Nitrate promotes the growth and the production of short-chain fatty acids and tryptophan from commensal anaerobe Veillonella dispar in the lactate-deficient environment by facilitating the catabolism of glutamate and aspartate.

Veillonella spp. are nitrate-reducing bacteria with anaerobic respiratory activity that reduce nitrate to nitrite. They are obligate anaerobic, Gram-negative cocci that ferment lactate as the main carbon source and produce short-chain fatty acids (SCFAs). Commensal Veillonella reside in the human body site where lactate level is, however, limited for Veillonella growth. In this study, nitrate was shown to promote the anaerobic growth of Veillonella in the lactate-deficient media. We aimed to investigate the underlying mechanisms and the metabolism involved in nitrate respiration. Nitrate (15 mM) was demonstrated to promote Veillonella dispar growth and viability in the tryptone-yeast extract medium containing 0.5 mM L-lactate. Metabolite and transcriptomic analyses revealed nitrate enabled V. dispar to actively utilize glutamate and aspartate from the medium and secrete tryptophan. Glutamate or aspartate was further supplemented to a medium to investigate individual catabolism during nitrate respiration. Notably, nitrate was demonstrated to elevate SCFA production in the glutamate-supplemented medium, and further increase tryptophan production in the aspartate-supplemented medium. We proposed that the increased consumption of glutamate provided reducing power for nitrate respiration and aspartate served as a substrate for fumarate formation. Both glutamate and aspartate were incorporated into the central metabolic pathways via reverse tricarboxylic acid cycle and were linked with the increased production of acetate, propionate, and tryptophan. This study provides further understanding of the promoted growth and metabolic mechanisms by commensal V. dispar utilizing nitrate and specific amino acids to adapt to the lactate-deficient environment.IMPORTANCENitrate is a pivotal ecological factor influencing microbial community and metabolism. Dietary nitrate provides health benefits including anti-diabetic and anti-hypertensive effects via microbial-derived metabolites such as nitrite. Unraveling the impacts of nitrate on the growth and metabolism of human commensal bacteria is imperative to comprehend the intricate roles of nitrate in regulating microbial metabolism, community, and human health. Veillonella are lactate-utilizing, nitrate-reducing bacteria that are frequently found in the human body site where lactate levels are low and nitrate is at millimolar levels. Here, we comprehensively described the metabolic strategies employed by V. dispar to thrive in the lactate-deficient environment using nitrate respiration and catabolism of specific amino acids. The elevated production of SCFAs and tryptophan from amino acids during nitrate respiration of V. dispar further suggested the potential roles of nitrate and Veillonella in the promotion of human health.

Transmission mode and dispersal traits correlate with host specificity in mammalian gut microbes.

Different host species associate with distinct gut microbes in mammals, a pattern sometimes referred to as phylosymbiosis. However, the processes shaping this host specificity are not well understood. One model proposes that barriers to microbial transmission promote specificity by limiting microbial dispersal between hosts. This model predicts that specificity levels measured across microbes is correlated to transmission mode (vertical vs. horizontal) and individual dispersal traits. Here, we leverage two large publicly available gut microbiota data sets (1490 samples from 195 host species) to test this prediction. We found that host specificity varies widely across bacteria (i.e., there are generalist and specialist bacteria) and depends on transmission mode and dispersal ability. Horizontally-like transmitted bacteria equipped with traits that facilitate switches between host (e.g., tolerance to oxygen) were found to be less specific (more generalist) than microbes without those traits, for example, vertically-like inherited bacteria that are intolerant to oxygen. Altogether, our findings are compatible with a model in which limited microbial dispersal abilities foster host specificity.

Enzyme-functionalized alginate microparticles enable anaerobic culture under ambient oxygen.

Methods for culturing oxygen-sensitive cells and organisms under anaerobic conditions are vital to biotechnology research. Here, we report a biomaterial-based platform for anaerobic culture that consists of glucose oxidase (GOX) functionalized alginate microparticles (ALG-GOX), which are designed to deplete dissolved [O2 ] through enzymatic activity. ALG-GOX microparticles were synthesized via a water-in-oil emulsion and had a size of 132.0 ± 51.4 µm. Despite having a low storage modulus, the microparticles remained stable under aqueous conditions due to covalent crosslinking through amide bonds. Enzyme activity was tunable based on the loaded GOX concentration, with a maximum activity of 3.6 ± 0.3 units/mg of microparticles being achieved at an initial loading concentration of 5 mg/mL of GOX in alginate precursor solution. High enzyme activity in ALG-GOX microparticles resulted in rapid oxygen depletion, producing a suitable environment for anaerobic culture. Microparticles loaded with both GOX and catalase (ALG-GOX-CAT) to reduce H2 O2 buildup exhibited sustained activity for potential long-term anaerobic culture. ALG-GOX-CAT microparticles were highly effective for the anaerobic culture of Bacteroides thetaiotaomicron, with 10 mg/mL of ALG-GOX-CAT microparticles supporting the same level of growth in an aerobic environment compared to an anaerobic chamber after 16 h (8.70 ± 0.96 and 10.03 ± 1.03 million CFU, respectively; N.S. p = 0.07). These microparticles could be a valuable tool for research and development in biotechnology.

An efficient cre-based workflow for genomic integration and expression of large biosynthetic pathways in Eubacterium limosum.

Acetogenic Clostridia are obligate anaerobes that have emerged as promising microbes for the renewable production of biochemicals owing to their ability to efficiently metabolize sustainable single-carbon feedstocks. Additionally, Clostridia are increasingly recognized for their biosynthetic potential, with recent discoveries of diverse secondary metabolites ranging from antibiotics to pigments to modulators of the human gut microbiota. Lack of efficient methods for genomic integration and expression of large heterologous DNA constructs remains a major challenge in studying biosynthesis in Clostridia and using them for metabolic engineering applications. To overcome this problem, we harnessed chassis-independent recombinase-assisted genome engineering (CRAGE) to develop a workflow for facile integration of large gene clusters (>10 kb) into the human gut acetogen Eubacterium limosum. We then integrated a non-ribosomal peptide synthetase gene cluster from the gut anaerobe Clostridium leptum, which previously produced no detectable product in traditional heterologous hosts. Chromosomal expression in E. limosum without further optimization led to production of phevalin at 2.4 mg/L. These results further expand the molecular toolkit for a highly tractable member of the Clostridia, paving the way for sophisticated pathway engineering efforts, and highlighting the potential of E. limosum as a Clostridial chassis for exploration of anaerobic natural product biosynthesis.

Adlercreutzia wanghongyangiae sp. nov., and Adlercreutzia shanghongiae sp. nov., two new members of the genus Adlercreutzia isolated from plateau pika (Ochotona curzoniae).

Four anaerobic, Gram-stain-positive, non-motile, non-sporulating rod-shaped bacterial strains (R7T, R21, R22 and R25T) were isolated from the intestinal contents of plateau pika (Ochotona curzoniae) collected from the Qinghai-Tibet Plateau, PR China. The four isolates grew at between 25 and 42 °C (optimally at 35-37 °C), and with 0.3-3.3% NaCl (w/v) [optimum, 1.3% (w/v)]. Adding l-arginine to the medium could promote their growth. Strains R7T and R21 were most closely related to Adlercreutzia caecimuris B7T (97.48% 16S rRNA gene sequence similarity). Strains R25T and R22 were most closely related to Adlercreutzia equolifaciens DSM 19450T (98.25% 16S rRNA gene sequence similarity). The genome sequences of R7T and R25T were 2.89 and 2.90 Mb in size with 63.6 and 62.8 mol% DNA G+C contents, respectively. Phylogenetic analysis based on 16S rRNA gene sequences and core genes revealed that R7T and R21 were most closely related to A. caecimuris B7T and Adlercreutzia mucosicola DSM 19490T, whereas R25T and R22 were most closely related to A. equolifaciens DSM 19450T and Adlercreutzia rubneri ResAG-91T. R7T, R25T and the closely related species had average nucleotide identity (ANI) values of 81.9-83.2% as well as digital DNA-DNA hybridisation (dDDH) values between 27.3 and 27.9%, which clearly indicated that they represent two novel species within the genus Adlercreutzia. For R7T and R25T, meso-diaminopimelic acid was the diagnostic diamino acid in the cell-wall peptidoglycan, and the whole cell sugars included galactose, glucose and ribose. On the basis of these results, we propose that strains R7T and R25T represent two novel species of the genus Adlercreutzia, namely Adlercreutzia wanghongyangiae sp. nov. and Adlercreutzia shanghongiae sp. nov., respectively. The type strains are R7T (=GDMCC 1.4459T=KCTC 25860T) and R25T (=GDMCC 1.4458T=KCTC 25861T).

Promethearchaeum syntrophicum gen. nov., sp. nov., an anaerobic, obligately syntrophic archaeon, the first isolate of the lineage 'Asgard' archaea, and proposal of the new archaeal phylum Promethearchaeota phyl. nov. and kingdom Promethearchaeati regn. nov.

An anaerobic, mesophilic, syntrophic, archaeon strain MK-D1T, was isolated as a pure co-culture with Methanogenium sp. strain MK-MG from deep-sea methane seep sediment. This organism is, to our knowledge, the first cultured representative of 'Asgard' archaea, an archaeal group closely related to eukaryotes. Here, we describe the detailed physiology and phylogeny of MK-D1T and propose Promethearchaeum syntrophicum gen. nov., sp. nov. to accommodate this strain. Cells were non-motile, small cocci, approximately 300-750 nm in diameter and produced membrane vesicles, chains of blebs and membrane-based protrusions. MK-D1T grew at 4-30 °C with optimum growth at 20 °C. The strain grew chemoorganotrophically with amino acids, peptides and yeast extract with obligate dependence on syntrophy with H2-/formate-utilizing organisms. MK-D1T showed the fastest growth and highest maximum cell yield when grown with yeast extract as the substrate: approximately 3 months to full growth, reaching up to 6.7×106 16S rRNA gene copies ml-1. MK-D1T had a circular 4.32 Mb chromosome with a DNA G+C content of 31.1 mol%. The results of phylogenetic analyses of the 16S rRNA gene and conserved marker proteins indicated that the strain is affiliated with 'Asgard' archaea and more specifically DHVC1/DSAG/MBG-B and 'Lokiarchaeota'/'Lokiarchaeia'. On the basis of the results of 16S rRNA gene sequence analysis, the most closely related isolated relatives were Infirmifilum lucidum 3507LTT (76.09 %) and Methanothermobacter tenebrarum RMAST (77.45 %) and the closest relative in enrichment culture was Candidatus 'Lokiarchaeum ossiferum' (95.39 %). The type strain of the type species is MK-D1T (JCM 39240T and JAMSTEC no. 115508). We propose the associated family, order, class, phylum, and kingdom as Promethearchaeaceae fam. nov., Promethearchaeales ord. nov., Promethearchaeia class. nov., Promethearchaeota phyl. nov., and Promethearchaeati regn. nov., respectively. These are in accordance with ICNP Rules 8 and 22 for nomenclature, Rule 30(3)(b) for validation and maintenance of the type strain, and Rule 31a for description as a member of an unambiguous syntrophic association.

Isolation and identification of hoylesella marshii causing pleural infection: a case report.

BACKGROUND: Hoylesella marshii can be isolated from human oral cavities affected by dental pulp and periodontal infections, as well as from the dental plaque of healthy individuals, making it a common bacterium within the oral microbiota. However, its role in causing pleural infections in humans is rare. CASE PRESENTATION: A case of purulent pleural effusion occurred shortly after discharge in an elderly patient who had undergone surgery for gastric cancer. The infection was identified as being caused by an obligate anaerobe through laboratory culture, and was further identified as Hoylesella marshii causing pleural infection through 16 S rRNA gene sequence analysis. Susceptibility testing guided precise treatment with cefoperazone-sulbactam and metronidazole. The patient's clinical symptoms improved rapidly, laboratory test indicators gradually returned to normal, and the patient ultimately recovered. CONCLUSION: Hoylesella marshii can cause pleural infections in humans. Clinical microbiology laboratories should pay special attention to the cultivation of obligate anaerobes when routine aerobic cultures do not show bacterial growth but bacteria are visible on smear staining, and when conventional identification methods fail to identify the bacterium, analysis based on the highly conserved 16 S rRNA gene sequence can accurately and specifically identify the bacterium, guiding clinicians in formulating precise anti-infection strategies.

Paralabilibaculum antarcticum gen. nov., sp. nov., an anaerobic marine bacterium of the family Marinifilaceae isolated from Antarctica sea ice.

A novel bacterial strain, designated DW002T, was isolated from the sea ice of Cape Evans, McMurdo Sound, Antarctica. Cells of the strain were Gram-negative, obligate anaerobic, motile, non-flagellated, and short rod-shaped. The strain DW002T grew at 4-32 â„ƒ (optimum at 22-28 â„ƒ) and thrived best at pH 7.0, NaCl concentration of 2.5% (w/v). The predominant isoprenoid quinone of strain DW002T was menaquinone-7 (MK-7). The major fatty acids (> 10%) of DW002T were iso-C15:0, anteiso-C15:0 and iso-C17:1ω9c. The predominant polar lipids of strain DW002T contained two phosphatidylethanolamines, one unidentified glycolipid, one unidentified aminolipid and four unidentified lipids. The DNA G + C content of the strain DW002T was 34.8%. Strain DW002T encoded 237 carbohydrate-active enzymes. The strain DW002T had genes associated with dissimilatory nitrate reduction and assimilatory sulfate reduction metabolic pathways. Based on distinct physiological, chemotaxonomic, genome analysis and phylogenetic differences compared to other members of the phylogenetically related genera in the family Marinifilaceae, strain DW002T is proposed to represent a novel genus within the family. Therefore, the name Paralabilibaculum antarcticum gen. nov., sp. nov. is proposed. The type strain is DW002T (=KCTC 25274T=MCCC 1K06067T).

Tubo-ovarian abscess caused by Clostridioides difficile after eight months of surgery: Case report and review of extraintestinal abdominal abscess cases.

We present a case of tubo-ovarian abscess (TOA) caused by Clostridioides difficile (CD) in a 43-year-old female. Despite lacking a history of sexually transmitted diseases, the patient had undergone paraovarian cystectomy nine months before admission. Transvaginal ultrasonography performed eight months post-surgery revealed left ovarian enlargement, accompanied by subsequent lower abdominal pain and fever exceeding 38 °C. As oral antibiotic treatment was ineffective, the patient was admitted to our hospital. Computed tomography upon admission revealed a massive TOA. Surgical drainage of the abscess was performed, and CD was identified in the culture from the pus. The TOA was treated with a three-month course of metronidazole and oral amoxicillin/clavulanic acid. While CD is commonly associated with colitis, extraintestinal manifestations are exceptionally rare. This case represents the inaugural report of TOA resulting from CD. A literature review on abdominal and pelvic CD abscesses found that patients undergoing surgical drainage had a favorable prognosis. Therefore, surgical intervention plays an important role in the management of CD abscesses.

Butyricimonas paravirosa bacteremia associated with acute terminal ileitis: case report and literature review.

We present the first described case of bacteremia due to Butyricimonas paravirosa, a commensal gram-negative anaerobic bacterium identified by whole-genome sequencing in an elderly patient with acute terminal ileitis, who was successfully treated with ceftriaxone and metronidazole. We reviewed eleven previous cases of infection due to other Butyricimonas spp, which can cause a range of diseases but may be treated conservatively with a short antimicrobial course in the appropriate clinical setting. Additionally, while most Butyricimonas spp are susceptible to empiric anaerobic therapy, drug resistance has been reported in some cases.

In Vivo Expression of Chicken Gut Anaerobes Identifies Carbohydrate- or Amino Acid-Utilising, Motile or Type VI Secretion System-Expressing Bacteria.

Complex gut microbiota increases chickens' resistance to enteric pathogens. However, the principles of this phenomenon are not understood in detail. One of the possibilities for how to decipher the role of gut microbiota in chickens' resistance to enteric pathogens is to systematically characterise the gene expression of individual gut microbiota members colonising the chicken caecum. To reach this aim, newly hatched chicks were inoculated with bacterial species whose whole genomic sequence was known. Total protein purified from the chicken caecum was analysed by mass spectrometry, and the obtained spectra were searched against strain-specific protein databases generated from known genomic sequences. Campylobacter jejuni, Phascolarctobacterium sp. and Sutterella massiliensis did not utilise carbohydrates when colonising the chicken caecum. On the other hand, Bacteroides, Mediterranea, Marseilla, Megamonas, Megasphaera, Bifidobacterium, Blautia, Escherichia coli and Succinatimonas fermented carbohydrates. C. jejuni was the only motile bacterium, and Bacteroides mediterraneensis expressed the type VI secretion system. Classification of in vivo expression is key for understanding the role of individual species in complex microbial populations colonising the intestinal tract. Knowledge of the expression of motility, the type VI secretion system, and preference for carbohydrate or amino acid fermentation is important for the selection of bacteria for defined competitive exclusion products.

Species Delineation and Comparative Genomics within the Campylobacter ureolyticus Complex.

Campylobacter ureolyticus is an emerging pathogen increasingly appreciated as a common cause of gastroenteritis and extra-intestinal infections in humans. Outside the setting of gastroenteritis, little work has been done to describe the genomic content and relatedness of the species, especially regarding clinical isolates. We reviewed the epidemiology of clinical C. ureolyticus cultured by our institution over the past 10 years. Fifty-one unique C. ureolyticus isolates were identified between January 2010 and August 2022, mostly originating from abscesses and blood cultures. To clarify the taxonomic relationships between isolates and to attribute specific genes with different clinical manifestations, we sequenced 19 available isolates from a variety of clinical specimen types and conducted a pangenomic analysis with publicly available C. ureolyticus genomes. Digital DNA:DNA hybridization suggested that these C. ureolyticus comprised a species complex of 10 species clusters (SCs) and several subspecies clusters. Although some orthologous genes or gene functions were enriched in isolates found in different SCs and clinical specimens, no association was significant. Nearly a third of the isolates possessed antimicrobial resistance genes, including the ermA resistance gene, potentially conferring resistance to macrolides, the treatment of choice for severe human campylobacteriosis. This work effectively doubles the number of publicly available C. ureolyticus genomes, provides further clarification of taxonomic relationships within this bacterial complex, and identifies target SCs for future analysis.

Selenomonas caprae sp. nov., an obligately anaerobic and volatile fatty acid producing bacterium from ruminal fluid of domestic goat (Capra hircus L.).

A novel Gram-stain-negative, motile, obligately anaerobic bacterium strain mPRGC8T was isolated from the ruminal fluid of a domestic goat (Capra hircus L.) in Nakhon Pathom province, Thailand. The strain grew at 20-45 °C (optimum, 37 °C), pH 6.0-9.0 (optimum, pH 7.5) and 3 % (w/v) NaCl. It produced acetate, propionate, valerate, caproate and heptanoate from glucose. The 16S rRNA gene sequence analysis indicated that strain mPRGC8T belonged to the genus Selenomonas and was closely related to Selenomonas ruminantium subsp. ruminantium DSM 2150T (98.0 %) and Selenomonas ruminantium subsp. lactilytica JCM 6582T (97.9 %). The in silico DNA G+C content was 53.0 mol %. Strain mPRGC8T showed average nucleotide identity, digital DNA-DNA hybridization and average animo acid identity values with Selenomonas montiformis JCM 34373T, S. ruminantium subsp. lactilytica JCM 6582T and S. ruminantium subsp. ruminantium DSM 2150T ranging from 84.9 to 86.0 %, 21.3 to 21.8 % and 73.8 to 76.1 %, respectively. The predominant cellular fatty acids were C16 : 1 ω9c and C18 : 1 ω9c. Phosphatidylethanolamine, three unidentified aminophospholipids, two unidentified ninhydrin positive glycolipids, an unidentified phospholipid and an unidentified lipid were detected as polar lipids. The genomic and phenotypic characteristics of strain mPRGC8T strongly support its classification as representative of new species of the genus Selenomonas for which the name Selenomonas caprae sp. nov. is proposed. The type strain is mPRGC8T (=JCM 33725T=KCTC 25178T).

Reclassification of Clostridium cocleatum, Clostridium ramosum, Clostridium spiroforme and Clostridium saccharogumia as Thomasclavelia cocleata gen. nov., comb. nov., Thomasclavelia ramosa comb. nov., gen. nov., Thomasclavelia spiroformis comb. nov. and Thomasclavelia saccharogumia comb. nov.

The genus Clostridium is phenotypically and genotypically diverse, with many species phylogenetically located outside Clostridium sensu stricto. One such group consists of the species Clostridium cocleatum, Clostridium ramosum, Clostridium spiroforme and Clostridium saccharogumia (formally clostridial rRNA cluster XVIII) [1]. Sequencing of the 16S rRNA and, more recently, the results of genomic analyses have demonstrated that these species represent a coherent cluster separated from other closely related genera located in the family Coprobacillaceae within the order Erysipelotrichales [2]. In addition to phenotypic, phylogenetic and genomic comparisons, chemotaxonomic features were consistent between all four species, the predominant fatty acids were C16 : 0 and C18 : 1ω9c, while glucose and ribose were the whole cell sugars present in the cell walls. Furthermore, he results of peptidoglycan analysis indicated that meso-2,6-diaminopimelic acid was present as the diagnostic diamino acid in all four species. Biochemical profiles were also concordant with them being closely related species. Therefore, on the basis of phylogenetic, genomic, phenotypic and chemotaxonomic information, a novel genus, Thomasclavelia gen. nov., is proposed. It is suggested that Clostridium cocleatum, Clostridium ramosum, Clostridium spiroforme and Clostridium saccharogumia be transferred to this genus as Thomasclavelia cocleata comb. nov., Thomasclavelia ramosa comb. nov., Thomasclavelia saccharogumia comb. nov. and Thomasclavelia spiroformis comb. nov. The type species of the genus is Thomasclavelia ramosa CCUG 24038T (=ATCC 25582T=DSM 1402T).

Crassaminicella indica sp. nov., a novel thermophilic anaerobic bacterium isolated from a deep-sea hydrothermal vent.

A novel moderately thermophilic heterotrophic bacterium, designated strain 143-21T, was isolated from a deep-sea hydrothermal chimney sample collected from the Central Indian Ridge at a depth of 2 440 m. Phylogenetic analysis indicated that strain 143-21T belongs to the genus Crassaminicella. It was most closely related to Crassaminicella thermophila SY095T (96.79 % 16S rRNA gene sequence similarity) and Crassaminicella profunda Ra1766HT (96.52 %). Genomic analysis showed that strain 143-21T shares 79.79-84.45 % average nucleotide identity and 23.50-29.20 % digital DNA-DNA hybridization with the species of the genus Crassaminicella, respectively. Cells were rod-shaped, non-motile, Gram-positive-staining. Terminal endospores were observed in stationary-phase cells when strain 143-21T was grown on Thermococcales rich medium. Strain 143-21T was able to grow at 30-60 °C (optimum, 50 °C), pH 6.5-8.5 (optimum, pH 7.0) and in 1.0-7.0 % NaCl (w/v; optimum 2.0 %, w/v). Strain 143-21T utilized fructose, glucose, maltose, mannose, ribose, N-acetyl-d-(+)-glucosamine and casamino acids, as well as amino acids including glutamate, lysine, histidine and cysteine. The main fermentation products from glucose were acetate (2.07 mM), H2 and CO2. It did not reduce elemental sulphur, sulphate, thiosulphate, sulphite, fumarate, nitrate, nitrite and Fe (III). The predominant cellular fatty acids were C14 : 0 (48.8 %), C16 : 0 (12.9 %), and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c; 10.2 %). The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol, as well as two unidentified phospholipids and four unidentified aminolipids. No respiratory quinones were detected. Based on its phylogenetic analysis and physiological characteristics, strain 143-21T is considered to represent a novel species of the genus Crassaminicella, for which the name Crassaminicella indica sp. nov. is proposed. The type strain is strain 143-21T (=DSM 114408T= MCCC 1K06400T).

Tepidibacter hydrothermalis sp. nov., a novel anaerobic bacterium isolated from a deep-sea hydrothermal vent.

A novel anaerobic heterotrophic bacterium, designated strain SWIR-1T, was isolated from a deep-sea hydrothermal vent field sample collected from the Southwest Indian Ridge at a depth of 2700 m. Phylogenetic analysis indicated that strain SWIR-1T belongs to the genus Tepidibacter, and the most closely related species are Tepidibacter mesophilus B1T (99.1 % 16S rRNA gene sequence similarity), Tepidibacter formicigenes DV1184T (94.6 %) and Tepidibacter thalassicus SC562T (93.9 %). Strain SWIR-1T shares 77.3-87.2 % average nucleotide identity and 21.5-35.7 % digital DNA-DNA hybridization values with the three type strains of Tepidibacter species. Cells of strain SWIR-1T were Gram-stain-positive, motile, short straight rods. Endospores were observed in stationary-phase cells when grown on Thermococcales rich medium. Strain SWIR-1T grew at 15-45 °C (optimum, 30°C), at pH 5.5-8.0 (optimum, pH 7.0) and with 1.0-6.0 % (w/v) NaCl (optimum, 2.0 %). Substrates utilized by strain SWIR-1T included complex proteinaceous, chitin, starch, lactose, maltose, fructose, galactose, glucose, rhamnose, arabinose, ribose, alanine, glycine and glycerol. The major fermentation products from glucose were acetate, lactate, H2 and CO2. Elemental sulphur, sulphate, thiosulphate, sulphite, fumarate, nitrate, nitrite and FeCl3 are not used as terminal electron acceptors. The main cellular fatty acids consisted of iso-C15 : 0 (28.4 %), C15 : 1 iso F (15.4 %) and C16 : 0 (9.8 %). The major polar lipids were phospholipids and glycolipids. No respiratory quinones were detected. Genomic comparison revealed a distinctive blended gene cluster comprising hyb-tat-hyp genes, which play a crucial role in the synthesis, maturation, activation and export of NiFe-hydrogenase. Based on the phylogenetic analysis, genomic, physiologic and chemotaxonomic characteristics, strain SWIR-1T is considered to represent a novel species within the genus Tepidibacter, for which the name Tepidibacter hydrothermalis sp. nov. is proposed. The type strain is strain SWIR-1T (=DSM 113848T=MCCC 1K07078T).

Clinical significance and outcomes of Clostridium tertium bacteremia: analysis of 62 cases in neutropenic and non-neutropenic patients.

The clinical significance of Clostridium tertium bacteremia is still uncertain. We evaluated the incidence, clinical characteristics, and outcomes of C. tertium bacteremia and identified differences between neutropenia and non-neutropenia. All adult patients with C. tertium bacteremia in a 2700-bed tertiary center between January 2004 and November 2021 were retrospectively enrolled. The first episode of C. tertium bacteremia in each patient was included in the analysis. Among 601 patients with Clostridium species bacteremia, 62 (10%) had C. tertium bacteremia, and of these 62 patients, 39 (63%) had had recent chemotherapy, and 31 (50%) had neutropenia or hematologic malignancy. C. tertium bacteremia originated frequently from a gastrointestinal tract infection such as enterocolitis (34%), primary bacteremia (29%), and secondary peritonitis (18%), and 34% of patients had polymicrobial bacteremia. Hematologic malignancy, prior antibiotic treatment, neutropenic enterocolitis, and primary bacteremia were significantly associated with C. tertium bacteremia in neutropenic patients, whereas solid tumor, hepatobiliary disease, secondary peritonitis, polymicrobial bacteremia, and a higher frequency of eradicable infection foci were significantly associated with C. tertium bacteremia in non-neutropenic patients. There was 15% 30-day mortality. APACHE II score (adjusted odds ratio [aOR], 1.5; 95% confidence interval [CI], 1.1-2.1) and secondary peritonitis (aOR, 25.9; 95% CI, 3.0-224.7) were independent risk factors for 30-day mortality. The prevalence of C. tertium bacteremia is low, and the characteristics of C. tertium bacteremia are significantly different between neutropenic and non-neutropenic patients. Appropriate investigation for gastrointestinal mucosal injury should be performed to improve treatment outcomes in this form of bacteremia.

Dialister pneumosintes and aortic graft infection - a case report.

BACKGROUND: Dialister pneumosintes is an anaerobic, Gram negative bacillus, found in the human oral cavity and associated with periodontitis. It has also been isolated from gastric mucosa and stool samples. Recent case reports implicate D. pneumosintes in local infection such as dental root canals, sinusitis, Lemierres syndrome and brain abscesses, as well as distal infections of the liver and lung through haematogenous spread. CASE PRESENTATION: We present a novel case of aortic graft infection and aortoenteric fistula (AEF) in a 75 year old Caucasian male, associated with D. pneumosintes bacteraemia. Microbiological evaluation of septic emboli in the lower limbs revealed other gastrointestinal flora. This suggests either AEF leading to graft infection and subsequent distal emboli and bacteraemia, or a dental origin of infection which seeded to the graft, resulting in AEF and systemic infection. To our knowledge this is the first report of D. pneumosintes associated aortic graft infection. The patient underwent surgical explantation, oversew of the aorta and placement of extra-anatomical bypass graft in conjunction with antimicrobial therapy, making a good recovery with discharge home after a 35-day hospital admission. CONCLUSION: We report a case of Dialister pneumosintes bacteraemia associated with aortic graft infection. To our knowledge, vascular graft-associated infection with D. pneumosintes has not been reported before.

The Combined Effect of Hg(II) Speciation, Thiol Metabolism, and Cell Physiology on Methylmercury Formation by Geobacter sulfurreducens.

The chemical and biological factors controlling microbial formation of methylmercury (MeHg) are widely studied separately, but the combined effects of these factors are largely unknown. We examined how the chemical speciation of divalent, inorganic mercury (Hg(II)), as controlled by low-molecular-mass thiols, and cell physiology govern MeHg formation by Geobacter sulfurreducens. We compared MeHg formation with and without addition of exogenous cysteine (Cys) to experimental assays with varying nutrient and bacterial metabolite concentrations. Cysteine additions initially (0-2 h) enhanced MeHg formation by two mechanisms: (i) altering the Hg(II) partitioning from the cellular to the dissolved phase and/or (ii) shifting the chemical speciation of dissolved Hg(II) in favor of the Hg(Cys)2 complex. Nutrient additions increased MeHg formation by enhancing cell metabolism. These two effects were, however, not additive since cysteine was largely metabolized to penicillamine (PEN) over time at a rate that increased with nutrient addition. These processes shifted the speciation of dissolved Hg(II) from complexes with relatively high availability, Hg(Cys)2, to complexes with lower availability, Hg(PEN)2, for methylation. This thiol conversion by the cells thereby contributed to stalled MeHg formation after 2-6 h Hg(II) exposure. Overall, our results showed a complex influence of thiol metabolism on microbial MeHg formation and suggest that the conversion of cysteine to penicillamine may partly suppress MeHg formation in cysteine-rich environments like natural biofilms.

Occult bacteremia in living donor liver transplantation: a prospective observational study of recipients and donors.

PURPOSE: To investigate the incidence and clinical impact of occult bacteremia in liver transplantation (LT). METHODS: This prospective observational study involved a fixed-point observation for up to 2 weeks after living donor LT in 20 recipients, with 20 donors as comparison subjects. Bacteria in the blood samples were detected using the ribosomal RNA-targeted reverse-transcription quantitative polymerase chain reaction method. To identify the causality with the gut microbiota (GM), fecal samples were collected and analyzed simultaneously. RESULTS: Occult bacteremia was identified in four recipients (20%) and three donors (15%) before the operation, and in seven recipients (35%) and five donors (25%) after the operation. Clostridium leptum subgroup, Prevotella, Colinesella, Enterobacteriaceae, and Streptococcus were the main pathogens responsible. Although it did not negatively affect the donor post-hepatectomy outcomes, the recipients with occult bacteremia had a higher rate of infectious complications post-LT. The GM analyses showed fewer post-LT predominant obligate anaerobes in both the recipients and donors with occult bacteremia. CONCLUSIONS: Occult bacteremia is a common condition that occurs in both donors and recipients. While occult bacteremia generally remains subclinical in the healthy population, there is potential risk of the development of an apparent post-LT infection in recipients who are highly immunosuppressed.