Increase in sedimentary organic carbon with a change from hypoxic to oxic conditions.

In the Seto Inland Sea, Japan, chemical oxygen demand has increased over recent decades, while average dissolved oxygen concentrations in the bottom water have increased. In this study, we investigated responses of organic carbon (OC) in hypoxic sediment to changes of redox conditions using experimental columns containing sediment and overlying water. Surface sediment showed an increase in OC along with the change to an aerobic condition. Microbial community analysis showed a predominance of sulfur-oxidizing bacteria (SOB) such as Sulfurovum sp. in the sediment. This dominance could account for the increased OC. Additionally, the dissolved organic carbon (DOC) concentration in the overlying water increased. Further experiments using sandy sediment showed that biodegradation of Sulfurimonas denitrificans was associated with DOC release. These results show that a change in the sedimentary environment (increase in dissolved oxygen) increased the sedimentary OC and DOC of overlying water by stimulating certain autotrophic bacteria, especially the SOB.

Sulfurimonas sediminis sp. nov., a novel hydrogen- and sulfur-oxidizing chemolithoautotroph isolated from a hydrothermal vent at the Longqi system, southwestern Indian ocean.

A novel marine hydrogen- and sulfur-oxidizing bacterium, designated strain S2-6 T, was isolated from the deep-sea sediment samples at the Longqi hydrothermal system, southwestern Indian Ocean. Cells were Gram-stain-negative, motile, short rods with a single polar flagellum. Growth was observed at 10-45 °C (optimum 33 °C), pH 5.0-8.0 (optimum pH 7.0) and 1.5 to 6.0% (w/v) NaCl with an optimum at 3.0% (w/v). The isolate was an obligate chemolithoautotroph capable of growth using thiosulfate, tetrathionate, elemental sulfur or sodium sulfide as the energy source, and oxygen or nitrate as the sole electron acceptor. When hydrogen was used as the energy source, strain S2-6 T could respire oxygen, nitrate or element sulfur. The major cellular fatty acids of strain S2-6 T were summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0 and summed feature 8 (C18:1ω7c and/or C18:1ω6c). The total size of its genome was 2,320,257 bp and the genomic DNA G + C content was 37.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and core genes showed that the novel isolate belonged to the genus Sulfurimonas and was most closely related to Sulfurimonas paralvinellae GO25T (96.8% sequence identity) and Sulfurimonas autotrophica OK10T (95.8% sequence identity). The average nucleotide identity and DNA-DNA hybridization values between strain S2-6 T and S. paralvinellae GO25T and S. autotrophica OK10T were 74.6%-81.2% and 19.1%-24.6%, respectively. Based on the polyphase taxonomical data, strain S2-6 T represents a novel species of the genus Sulfurimonas, for which the name Sulfurimonas sediminis sp. nov. is proposed, with the type strain S2-6 T (= MCCC 1A14513T = KCTC 15854 T).

Elemental sulfur reduction by a deep-sea hydrothermal vent Campylobacterium Sulfurimonas sp. NW10.

Sulfurimonas species (class Campylobacteria, phylum Campylobacterota) were globally distributed and especially predominant in deep-sea hydrothermal environments. They were previously identified as chemolithoautotrophic sulfur-oxidizing bacteria (SOB), whereas little is known about their potential in sulfur reduction. In this report, we found that the elemental sulfur reduction is quite common in different species of genus Sulfurimonas. To gain insights into the sulfur reduction mechanism, growth tests, morphology observation, as well as genomic and transcriptomic analyses were performed on a deep-sea hydrothermal vent bacterium Sulfurimonas sp. NW10. Scanning electron micrographs and dialysis tubing tests confirmed that elemental sulfur reduction occurred without direct contact of cells with sulfur particles while direct access strongly promoted bacterial growth. Furthermore, we demonstrated that most species of Sulfurimonas probably employ both periplasmic and cytoplasmic polysulfide reductases, encoded by genes psrA1 B1 CDE and psrA2 B2 , respectively, to accomplish cyclooctasulfur reduction. This is the first report showing two different sulfur reduction pathways coupled to different energy conservations could coexist in one sulfur-reducing microorganism, and demonstrates that most bacteria of Sulfurimonas could employ both periplasmic and cytoplasmic polysulfide reductases to perform cyclooctasulfur reduction. The capability of sulfur reduction coupling with hydrogen oxidation may partially explain the prevalenceof Sulfurimonas in deep-sea hydrothermal vent environments.

Sulfurimonas indica sp. nov., a hydrogen- and sulfur-oxidizing chemolithoautotroph isolated from a hydrothermal sulfide chimney in the Northwest Indian Ocean.

A novel mesophilic, hydrogen- and sulfur-oxidizing bacterium, designated strain NW8NT, was collected from a sulfide chimney at the deep-sea hydrothermal vent on the Carlsberg Ridge of the Northwest Indian Ocean. The cells were Gram-stain-negative, motile, short rods with a single polar flagellum. The temperature, pH and salinity ranges for growth of strain NW8NT were 4-40 °C (optimum, 33 °C), pH 4.5-7.5 (optimum, pH 5.5) and 340-680 mM NaCl (optimum, 510 mM). The isolate was an obligate chemolithoautotroph capable of growth using hydrogen, thiosulfate, sulfide or elemental sulphur as the sole energy source, carbon dioxide as the sole carbon source and molecular oxygen as the sole electron acceptor. The major cellular fatty acids of strain NW8NT were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0 and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The total size of its genome was 2 093 492 bp and the genomic DNA G+C content was 36.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and core genes showed that the novel isolate belonged to the genus Sulfurimonas and was most closely related to Sulfurimonas paralvinellae GO25T (97.4 % sequence identity). The average nucleotide identity and DNA-DNAhybridization values between strain NW8NT and S. paralvinellae GO25T was 77.8 and 21.1 %, respectively. Based on the phylogenetic, genomic and phenotypic data presented here, strain NW8NT represents a novel species of the genus Sulfurimonas, for which the name Sulfurimonas indica sp. nov. is proposed, with the type strain NW8NT (=MCCC 1A13988T=KTCC 15780T).

Perturbations of the gut microbiome in anti-CCP positive individuals at risk of developing rheumatoid arthritis.

OBJECTIVE: Individuals with newly diagnosed RA have a distinct microbiome when compared with healthy controls. However, little is known as to when these microbiome perturbations begin. Using a prospective at-risk cohort of individuals positive for anti-citrullinated protein (anti-CCP) antibody with new onset musculoskeletal symptoms, but without clinical arthritis, we investigated for the presence of a gut dysbiosis before the onset of RA. METHODS: The gut microbiota of 25 anti-CCP positive individuals without clinical synovitis were sequenced targeting the V4 region of the 16S rRNA gene. Using a publicly available database, a control population of 44 individuals, approximately matched in age, gender, diet and ethnicity was selected for comparison, using the same sequencing methodology. Median interval between sample collection and progression to RA was 188 days. Taxonomic analysis was performed using QIIME and MEGAN, and statistical analysis using R software. RESULTS: There were significant differences (P =0.01) at family level in gut microbiomes of anti-CCP positive individuals vs controls. The anti-CCP positive population had an overabundance of Lachnospiraceae, Helicobacteraceae, Ruminococcaceae, Erysipelotrichaceae and Bifidobacteriaceae, among others. Five individuals progressed to RA between sample collection and analysis. Clustering of the progressor population was observed on a phylogenetic network created using a probabilistic similarity index (Goodall's index). CONCLUSIONS: Anti-CCP positive at-risk individuals without clinical synovitis appear to have a distinct gut microbiome compared with healthy controls. Phylogenetic clustering was observed in individuals who progressed to RA, suggesting that distinct taxa are associated with the development of RA many months before its onset.

Sulfurimonas xiamenensis sp. nov. and Sulfurimonas lithotrophica sp. nov., hydrogen- and sulfur-oxidizing chemolithoautotrophs within the Epsilonproteobacteria isolated from coastal sediments, and an emended description of the genus Sulfurimonas.

Strains 1-1NT and GYSZ_1T were isolated from marine sediments collected from the coast of Xiamen, PR China. Cells of the two strains were Gram-stain-negative, rod-shaped or slightly curved. Strain 1-1NT was non-motile, whereas strain GYSZ_1T was motile by means of one polar flagellum. The temperature, pH and salinity concentration ranges for growth of 1-1NT were 10-45 °C (optimum 30 °C), pH 5.5-8.0 (optimum 7.0) and 0-90 g l-1 NaCl (optimum 50 g l-1), while the growth of GYSZ_1T occurred at 4-45 °C (optimum 33 °C), pH 5.0-8.5 (optimum 6.5) and 5-90 g l-1 NaCl (optimum 20 g l-1). The two novel isolates were obligate chemolithoautotrophs capable of growth using hydrogen, thiosulfate, sulfide or elemental sulfur as the sole energy source, and nitrate, elemental sulfur or molecular oxygen as an electron acceptor. The major fatty acids of 1-1NT were C16 : 1ω7c, C16 : 0, C18 : 1ω7c and C18 : 0, while the predominant fatty acids of strain GYSZ_1T were C16 : 1ω7c, C16 : 0, C18 : 1ω7c and C14 : 0 3-OH. The DNA G+C contents of 1-1NT and GYSZ_1T were 34.5 mol% and 33.2 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that 1-1NT and GYSZ_1T represented members of the genus Sulfurimonas, with the highest sequence similarities to Sulfurimonas crateris SN118T (97.4 %) and Sulfurimonas denitrificans DSM 1251T (94.7 %), respectively. However, 1-1NT and GYSZ_1T shared 95.5 % similarity of 16S rRNA gene sequences, representing different species of the genus Sulfurimonas. On the basis of the physiological properties and the results of phylogenetic analyses, including average nucleotide identity and in silico DNA-DNA hybridization values, strains 1-1NT and GYSZ_1T represent two novel species within the genus Sulfurimonas, for which the names Sulfurimonas xiamenensis sp. nov. and Sulfurimonas lithotrophica sp. nov. are proposed, with the type strains 1-1NT (=MCCC 1A14514T=KCTC 15851T) and GYSZ_1T (=MCCC 1A14739T=KCTC 15853T), respectively. Our results also justify an emended description of the genus Sulfurimonas.

Sulfurimonas crateris sp. nov., a facultative anaerobic sulfur-oxidizing chemolithoautotrophic bacterium isolated from a terrestrial mud volcano.

A novel mesophilic facultative anaerobic bacterium, strain SN118T, was isolated from a terrestrial mud volcano in Taman Peninsula, Russia. The cells were Gram-negative, motile, short, straight or curved rods with a single polar flagellum. Growth was observed at 5-40 °C (optimum, 30 °C) and pH 5.5-9.5 (optimum, pH 8.0). Growth of strain SN118T was observed in NaCl concentrations ranging from 0.5 to 8.0 % (w/v) with an optimum at 2.0-3.0 % (w/v). The isolate grew chemolithoautotrophically with sulfide, elemental sulfur or thiosulfate as electron donor, oxygen, nitrate or nitrite as an electron acceptor and CO2/HCO3 - as a carbon source. Molecular hydrogen or organic substances did not support growth. Nitrate was reduced to N2. The dominant fatty acids were C16 : 1ω7c, C16 : 0 and C18  :  1ω7c. The total size of the genome of the novel isolate was 2 209 279 bp and the genomic DNA G+C content was 38.8 mol%. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel isolate belonged to the genus Sulfurimonas and was most closely related to Sulfurimonas denitrificans DSM 1251T (96.74 %). Based on its physiological properties and results from phylogenetic analyses, including average nucleotide identity and in silico DNA-DNA hybridization values, the isolate is considered to represent a novel species of the genus Sulfurimonas, for which the name Sulfurimonas crateris sp. nov. is proposed. The type strain is SN118T (=DSM 109248T=VKM B-3378T).

Comparison of sulfide-oxidizing Sulfurimonas strains reveals a new mode of thiosulfate formation in subsurface environments.

Sulfur-oxidizing Sulfurimonas spp. are widespread in sediments, hydrothermal vent fields, aquifers and subsurface environments such as oil reservoirs where they play an important role in the sulfur cycle. We determined the genome sequence of the oil field isolate Sulfurimonas sp. strain CVO and compared its gene expression during nitrate-dependent sulfide oxidation to the coastal sediment isolate Sulfurimonas denitrificans. Formation of elemental sulfur (S0 ) and high expression of sulfide quinone oxidoreductase (SQR) genes indicates that sulfide oxidation in both strains is mediated by SQR. Subsequent oxidation of S0 was achieved by the sulfur oxidation enzyme complex (SOX). In the coastal S. denitrificans, the genes are arranged and expressed as two clusters: soxXY1 Z1 AB and soxCDY2 Z2 H, and sulfate was the sole metabolic end product. By contrast, the oil field strain CVO has only the soxCDY2 Z2 H cluster and not soxXY1 Z1 AB. Despite the absence of the soxXY1 Z1 AB cluster, strain CVO oxidized S0 to thiosulfate and sulfate, demonstrating that soxCDY2 Z2 H genes alone are sufficient for S0 oxidation in Sulfurimonas spp. and that thiosulfate is an additional metabolic end product. Screening of publicly available metagenomes revealed that Sulfurimonas spp. with only the soxCDY2 Z2 H cluster are widespread suggesting this mechanism of thiosulfate formation is environmentally significant.

Transition to bound states for bacteria swimming near surfaces.

It is well known that flagellated bacteria swim in circles near surfaces. However, recent experiments have shown that a sulfide-oxidizing bacterium named Thiovulum majus can transition from swimming in circles to a surface bound state where it stops swimming while remaining free to move laterally along the surface. In this bound state, the cell rotates perpendicular to the surface with its flagella pointing away from it. Using numerical simulations and theoretical analysis, we demonstrate the existence of a fluid-structure interaction instability that causes cells with relatively short flagella to become surface bound.

Effects of sialylated lactulose on the mouse intestinal microbiome using Illumina high-throughput sequencing.

Sialylated oligosaccharides are known to have beneficial effects, such as increasing the level of bifidobacteria, reducing the levels of blood endotoxin and blood ammonia, and enhancing the body's immune system. However, it is unknown whether sialylated lactuloses have modulatory effects on the intestinal microbiota. In this study, 60 healthy mice were randomly divided into six groups, namely, a normal control group, a lactulose group, a Kdn-α2,3-lactulose group, a Kdn-α2,6-lactulose group, a Neu5Ac-α2,3-lactulose group, and a Neu5Ac-α2,6-lactulose group. After 14 days of lactulose administration, the feces of three mice from each group were collected, and the intestinal microbiota were detected by Illumina MiSeq high-throughput sequencing targeting the V3-V4 region of the 16S rDNA gene. At the phylum level, the relative abundance of Firmicutes was increased in the sialylated lactulose groups, while the abundance of Bacteroidetes was decreased. At the family level, sialylated lactulose intervention decreased the relative abundance of Bacteroidales S24-7 group and Helicobacteraceae and enhanced the abundance of Lactobacillaceae, which reflects the modulatory effect of sialylated lactulose on intestinal microbiota. Diversity analysis indicated that the index of Chao was higher in the sialylated lactulose groups than in the normal control group, and the Shannon and Simpson diversity indices were higher in the Kdnα-2,6-lactulose group and the Neu5Ac-α2,3-lactulose group than in the normal control group. The results of the intestinal microbiota sample composition indicated that there were differences between the sialylated lactulose groups and the normal control group. Thus, sialylated lactulose could be used as a functional food component with potential therapeutic applications in manipulating intestinal microbiota to exert beneficial effects on the host's health.

Sulfide-driven denitrification: detecting active microorganisms in fed-batch enrichment cultures by DNA stable isotope probing.

A microbial community was enriched in the anoxic compartment of a pilot-scale bioreactor that was operated for 180 days, fed with sewage and designed for organic matter, nitrogen and sulfide removal by coupling anaerobic digestion, nitrification and mixotrophic denitrification. Denitrification occurred with endogenous electron donors, mainly sulfide and residual organic matter, coming from the anaerobic compartment. The microorganisms involved in denitrification with sulfide as electron donor were identified by DNA-stable isotope probing with [U-13C]-labelled CO2 and NaHCO3. Complete denitrification occurred every two days, and the applied NO3-/S2- ratio was 1.6. Bacteria belonging to the Sulfurimonas denitrificans was identified as a chemoautotrophic denitrifier, and those related to Georgfuchisa toluolica, Geothrix fermentans and Ferritrophicum radicicola were most probably associated with heterotrophic denitrification using endogenous cells and/or intermediate metabolites. This study showed that DNA-SIP was a suitable technique to identify the active microbiota involved in sulfide-driven denitrification in a complex environment, which may contribute to improve design and operation of bioreactors aiming for carbon-nitrogen-sulfur removal.

Pharmaceuticals and Personal Care Products Can Be Transformed by Anaerobic Microbiomes in the Environment and in Waste-Treatment Processes.

Pharmaceuticals and personal care products (PPCPs) are emerging environmental contaminants that can be transformed by anaerobic microorganisms in anoxic environments. The present study examined 2 consortia, enriched under methanogenic and sulfate-rich conditions, that demethylate the phenylmethyl ether anti-inflammatory drug naproxen to 6-O-desmethylnaproxen. Both enriched consortia were also able to demethylate a range of phenylmethyl ether compounds of plant-based origin or used as PPCPs. Results from 16S rRNA gene sequencing showed that the 2 communities were very different despite sharing the same PPCP metabolism. In most cases, the demethylated metabolite was not further degraded but rather accumulated in the culture medium. For the expectorant guaifenesin, this resulted in a novel microbial metabolite. Furthermore, to our knowledge, this is the first report of methylparaben metabolism under methanogenic conditions. The wide range of phenylmethyl ether substrates that underwent O-demethylation in both methanogenic and sulfate-rich conditions suggests that there are potentially bioactive transformation products in the environment that have not yet been quantified. Environ Toxicol Chem 2019;38:1585-1593. © 2019 SETAC.

Transcriptomic and proteomic insight into the mechanism of cyclooctasulfur- versus thiosulfate-oxidation by the chemolithoautotroph Sulfurimonas denitrificans.

Chemoautotrophic bacteria belonging to the genus Sulfurimonas (class Campylobacteria) were previously identified as key players in the turnover of zero-valence sulfur, a central intermediate in the marine sulfur cycle. S. denitrificans was further shown to be able to oxidize cyclooctasulfur (S8 ). However, at present the mechanism of activation and metabolism of cyclooctasulfur is not known. Here, we assessed the transcriptome and proteome of S. denitrificans grown with either thiosulfate or S8 as the electron donor. While the overall expression profiles under the two growth conditions were rather similar, distinct differences were observed that could be attributed to the utilization of S8 . This included a higher abundance of expressed genes related to surface attachment in the presence of S8 , and the differential regulation of the sulfur-oxidation multienzyme complex (SOX), which in S. denitrificans is encoded in two gene clusters: soxABXY 1 Z 1 and soxCDY 2 Z 2 . While the proteins of both clusters were present with thiosulfate, only proteins of the soxCDY 2 Z 2 were detected at significant levels with S8 . Based on these findings a model for the oxidation of S8 is proposed. Our results have implications for interpreting metatranscriptomic and -proteomic data and for the observed high level of diversification of soxY 2 Z 2 among sulfur-oxidizing Campylobacteria.

Metabolites of an Oil Field Sulfide-Oxidizing, Nitrate-Reducing Sulfurimonas sp. Cause Severe Corrosion.

Oil reservoir souring and associated material integrity challenges are of great concern to the petroleum industry. The bioengineering strategy of nitrate injection has proven successful for controlling souring in some cases, but recent reports indicate increased corrosion in nitrate-treated produced water reinjection facilities. Sulfide-oxidizing, nitrate-reducing bacteria (soNRB) have been suggested to be the cause of such corrosion. Using the model soNRB Sulfurimonas sp. strain CVO obtained from an oil field, we conducted a detailed analysis of soNRB-induced corrosion at initial nitrate-to-sulfide (N/S) ratios relevant to oil field operations. The activity of strain CVO caused severe corrosion rates of up to 0.27 millimeters per year (mm y-1) and up to 60-µm-deep pitting within only 9 days. The highest corrosion during the growth of strain CVO was associated with the production of zero-valent sulfur during sulfide oxidation and the accumulation of nitrite, when initial N/S ratios were high. Abiotic corrosion tests with individual metabolites confirmed biogenic zero-valent sulfur and nitrite as the main causes of corrosion under the experimental conditions. Mackinawite (FeS) deposited on carbon steel surfaces accelerated abiotic reduction of both sulfur and nitrite, exacerbating corrosion. Based on these results, a conceptual model for nitrate-mediated corrosion by soNRB is proposed.IMPORTANCE Ambiguous reports of corrosion problems associated with the injection of nitrate for souring control necessitate a deeper understanding of this frequently applied bioengineering strategy. Sulfide-oxidizing, nitrate-reducing bacteria have been proposed as key culprits, despite the underlying microbial corrosion mechanisms remaining insufficiently understood. This study provides a comprehensive characterization of how individual metabolic intermediates of the microbial nitrogen and sulfur cycles can impact the integrity of carbon steel infrastructure. The results help explain the dramatic increases seen at times in corrosion rates observed during nitrate injection in field and laboratory trials and point to strategies for reducing adverse integrity-related side effects of nitrate-based souring mitigation.

Western diet feeding influences gut microbiota profiles in apoE knockout mice.

BACKGROUND: Gut microbiota plays an important role in many metabolic diseases such as diabetes and atherosclerosis. Apolipoprotein E (apoE) knock-out (KO) mice are frequently used for the study of hyperlipidemia and atherosclerosis. However, it is unknown whether apoE KO mice have altered gut microbiota when challenged with a Western diet. METHODS: In the current study, we assessed the gut microbiota profiling of apoE KO mice and compared with wild-type mice fed either a normal chow or Western diet for 12 weeks using 16S pyrosequencing. RESULTS: On a western diet, the gut microbiota diversity was significantly decreased in apoE KO mice compared with wild type (WT) mice. Firmicutes and Erysipelotrichaceae were significantly increased in WT mice but Erysipelotrichaceae was unchanged in apoE KO mice on a Western diet. The weighted UniFrac principal coordinate analysis exhibited clear separation between WT and apoE KO mice on the first vector (58.6%) with significant changes of two dominant phyla (Bacteroidetes and Firmicutes) and seven dominant families (Porphyromonadaceae, Lachnospiraceae, Ruminococcaceae, Desulfovibrionaceae, Helicobacteraceae, Erysipelotrichaceae and Veillonellaceae). Lachnospiraceae was significantly enriched in apoE KO mice on a Western diet. In addition, Lachnospiraceae and Ruminococcaceae were positively correlated with relative atherosclerosis lesion size in apoE KO. CONCLUSIONS: Collectively, our study showed that there are marked changes in the gut microbiota of apoE KO mice, particularly challenged with a Western diet and these alterations may be possibly associated with atherosclerosis.

Minimal standards for describing new species belonging to the families Campylobacteraceae and Helicobacteraceae: Campylobacter, Arcobacter, Helicobacter and Wolinella spp.

Ongoing changes in taxonomic methods, and in the rapid development of the taxonomic structure of species assigned to the Epsilonproteobacteria have lead the International Committee of Systematic Bacteriology Subcommittee on the Taxonomy of Campylobacter and Related Bacteria to discuss significant updates to previous minimal standards for describing new species of Campylobacteraceae and Helicobacteraceae. This paper is the result of these discussions and proposes minimum requirements for the description of new species belonging to the families Campylobacteraceae and Helicobacteraceae, thus including species in Campylobacter, Arcobacter, Helicobacter, and Wolinella. The core underlying principle remains the use of appropriate phenotypic and genotypic methods to characterise strains sufficiently so as to effectively and unambiguously determine their taxonomic position in these families, and provide adequate means by which the new taxon can be distinguished from extant species and subspecies. This polyphasic taxonomic approach demands the use of appropriate reference data for comparison to ensure the novelty of proposed new taxa, and the recommended study of at least five strains to enable species diversity to be assessed. Methodological approaches for phenotypic and genotypic (including whole-genome sequence comparisons) characterisation are recommended.

Isoliquiritigenin decreases the incidence of colitis-associated colorectal cancer by modulating the intestinal microbiota.

Imbalances in intestinal bacteria correlate with colitis-associated colorectal cancer (CAC). Traditional Chinese medicines have been used to adjust the gut microbiota, and isoliquiritigenin (ISL), a flavonoid extracted from licorice, has shown antitumor efficacy. In this study, the effects of ISL on CAC development and the gut microbiota were evaluated using an azoxymethane and dextran sulphate sodium (AOM/DSS)-induced mouse model of CAC (CACM). Histopathological analysis suggested that ISL reduced tumor incidence in vivo. Moreover, high-throughput sequencing and terminal restriction fragment length polymorphism (T-RFLP) studies of the bacterial 16S rRNA gene revealed that the structure of the gut microbial community shifted significantly following AOM/DSS treatment, and that effect was alleviated by treatment with high-dose ISL (150 mg/kg). Compared to the microbiota in the control mice (CK), the levels of Bacteroidetes decreased and the levels of Firmicutes increased during CAC development. ISL reversed the imbalance at the phylum level and altered the familial constituents of the gut microbiota. Specifically, the abundance of Helicobacteraceae increased after treatment with high-dose ISL, while the abundance of Lachnospiraceae and Rikenellaceae decreased. At the genus level, ISL reduced the abundance of opportunistic pathogens (Escherichia and Enterococcus), and increased the levels of probiotics, particularly butyrate-producing bacteria (Butyricicoccus, Clostridium, and Ruminococcus). Thus, ISL protects mice from AOM/DSS-induced CAC, and ISL and the gut microbiota may have synergistic anti-cancer effects.

Hydrodynamics with spin in bacterial suspensions.

We describe a kind of self-propelling motion of bacteria based on the cooperative action of rotating flagella on the surface of bacteria. Describing the ensemble of rotating flagella in the framework of the hydrodynamics with spin, the reciprocal theorem of Stokesian hydrodynamics is generalized accordingly. The velocity of the self-propulsion is expressed in terms of the characteristics of the vector field of flagella orientation and it is shown that the unusually high velocities of Thiovulum majus bacteria may be explained by the cooperative action of the rotating flagella. The expressions obtained enable us to estimate the torque created by the rotary motors of the bacterium and show quantitative agreement with the existing experimental data.