Deep-sea Bacteroidetes from the Mariana Trench specialize in hemicellulose and pectin degradation typically associated with terrestrial systems.

BACKGROUND: Hadal trenches (>6000 m) are the deepest oceanic regions on Earth and depocenters for organic materials. However, how these enigmatic microbial ecosystems are fueled is largely unknown, particularly the proportional importance of complex polysaccharides introduced through deposition from the photic surface waters above. In surface waters, Bacteroidetes are keystone taxa for the cycling of various algal-derived polysaccharides and the flux of carbon through the photic zone. However, their role in the hadal microbial loop is almost unknown. RESULTS: Here, culture-dependent and culture-independent methods were used to study the potential of Bacteroidetes to catabolize diverse polysaccharides in Mariana Trench waters. Compared to surface waters, the bathypelagic (1000-4000 m) and hadal (6000-10,500 m) waters harbored distinct Bacteroidetes communities, with Mesoflavibacter being enriched at ≥ 4000 m and Bacteroides and Provotella being enriched at 10,400-10,500 m. Moreover, these deep-sea communities possessed distinct gene pools encoding for carbohydrate active enzymes (CAZymes), suggesting different polysaccharide sources are utilised in these two zones. Compared to surface counterparts, deep-sea Bacteroidetes showed significant enrichment of CAZyme genes frequently organized into polysaccharide utilization loci (PULs) targeting algal/plant cell wall polysaccharides (i.e., hemicellulose and pectin), that were previously considered an ecological trait associated with terrestrial Bacteroidetes only. Using a hadal Mesoflavibacter isolate (MTRN7), functional validation of this unique genetic potential was demonstrated. MTRN7 could utilize pectic arabinans, typically associated with land plants and phototrophic algae, as the carbon source under simulated deep-sea conditions. Interestingly, a PUL we demonstrate is likely horizontally acquired from coastal/land Bacteroidetes was activated during growth on arabinan and experimentally shown to encode enzymes that hydrolyze arabinan at depth. CONCLUSIONS: Our study implies that hadal Bacteroidetes exploit polysaccharides poorly utilized by surface populations via an expanded CAZyme gene pool. We propose that sinking cell wall debris produced in the photic zone can serve as an important carbon source for hadal heterotrophs and play a role in shaping their communities and metabolism. Video Abstract.

Gut microbiota-derived short-chain fatty acids promote prostate cancer progression via inducing cancer cell autophagy and M2 macrophage polarization.

We have previously demonstrated abnormal gut microbial composition in castration-resistant prostate cancer (CRPC) patients, here we revealed the mechanism of gut microbiota-derived short-chain fatty acids (SCFAs) as a mediator linking CRPC microbiota dysbiosis and prostate cancer (PCa) progression. By using transgenic TRAMP mouse model, PCa patient samples, in vitro PCa cell transwell and macrophage recruitment assays, we examined the effects of CRPC fecal microbiota transplantation (FMT) and SCFAs on PCa progression. Our results showed that FMT with CRPC patients' fecal suspension increased SCFAs-producing gut microbiotas such as Ruminococcus, Alistipes, Phascolarctobaterium in TRAMP mice, and correspondingly raised their gut SCFAs (acetate and butyrate) levels. CRPC FMT or SCFAs supplementation significantly accelerated mice's PCa progression. In vitro, SCFAs enhanced PCa cells migration and invasion by inducing TLR3-triggered autophagy that further activated NF-κB and MAPK signalings. Meanwhile, autophagy of PCa cells released higher level of chemokine CCL20 that could reprogramme the tumor microenvironment by recruiting more macrophage infiltration and simultaneously polarizing them into M2 type, which in turn further strengthened PCa cells invasiveness. Finally in a cohort of 362 PCa patients, we demonstrated that CCL20 expression in prostate tissue was positively correlated with Gleason grade, pre-operative PSA, neural/seminal vesical invasion, and was negatively correlated with post-operative biochemical recurrence-free survival. Collectively, CRPC gut microbiota-derived SCFAs promoted PCa progression via inducing cancer cell autophagy and M2 macrophage polarization. CCL20 could become a biomarker for prediction of prognosis in PCa patients. Intervention of SCFAs-producing microbiotas may be a useful strategy in manipulation of CRPC.

Effects of hemoglobin extracted from Tegillarca granosa on the gut microbiota in iron deficiency anemia mice.

Iron deficiency anemia (IDA) is a serious threat to the health of humans around the world. Tegillarca granosa (T. granosa) is considered as an excellent source of iron due to its abundant iron-binding protein hemoglobin. This study aimed to investigate the effects of hemoglobin from T. granosa on the gut microbiota and iron bioavailability in IDA mice. Compared to normal mice, IDA mice showed reduced microbiota diversity and altered relative abundance (reduced Muribaculaceae and increased Bacteroides). After 4 weeks of administration, hemoglobin restored the dysbiosis of the intestinal microbiota induced by IDA and decreased the Firmicutes/Bacteroidota ratio and the abundance of Proteobacteria. Analysis of the hemoglobin regeneration efficiency of mice treated with hemoglobin confirmed that hemoglobin exhibited high iron bioavailability, particularly at low-dose administration, suggesting that a small amount of hemoglobin from T. granosa markedly elevated the blood hemoglobin level in mice. These findings suggested that IDA could be alleviated by administration of hemoglobin with excellent iron bioavailability, and its therapeutic mechanism may be partially attributed to the regulation of the intestinal microbiota composition and relative abundance. These results indicated that T. granosa hemoglobin may be a promising iron supplement to treat IDA and promote the utilization of aquatic-derived proteins.

Pectin alleviates the pulmonary inflammatory response induced by PM2.5 from a pig house by modulating intestinal microbiota.

This study aimed to investigate whether dietary fiber pectin can alleviate PM2.5-induced pulmonary inflammation and the potential mechanism. PM2.5 samples were collected from a nursery pig house. The mice were divided into three groups: the control group, PM2.5 group and PM2.5 + pectin group. The mice in the PM2.5 group were intratracheally instilled with PM2.5 suspension twice a week for four consecutive weeks, and those in the PM2.5 + pectin group were subject to the same PM2.5 exposure, but fed with a basal diet supplemented with 5% pectin. The results showed that body weight and feed intake were not different among the treatments (p > 0.05). However, supplementation with pectin relieved PM2.5-induced pulmonary inflammation, presenting as slightly restored lung morphology, decreased mRNA expression levels of IL-1ß, IL-6 and IL-17 in the lung, decreased MPO content in bronchoalveolar lavage fluid (BLAF), and even decreased protein levels of IL-1ß and IL-6 in the serum (p < 0.05). Dietary pectin altered the composition of the intestinal microbiota, increasing the relative abundance of Bacteroidetes and decreasing the ratio of Firmicutes/Bacteroidetes. At the genus level, short-chain fatty acid (SCFA)-producing bacteria, such as Bacteroides, Anaerotruncus, Prevotella 2, Parabacteroides, Ruminococcus 2 and Butyricimonas, were enriched in the PM2.5 +pectin group. Accordingly, dietary pectin increased the concentrations of SCFAs, including acetate, propionate, butyrate and valerate, in mice. In conclusion, dietary fermentable fiber pectin can relieve PM2.5-induced pulmonary inflammation via alteration of intestinal microbiota composition and SCFA production. This study provides a new insight into reducing the health risk associated with PM2.5 exposure.

A widely distributed phosphate-insensitive phosphatase presents a route for rapid organophosphorus remineralization in the biosphere.

The regeneration of bioavailable phosphate from immobilized organophosphorus represents a key process in the global phosphorus cycle and is facilitated by enzymes known as phosphatases. Most bacteria possess at least one of three phosphatases with broad substrate specificity, known as PhoA, PhoX, and PhoD, whose activity is optimal under alkaline conditions. The production and activity of these phosphatases is repressed by phosphate availability. Therefore, they are only fully functional when bacteria experience phosphorus-limiting growth conditions. Here, we reveal a previously overlooked phosphate-insensitive phosphatase, PafA, prevalent in Bacteroidetes, which is highly abundant in nature and represents a major route for the regeneration of environmental phosphate. Using the enzyme from Flavobacterium johnsoniae, we show that PafA is highly active toward phosphomonoesters, is fully functional in the presence of excess phosphate, and is essential for growth on phosphorylated carbohydrates as a sole carbon source. These distinct properties of PafA may expand the metabolic niche of Bacteroidetes by enabling the utilization of abundant organophosphorus substrates as C and P sources, providing a competitive advantage when inhabiting zones of high microbial activity and nutrient demand. PafA, which is constitutively synthesized by soil and marine flavobacteria, rapidly remineralizes phosphomonoesters releasing bioavailable phosphate that can be acquired by neighboring cells. The pafA gene is highly diverse in plant rhizospheres and is abundant in the global ocean, where it is expressed independently of phosphate availability. PafA therefore represents an important enzyme in the context of global biogeochemical cycling and has potential applications in sustainable agriculture.

Nitrite as a causal factor for nitrate-dependent anaerobic corrosion of metallic iron induced by Prolixibacter strains.

Microbially influenced corrosion (MIC) may contribute significantly to overall corrosion risks, especially in the gas and petroleum industries. In this study, we isolated four Prolixibacter strains, which belong to the phylum Bacteroidetes, and examined their nitrate respiration- and Fe0 -corroding activities, together with two previously isolated Prolixibacter strains. Four of the six Prolixibacter strains reduced nitrate under anaerobic conditions, while the other two strains did not. The anaerobic growth of the four nitrate-reducing strains was enhanced by nitrate, which was not observed in the two strains unable to reduce nitrate. When the nitrate-reducing strains were grown anaerobically in the presence of Fe0 or carbon steel, the corrosion of the materials was enhanced by more than 20-fold compared to that in aseptic controls. This enhancement was not observed in cultures of the strains unable to reduce nitrate. The oxidation of Fe0 in the anaerobic cultures of nitrate-reducing strains occurred concomitantly with the formation of nitrite. Since nitrite chemically oxidized Fe0 under anaerobic and aseptic conditions, the corrosion of Fe0 - and carbon steel by the nitrate-reducing Prolixibacter strains was deduced to be mainly enhanced via the biological reduction of nitrate to nitrite, followed by the chemical oxidation of Fe0 to Fe2+ and Fe3+ coupled to the reduction of nitrite.

Effects of Anthocyanin on Intestinal Health: A Systematic Review.

Intestinal health relies on the association between the mucosal immune system, intestinal barrier and gut microbiota. Bioactive components that affect the gut microbiota composition, epithelial physical barrier and intestinal morphology were previously studied. The current systematic review evaluated evidence of anthocyanin effects and the ability to improve gut microbiota composition, their metabolites and parameters of the physical barrier; this was conducted in order to answer the question: "Does food source or extract of anthocyanin promote changes on intestinal parameters?". The data analysis was conducted following the PRISMA guidelines with the search performed at PubMed, Cochrane and Scopus databases for experimental studies, and the risk of bias was assessed by the SYRCLE tool. Twenty-seven studies performed in animal models were included, and evaluated for limitations in heterogeneity, methodologies, absence of information regarding allocation process and investigators' blinding. The data were analyzed, and the anthocyanin supplementation demonstrated positive effects on intestinal health. The main results identified were an increase of Bacteroidetes and a decrease of Firmicutes, an increase of short chain fatty acids production, a decrease of intestinal pH and intestinal permeability, an increase of the number of goblet cells and tight junction proteins and villi improvement in length or height. Thus, the anthocyanin supplementation has a potential effect to improve the intestinal health. PROSPERO (CRD42020204835).

Stability of pure oxygen aeration-activated sludge system under non-steady food-to-microorganism ratio conditions during petrochemical wastewater treatment.

This study investigates the stability of a pure oxygen aeration-activated sludge system for petrochemical wastewater treatment under high organic concentration and non-steady food-to-microorganism (F/M) ratio conditions. Sludge settling characteristics maintained relatively stable conditions with an F/M ratio variation from 0.15 ± 0.04 to 0.33 ± 0.07 kg COD/kg MLSS⋅d, while the excess F/M ratio (0.44 ± 0.16 kg COD/kg MLSS⋅d) resulted in deterioration of the organic removal and sludge-water separation performances. Loosely bound extracellular polymeric substances (EPS) showed more significant effect on sludge settleability than the tightly bound EPS. The genus Hydrogenophaga was related to organic removal performance, while Zoogloea and Chitinophaga were related to the effluent quality of suspended solids. The excess F/M ratio also caused an increase in Zoogloea and Chitinophaga, whereas the toxicity of petrochemical wastewater resulted in decreased abundance of Hydrogenophaga. These changes caused deterioration of the organic removal and sludge-water separation performances.

In vitro gastrointestinal digestion and fecal fermentation reveal the effect of different encapsulation materials on the release, degradation and modulation of gut microbiota of blueberry anthocyanin extract.

In this study, four different selected wall materials (namely gelatin, soy protein isolate, maltodextrin and Arabic gum) were applied for blueberry anthocyanin extract encapsulation. The effect of these wall material types on the release and degradation of anthocyanin and the modulation of gut microbiota during in vitro simulated gastrointestinal digestion and colonic fermentation were investigated. It was found that the encapsulation of anthocyanin extract using appropriate wall material could significantly enhance the colonic accessibility of anthocyanins. Soy protein isolate and gelatin delayed the release of anthocyanins, whereas the other two wall materials displayed no significant effect on the release time of anthocyanins. Gut microbiota mainly metabolized some phenolic compounds such as 4-hydroxycinnamic acid and chlorogenic acid. Meanwhile, different fermented anthocyanin extract microcapsule broth could significantly decrease the composition and abundance of Firmicutes and increase that of Bacteroidetes. Furthermore, the presence of anthocyanin extract microcapsules, especially those encapsulated with soy protein isolate, promoted the biosynthesis of short-chain fatty acids by gut microbiota. It is concluded that, amongst the wall materials studied, soy protein isolate appeared to be a functional and suitable candidate to delay anthocyanin release and prevent disease through the promotion of gut health.

Evidence in the Japan Sea of microdolomite mineralization within gas hydrate microbiomes.

Over the past 15 years, massive gas hydrate deposits have been studied extensively in Joetsu Basin, Japan Sea, where they are associated primarily with active gas chimney structures. Our research documents the discovery of spheroidal microdolomite aggregates found in association with other impurities inside of these massive gas hydrates. The microdolomites are often conjoined and show dark internal cores occasionally hosting saline fluid inclusions. Bacteroidetes sp. are concentrated on the inner rims of microdolomite grains, where they degrade complex petroleum-macromolecules present as an impurity within yellow methane hydrate. These oils show increasing biodegradation with depth which is consistent with the microbial activity of Bacteroidetes. Further investigation of these microdolomites and their contents can potentially yield insight into the dynamics and microbial ecology of other hydrate localities. If microdolomites are indeed found to be ubiquitous in both present and fossil hydrate settings, the materials preserved within may provide valuable insights into an unusual microhabitat which could have once fostered ancient life.

Complete genome sequence of Echinicola rosea JL3085, a xylan and pectin decomposer.

Marine Bacteroidetes are well known for their functional specialization on the decomposition of polysaccharides which results from a great number of carbohydrate-active enzymes. Here we represent the complete genome of a Bacteroitedes member Echinicola rosea JL3085T that was isolated from surface seawater of the South China Sea. The genome is 6.06 Mbp in size with a GC content of 44.1% and comprises 4613 protein coding genes. A remarkable genomic feature is that the number of glycoside hydrolase genes in the genome of E. rosea JL3085T is high in comparison with most of the sequenced members of marine Bacteroitedes. E. rosea JL3085T genome harbored multi-gene polysaccharide utilization loci (PUL) systems involved in the degradation of pectin, xylan and arabinogalactan. The large diversity of hydrolytic enzymes supports the use of E. rosea JL3085T as a candidate for biotechnological applications in enzymatic conversion of plant polysaccharides.

Characterizations of microbial diversity and machine oil degrading microbes in machine oil contaminated soil.

Microbial diversity in machine oil contaminated soil was determined by high-throughput amplicon sequencing technology. The diversity of culturable microbes in the contaminated soil was further characterized using polymerase chain reaction method. Proteobacteria and Bacteroidetes were the most dominant phyla and occupied 52.73 and 16.77%, respectively, while the most abundant genera were Methylotenera (21.62%) and Flavobacterium (3.06%) in the soil. In the culturable microbes, the major phyla were Firmicutes (46.15%) and Proteobacteria (37.36%) and the most abundant genera were Bacillus (42.86%) and Aeromonas (34.07%). Four isolated microbes with high machine oil degradation efficiency were selected to evaluate their characteristics on the oil degradation. All of them reached their highest oil degradation rate after 7 days of incubation. Most of them significantly increased their oil degradation rate by additional carbon or organic nitrogen source in the incubation medium. The oil degradation rate by combination of the four microbes at the same inoculation level was also higher than the rate from each individual microbe. The protocol and findings of this study are very useful for developing micro-bioremediation method to eliminate machine oil contaminants from soil.

Effects of BARLEYmax and high-ß-glucan barley line on short-chain fatty acids production and microbiota from the cecum to the distal colon in rats.

We investigated whether supplementation with the barley line BARLEYmax (Tantangara; BM), which contains three fermentable fibers (fructan, ß-glucan, and resistant starch), modifies the microbiota in cecal and distal colonic digesta in addition to short-chain fatty acids (SCFAs) production more favorably than supplementation with a high-ß-glucan barley line (BG012; BG). Male Sprague-Dawley rats were randomly divided into 3 groups that were fed an AIN-93G-based diet that contained 5% fiber provided by cellulose (control), BM or BG. Four weeks after starting the respective diets, the animals were sacrificed and digesta from the cecum, proximal colon and distal colon were collected and the SCFA concentrations were quantified. Microbiota in the cecal and distal colonic digesta were analyzed by 16S rRNA sequencing. The concentrations of acetate and n-butyrate in cecal digesta were significantly higher in the BM and BG groups than in the control group, whereas the concentration of total SCFAs in cecal digesta was significantly higher only in the BM group than in the control group. The concentrations of acetate and total SCFAs in the distal colonic digesta were significantly higher only in the BM group than in the control group. The abundance of Bacteroidetes in cecal digesta was significantly higher in the BM group than in the control group. In contrast, the abundance of Firmicutes in cecal digesta was significantly lower in the BM and BG groups than in the control group. These results indicated that BM increased the concentration of total SCFAs in the distal colonic digesta. These changes might have been caused by fructan and resistant starch in addition to ß-glucan. In conclusion, fermentable fibers in BM reached the distal colon and modified the microbiota, leading to an increase in the concentration of total SCFAs in the distal colonic digesta, more effectively compared with the high-ß-glucan barley line (BG).

Variations in pH significantly affect cadmium uptake in grafted muskmelon (Cucumis melo L.) plants and drive the diversity of bacterial communities in a seedling substrate.

Substrates are fundamental prerequisites for growing grafted seedlings. In this study, substrates with different pH levels (5.0, 5.5, 6.0, 6.5, 7.0, and 8.0) were set up to elucidate the effect of pH on cadmium (Cd) uptake in grafted muskmelon (Cucumis melo L.) plants. Bacterial diversity was also investigated. Results showed that pH and high Cd concentration greatly affected the growth of grafted plants. The chlorophyll content of the muskmelon leaves decreased at 100 µM Cd. The majority of the Cd ions accumulated in the rootstock rather than in the shoot tissue in all of the treatments. The shoots and roots showed the highest Cd content at pH 5.5 and the lowest Cd content at pH 8.0 regardless of the Cd concentration. The operational taxonomic units belonging to Proteobacteria and Bacteroidetes were significantly (p < 0.05) enriched at different substrate pH levels compared with those at pH 5.0. The operational taxonomic units belonging to the phyla Firmicutes, Acidobacteria, and Chloroflexi were significantly decreased. The available nitrogen, phosphorus, Cd, and pH were strongly linked to bacterial community compositions. On the contrary, the available potassium was weakly correlated with the bacterial structure. This study demonstrates that pH greatly affects Cd uptake in grafted muskmelon plants and predicts microbial community structures in breeding substrates with different pH levels. Our results suggest that Cd accumulation in grafted plants can be reduced by setting the appropriate substrate pH. This work can serve as a reference for growing high-quality grafted plants and ensuring food safety in the presence of Cd contamination.

Effects of Panax ginseng polysaccharides on the gut microbiota in mice with antibiotic-associated diarrhea.

Panax ginseng is a traditional medicinal plant used in most Asian countries to cure many diseases. The benefits of ginseng are due to its primary active component, polysaccharides. Gut microbiota dysbiosis is a worldwide problem associating with antibiotic use. The objective of this study was to investigate the effects of ginseng polysaccharides (WGP) on the diversity of the gut microbiota in mice with antibiotic-associated diarrhea. Compared to diarrhea mice, WGP significantly changed the composition and diversity of the gut microbiota. Specifically, WGP increased the relative abundance of the phylum Firmicutes and decreased the relative abundance of the phyla Bacteroidetes, Proteobacteria and Actinobacteria. At the genus level, WGP increased the relative abundance of Lactobacillus, Lactococcus, and Streptococcus, but decreased the relative abundance of Bacteroides. The key phylotype of beneficial bacteria in the gut microbiota that responded to WGP was Lactobacillus. In addition, WGP also reversed carbohydrate, amino acid and energy metabolism to normal levels, thereby promoting the recovery of the mucosal structure. Taken collectively, our results indicate that WGP altered the composition and diversity of the gut microbiota in mice with antibiotic-associated diarrhea, restored the gut microbiota, balanced metabolic processes, and promoted the recovery of the mucosa.

Influence of application of manganese ore in constructed wetlands on the mechanisms and improvement of nitrogen and phosphorus removal.

Vertical up-flow constructed wetlands (CWs) with manganese ore (Mn ore) as media (M-CWs) were developed to treat simulated polluted river water. The results showed that the average removal efficiencies for NH4-N, NO3-N, TN and TP were 91.74%, 83.29%, 87.47% and 65.12% in M-CWs, respectively, which were only 79.12%, 72.90%, 75.85% and 43.23% in the CWs without Mn ore (C-CWs). Nutrient mass balance showed that nitrogen (N) removal was improved by enhanced microbial processes, media storage and plant uptake in M-CWs. Moreover, almost 50% of phosphorus (P) was retained by media storage because of the adsorption processes on Mn ore. It was found that addition of Mn ore enhanced denitrification as the relative abundance of denitrifying bacteria increased. The produced Mn(II) and more abundant Gammaproteobacteria confirmed alternative N removal pathways including anoxic nitrification coupled to Mn ore reduction and denitrification using Mn(II) as electron donor. Mn(II) concentration in the effluent of M-CWs was below the drinking water limit of 0.1 mg/L, which makes them environmentally-friendly.

Antidiabetic Potential of Green Seaweed Enteromorpha prolifera Flavonoids Regulating Insulin Signaling Pathway and Gut Microbiota in Type 2 Diabetic Mice.

This study aimed to investigate the antidiabetic activity of water-ethanol extract of green macroalgae Enteromorpha prolifera (EPW) and its flavonoid-rich fraction less than 3 kDa (EPW3) in type 2 diabetic mice induced by streptozotocin and a high-sucrose/high-fat diet. The major active compounds were identified using ultra-performance liquid chromatography coupled with quadrupole-time-of-flight-tandem mass spectrometry. Quantitative gene expression analysis of the insulin signaling pathway was performed. The effects of EPW3 on gut microflora in diabetic mice were analyzed by high-throughput 16S rRNA gene sequencing. The results showed EPW3 treatment decreased the fasting blood glucose, improved oral glucose tolerance, and protected against liver and kidney injury with reduced inflammation in diabetic mice. The active principle of EPW3 revealed hypoglycemic effect as indicated by activation of the IRS1/PI3K/AKT and inhibition of the JNK1/2 insulin pathway in liver. Furthermore, the treatment significantly enriched the abundance of Lachnospiraceae and Alisties, which were positive correlation of metabolic phenotypes. These findings indicated that EPW3 possessed great therapeutic potential as adjuvant therapy for type 2 diabetes.

Response of marine bacteria to oil contamination and to high pressure and low temperature deep sea conditions.

The effect of pressure and temperature on microbial communities of marine environments contaminated with petroleum hydrocarbons is understudied. This study aims to reveal the responses of marine bacterial communities to low temperature, high pressure, and contamination with petroleum hydrocarbons using seawater samples collected near an offshore Brazilian platform. Microcosms containing only seawater and those containing seawater contaminated with 1% crude oil were subjected to three different treatments of temperature and pressure as follows: (1) 22°C/0.1 MPa; (2) 4°C/0.1 MPa; and (3) 4°C/22 MPa. The effect of depressurization followed by repressurization on bacterial communities was also evaluated (4°C/22 MPaD). The structure and composition of the bacterial communities in the different microcosms were analyzed by PCR-DGGE and DNA sequencing, respectively. Contamination with oil influenced the structure of the bacterial communities in microcosms incubated either at 4°C or 22°C and at low pressure. Incubation at low temperature and high pressure greatly influenced the structure of bacterial communities even in the absence of oil contamination. The 4°C/22 MPa and 4°C/22 MPaD treatments resulted in similar DGGE profiles. DNA sequencing (after 40 days of incubation) revealed that the diversity and relative abundance of bacterial genera were related to the presence or absence of oil contamination in the nonpressurized treatments. In contrast, the variation in the relative abundances of bacterial genera in the 4°C/22 MPa-microcosms either contaminated or not with crude oil was less evident. The highest relative abundance of the phylum Bacteroidetes was observed in the 4°C/22 MPa treatment.

Shift in bacterioplankton diversity and structure: Influence of anthropogenic disturbances along the Yarlung Tsangpo River on the Tibetan Plateau, China.

River systems have critical roles in the natural water environment and the transportation of nutrients. Anthropogenic activities, including wastewater discharge and river damming, raise adverse impacts on ecosystem and continuum of rivers. An increasing amount of attention has been paid to riverine bacterioplankton as they make vital contributions to biogeochemical nutrient cycle. A comprehensive study was conducted on the bacterioplankton community along the Yarlung Tsangpo River, which is the longest plateau river in China and is suffering from various anthropogenic impacts. The results indicated that nutrient variations corresponded to anthropogenic activities, and silica, nitrogen and phosphorus were retained by the dam. River damming influenced the biomass and diversity of the bacterioplankton, but significant alterations in the community structure were not observed between upstream and downstream of the dam. Moreover, the spatial distribution of the bacterioplankton community changed gradually along the river, and the dominant bacterioplankton in the upstream, midstream and downstream portions of the river were Firmicutes, Bacteroidetes and Proteobacteria, respectively. Soluble reactive phosphorus, elevation, ammonium nitrogen, velocity and turbidity were the main environmental factors that shape the bacterioplankton community. Our study offers the first insights into the variation of a bacterioplankton community of a large river in plateau region.

Impact of ß2-1 fructan on faecal community change: results from a placebo-controlled, randomised, double-blinded, cross-over study in healthy adults.

Healthy adults (n 30) participated in a placebo-controlled, randomised, double-blinded, cross-over study consisting of two 28 d treatments (ß2-1 fructan or maltodextrin; 3×5 g/d) separated by a 14-d washout. Subjects provided 1 d faecal collections at days 0 and 28 of each treatment. The ability of faecal bacteria to metabolise ß2-1 fructan was common; eighty-seven species (thirty genera, and four phyla) were isolated using anaerobic medium containing ß2-1 fructan as the sole carbohydrate source. ß2-1 fructan altered the faecal community as determined through analysis of terminal restriction fragment length polymorphisms and 16S rRNA genes. Supplementation with ß2-1 fructan reduced faecal community richness, and two patterns of community change were observed. In most subjects, ß2-1 fructan reduced the content of phylotypes aligning within the Bacteroides, whereas increasing those aligning within bifidobacteria, Faecalibacterium and the family Lachnospiraceae. In the remaining subjects, supplementation increased the abundance of Bacteroidetes and to a lesser extent bifidobacteria, accompanied by decreases within the Faecalibacterium and family Lachnospiraceae. ß2-1 Fructan had no impact on the metagenome or glycoside hydrolase profiles in faeces from four subjects. Few relationships were found between the faecal bacterial community and various host parameters; Bacteroidetes content correlated with faecal propionate, subjects whose faecal community contained higher Bacteroidetes produced more caproic acid independent of treatment, and subjects having lower faecal Bacteroidetes exhibited increased concentrations of serum lipopolysaccharide and lipopolysaccharide binding protein independent of treatment. We found no evidence to support a defined health benefit for the use of ß2-1 fructans in healthy subjects.