Paraclostridium with potential pathogenic character, from the buffalo uterine environment. This study analysis of the GBRC strain serves as a key reference point for the investigation of potential pathogenic strains that may cause endometritis and metritis in bovine.

Effectiveness of oral care interventions on malodour in dogs.

BackgroundOral malodour is identified by pet owners as an unpleasant inconvenience, but they may not recognise this likely indicates underlying disease. The primary cause of oral malodour relates to the presence of bacteria in the oral cavity often associated with gingivitis and periodontitis. The purpose of this study was to determine the effect of feeding two oral care chews with different textural properties on oral malodour and the proportion of bacterial species involved in the production of volatile sulphur compounds (VSCs).MethodsFourteen dogs (9 Petit Basset Griffon Vendéen (PBGV) and 5 Beagle dogs) participated in the randomised cross-over study for a total of 14 weeks. The cohort was divided into four groups with each exposed to a different intervention per week: chew A, chew B, tooth brushing control or a no intervention control. An induced malodour method was used to assess VSCs in breath samples using a portable gas chromatograph (OralChroma™). Microbiological samples (supragingival plaque and tongue coating scrapes) were analysed for VSC-producing bacteria using Oral Hydrogen Sulfide agar with lead acetate.ResultsVSCs were detected in the dogs’ breath samples and levels of hydrogen sulphide and methyl mercaptan were found to be reduced following an intervention. Chew B significantly reduced the levels of both hydrogen sulphide (p < 0.001) and methyl mercaptan (p < 0.05) compared to no intervention. Reductions in methyl mercaptan were also observed for chew A and tooth brushing but these were not statistically significant. When compared to no intervention, all interventions significantly reduced the total bacterial load and VSC producing bacterial load in plaque (p < 0.001). For tongue samples, only chew B significantly reduced the total bacterial load and VSC-producing bacterial load (p < 0.001) compared to no intervention.ConclusionsBy inducing oral malodour and subsequently applying the one-time interventions, significant reductions in the levels of VSCs were observed. The use of oral care chews texturally designed to deliver a deep, all-round cleaning action can be particularly effective at managing oral malodour in dogs, likely through an enhanced ability to remove bacteria.

Effect of lemon essential oil on halitosis.

To evaluate the effect of lemon essential oil (LEO) on salivary bacteria and volatile sulfur compound (VSC) production of patients with halitosis. Saliva of five patients with halitosis was collected, after adding different concentrations (0.563-9mg/ml) of LEO, detecting the growth of salivary bacteria, the formation of biofilm, and VSC production, and compare the difference of different concentrations of LEO on bacterial growth and VSC production. 48 volunteers were randomly divided into 4groups. After gargling with LEO, cetylpyridinium chloride (CPC), chlorhexidine (CHX), and hydrogen peroxide (H2 O2 ) separately measure changes of VSC production and pH values at 30, 45, 60, 90, and 120min and then compare the differences at different time points within group. Compared with the negative control group, under subinhibitory concentrations of LEO (0.563-2.25mg/ml), the biofilm formation and VSC production of salivary bacteria in LEO group were significantly inhibited (p<0.05). Compared with the baseline, the VSC production of subjects decreased after rinsing with the LEO in 60min (p<0.05). After gargling with LEO, the pH value rose significantly in 30min and reverted to the baseline level at 120min (p<0.05). Lemon essential oil can inhibit the growth of salivary bacteria and reduce VSC production of patients with halitosis.

Relationships between Solobacterium moorei and Prevotella intermedia in subgingival microbiota of periodontitis patients with halitosis: A preliminary study using qPCR

ObjectiveSolobacterium moorei is suggested to be associated with the production of volatile sulphur compounds (VSCs) and can be found in subgingival plaques of deep periodontal pockets. We examined whether this bacterium’s count was reduced in periodontitis patients with halitosis following non-surgical periodontal treatment, while the bacterial count of Prevotella intermedia was measured simultaneously as a control. Material & methodsThis clinical study included 20 adults with chronic periodontitis who complained of halitosis. The bacterial relationship in the subgingival plaque sample was measured after 8 weeks post-treatment, including the probing pocket depth (PPD). Quantitative real-time PCR (qPCR) was used to measure the proportion of S. moorei, while the concentrations of H2S and CH3SH were determined using oral ChromaTM. ResultsThe presence of S. moorei was consistently observed in participants with periodontitis before and after non-surgical periodontal treatment and consistent showed a significantly lower proportion compared with P. intermedia. Solobacterium moorei showed a strong positive correlation with H2S and CH3SH concentrations, but a negative correlation with deep periodontal pocket measurements. Conversely, reduced P. intermedia may be more associated with a deep pocket, independent of the concentration of CH3SH. ConclusionThe study data showed that the proportion of S. moorei in the subgingival biofilm can be related to halitosis in periodontitis patients.

Identification of a New Family of Prenylated Volatile Sulfur Compounds in Cannabis Revealed by Comprehensive Two-Dimensional Gas Chromatography.

Cannabis sativa L. produces over 200 known secondary metabolites that contribute to its distinctive aroma. Studies on compounds traditionally associated with the scent of this plant have focused on those within the terpenoid class. These isoprene-derived compounds are ubiquitous in nature and are the major source of many plant odors. Nonetheless, there is little evidence that they provide the characteristic “skunk-like” aroma of cannabis. To uncover the chemical origins of this scent, we measured the aromatic properties of cannabis flowers and concentrated extracts using comprehensive two-dimensional gas chromatography equipped with time-of-flight mass spectrometry, flame ionization detection, and sulfur chemiluminescence. We discovered a new family of volatile sulfur compounds (VSCs) containing the prenyl (3-methylbut-2-en-1-yl) functional group that is responsible for this scent. In particular, the compound 3-methyl-2-butene-1-thiol was identified as the primary odorant. We then conducted an indoor greenhouse experiment to monitor the evolution of these compounds during the plant’s lifecycle and throughout the curing process. We found that the concentrations of these compounds increase substantially during the last weeks of the flowering stage, reach a maximum during curing, and then drop after just one week of storage. These results shed light on the chemical origins of the characteristic aroma of cannabis and how volatile sulfur compound production evolves during plant growth. Furthermore, the chemical similarity between this new family of VSCs and those found in garlic (allium sativum) suggests an opportunity to also investigate their potential health benefits.

How to modulate the formation of negative volatile sulfur compounds during wine fermentation?

ABSTRACTBeyond the production of positive aromas during alcoholic fermentation, Saccharomyces cerevisiae metabolism also results in the formation of volatile compounds detrimental to wine quality, including a wide range of volatile sulfur compounds (VSCs). The formation of these VSCs during wine fermentation is strongly variable and depends on biological and environmental factors. First, the comparison of the VSCs profile of 22 S. cerevisiae strains provided a comprehensive overview of the intra-species diversity in VSCs production: according to their genetic background, strains synthetized from 1 to 6 different sulfur molecules, in a 1- to 30-fold concentration range. The impact of fermentation parameters on VSCs production was then investigated. We identified yeast assimilable nitrogen, cysteine, methionine and pantothenic acid contents – but not SO2 content – as the main factors modulating VSCs production. In particular, ethylthioacetate and all the VSCs deriving from methionine catabolism displayed a maximal production at yeast assimilable nitrogen concentrations around 250 mg/L; pantothenic acid had a positive impact on compounds deriving from methionine catabolism through the Ehrlich pathway but a negative one on the production of thioesters. Overall, these results highlight those factors to be taken into account to modulate the formation of negative VSCs and limit their content in wines.

Effects of Labrador Tea, Peppermint, and Winter Savory Essential Oils on Fusobacterium nucleatum.

Bad breath or halitosis is an oral condition caused by volatile sulfur compounds (VSC) produced by bacteria found in the dental and tongue biofilms. Fusobacterium nucleatum is a Gram-negative anaerobic bacterium that has been strongly associated with halitosis. In this study, essential oils (EO) from three plants, Labrador tea (Rhododendron groenlandicum [Oeder] Kron & Judd), peppermint (Mentha x piperita L.), and winter savory (Satureja montana L.), were investigated for their effects on growth, biofilm formation and killing, and VSC production by F. nucleatum. Moreover, their biocompatibility with oral keratinocytes was investigated. Using a broth microdilution assay, winter savory EO and to a lesser extent Labrador tea and peppermint EO showed antibacterial activity against F. nucleatum. A treatment of pre-formed biofilms of F. nucleatum with EO also significantly decreased bacterial viability as determined by a luminescence assay monitoring adenosine triphosphate production. The EO were found to permeabilize the bacterial cell membrane, suggesting that it represents the target of the tested EO. The three EO under investigation were able to dose-dependently reduce VSC production by F. nucleatum. Lastly, no significant loss of cell viability was observed when oral keratinocytes were treated with the EO at concentrations effective against F. nucleatum. This study supports the potential of Labrador tea, peppermint, and winter savory EO as promising agents to control halitosis and promote oral health.

Contribution of aging oral microbiota in getting neurodegenerative diseases

Nowadays aging-related neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease are as important as infectious diseases for human communities. 60–80% of dementia cases are related to Alzheimer's disease while only 2–3% of cases are associated with Parkinson's disease. Oral bacteria produce some chemical compounds such as volatile sulfur compounds and therefore are responsible for halitosis (malodor). This is while most of the cases (80–90%) of halitosis caused following the production of volatile sulfur compounds in the oral cavity. Some periodontal pathogens such as Aggregatibacter actinomycetemcomitans, Tannerella forsythia, and Prevotella gingivalis are detectable in Alzheimer's patients. On the other hand, Prevotella genus members, (e.g., P. intermedia, P. nigrescens, and P. melaninogenica) increase in Parkinson's disease patients, and most likely, it is associated with a reduction in hygiene oral care. Although many aspects of these diseases are still unknown, we have studied the Alzheimer's disease and Parkinson's disease diseases and also the role of oral microbiota infections in these diseases in older persons.

Paraclostridium dentum, a novel species with pathogenic features isolated from human dental plaque sample

A strictly anaerobic bacterial strain designated as SKVG24 was isolated from subgingival dental plaque samples of patients suffering from periodontitis. Cells were stained Gram-positive, rod shaped with endospore. The strain showed negative reaction to catalase and oxidase enzymes, but positive for gelatinase activity. Optimal growth was observed at 37 °C temperature and 7.0 pH. The 16S rRNA gene sequence BLAST analysis assigned strain SKVG24 to the genus Paraclostridium as it displayed 99.93% identity with P. benzoelyticum JC272T followed by P. bifermentans ATCC 638T (99.79%). However, average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) of the whole genome sequence showed <97% and <70% identity, respectively, with type strains of all closely related species. The G + C content of the DNA was 28.7 mol%. Total lipids profile showed presence of glycolipids as major lipids. Pathogenic features like hemolysis, gelatin hydrolysis and production of volatile sulfur compounds exhibited by strain SKVG24T were analogous to those observed in the established oral pathogenic strains. Further, whole genome sequence analysis confirmed the presence of genes encoding virulence factors and provided genomic insights on adaptation of the strain in oral environment. Based on the phenotypic and genetic differences with phylogenetic relatives, strain SKVG24T is proposed to represent a new species of the genus Paraclostridium with potential pathogenic ability, for which the name Paraclostridium dentum sp. nov., is suggested. The proposed type strain is SKVG24T (MTCC 12836T; = JCM 32760T).

Effects of academic stress on the levels of oral volatile sulfur compounds, halitosis-related bacteria and stress biomarkers of healthy female undergraduate students

To investigate whether academic stress changes the salivary microbiota and its relationship with salivary parameters, evaluating the effects on the production of volatile sulfur compounds (VSCs) in healthy women. Fifty-five women who were enrolled in a four-year Dentistry course were assessed for academic stress by the questionnaire Maslach Burnout Inventory—Student Survey and were then classified into ‘Not Stressed’ and ‘Stressed’ groups. Cortisol and alpha-amylase (AA) were measured as physiological stress biomarkers. Oral Chroma™ gas chromatograph was used to measure concentrations of hydrogen sulfide (H2S), methyl mercaptan and dimethyl sulfide. Salivary proteins were evaluated by western blot. Quantitative polymerase chain reaction was used to identify the salivary amounts of halitosis-associated bacteria. The ‘Stressed’ volunteers showed higher levels of H2S, AA, Fusobacterium nucleatum and total bacteria, compared to the ‘Not Stressed’ individuals (p < 0.05; Mann–Whitney test). Salivary proteins showed no differences between groups (p > 0.05; Mann–Whitney test). Academic stress was positively correlated with H2S, total bacteria and F. nucleatum counts, while F. nucleatum was positively correlated with AA. H2S showed positive correlations with AA and Solobacterium moorei (p < 0.05; Spearman correlation). Beta-defensin (BD) presented negative correlations with H2S and S. moorei (p < 0.05; Spearman correlation). Academic stress increased salivary F. nucleatum and total bacteria, as well as AA activity. The protein BD showed important correlations with bacteria and VSC. These changes appeared to be accountable for increased H2S production in the stressed women.

Management of common root rot and Fusarium foot rot of wheat using Brassica carinata break crop green manure

Brassica crop rotations have been associated with the reduction of pathogens, due to both the production of volatile sulfur compounds and changes in soil microbial community composition. In this research Brassica carinata, as break crop green manure, was evaluated for the control of common root rot and Fusarium foot rot of durum wheat in a complete randomized experimental scheme. Field trials were performed on seven farms, in some of the most representative areas of cereal production in Sicily, from 2011 to 2013. A total eradication of Bipolaris sorokiniana and Microdochium nivale populations following the B. carinata break crop, as compared to wheat monoculture, was found in all experimental fields. Fusarium culmorum population reduction ranged between 90% and 66%, with an average of 82% considering all field trials data. Symptoms or signs of common root rot were absent on wheat plants grown after the B. carinata break crop but were detectable on the wheat monoculture. Both incidence and severity of Fusarium foot rot were also reduced, by an average of 40.6% and 56.3%, respectively, following the B. carinata break crop in six of the seven field trials. After B. carinata break crop, wheat plant growth showed significant increases in height and weight, with an average increase of 48.3% and 49.0% respectively. Durum wheat grain yield was also significantly greater following the Brassica green manure, with increases ranging from 9.5% to 62.2%, as compared to wheat monoculture. B. carinata break crop green manure was also characterized by interesting results in terms of disease management in comparison to controls. These results suggest that the use of Brassicas such as B. carinata, as a break crop green manure, may potentially provide significant reduction of pathogens and disease development as well as improvement in grain yield of the succeeding crop.