Desulfovibrio desulfuricans and its derived metabolites confer resistance to FOLFOX through METTL3

BACKGROUND

Chemoresistance is a critical factor contributing to poor prognosis in clinical patients with cancer undergoing postoperative adjuvant chemotherapy. The role of gut microbiota in mediating resistance to tumour chemotherapy remains to be investigated.

METHODS

Patients with CRC were categorised into clinical benefit responders (CBR) and no clinical benefit responders (NCB) based on chemotherapy efficacy. Differential bacterial analysis using 16S rRNA sequencing revealed Desulfovibrio as a distinct microbe between the two groups. Employing a syngeneic transplantation model, we assessed the effect of Desulfovibrio on chemotherapy by measuring tumour burden, weight, and Ki-67 expression. We further explored the mechanisms underlying the compromised chemotherapeutic efficacy of Desulfovibrio using metabolomics, western blotting, colony formation, and cell apoptosis assays.

FINDINGS

In comparison, Desulfovibrio was more abundant in the NCB group. In vivo experiments revealed that Desulfovibrio colonisation in the gut weakened the efficacy of FOLFOX. Treatment with Desulfovibrio desulfuricans elevates serum S-adenosylmethionine (SAM) levels. Interestingly, SAM reduced the sensitivity of CRC cells to FOLFOX, thereby promoting the growth of CRC tumours. These experiments suggest that SAM promotes the growth and metastasis of CRC by driving the expression of methyltransferase-like 3 (METTL3).

INTERPRETATION

A high abundance of Desulfovibrio in the intestines indicates poor therapeutic outcomes for postoperative neoadjuvant FOLFOX chemotherapy in CRC. Desulfovibrio drives the manifestation of METTL3 in CRC, promoting resistance to FOLFOX chemotherapy by increasing the concentration of SAM.

FUNDING

This study is supported by Wuxi City Social Development Science and Technology Demonstration Project (N20201005).

Moringa oleifera leaf alleviates functional constipation via regulating the gut microbiota and the enteric nervous system in mice

Moringa oleifera Lam. leaf is not only a new food resource in China, but also a traditional medicinal plant. It is commonly used in the folk to alleviate constipation, but its laxative mechanism is not fully understood. Hence we investigated it in loperamide-induced functional constipation (FC) mice. The results showed that MOAE significantly regulated not only gastrointestinal hormones and neurotransmitters in serum but also important gastrointestinal motility factors in the enteric nervous system (ENS)-interstitial cells of Cajal (ICCs)-smooth muscle cell (SMC) network. Meanwhile, MOAE attenuated intestinal inflammation, increased cecal short-chain fatty acid levels and colonic antimicrobial peptide expression, and improved the impaired intestinal barrier function in loperamide-induced FC mice. In addition, MOAE also increased fecal water content by inhibiting the mRNA expression of colonic aquaporins (Aqp3 and Aqp4) in FC mice. Interestingly and importantly, MOAE affected the intestinal microbiota by inhibiting some key "constipation-causing" microbiota, such as Bacteroidaceae, Clostridiaceae, Bacteroides, and Ruminococcus, and promoting the growth of other important "constipation-curing" microbiota, such as Butyricoccus, Tyzzerella, and Desulfovibrio. These important taxa are significantly associated with a variety of indicators of constipation. These findings suggest that MOAE can promote defecation through its rich chemical composition to modulate the ENS-ICCs-SMCs network and the gut microecosystem.

Fecal microbiota as a predictor of acupuncture responses in patients with postpartum depressive disorder

Background

There are several clinical and molecular predictors of responses to antidepressant therapy. However, these markers are either too subjective or complex for clinical use. The gut microbiota could provide an easily accessible set of biomarkers to predict therapeutic efficacy, but its value in predicting therapy responses to acupuncture in patients with depression is unknown. Here we analyzed the predictive value of the gut microbiota in patients with postpartum depressive disorder (PPD) treated with acupuncture.

Methods

Seventy-nine PPD patients were enrolled: 55 were treated with acupuncture and 24 did not received any treatment. The 17-item Hamilton depression rating scale (HAMD-17) was used to assess patients at baseline and after eight weeks. Patients receiving acupuncture treatment were divided into an acupuncture-responsive group or non-responsive group according to HAMD-17 scores changes. Baseline fecal samples were obtained from the patients receiving acupuncture and were analyzed by high-throughput 16S ribosomal RNA sequencing to characterize the gut microbiome.

Results

47.27% patients responded to acupuncture treatment and 12.5% patients with no treatment recovered after 8-week follow-up. There was no significant difference in α-diversity between responders and non-responders. The β-diversity of non-responders was significantly higher than responders. Paraprevotella and Desulfovibrio spp. were significantly enriched in acupuncture responders, and these organisms had an area under the curve of 0.76 and 0.66 for predicting responder patients, respectively.

Conclusions

Paraprevotella and Desulfovibrioare may be useful predictive biomarkers to predict PPD patients likely to respond to acupuncture. Larger studies and validation in independent cohorts are now needed to validate our findings.

Hyperimmune bovine colostrum containing lipopolysaccharide antibodies (IMM124-E) has a nondetrimental effect on gut microbial communities in unchallenged mice

Enterotoxigenic Escherichia coli (ETEC) is a leading cause of bacterial diarrhea with the potential to cause long-term gastrointestinal (GI) dysfunction. Preventative treatments for ETEC-induced diarrhea exist, yet the effects of these treatments on GI commensals in healthy individuals are unclear. Whether administration of a prophylactic preventative treatment for ETEC-induced diarrhea causes specific shifts in gut microbial populations in controlled environments is also unknown. Here, we studied the effects of a hyperimmune bovine colostrum (IMM-124E) used in the manufacture of Travelan (AUST L 106709) on GI bacteria in healthy C57BL/6 mice. Using next-generation sequencing, we aimed to test the onset and magnitude of potential changes to the mouse gut microbiome in response to the antidiarrheagenic hyperimmune bovine colostrum product, rich in immunoglobulins against select ETEC strains (Travelan, Immuron Ltd). We show that in mice administered colostrum containing lipopolysaccharide (LPS) antibodies, there was an increased abundance of potentially gut-beneficial bacteria, such as Akkermansia and Desulfovibrio, without disrupting the underlying ecology of the GI tract. Compared to controls, there was no difference in overall weight gain, body or cecal weights, or small intestine length following LPS antibody colostrum supplementation. Overall, dietary supplementation with colostrum containing LPS antibodies produced subtle alterations in the gut bacterial composition of mice. Primarily, Travelan LPS antibody treatment decreased the ratio of Firmicutes/Bacteroidetes in gut microbial populations in unchallenged healthy mice. Further studies are required to examine the effect of Travelan LPS antibody treatment to engineer the microbiome in a diseased state and during recovery.

Coexistence of Psychrophilic, Mesophilic, and Thermophilic Sulfate-Reducing Bacteria in a Deep Subsurface Aquifer Associated with Coal-Bed Methane Production

The microbial community of subsurface environments remains understudied due to limited access to deep strata and aquifers. Coal-bed methane (CBM) production is associated with a large number of wells pumping water out of coal seams. CBM wells provide access to deep biotopes associated with coal-bed water. Temperature is one of the key constraints for the distribution and activity of subsurface microorganisms, including sulfate-reducing prokaryotes (SRP). The 16S rRNA gene amplicon sequencing coupled with in situ sulfate reduction rate (SRR) measurements with a radioactive tracer and cultivation at various temperatures revealed that the SRP community of the coal bed water of the Kuzbass coal basin is characterized by an overlapping mesophilic-psychrophilic boundary. The genus Desulfovibrio comprised a significant share of the SRP community. The D. psychrotolerans strain 1203, which has a growth optimum below 20 °C, dominated the cultivated SRP. SRR in coal bed water varied from 0.154 ± 0.07 to 2.04 ± 0.048 nmol S cm-3 day-1. Despite the ambient water temperature of ~ 10-20 °C, an active thermophilic SRP community occurred in the fracture water, which reduced sulfate with the rate of 0.159 ± 0.023 to 0.198 ± 0.007 nmol S cm-3 day-1 at 55 °C. A novel moderately thermophilic "Desulforudis audaxviator"-clade SRP has been isolated in pure culture from the coal-bed water.

Syntrophic Interactions Ameliorate Arsenic Inhibition of Solvent-Dechlorinating Dehalococcoides mccartyi

Interactions and nutrient exchanges among members of microbial communities are important for understanding functional relationships in environmental microbiology. We can begin to elucidate the nature of these complex systems by taking a bottom-up approach utilizing simplified, but representative, community members. Here, we assess the effects of a toxic stress event, the addition of arsenite (As(III)), on a syntrophic co-culture containing lactate-fermenting Desulfovibrio vulgaris Hildenborough and solvent-dechlorinating Dehalococcoides mccartyi strain 195. Arsenic and trichloroethene (TCE) are two highly prevalent groundwater contaminants in the United States, and the presence of bioavailable arsenic is of particular concern at remediation sites in which reductive dechlorination has been employed. While we previously showed that low concentrations of arsenite (As(III)) inhibit the keystone TCE-reducing microorganism, D. mccartyi, this study reports the utilization of physiological analysis, transcriptomics, and metabolomics to assess the effects of arsenic on the metabolisms, gene expression, and nutrient exchanges in the described co-culture. It was found that the presence of D. vulgaris ameliorated arsenic stress on D. mccartyi, improving TCE dechlorination under arsenic-contaminated conditions. Nutrient and amino acid export by D. vulgaris may be a stress-ameliorating exchange in this syntrophic co-culture under arsenic stress, based on upregulation of transporters and increased extracellular nutrients like sarcosine and ornithine. These results broaden our knowledge of microbial community interactions and will support the further development and implementation of robust bioremediation strategies at multi-contaminant sites.

A Comparative Multi-Frequency EPR Study of Dipolar Interaction in Tetra-Heme Cytochromes

Distances between Fe ions in multiheme cytochromes are sufficiently short to make the intramolecular dipole-dipole interaction between hemes probable. In the analysis of EPR data from cytochromes, this interaction has thus far been ignored under the assumption that spectra are the simple sum of non-interacting components. Here, we use a recently developed low-frequency broadband EPR spectrometer to establish the extent of dipolar interaction in the example cytochromes, characterize its spectral signatures, and identify present limitations in the analysis. Broadband EPR spectra of Shewanella oneidensis MR-1 small tetraheme cytochrome (STC) have been collected over the frequency range of 0.45 to 13.11 GHz, and they have been compared to similar data from Desulfovibrio vulgaris Hildenborough cytochrome c3. The two cases are representative examples of two very different heme topologies and corresponding electron-transfer properties in tetraheme proteins. While in cytochrome c3, the six Fe-Fe distances can be sorted into two well-separated groups, those in STC are diffuse. Since the onset of dipolar interaction between Fe-Fe pairs is already observed in the X-band, the g values are determined in the simulation of the 13.11 GHz spectrum. Low-frequency spectra are analyzed with the inclusion of dipolar interaction based on available structural data on mutual distances and orientations between all hemes. In this procedure, all 24 possible assignments of individual heme spectra to heme topologies are sampled. The 24 configurations can be reduced to a few, but inspection falls short of a unique assignment, due to a remaining lack of understanding of the fine details of these complex spectra. In general, the EPR analysis suggests the four-heme system in c3 to be more rigid than that in STC, which is proposed to be related to different physiological roles in electron transfer.

Study on the treatment of sulfite wastewater by Desulfovibrio

In the wet flue gas desulfurization (WFGD) process, SO₂ is adsorbed by alkaline liquor to produce alkaline wastewater containing sulfate and sulfite. Although the traditional chemical treatment method can achieve a high removal rate, it consumes a large number of chemicals and yields a large number of low-value by-products. The biological treatment process is a greener and more environmentally friendly treatment method. The current work studies microbial flue gas desulfurization directly using sulfite as the electron acceptor in the reduction process. Desulfovibrio were obtained by isolation and purification, and their growth conditions in sulfite wastewater and desulfurization process conditions were investigated by intermittent and continuous experiments. The results of intermittent experiments indicated that the optimal growth conditions of Desulfovibrio were a temperature of 38 °C, a pH value of 8.0, a COD/SO₃^2- of 2 and that the growth of bacteria would be inhibited at a pH above 9.0 or below 7.3. Furthermore, Desulfovibrio could grow in simulated wastewater with a high SO₃^2- concentration of 8000 mg/L. The results of continuous experiments showed that the removal of sulfite and the recovery of elemental sulfur was realized by a micro-oxygen depletion process, and the removal rate of sulfite of 99%, the yield of elemental sulfur is more than 80% and can reach 90% under the condition of low influent concentration. The bacteria grew well at a temperature of 40 °C and a pH value of the influent water of 7.5. To ensure the treatment effect, the hydraulic retention time (HRT) should be more than doubled for each 1000 mg/L increase in the influent sulfite concentration under the same reflux ratio. When the influent sulfite concentration was 1000 mg/L, 2000 mg/L, 3000 mg/L, and 4000 mg/L, the corresponding HRT was 3.01 h, 6.94 h, 17.4 h, and 31.9 h, respectively. The dominant species in the reactor was Desulfovibrio bacteria at 63.9% abundance. This study demonstrated the feasibility of using sulfite as an electron acceptor for microbial desulfurization, which can optimize the initial process and provide the possibility of treating high-concentration sulfite wastewater.

Desulfovibrio in the Gut: The Enemy within?

Desulfovibrio (DSV) are sulfate-reducing bacteria (SRB) that are ubiquitously present in the environment and as resident commensal bacteria within the human gastrointestinal tract. Though they are minor residents of the healthy gut, DSV are opportunistic pathobionts that may overgrow in the setting of various intestinal and extra-intestinal diseases. An increasing number of studies have demonstrated a positive correlation between DSV overgrowth (bloom) and various human diseases. While the relationship between DSV bloom and disease pathology has not been clearly established, mounting evidence suggests a causal role for these bacteria in disease development. As DSV are the most predominant genera of SRB in the gut, this review summarizes current knowledge regarding the relationship between DSV and a variety of diseases. In this study, we also discuss the mechanisms by which these bacteria may contribute to disease pathology.

Genomic insight into iron acquisition by sulfate-reducing bacteria in microaerophilic environments

Historically, sulfate-reducing bacteria (SRB) have been considered to be strict anaerobes, but reports in the past couple of decades indicate that SRB tolerate exposure to O2 and can even grow in aerophilic environments. With the transition from anaerobic to microaerophilic conditions, the uptake of Fe(III) from the environment by SRB would become important. In evaluating the metabolic capability for the uptake of iron, the genomes of 26 SRB, representing eight families, were examined. All SRB reviewed carry genes (feoA and feoB) for the ferrous uptake system to transport Fe(II) across the plasma membrane into the cytoplasm. In addition, all of the SRB genomes examined have putative genes for a canonical ABC transporter that may transport ferric siderophore or ferric chelated species from the environment. Gram-negative SRB have additional machinery to import ferric siderophores and ferric chelated species since they have the TonB system that can work alongside any of the outer membrane porins annotated in the genome. Included in this review is the discussion that SRB may use the putative siderophore uptake system to import metals other than iron.

Sulfate-Reducing Bacteria in Patients Undergoing Fixed Orthodontic Treatment

OBJECTIVES

The oral microbiological environment may be implicated in the corrosion of orthodontic metals. This study aimed to examine the prevalence of sulfate-reducing bacteria (SRB) in orthodontic patients undergoing fixed appliance treatment.

METHODS

Sixty-nine orthodontic and 69 healthy non-orthodontic participants were enrolled in the study. Supragingival and subgingivaloral biofilm were collected and tested for the presence of SRB. The DNA extraction, polymerase chain reaction (PCR), and 16sRNA Sanger sequencing method was performed from the SRB-positive samples. The sequenced PCR products were analysed and compared with databases to identify the bacterial genus.

RESULTS

Amongst 69 orthodontic patients, characteristic black precipitates developed in 14, indicating the presence of iron sulfides which demonstrates the likelihood of SRB. Alternatively, 2 out of 69 showed the presence of SRB in healthy non-orthodontic participants (controls). Desulfovibrio spp was confirmed by analyses of 16sRNA sequencing, which revealed that the SRB prevalence was 20% in the examined participants with orthodontic appliances.

CONCLUSIONS

The prevalence of SRB was found to be significantly higher amongst orthodontic patients compared to non-orthodontic participants. Presence of stainless steel in the oral environment may have facilitated the colonisation of SRB.

The link between increased Desulfovibrio and disease severity in Parkinson's disease

Parkinson's disease (PD), a progressive and incurable neurodegenerative disease, has taken a huge economic toll and medical burden on our society. Increasing evidence has shown a strong link between PD and the gut microbiome, but studies on the relationship between the gut microbiome and the severity of PD are limited. In this study, 90 fecal samples were collected from newly diagnosed and untreated patients with PD (n = 47) and matched healthy control subjects (n = 43). The 16S rRNA amplicon and shotgun metagenomic sequencing was performed, aiming to uncover the connection between the gut microbiome and disease severity in PD. The results showed that Desulfovibrio was significantly increased in PD compared to healthy controls and positively correlated with disease severity. The increase in Desulfovibrio was mainly driven by enhanced homogeneous selection and weakened drift. Moreover, through metagenome-assembled genomes (MAGs) analysis, a Desulfovibrio MAG (MAG58) was obtained which was also positively correlated with disease severity. MAG58 possesses a complete assimilatory sulfate reduction pathway and a near-complete dissimilatory sulfate reduction pathway to produce hydrogen sulfide which may influence the development of PD. Based on these results, a potential pathogenic mechanism was presented to illustrate how the increased Desulfovibrio accelerates the development of PD by producing excessive hydrogen sulfide. The present study highlighted the vital role of Desulfovibrio in the development of PD, which may provide a new target for the diagnosis and treatment of PD. KEY POINTS: • The evidence for the link between increased Desulfovibrio and disease severity in PD • A Desulfovibrio MAG was obtained which was correlated with PD • A model was presented to illustrate how increased Desulfovibrio causes PD.

nov., a sulfate-reducing bacterium isolated from mangrove sediments: a member of the proposed genus "Psychrodesulfovibrio"

"Psychrodesulfovibrio", a proposed genus within the family Desulfovibrionaceae, is a group of sulfate-reducing bacteria with biogeochemical significance but restricted child taxa availability. In this study, a strictly anaerobic bacterium, designed strain FT415^T, was isolated from mangrove sediments in Futian Mangrove Nature Reserve in Shenzhen, China. The strain was Gram-stain-negative, motile, and vibrio-shaped with a single polar flagellum, which grew at the temperature range of 15-42 °C (optimum 37 °C), pH range of 6.0-7.5 (optimum 6.8), and in the presence of 0-36 g l^-1 NaCl (optimum 6 g l^-1 NaCl). In the presence of sulfate, electron donors including lactate, ethanol, pyruvate, malate, fumarate, succinate, cysteine, and glycerol were incompletely oxidized to acetate, and H₂ and formate were used as electron donors with acetate as the carbon source by strain FT415^T. Sulfate, thiosulfate, sulfide, and anthraquinone-2,6-disulfonate were reduced in the presence of lactate. Fe(III) oxide was reduced without cell growth. Fermentative growth was observed with pyruvate and cysteine. Vitamins were not required for growth. The major cellular fatty acids (> 10%) were C_16:0, summed feature 10 (C_18:1 c11/t9/t6 and/or unknown ECL 17.834), C_16:1 cis 9, and C_18:0. The major polar lipids were phosphatidylethanolamine, phospholipids, and aminolipids. The predominant menaquinone was MK-6(H₂). The genomic DNA G+C content was 56.7%. Phylogenetic analysis showed that strain FT415^T shared a 98.1% similarity in 16S rRNA gene sequence, an average nucleotide identity value of 84.0%, an average amino-acid identity value of 85.4%, and a digital DNA-DNA hybridization value of 25.7% with its closest relative Desulfovibrio subterraneus HN2^T, which has been proposed to be transferred to the genus "Psychrodesulfovibrio". Based on phenotypic, phylogenetic, and genotypic evidence, a new species of the family Desulfovibrionaceae, Desulfovibrio mangrovi sp. nov. was proposed with the type strain FT415^T (=GDMCC 1.3410^T=KCTC 25525^T).

NMR-based metabolomic analysis of the physiological role of the electron-bifurcating FeFe-hydrogenase Hnd in Solidesulfovibrio fructosivorans under pyruvate fermentation

Solidesulfovibrio fructosivorans (formely Desulfovibrio fructosovorans), an anaerobic sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of hydrogen gas (H₂) into protons and electrons. One of these, named Hnd, was demonstrated to be an electron-bifurcating hydrogenase Hnd (Kpebe et al., 2018). It couples the exergonic reduction of NAD⁺ to the endergonic reduction of a ferredoxin with electrons derived from H₂ and whose function has been recently shown to be involved in ethanol production under pyruvate fermentation (Payne 2022). To understand further the physiological role of Hnd in S. fructosivorans, we compared the mutant deleted of part of the hnd gene with the wild-type strain grown on pyruvate without sulfate using NMR-based metabolomics. Our results confirm that Hnd is profoundly involved in ethanol metabolism, but also indirectly intervenes in global carbon metabolism and additional metabolic processes such as the biosynthesis of branched-chain amino acids. We also highlight the metabolic reprogramming induced by the deletion of hndD that leads to the upregulation of several NADP-dependent pathways.

Active Sulfate-Reducing Bacterial Community in the Camel Gut

The diversity and activity of sulfate-reducing bacteria (SRB) in the camel gut remains largely unexplored. An abundant SRB community has been previously revealed in the feces of Bactrian camels (Camelus bactrianus). This study aims to combine the 16S rRNA gene profiling, sulfate reduction rate (SRR) measurement with a radioactive tracer, and targeted cultivation to shed light on SRB activity in the camel gut. Fresh feces of 55 domestic Bactrian camels grazing freely on semi-arid mountain pastures in the Kosh-Agach district of the Russian Altai area were analyzed. Feces were sampled in early winter at an ambient temperature of -15 °C, which prevented possible contamination. SRR values measured with a radioactive tracer in feces were relatively high and ranged from 0.018 to 0.168 nmol S cm^-3 day^-1. The 16S rRNA gene profiles revealed the presence of Gram-negative Desulfovibrionaceae and spore-forming Desulfotomaculaceae. Targeted isolation allowed us to obtain four pure culture isolates belonging to Desulfovibrio and Desulforamulus. An active SRB community may affect the iron and copper availability in the camel intestine due to metal ions precipitation in the form of sparingly soluble sulfides. The copper-iron sulfide, chalcopyrite (CuFeS₂), was detected by X-ray diffraction in 36 out of 55 analyzed camel feces. In semi-arid areas, gypsum, like other evaporite sulfates, can be used as a solid-phase electron acceptor for sulfate reduction in the camel gastrointestinal tract.

Diversity and Comparison of Intestinal Desulfovibrio in Patients with Liver Cirrhosis and Healthy People

Desulfovibrio belongs to Sulfate-reducing bacteria (SRB), which are widely present in anaerobic environments, including the human gut. Desulfovibrio has been associated with many human diseases, including chronic liver disease. However, the characteristics and difference of Desulfovibrio from fecal samples of healthy volunteers (HV) and patients with liver cirrhosis (LC) have not been fully elucidated. Here, we isolated Desulfovibrio from the feces of 6 HV and 9 LC, and 88 Desulfovibrio strains were obtained. In the feces of HV, 55% of isolated strains were D. desulfuricans, followed by D. intestinalis (15%), D. simplex (11%), D. piger (9%), D. legallii (4%), Cupidesulfovibrio oxamicus (4%) and D. fairfieldensis (2%). However, only D. desulfuricans (60%) and C. oxamicus (40%) were isolated from fecal samples of patients with LC. Our results suggest that there was a significant difference in the desulfurization ability and the H₂S production ability of different Desulfovibrio. Desulfovibrio. Furthermore, we found that Desulfovibrio isolated from the patients with LC generally had a higher hydrogen sulfide production capacity, gastrointestinal tolerance, and levels of antibiotic resistance than the same species isolated from HV. Our findings suggested that Desulfovibrio may be associated with the occurrence and development of liver cirrhosis.

Gas-Mediated Intestinal Microbiome Regulation Prompts the Methanol Extract of Schizonepetae Spica to Relieve Colitis

Intestinal dysbiosis plays an important role in the pathogenesis of colitis (UC). Schizonepetae Herba can achieve anti-inflammatory effects as a medicine and food homologous vegetable. Luteolin, eriodictyol, fisetin, and kaempferol are the main anti-inflammatory active compounds obtained through mass spectrometry from the methanol extract of Schizonepetae Spica (JJSM). JJSM intervention resulted in attenuated weight loss, high disease-activity-index score, colon length shortening and colonic pathological damage in DSS-induced colitis mice. Interestingly, hydrogen sulfide (H₂S) was inhibited remarkably, which is helpful to elucidate the relationship between active substance and intestinal flora. Furthermore, JJSM administration improved intestinal flora with down-regulating the abundance of harmful bacteria such as Clostridiales and Desulfovibrio and up-regulating the abundance of beneficial bacteria such as Muribaculaceae and Ligolactobacillus and enhanced the production of SCFAs. It is worth noticing that Desulfovibrio is related to the production of intestinal gas H₂S. The elevated levels of Desulfovibrio and H₂S will hasten the onset of colitis, which is a crucial risk factor for colitis. The results displayed that JJSM could considerably ameliorate colitis by rebuilding H₂S-related intestinal flora, which provides a new therapeutic strategy for Schizonepetae Spica to be utilized as a functional food and considered as an emerging candidate for intestinal inflammation.

Desulfovibrio confers resilience to the comorbidity of pain and anxiety in a mouse model of chronic inflammatory pain

BACKGROUND

Patients with chronic pain frequently suffer from anxiety symptoms. It has been well established that gut microbiota is associated with the pathogenesis of pain and anxiety. However, it is unknown whether the gut microbiota, particularly the specific bacteria, play a role in the comorbidity of chronic pain and anxiety.

METHODS

Chronic inflammatory pain was induced in mice by a single injection of complete Freund's adjuvant (CFA). Mice were then separated into anxiety-susceptible and anxiety-resilient phenotypes by hierarchical clustering analysis of behaviors. Fecal samples were collected to perform 16S rRNA gene sequencing. Chronic diazepam intervention served as a therapeutic strategy and its effect on the composition of gut microbiota was also determined.

RESULTS

α-Diversity and β-diversity both showed significant differences among the groups. A total of 12 gut bacteria were both altered after CFA injection and reversed by chronic diazepam treatment. More importantly, the pain hypersensitivity and anxiety-like behaviors were relieved by chronic diazepam treatment. Interestingly, we also found that Desulfovibrio was increased in anxiety-resilient group compared to control and anxiety-susceptible groups.

CONCLUSION

Abnormal composition of gut microbiota plays an essential role in chronic pain as well as in anxiety. Besides, the increased level of Desulfovibrio in anxiety-resilient mice indicated its therapeutic effects on the comorbidity of pain and anxiety. Collectively, targeting gut microbiota, especially increasing the Desulfovibrio level, might be effective in the alleviation of chronic pain-anxiety comorbidity.

Microbiota-host crosstalk in the newborn and adult rumen at single-cell resolution

BACKGROUND

The rumen is the hallmark organ of ruminants, playing a vital role in their nutrition and providing products for humans. In newborn suckling ruminants milk bypasses the rumen, while in adults this first chamber of the forestomach has developed to become the principal site of microbial fermentation of plant fibers. With the advent of single-cell transcriptomics, it is now possible to study the underlying cell composition of rumen tissues and investigate how this relates the development of mutualistic symbiosis between the rumen and its epithelium-attached microbes.

RESULTS

We constructed a comprehensive cell landscape of the rumen epithelium, based on single-cell RNA sequencing of 49,689 high-quality single cells from newborn and adult rumen tissues. Our single-cell analysis identified six immune cell subtypes and seventeen non-immune cell subtypes of the rumen. On performing cross-species analysis of orthologous genes expressed in epithelial cells of cattle rumen and the human stomach and skin, we observed that the species difference overrides any cross-species cell-type similarity. Comparing adult with newborn cattle samples, we found fewer epithelial cell subtypes and more abundant immune cells, dominated by T helper type 17 cells in the rumen tissue of adult cattle. In newborns, there were more fibroblasts and myofibroblasts, an IGFBP3⁺ epithelial cell subtype not seen in adults, while dendritic cells were the most prevalent immune cell subtype. Metabolism-related functions and the oxidation-reduction process were significantly upregulated in adult rumen epithelial cells. Using 16S rDNA sequencing, fluorescence in situ hybridization, and absolute quantitative real-time PCR, we found that epithelial Desulfovibrio was significantly enriched in the adult cattle. Integrating the microbiome and metabolome analysis of rumen tissues revealed a high co-occurrence probability of Desulfovibrio with pyridoxal in the adult cattle compared with newborn ones while the scRNA-seq data indicated a stronger ability of pyroxidal binding in the adult rumen epithelial cell subtypes. These findings indicate that Desulfovibrio and pyridoxal likely play important roles in maintaining redox balance in the adult rumen.

CONCLUSIONS

Our integrated multi-omics analysis provides novel insights into rumen development and function and may facilitate the future precision improvement of rumen function and milk/meat production in cattle.

Pathogenic effects of Desulfovibrio in the gut on fatty liver in diet-induced obese mice and children with obesity

BACKGROUND

Although we know the key role of gut dysbiosis in nonalcoholic fatty liver disease (NAFLD), it remains unclear what microbe(s) are responsible. This study aims to identify the microbes that cause NAFLD.

METHODS

C57BL/6JNarl male mice fed a high-fat diet (HFD) were orally administered Lactobacillus reuteri (L. reuteri) or Lactobacillus rhamnosus GG plus Bifidobacterium animalis subsp. lactis BB12 (LGG plus BB12). Their fecal microbiomes identified by 16S rRNA sequencing were correlated with the severity of fatty liver. We then used a human cohort to confirm the role of the microbe(s). The HFD-fed mice were administrated with the identified bacterium, Desulfovibrio. The histopathological changes in the liver and ileum were analyzed.

RESULTS

Lactobacillus and Bifidobacterium improved hepatic steatosis and fibrosis in HFD-fed mice, which was related to the decreased abundance of Desulfovibrio in feces. Further human study confirmed the amount of D. piger in the fecal microbiota of obese children with NAFLD was increased. We then administered D. piger and found aggravated hepatic steatosis and fibrosis in HFD-fed mice. Hepatic expression of CD36 was significantly increased in HFD-fed mice gavaged with D. piger. In HepG2 cells, overexpression of CD36 increased lipid droplets, whereas knockdown of CD36 decreased lipid droplets. HFD-fed mice gavaged with D. piger had a decrease in the villus length, crypt depth, and zonula occludens-1 density in the ileum tissue.

CONCLUSIONS

Our findings provide novel insights into the role of Desulfovibrio dysregulation in NAFLD. Modulation of Desulfovibrio may be a potential target for the treatment of NAFLD.

Multi-omic Analysis of the Gut Microbiome in Rats with Lithium-Pilocarpine-Induced Temporal Lobe Epilepsy

Evidence supports that the gut microbiota and bacteria-dependent metabolites influence the maintenance of epileptic brain activity. However, the alterations in the gut microbiota between epileptic versus healthy individuals are poorly understood. We used a multi-omic approach to evaluate the changes in the composition of gut metagenome as well in the fecal metabolomic profile in rats before and after being submitted to status epilepticus (SE)-induced temporal lobe epilepsy (TLE). The 16S ribosomal RNA (rRNA) sequencing of fecal samples coupled to bioinformatic analysis revealed taxonomic, compositional, and functional shifts in epileptic rats. The species richness (Chao1 index) was significantly lower in the post-TLE group, and the β-diversity analysis revealed clustering separated from the pre-TLE group. The taxonomic abundance analysis showed a significant increase of phylum Desulfobacterota and a decrease of Patescibacteria in the post-TLE group. The DESEq2 and LEfSe analysis resulted in 18 genera significantly enriched between post-TLE and pre-TLE groups at the genus level. We observed that epileptic rats present a peculiar metabolic phenotype, including a lower concentration of D-glucose and L-lactic acid and a higher concentration of L-glutamic acid and glycine. The microbiota-host metabolic correlation analysis showed that the genera differentially abundant in post-TLE rats are associated with the altered metabolites, especially the proinflammatory Desulfovibrio and Marvinbryantia, which were enriched in epileptic animals and positively correlated with these excitatory neurotransmitters and carbohydrate metabolites. Therefore, our data revealed a correlation between dysbacteriosis in epileptic animals and fecal metabolites that are known to be relevant for maintaining epileptic brain activity by enhancing chronic inflammation, an excitatory-inhibitory imbalance, and/or a metabolic disturbance. These data are promising and suggest that targeting the gut microbiota could provide a novel avenue for preventing and treating acquired epilepsy. However, the causal relationship between these microbial/metabolite components and the SRS occurrence still needs further exploration.

Chondroitin sulfate stimulates the secretion of H2S by Desulfovibrio to improve insulin sensitivity in NAFLD mice

Hydrogen sulfide (H₂S) is a bioactive gas regulating insulin secretion and sensitivity, produced by sulfate-reducing bacteria in the gut. The present study investigated the effect of chondroitin sulfate (CS) treatment, which indirectly increased the H₂S production on nonalcoholic fatty liver disease (NAFLD). A 7-week CS supplementation had beneficial effects on body weight gain, liver function, hepatic histology, and serum lipid levels. CS could ameliorate diet-induced insulin resistance and improve insulin sensitivity via the AKT pathway, and modulate gut microbiota composition, especially increased the abundance of Desulfovibrio and elevated levels of hydrogen sulfide (H₂S). Collectively, these findings suggested that CS treatment was positively correlated with Desulfovibrio in the gut, and the metabolic H₂S flowed into the liver via the gut-liver axis, thereby triggering the AKT signaling pathway and improving insulin resistance. Thus, CS-induced alterations in the gut microbiota seem a promising for ameliorating NAFLD.

High-Fat Diet Enhances the Liver Metastasis Potential of Colorectal Cancer through Microbiota Dysbiosis

Simple Summary

High-fat diet (HFD) is hypothesized to induce gut dysbiosis and promote colorectal cancer (CRC). However, the specific mechanisms involved require investigation. In this study, we established an animal model and utilized 16S sequencing to determine the effects of HFD on gut microbiota, as well as on the colon and liver. Furthermore, due to the abundance of Desulfovibrio (DSV) in the faecal samples of HFD-fed rats and CRC hepatic metastasis patients, we also conducted a DSV gavage animal experiment to determine the role of DSV in CRC development. Our study confirmed that HFD could cause microbiota dysbiosis, especially DSV enrichment, and may promote CRC initiation and metastasis.

Abstract

Obesity, metabolic changes, and intestinal microbiota disruption significantly affect tumorigenesis and metastasis in colorectal cancer (CRC). However, the relationships among these factors remain poorly understood. In this study, we found that a high-fat diet (HFD) promoted gut barrier dysfunction and inflammation in the colorectum and liver. We further investigated gut microbiota changes through 16S rRNA sequencing of faecal samples from HFD-fed rats and CRC hepatic metastasis patients and found an abundance of Desulfovibrio (DSV). DSV could also induce barrier dysfunction in the colorectum and inflammation in the colorectum and liver, suggesting that it contributes to the formation of a microenvironment conducive to CRC tumorigenesis and metastasis. These findings highlight that HFD-induced microbiota dysbiosis, especially DSV abundance, could promote CRC initiation and metastasis.

Quantification of Organic Carbon Sequestered by Biogenic Iron Sulfide Minerals in Long-Term Anoxic Laboratory Incubations

Organic carbon sequestration in sedimentary environments controls oxygen and carbon dioxide concentrations in the atmosphere. While minerals play an important role in the preservation of organic carbon, there is a lack of understanding about the formation and stability of organo-mineral interactions in anoxic environments, especially those involving authigenic iron sulfide minerals. In this study, we quantified organic carbon and nitrogen sequestered in biogenic iron sulfide minerals co-precipitated with sulfate-reducing bacteria (SRB) in freshwater and marine conditions in long-term laboratory experiments. The amounts of C and N associated with biogenic iron sulfide minerals increased with increasing cell biomass concentrations available in the media. C and N levels stabilized over the first 2 months of incubation and remained stable for up to 1 year. Crystalline mackinawite (FeS) formed in all experimental conditions and transformed to greigite only in some experimental conditions. We did not find evidence that this mineral transformation affected C and N levels, neither could we identify the factors that controlled greigite formation. Pyrite did not form in our experimental conditions. While C concentrations in minerals correlated with concentrations of reduced sulfate in both the freshwater and marine media, removal of OC by iron sulfide minerals was more efficient in freshwater than marine conditions. Removal of OC by iron sulfide minerals was also more efficient when cells were present (SRB biomass) in comparison with abiotic incubations with organic mixtures (e.g., tryptone, yeast extract, and casamino acids). Our study highlights the potential for biogenic iron sulfide minerals to quantitatively contribute to organic carbon preservation in anoxic environments.

Hydrogen Sulfide Produced by Gut Bacteria May Induce Parkinson's Disease

Several bacterial species can generate hydrogen sulfide (H2S). Study evidence favors the view that the microbiome of the colon harbors increased amounts of H2S producing bacteria in Parkinson's disease. Additionally, H2S can easily penetrate cell membranes and enter the cell interior. In the cells, excessive amounts of H2S can potentially release cytochrome c protein from the mitochondria, increase the iron content of the cytosolic iron pool, and increase the amount of reactive oxygen species. These events can lead to the formation of alpha-synuclein oligomers and fibrils in cells containing the alpha-synuclein protein. In addition, bacterially produced H2S can interfere with the body urate metabolism and affect the blood erythrocytes and lymphocytes. Gut bacteria responsible for increased H2S production, especially the mucus-associated species of the bacterial genera belonging to the Desulfovibrionaceae and Enterobacteriaceae families, are likely play a role in the pathogenesis of Parkinson's disease. Special attention should be devoted to changes not only in the colonic but also in the duodenal microbiome composition with regard to the pathogenesis of Parkinson's disease. Influenza infections may increase the risk of Parkinson's disease by causing the overgrowth of H2S-producing bacteria both in the colon and duodenum.

The electron-bifurcating FeFe-hydrogenase Hnd is involved in ethanol metabolism in Desulfovibrio fructosovorans grown on pyruvate

Desulfovibrio fructosovorans, a sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of H₂ into protons and electrons. Among them, Hnd is an electron-bifurcating hydrogenase, coupling the exergonic reduction of NAD⁺ to the endergonic reduction of a ferredoxin with electrons derived from H₂ . It was previously hypothesized that its biological function involves the production of NADPH necessary for biosynthetic purposes. However, it was subsequently demonstrated that Hnd is instead a NAD⁺ -reducing enzyme, thus its specific function has yet to be established. To understand the physiological role of Hnd in D. fructosovorans, we compared the hnd deletion mutant with the wild-type strain grown on pyruvate. Growth, metabolites production and comsumption, and gene expression were compared under three different growth conditions. Our results indicate that hnd is strongly regulated at the transcriptional level and that its deletion has a drastic effect on the expression of genes for two enzymes, an aldehyde ferredoxin oxidoreductase and an alcohol dehydrogenase. We demonstrated here that Hnd is involved in ethanol metabolism when bacteria grow fermentatively and proposed that Hnd might oxidize part of the H₂ produced during fermentation generating both NADH and reduced ferredoxin for ethanol production via its electron bifurcation mechanism.

Effects of metals on activity and community of sulfate-reducing bacterial enrichments and the discovery of a new heavy metal-resistant SRB from Santos Port sediment (São Paulo, Brazil)

Sulfate-reducing bacteria (SRB) can be used to remove metals from wastewater, sewage, and contaminated areas. However, metals can be toxic to this group of bacteria. Sediments from port areas present abundance of SRB and also metal contamination. Their microbial community has been exposed to metals and can be a good inoculum for isolation of metal-resistant SRB. The objective of the study was to analyze how metals influence activity and composition of sulfate-reducing bacteria. Enrichment cultures were prepared with a different metal (Zn, Cr, Cu, and Cd) range concentration tracking activity of SRB and 16S rRNA sequencing in order to access the community. The SRB activity decreased when there was an increase in the concentration of the metals tested. The highest concentration of metals precipitated were 0.2 mM of Cd, 5.4 mM of Zn, 4.5 mM of Cu, and 9.6 mM of Cr. The more toxic metals were Cd and Cu and had a greater community similarity with less SRB and more fermenters (e.g., Citrobacter and Clostridium). Meanwhile, the enrichments with less toxic metals (Cr and Zn) had more sequences affiliated to SRB genera (mainly Desulfovibrio). A new Desulfovibrio species was isolated. This type of study can be useful to understand the effects of metals in SRB communities and help to optimize wastewater treatment processes contaminated by metals. The new Desulfovibrio species may be important in future studies on bioremediation of neutral pH effluents contaminated by metals.

Glucose but Not Fructose Alters the Intestinal Paracellular Permeability in Association With Gut Inflammation and Dysbiosis in Mice

A causal correlation between the metabolic disorders associated with sugar intake and disruption of the gastrointestinal (GI) homeostasis has been suggested, but the underlying mechanisms remain unclear. To unravel these mechanisms, we investigated the effect of physiological amounts of fructose and glucose on barrier functions and inflammatory status in various regions of the GI tract and on the cecal microbiota composition. C57BL/6 mice were fed chow diet and given 15% glucose or 15% fructose in drinking water for 9 weeks. We monitored caloric intake, body weight, glucose intolerance, and adiposity. The intestinal paracellular permeability, cytokine, and tight junction protein expression were assessed in the jejunum, cecum, and colon. In the cecum, the microbiota composition was determined. Glucose-fed mice developed a marked increase in total adiposity, glucose intolerance, and paracellular permeability in the jejunum and cecum while fructose absorption did not affect any of these parameters. Fructose-fed mice displayed increased circulation levels of IL6. In the cecum, both glucose and fructose intake were associated with an increase in Il13, Ifnγ, and Tnfα mRNA and MLCK protein levels. To clarify the relationships between monosaccharides and barrier function, we measured the permeability of Caco-2 cell monolayers in response to IFNγ+TNFα in the presence of glucose or fructose. In vitro, IFNγ+TNFα-induced intestinal permeability increase was less pronounced in response to fructose than glucose. Mice treated with glucose showed an enrichment of Lachnospiracae and Desulfovibrionaceae while the fructose increased relative abundance of Lactobacillaceae. Correlations between pro-inflammatory cytokine gene expression and bacterial abundance highlighted the potential role of members of Desulfovibrio and Lachnospiraceae NK4A136 group genera in the inflammation observed in response to glucose intake. The increase in intestinal inflammation and circulating levels of IL6 in response to fructose was observed in the absence of intestinal permeability modification, suggesting that the intestinal permeability alteration does not precede the onset of metabolic outcome (low-grade inflammation, hyperglycemia) associated with chronic fructose consumption. The data also highlight the deleterious effects of glucose on gut barrier function along the GI tract and suggest that Desulfovibrionaceae and Lachnospiraceae play a key role in the onset of GI inflammation in response to glucose.

P16 I NK 4a Deletion Ameliorates Damage of Intestinal Epithelial Barrier and Microbial Dysbiosis in a Stress-Induced Premature Senescence Model of Bmi-1 Deficiency

This study aimed to determine whether Bmi-1 deficiency leads to intestinal epithelial barrier destruction and microbiota dysfunction, which members of the microbial community alter barrier function with age, and whether p16^INK4a deletion could reverse the damage of intestinal epithelial barrier and microbial dysbiosis. Intestines from Bmi-1–deficient (Bmi-1^–/–), Bmi-1 and p16^INK4a double-knockout (Bmi-1^–/–p16^INK4a–/–), and wild-type mice were observed for aging and inflammation. Duolink Proximity Ligation Assay, immunoprecipitation, and construction of p16^INK4a overexpressed adenovirus and the overexpressed plasmids of full-length, mutant, or truncated fragments for occludin were used for analyzing the interaction between p16^INK4a and occludin. High-throughput sequencing of V4 region amplicon of 16S ribosomal RNA was conducted using intestinal microbiota. We found Bmi-1 deficiency destructed barrier structure, barrier function, and tight junction (TJ) in intestinal epithelium; decreased the TJ proteins; increased tumor necrosis factor α (TNF-α)–dependent barrier permeability; and up-regulated proinflammatory level of macrophages induced by intestinal microbial dysbiosis. The transplantation of fecal microbiota from wild-type mice ameliorated TJ in intestinal epithelium of Bmi-1^–/– and Bmi-1^–/–p16^INK4a–/– mice. Harmful bacteria including Desulfovibrio, Helicobacter, and Oscillibacter were at a higher level in Bmi-1^–/– mice. More harmful bacteria Desulfovibrio entered the epithelium and promoted macrophages-secreted TNF-α and caused TNF-α–dependent barrier permeability and aging. Accumulated p16^INK4a combined with occludin at the 1st–160th residue in cytoplasm of intestinal epithelium cells from Bmi-1^–/– mice, which blocked formation of TJ and the repair of intestinal epithelium barrier. P16^INK4a deletion could maintain barrier function and microbiota balance in Bmi-1^–/– mice through strengthening formation of TJ and decreasing macrophages-secreted TNF-α induced by Desulfovibrio entering the intestinal epithelium. Thus, Bmi-1 maintained intestinal TJ, epithelial barrier function, and microbiota balance through preventing senescence characterized by p16^INK4a accumulation. The clearance of p16^INK4a-positive cells in aging intestinal epithelium would be a new method for maintaining barrier function and microbiota balance. The residues 1–160 of occludin could be a novel therapeutic target for identifying small molecular antagonistic peptides to prevent the combination of p16^INK4a with occludin for protecting TJ.

Desulfovibrio is not always associated with adverse health effects in the Guangdong Gut Microbiome Project

Desulfovibrio (DSV) is frequently found in the human intestine but limited knowledge is available regarding the relationship between DSV and host health. In this study, we analyzed large-scale cohort data from the Guangdong Gut Microbiome Project to study the ecology of DSV and the associations of DSV and host health parameters. Phylogenetic analysis showed that Desulfovibrio piger might be the most common and abundant DSV species in the GGMP. Predominant sub-OTUs of DSV were positively associated with bacterial community diversity. The relative abundance of DSV was positively correlated with beneficial genera, including Oscillospira, Coprococcus,Ruminococcus,Akkermansia, Roseburia,Faecalibacterium, andBacteroides, and was negatively associated with harmful genera, such as Clostridium,Escherichia,Klebsiella, and Ralstonia. Moreover, the relative abundance of DSV was negatively correlated with body mass index, waist size, triglyceride levels, and uric acid levels. This suggests that DSV is associated with healthy hosts in some human populations.

Desulfovibrio feeding Methanobacterium with electrons in conductive methanogenic aggregates from coastal zones

Geobacter, as a typical electroactive microorganism, is the "engine" of interspecies electron transfer (IET) between microorganisms. However, it does not have a dominant position in all natural environments. It is not known what performs a similar function as Geobacter in coastal zones. Metagenomic and metatranscriptomic analysis revealed that Desulfovibrio and Methanobacterium species were the most abundant in electrochemically active aggregates. Metatranscriptomic analysis showed that Desulfovibrio species highly expressed genes for ethanol metabolism and extracellular electron transfer involving cytochromes, pili and flagella. Methanobacterium species in the aggregates also expressed genes for enzymes involved in reducing carbon dioxide to methane. Pure cultures demonstrated that the isolated Desulfovibrio sp. strain JY contributed to aggregate conductivity and directly transferred electrons to Methanothrix harundinacea, which is unable to use H₂ or formate. Most importantly, further coculture studies indicated that Methanobacterium strain YSL might directly accept electrons from the Desulfovibrio strain JY for the reduction of carbon dioxide to methane in the aggregate. This finding suggested that the possibility of DIET by Desulfovibrio similar to Geobacter species in conductive methanogenic aggregates can not be excluded.

Electroactive bacterial community augmentation enhances the performance of a pilot scale constructed wetland microbial fuel cell for treatment of textile dye wastewater

This study evaluated the effect of bioaugmentation of a newly enriched electroactive bacterial community DC5 on the performance of a pilot scale sequential two-step Horizontal Sub-surface flow Constructed Wetland-Microbial Fuel Cell (HSCW-MFC) system treating textile dye wastewater. The system consisted of CW-MFC-1 planted with Fimbristylis ferruginea and CW-MFC-2 planted with consortium of Fimbristylis ferruginea and Elymus repens plant species. Before bioaugmentation, HSCW-MFC system showed 62 ± 2% Chemical Oxygen Demand (COD) and 90 ± 1.5% American Dye Manufacturer's Institute (ADMI) removal and 177.3 mW/m² maximum power density (CW-MFC-1). After bioaugmentation of DC5 into the HSCW-MFC, COD and ADMI removal was enhanced to 74.10 ± 1.75% and 97.32 ± 1.90% with maximum power density of 197.94 mW/m² (CW-MFC-1). The genera Exiguobacterium, Desulfovibrio and Macellibacteroides of DC5 were significantly enriched at the electrodes of HSCW-MFC after bioaugmentation. These results demonstrate that the performance of the CW-MFC treating textile dye wastewater can be improved by bioaugmentation of electroactive bacterial community.

Microbial communities of biofilms developed in a chlorinated drinking water distribution system: A field study of antibiotic resistance and biodiversity

Antibiotic resistance and biodiversity were investigated in microbial communities attached to inner surfaces of water supply fittings in a chlorinated drinking water distribution system (DWDS) supplied by two independent water treatment plants (WTPs) drawing the same source water. The investigation of the effect of the season, the applied water treatment technology, and type, material, and age of water supply fittings on both antibiotic resistance and biodiversity in biofilms involved collection of tubercles during summer and winter seasons throughout the DWDS. A total of 16 samples were collected (8 per season) from areas supplied by two independent WTPs. Culturable aerobic antibiotic resistant bacteria (ARB) proved more prevalent in summer. Various antibiotic resistance genes (ARGs) were detected, confirming the role of biofilms as ARGs reservoirs, but the abundances of quantified genes (sulI, ermB, qacEΔ1, intI1) were low (a range of <LOQ to 2313 gene copies/mg dry mass of tubercles) throughout the DWDS. In terms of microbial community composition, Proteobacteria were dominant in each sample (51.51-97.13%), and the most abundant genus was Desulfovibrio (0.01-66.69%) belonging to sulphate-reducing bacteria. Biodiversity of microbial communities was shaped by many coexisting factors, including season, water supply fitting material, and sampling site location. Spatial distribution analysis revealed that although only samples collected at the same sampling sites were similar to each other in terms of antibiotic resistance, some samples collected in the close proximity were similar in terms of biodiversity. This suggests that antibiotic resistance spreads only locally over small distances in drinking water biofilms. Although actual drinking water biofilms have been previously investigated in terms of microbial biodiversity, this is the first study that characterised both antibiotic resistance and biodiversity of microbial communities attached to inner surfaces of a real DWDS functioning for decades.

Interactions Between Iron Sulfide Minerals and Organic Carbon: Implications for Biosignature Preservation and Detection

Microbe-mineral interactions can produce unique composite materials, which can preserve biosignatures. Geological evidence suggests that iron sulfide (Fe-S) minerals are abundant in the subsurface of Mars. On Earth, the formation of Fe-S minerals is driven by sulfate-reducing microorganisms (SRM) that produce reactive sulfide. Moreover, SRM metabolites, as well as intact cells, can influence the morphology, particle size, aggregation, and composition of biogenic Fe-S minerals. In this work, we evaluated how simple and complex organic molecules-hexoses and amino acid/peptide mixtures, respectively-influence the formation of Fe-S minerals (simulated prebiotic conditions), and whether the observed patterns mimic the biological influence of SRM. To this end, organo-mineral aggregates were characterized with X-ray diffraction, scanning electron microscopy, and scanning transmission X-ray microscopy coupled to near-edge X-ray absorption fine structure spectroscopy. Overall, Fe-S minerals were found to have a strong affinity for proteinaceous organic matter. Fe-S minerals precipitated at simulated prebiotic conditions yielded organic carbon distributions that were more homogeneous than treatments with whole SRM cells. In prebiotic experiments, spectroscopy detected potential organic transformations during Fe-S mineral formation, including conversion of hexoses to sugar acids and polymerization of amino acids/peptides into larger peptides/proteins. In addition, prebiotic mineral-carbon assemblages produced nanometer-scaled filamentous aggregated morphologies. On the contrary, in biotic treatments with cells, organic carbon in minerals displayed a more heterogeneous distribution. Notably, "hot spots" of organic carbon and oxygen-containing functional groups, with the size, shape, and composition of microbial cells, were preserved in mineral aggregates. We propose a list of characteristics that could be used to help distinguish biogenic from prebiotic/abiotic Fe-S minerals and help refine the search of extant or extinct microbial life in the martian subsurface.

Microscopic Methods for Identification of Sulfate-Reducing Bacteria from Various Habitats

This paper is devoted to microscopic methods for the identification of sulfate-reducing bacteria (SRB). In this context, it describes various habitats, morphology and techniques used for the detection and identification of this very heterogeneous group of anaerobic microorganisms. SRB are present in almost every habitat on Earth, including freshwater and marine water, soils, sediments or animals. In the oil, water and gas industries, they can cause considerable economic losses due to their hydrogen sulfide production; in periodontal lesions and the colon of humans, they can cause health complications. Although the role of these bacteria in inflammatory bowel diseases is not entirely known yet, their presence is increased in patients and produced hydrogen sulfide has a cytotoxic effect. For these reasons, methods for the detection of these microorganisms were described. Apart from selected molecular techniques, including metagenomics, fluorescence microscopy was one of the applied methods. Especially fluorescence in situ hybridization (FISH) in various modifications was described. This method enables visual identification of SRB, determining their abundance and spatial distribution in environmental biofilms and gut samples.

Synergistic interactions of Desulfovibrio and Petrimonas for sulfate-reduction coupling polycyclic aromatic hydrocarbon degradation

Microbial sulfate-reduction coupling polycyclic aromatic hydrocarbon (PAH) degradation is an important process for the remediation of contaminated sediments. However, little is known about core players and their mechanisms in this process due to the complexity of PAH degradation and the large number of microorganisms involved. Here we analyzed potential core players in a black-odorous sediment using gradient-dilution culturing, isolation and genomic/metagenomic approaches. Along the dilution gradient, microbial PAH degradation and sulfate consumption were not decreased, and even a significant (p = 0.003) increase was observed in the degradation of phenanthrene although the microbial diversity declined. Two species, affiliated with Desulfovibrio and Petrimonas, were commonly present in all of the gradients as keystone taxa and showed as the dominant microorganisms in the single colony (SB8) isolated from the highest dilution culture with 93.49% and 4.73% of the microbial community, respectively. Desulfovibrio sp. SB8 and Petrimonas sp. SB8 could serve together as core players for sulfate-reduction coupling PAH degradation, in which Desulfovibrio sp. SB8 could degrade PAHs to hexahydro-2-naphthoyl through the carboxylation pathway while Petrimonas sp. SB8 might degrade intermediate metabolites of PAHs. This study provides new insights into the microbial sulfate-reduction coupling PAH degradation in black-odorous sediments.

nov., a mesophilic sulfate-reducing deltaproteobacterium isolated from a deep siliceous mudstone formation

A novel mesophilic sulfate-reducing bacterium, strain HN2^T, was isolated from groundwater sampled from the subsurface siliceous mudstone of the Wakkanai Formation located in Horonobe, Hokkaido, Japan. The bacterium was Gram-negative and vibrio-shaped, and its motility was conferred by a single polar flagellum. Cells had desulfoviridin. Catalase and oxidase activities were not detected. It grew in the temperature range of 25-40 °C (optimum, 35 °C) and pH range of 6.3-8.1 (optimum, pH 7.2-7.6). It used sulfate, thiosulfate, dimethyl sulfoxide, anthraquinone-2,6-disulfonate, Fe³⁺, and manganese oxide, but not elemental sulfur, nitrite, nitrate, or fumarate as electron acceptors. The strain showed weak growth with sulfite as the electron acceptor. Fermentative growth with pyruvate, lactate and cysteine was observed in the absence of sulfate, but not with malate or fumarate. NaCl was not required, but the strain tolerated up to 40 g l^-1. Strain HN2^T did not require vitamins. The major cellular fatty acids were iso-C_15 : 0 (23.8 %), C_18 : 1  ω9t (18.4 %), C_18 : 0 (15.0 %), C_16 : 0 (14.5 %), and anteiso-C_17 :0 (10.1 %). The major respiratory quinone was menaquinone MK-6(H₂). The G+C content of the genomic DNA was 56.7 mol%. Based on 16S rRNA gene sequence analysis, the closest phylogenetic relative of strain HN2^T is Desulfovibrio psychrotolerans JS1^T (97.0 %). Digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values of the strains HN2^T and D. psychrotolerans JS1^T were 22.2 and 79.8 %, respectively. Based on the phenotypic and molecular genetic evidence, we propose a novel species, D. subterraneus sp. nov. with the type strain HN2^T (=DSM 101010^T=NBRC 112213^T).

Long-term dietary intake from infancy to late adolescence is associated with gut microbiota composition in young adulthood

BACKGROUND

Gut microbiota composition as influenced by long-term diet may be associated with the risk of adult chronic diseases. Thus, establishing the relation of long-term diet, particularly starting from early life, with adult microbiota composition would be an important research advance.

OBJECTIVE

We aimed to investigate the association of long-term intake of energy, carbohydrate, fiber, protein, and fat from infancy to late adolescence with microbiota composition in adulthood.

METHODS

Within the prospective DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study, we sampled stool 1 or 2 times within 1 y from 128 adults (median age: 29 y). Microbiota composition was profiled by 16S ribosomal RNA sequencing. Annual dietary records from age 1 to 18 y were retrieved. We estimated trajectories of energy, energy-adjusted carbohydrate, fiber, protein, and fat intake with multilevel models, producing predicted intake at age 1 y and rates of change in intake. A multivariate, zero-inflated, logistic-normal model was used to model the association between intake trajectories and the composition of 158 genera in single-sampled individuals. Associations found in this model were confirmed in double-sampled individuals using a zero-inflated Beta regression model.

RESULTS

Adjusting for covariates and temporal differences in microbiota composition, long-term carbohydrate intake was associated with 3 genera. Specifically, carbohydrate intake at age 1 y was negatively associated with Phascolarctobacterium [coefficient = -4.31; false discovery rate (FDR)-adjusted P = 0.006] and positively associated with Dialister (coefficient = 3.06; FDR-adjusted P = 0.003), and the rate of change in carbohydrate intake was positively associated with Desulfovibrio (coefficient = 13.16; FDR-adjusted P = 0.00039). Energy and other macronutrients were not associated with any genus.

CONCLUSIONS

This work links long-term carbohydrate intake to microbiota composition. Considering the associations of high carbohydrate intake and microbiota composition with some diseases, these findings could inform the development of gut microbiota-targeted dietary recommendations for disease prevention.

OrpR is a σ54 -dependent activator using an iron-sulfur cluster for redox sensing in Desulfovibrio vulgaris Hildenborough

Enhancer binding proteins (EBPs) are key players of σ⁵⁴ -regulation that control transcription in response to environmental signals. In the anaerobic microorganism Desulfovibrio vulgaris Hildenborough (DvH), orp operons have been previously shown to be coregulated by σ⁵⁴ -RNA polymerase, the integration host factor IHF and a cognate EBP, OrpR. In this study, ChIP-seq experiments indicated that the OrpR regulon consists of only the two divergent orp operons. In vivo data revealed that (i) OrpR is absolutely required for orp operons transcription, (ii) under anaerobic conditions, OrpR binds on the two dedicated DNA binding sites and leads to high expression levels of the orp operons, (iii) increasing the redox potential of the medium leads to a drastic down-regulation of the orp operons expression. Moreover, combining functional and biophysical studies on the anaerobically purified OrpR leads us to propose that OrpR senses redox potential variations via a redox-sensitive [4Fe-4S]²⁺ cluster in the sensory PAS domain. Overall, the study herein presents the first characterization of a new Fe-S redox regulator belonging to the σ⁵⁴ -dependent transcriptional regulator family probably advantageously selected by cells adapted to the anaerobic lifestyle to monitor redox stress conditions.

Intestinal bacteria are potential biomarkers and therapeutic targets for gastric cancer

The diagnostic and therapeutic role of intestinal microbiota in gastric carcinogenesis remains unclear. In this study, feces from gastric cancer patients and healthy people were sequenced for microbiota analysis, and the correlation between fecal bacteria and the occurrence of gastric cancer was explored. The β-diversity results showed that microbial compositions varied between gastric cancer patients and healthy people. Interestingly, the dissection of microbial structure revealed that all facultative anaerobic genera with relatively high abundances expanded significantly in gastric cancer patients. The succeeding correlation analysis demonstrated a distorted interaction of intestinal bacteria in gastric cancer. The application of some differential bacteria, Desulfovibrio, Escherichia, Faecalibacterium or Oscillospira, as biomarkers to predict gastric cancer could all reach an accuracy of 0.900 or above. The shift in Desulfovibrio was specifically verified by qPCR in newly collected fecal samples, and the patients with stage IV gastric cancer were identified to have significantly more Desulfovibrio than those with stage I, II and III gastric cancer. The possible role of Desulfovibrio in gastric cancer was assessed with H₂S-treated HT-29 cells, and the results showed that H₂S induced NO, IL-1β and IL-18 production, which is important for inflammation promotion and can be delivered through the bloodstream. This study suggests a correlation of intestinal microbiota and the development of gastric cancer.

Biocorrosive behavior of sulphate-reducing bacteria in kerr endodontic files: Determination of the corrosion

Aims:

This study determined the corrosion rate by mass loss caused by oral strains of sulphate-reducing bacteria (SRB) in Kerr endodontic files (KF), aiming the development of a biopharmaceutical that facilitates the removal of endodontic limb fragments from root canals.

Materials and Methods:

Nine new KF were analyzed after immersion in the modified Postgate E culture medium inoculated with Desulfovibrio desulfuricans oral (84 days), Desulfovibrio fairfieldensis in the consortium (84 days) and environmental D. desulfuricans (119 days).

Results:

Optical microscopy revealed corrosion suggestive areas in all files submitted to immersion in SRB cultures, presenting a statistical difference (P < 0.05) between the samples environmental D. desulfuricans and KF control and between oral D. desulfuricans and KF control. Epifluorescence microscopy revealed an active SRB biofilm over the entire metal surface of the KF, as evidenced by the SYTO^® 9 fluorophore.

Conclusion:

SRB were capable of promoting biocorrosion in Kerr type endodontic files, but with low rate.

Using intestinal flora to distinguish non-alcoholic steatohepatitis from non-alcoholic fatty liver

Objective

To explore specific flora in mouse models of non-alcoholic steatohepatitis (NASH) to improve NASH diagnostic protocols.

Methods

Sixty mice were divided into normal diet (ND, 20 mice) and high-fat/high-sugar diet (HFSD) groups (40 mice). After 8 weeks of feeding, 10 mice in the ND group and 20 mice in the HFSD group were sacrificed to create the short-term ND and non-alcoholic fatty liver (NAFL) groups, respectively. After 16 weeks of feeding, the remaining mice were sacrificed to create the long-term ND and NASH groups, respectively. We then examined fecal flora, serum biochemical indices, and lipopolysaccharide and tumor necrosis factor-α levels and analyzed liver tissue.

Results

The relative abundance of Lactobacillus, Desulfovibrio, Ruminiclostridium 9, and Turicibacter differed between NASH and NAFL mice, and the areas under the receiver operating characteristic curve of the four genera for diagnosing NASH were 0.705, 0.734, 0.737, and 0.937. The non-alcoholic fatty liver disease activity score was positively correlated with the relative abundance of Desulfovibrio (r = 0.353), Ruminiclostridium 9 (r = 0.431), and Turicibacter (r = 0.688).

Conclusions

The relative abundance of Lactobacillus, Desulfovibrio, Ruminiclostridium, and Turicibacter may help distinguish NASH from NAFL.

Novel Mode of Molybdate Inhibition of Desulfovibrio vulgaris Hildenborough

Sulfate-reducing microorganisms (SRM) are found in multiple environments and play a major role in global carbon and sulfur cycling. Because of their growth capabilities and association with metal corrosion, controlling the growth of SRM has become of increased interest. One such mechanism of control has been the use of molybdate (MoO4 2-), which is thought to be a specific inhibitor of SRM. The way in which molybdate inhibits the growth of SRM has been enigmatic. It has been reported that molybdate is involved in a futile energy cycle with the sulfate-activating enzyme, sulfate adenylyl transferase (Sat), which results in loss of cellular ATP. However, we show here that a deletion of this enzyme in the model SRM, Desulfovibrio vulgaris Hildenborough, remained sensitive to molybdate. We performed several subcultures of the ∆sat strain in the presence of increasing concentrations of molybdate and obtained a culture with increased resistance to the inhibitor (up to 3 mM). The culture was re-sequenced and three single nucleotide polymorphisms (SNPs) were identified that were not present in the parental strain. Two of the SNPs seemed unlikely candidates for molybdate resistance due to a lack of conservation of the mutated residues in homologous genes of closely related strains. The remaining SNP was located in DVU2210, a protein containing two domains: a YcaO-like domain and a tetratricopeptide-repeat domain. The SNP resulted in a change of a serine residue to arginine in the ATP-hydrolyzing motif of the YcaO-like domain. Deletion mutants of each of the three genes apparently enriched with SNPs in the presence of inhibitory molybdate and combinations of these genes were generated in the Δsat and wild-type strains. Strains lacking both sat and DVU2210 became more resistant to molybdate. Deletions of the other two genes in which SNPs were observed did not result in increased resistance to molybdate. YcaO-like proteins are distributed across the bacterial and archaeal domains, though the function of these proteins is largely unknown. The role of this protein in D. vulgaris is unknown. Due to the distribution of YcaO-like proteins in prokaryotes, the veracity of molybdate as a specific SRM inhibitor should be reconsidered.

CMX

The process of nitrate dissimilation to ammonium (DNRA) is an important way for storing nitrogen in nature and DNRA is a key step in efficient recovery of nitrogen in wastewater. However, in view of the low conversion efficiency of DNRA, zero-valent iron (ZVI) was used to enhance the DNRA process of Desulfovibrio sp. CMX. ZVI can obviously promote the nitrate/nitrite reduction. The experiment indicated that 5 g/L 300 mesh ZVI could convert 5 mmol/L nitrate or nitrite to ammonium in 48 h or 36 h respectively, and the conversion ratio of NO₂^- to NH₄⁺ could reach more than 90%. The ZVI provided a suitable growth environment for the Desulfovibrio sp. CMX through chemical reduction of nitrite, production of divalent iron (Fe²⁺), reduction of oxidation-reduction potential (ORP) and adjustment of pH, which strengthened the DNRA performance. This experiment is advantageous for increasing efficiency of DNRA and provides a new idea for efficient recovery of nitrogen resources.

Assessment of the tolerance to Fe, Cu and Zn of a sulfidogenic sludge generated from hydrothermal vents sediments as a basis for its application on metals precipitation

A paramour factor limiting metal-microorganism interaction is the metal ion concentration, and the metal precipitation efficiency driven by microorganisms is sensitive to metal ion concentration. The aim of the work was to determine the tolerance of the sulfidogenic sludge generated from hydrothermal vent sediments at microcosms level to different concentrations of Fe, Cu and Zn and the effect on the microbial community. In this study the chemical oxygen demand (COD) removal, sulfate-reducing activity (SRA) determination, inhibition effect through the determination of IC₅₀, and the characterization of the bacterial community´s diversity were conducted. The IC₅₀ on SRA was 34 and 81 mg/L for Zn and Cu, respectively. The highest sulfide concentration (H₂S mg/L) and % of sulfate reduction obtained were: 511.30 ± 0.75 and 35.34 ± 0.51 for 50 mg/L of Fe, 482.48 ± 6.40 and 33.35 ± 0.44 for 10 mg/L of Cu, 442.26 ± 17.1 and 30.57 ± 1.18 for 10 mg/L of Zn, respectively. The COD removal rates were of 71.81 ± 7.6, 53.92 ± 1.07 and 57.68 ± 10.2 mg COD/ L d for Fe (50 mg/L), Cu (40 mg/L) and Zn (20 mg/L), respectively. Proteobacteria, Firmicutes, Chloroflexi and Actinobacteria were common phyla to four microcosms (stabilized sulfidogenic and added with Fe, Cu or Zn). The dsrA genes of Desulfotomaculum acetoxidans, Desulfotomaculum gibsoniae and Desulfovibrio desulfuricans were expressed in the microcosms supporting the SRA results. The consortia could be explored for ex-situ bioremediation purposes in the presence of the metals tested in this work.

Fecal microbiota transplantation improves metabolism and gut microbiome composition in db/db mice

Fecal microbiota transplantation (FMT) has become an effective strategy to treat metabolic diseases, including type 2 diabetes mellitus (T2DM). We previously reported that the intestinal microbiome had significant difference between individuals with normal glucose tolerance and T2DM in Chinese Kazak ethnic group. In this study, we investigated the effects of transplanted fecal bacteria from Kazaks with normal glucose tolerance (KNGT) in db/db mice. The mice were treated with 0.2 mL of fecal bacteria solution from KNGT daily for 10 weeks. We showed that the fecal bacteria from KNGT successfully colonized in the intestinal tract of db/db mice detected on day 14. In the FMT-treated db/db mice, the levels of fasting blood glucose, postprandial glucose, total cholesterol, triglyceride, and low-density lipoprotein–cholesterol were significantly downregulated, whereas high-density lipoprotein–cholesterol levels were upregulated. In the FMT-treated db/db mice, Desulfovibrio and Clostridium coccoides levels in gut were significantly decreased, but the fecal levels of Akkermansia muciniphila and colon histone deacetylase-3 (HDAC3) protein expression were increased. At 8 weeks, both intestinal target bacteria and HDAC3 were correlated with glycolipid levels; Akkermansia muciniphila level was positively correlated with HDAC3 protein expression (r = +0.620, P = 0.037). Our results suggest that fecal bacteria from KNGT could potentially be used to treat diabetic patients.

A Novel "Microbial Bait" Technique for Capturing Fe(III)-Reducing Bacteria

Microbial reduction of Fe(III) is a key geochemical process in anoxic environments, controlling the degradation of organics and the mobility of metals and radionuclides. To further understand these processes, it is vital to develop a reliable means of capturing Fe(III)-reducing microorganisms from the field for analysis and lab-based investigations. In this study, a novel method of capturing Fe(III)-reducing bacteria using Fe(III)-coated pumice "microbe-baits" was demonstrated. The methodology involved the coating of pumice (approximately diameter 4 to 6 mm) with a bioavailable Fe(III) mineral (akaganeite), and was verified by deployment into a freshwater spring for 2 months. On retrieval, the coated pumice baits were incubated in a series of lab-based microcosms, amended with and without electron donors (lactate and acetate), and incubated at 20°C for 8 weeks. 16S rRNA gene sequencing using the Illumina MiSeq platform showed that the Fe(III)-coated pumice baits, when incubated in the presence of lactate and acetate, enriched for Deltaproteobacteria (relative abundance of 52% of the sequences detected corresponded to Geobacter species and 24% to Desulfovibrio species). In the absence of added electron donors, Betaproteobacteria were the most abundant class detected, most heavily represented by a close relative to Rhodoferax ferrireducens (15% of species detected), that most likely used organic matter sequestered from the spring waters to support Fe(III) reduction. In addition, TEM-EDS analysis of the Fe(III)-coated pumice slurries amended with electron donors revealed that a biogenic Fe(II) mineral, magnetite, was formed at the end of the incubation period. These results demonstrate that Fe(III)-coated pumice "microbe baits" can potentially help target metal-reducing bacteria for culture-dependent studies, to further our understanding of the nano-scale microbe-mineral interactions in aquifers.

Shotgun proteomic analysis of nanoparticle-synthesizing Desulfovibrio alaskensis in response to platinum and palladium

Platinum and palladium are much sought-after metals of critical global importance in terms of abundance and availability. At the nano-scale these metals are of even higher value due to their catalytic abilities for industrial applications. Desulfovibrio alaskensis is able to capture ionic forms of both of these metals, reduce them and synthesize elemental nanoparticles. Despite this ability, very little is known about the biological pathways involved in the formation of these nanoparticles. Proteomic analysis of D. alaskensis in response to platinum and palladium has highlighted those proteins involved in both the reductive pathways and the wider stress-response system. A core set of 13 proteins was found in both treatments and consisted of proteins involved in metal transport and reduction. There were also seven proteins that were specific to either platinum or palladium. Overexpression of one of these platinum-specific genes, a NiFe hydrogenase small subunit (Dde_2137), resulted in the formation of larger nanoparticles. This study improves our understanding of the pathways involved in the metal resistance mechanism of Desulfovibrio and is informative regarding how we can tailor the bacterium for nanoparticle production, enhancing its application as a bioremediation tool and as a way to capture contaminant metals from the environment.

Hydrogen Sulfide as a Toxic Product in the Small-Large Intestine Axis and its Role in IBD Development

The small-large intestine axis in hydrogen sulfide accumulation and testing of sulfate and lactate in the gut-gut axis of the intestinal environment has not been well described. Sulfate reducing bacteria (SRB) of the Desulfovibrio genus reduce sulfate to hydrogen sulfide and can be involved in ulcerative colitis development. The background of the research was to find correlations between hydrogen sulfide production under the effect of an electron acceptor (sulfate) and donor (lactate) at different concentrations and Desulfovibrio piger Vib-7 growth, as well as their dissimilatory sulfate reduction in the intestinal small-large intestinal environment.

METHODS

Microbiological, biochemical, and biophysical methods, and statistical processing of the results (principal component and cross-correlation analyses) were used.

RESULTS

D. piger Vib-7 showed increased intensity of bacterial growth and hydrogen sulfide production under the following concentrations of sulfate and lactate: 17.4 mM and 35.6 mM, respectively. The study showed in what kind of intestinal environment D. piger Vib-7 grows at the highest level and produces the highest amount of hydrogen sulfide.

CONCLUSIONS

The optimum intestinal environment of D. piger Vib-7 can serve as a good indicator of the occurrence of inflammatory bowel diseases; meaning that these findings can be broadly used in medicine practice dealing with the monitoring and diagnosis of intestinal ailments.

Bulk phase resource ratio alters carbon steel corrosion rates and endogenously produced extracellular electron transfer mediators in a sulfate-reducing biofilm

Desulfovibrio alaskensis G20 biofilms were cultivated on 316 steel, 1018 steel, or borosilicate glass under steady-state conditions in electron-acceptor limiting (EAL) and electron-donor limiting (EDL) conditions with lactate and sulfate in a defined medium. Increased corrosion was observed on 1018 steel under EDL conditions compared to 316 steel, and biofilms on 1018 carbon steel under the EDL condition had at least twofold higher corrosion rates compared to the EAL condition. Protecting the 1018 metal coupon from biofilm colonization significantly reduced corrosion, suggesting that the corrosion mechanism was enhanced through attachment between the material and the biofilm. Metabolomic mass spectrometry analyses demonstrated an increase in a flavin-like molecule under the 1018 EDL condition and sulfonates under the 1018 EAL condition. These data indicate the importance of S-cycling under the EAL condition, and that the EDL is associated with increased biocorrosion via indirect extracellular electron transfer mediated by endogenously produced flavin-like molecules.