Robertkochia solimangrovi sp. nov., isolated from mangrove soil, and emended description of the genus Robertkochia.

To date, there is sparse information for the genus Robertkochia with Robertkochia marina CC-AMO-30DT as the only described member. We report here a new species isolated from mangrove soil collected at Malaysia Tanjung Piai National Park and perform polyphasic characterization to determine its taxonomic position. Strain CL23T is a Gram-negative, yellow-pigmented, strictly aerobic, catalase-positive and oxidase-positive bacterium. The optimal growth conditions were determined to be at pH 7.0, 30-37 °C and in 1-2 % (w/v) NaCl. The major respiratory quinone was menaquinone-6 (MK-6) and the highly abundant polar lipids were four unidentified lipids, a phosphatidylethanolamine and two unidentified aminolipids. The 16S rRNA gene similarity between strain CL23T and R. marina CC-AMO-30DT is 96.67 %. Strain CL23T and R. marina CC-AMO-30DT clustered together and were distinguished from taxa of closely related genera in 16S rRNA gene phylogenetic analysis. Genome sequencing revealed that strain CL23T has a genome size of 4.4 Mbp and a G+C content of 40.72 mol%. Overall genome related indexes including digital DNA-DNA hybridization value and average nucleotide identity are 17.70 % and approximately 70%, below the cutoffs of 70 and 95%, respectively, indicated that strain CL23T is a distinct species from R. marina CC-AMO-30DT. Collectively, based on the phenotypic, chemotaxonomic, phylogenetic and genomic evidences presented here, strain CL23T is proposed to represent a new species with the name Robertkochia solimangrovi sp. nov. (KCTC 72252T=LMG 31418T). An emended description of the genus Robertkochia is also proposed.

Alterations in gut microbiota composition and metabolic parameters after dietary intervention with barley beta glucans in patients with high risk for metabolic syndrome development.

Metabolic syndrome is a complex disease that is exponentially increasing in the western world, and diet is one of the possible ways to improve the metabolic status of patients. Barley beta glucans are dietary fibres that show promise for improvement cholesterol levels and postprandial glucose response, but they have been rarely investigated in human trials with concurrent focus on gut microbiota. A double-blind, placebo-controlled, randomised clinical trial was conducted with 43 volunteers with high risk for metabolic syndrome development or with diagnosed metabolic syndrome. During a four-week intervention study, participants consumed experimental bread containing 6 g of barley beta glucans or equal bread but without beta glucans. After dietary intervention, total plasma cholesterol decreased in the test group (-0.26 ±â€¯0.54, p = 0.019), but not in the control group. Short chain fatty acids (SCFA) composition in faeces significantly changed with increase of propionic acid in test group (43.2%, p = 0.045) and with decrease of acetic acid in control group (41.8%, p = 0.011). The microbiome analysis based on Illumina paired end sequencing of 16S rRNA genes showed a decrease in microbial diversity and richness in the test group. The pre-intervention gut microbiota composition showed higher abundance of health associated Bifidobacterium spp. and Akkermansia municiphila within cholesterol-responsive group, showing that diet-induced metabolic response is possibly dependent on individual gut microbiota composition.

Expanding the rumen Prevotella collection: The description of Prevotella communis, sp. nov. of ovine origin.

27 strains representing eight new Prevotella species were isolated from rumen of a single sheep in eight weeks interval. One of the putative species encompassing the highest number of isolated strains which also exhibited some genetic variability in preliminary data, was then selected for description of a novel species. We examined six strains in genomic and phenotypic detail, two of which may actually be the same strain isolated nearly three weeks apart. Other strains formed clearly diverged intraspecies lineages as evidenced by core genome phylogeny and phenotypic differences. Strains of the proposed new Prevotella species are strictly saccharolytic as is usual for rumen Prevotella, and use plant cell-wall xylans and pectins for growth. However, the range of cell-wall polysaccharides utilised for growth is rather limited compared to rumen generalists such as Prevotella bryantii or Prevotella ruminicola and this extends also to the inability to utilise starch, which is unexpected for the members of the genus Prevotella. Based on the data obtained, we propose Prevotella communis sp. nov. to accommodate strain E1-9T as well as other strains with the similar properties. The proposed species is widespread: two other strains were previously isolated from sheep in Japan and is also common in metagenomic data of cattle and sheep rumen samples from Scotland and New Zealand. It was also found in a collection of metagenome-assembled genomes originating from cattle in Scotland. Thus, it is a ubiquitous bacterium of domesticated ruminants specialising in degradation of a somewhat restricted set of plant cell wall components.

Membrane Changes Associated with Exposure of Pseudomonas putida to Selected Environmental Pollutants and their Possible Roles in Toxicity.

A bacterial model system (Pseudomonas putida DSM 50026) was used in this research to assess potential effect of five selected chemically diverse environmental pollutants on cell membranes. Long chain fatty acid profiles of cultures exposed to environmentally relevant concentrations of atrazine (ATR), metolachlor (MET), pentachlorobiphenyl (PCB), hexachlorobenzene (HCB) and fluoranthene (FL), were analyzed and compared to non-exposed cultures. To assess sensitivity of membrane-based responses, the impact of each toxicant on culture growth was also followed spectrophotometrically. Results revealed changes in fatty acid profiles when cells were exposed to PCB, HCB and FL in concentrations below the inhibitory levels. Moreover, the observed membrane responses were similar to the ones previously associated with adaptation to some membrane-active compounds. On the other hand, exposure of cells to any of the two herbicides, ATR or MET, did not induce any significant changes in fatty acid profiles. However, when combined with a commonly used fertilizer compound, NH4NO3 growth impairment was observed. Synergistic effect of the two herbicides with NH4NO3 might be a consequence of changes in fatty acid profile increasing membrane fluidity, likely induced by NH4+ ions.

Prodigiosin - A Multifaceted Escherichia coli Antimicrobial Agent.

Despite a considerable interest in prodigiosin, the mechanism of its antibacterial activity is still poorly understood. In this work, Escherichia coli cells were treated with prodigiosin to determine its antimicrobial effect on bacterial physiology. The effect of prodigiosin was concentration dependent. In prodigiosin treated cells above MIC value no significant DNA damage or cytoplasmic membrane disintegration was observed. The outer membrane, however, becomes leaky. Cells had severely decreased respiration activity. In prodigiosin treated cells protein and RNA synthesis were inhibited, cells were elongated but could not divide. Pre-treatment with prodigiosin improved E. coli survival rate in media containing ampicillin, kanamycin and erythromycin but not phleomycin. The results suggest that prodigiosin acts as a bacteriostatic agent in E. coli cells. If prodigiosin was diluted, cells resumed growth. The results indicate that prodigiosin has distinct mode of antibacterial action in different bacteria.

Prodigiosin Induces Autolysins in Actively Grown Bacillus subtilis Cells.

Prodigiosin produced by marine bacterium Vibrio ruber DSM 14379 exhibits a potent antimicrobial activity against a broad range of Gram positive and Gram negative bacteria. The mechanism of prodigiosin antimicrobial action, however, is not known. In this work, the effect of prodigiosin on Bacillus subtilis growth, cell membrane leakage, and induction of autolysins was studied. Treating B. subtilis with prodigiosin resulted in rapid decline of optical density and increased cell membrane leakage measured by ß-galactosidase activity. Cell lysis was initiated immediately after treatment with prodigiosin in the middle exponential phase and was completed within 2 h. Lytic activity of prodigiosin in mutant strains with impaired autolysin genes lytABCD decreased for 80% compared to the wild type strain, while in lytABCDEF mutant strain prodigiosin had no bacteriolytic but only bacteriostatic effect. Fast prodigiosin lytic activity on individual B. subtilis cells was confirmed by a modified comet assay. The results indicate that prodigiosin autolysin induction in B. subtilis is growth phase dependent.

Exposure to Al2O3 nanoparticles changes the fatty acid profile of the anaerobe Ruminococcus flavefaciens.

One of the main mechanisms of nanoparticle toxicity is known to be the generation of reactive oxygen species (ROS) which primarily damage cell membranes. However, very limited data on membrane effects in anaerobic environments (where ROS could not be the cause of membrane damage) are available. In the following study, rumen anaerobe Ruminococcus flavefaciens 007C was used as a bacterial model to assess the potential effects of Al(2)O(3) and TiO(2) nanoparticles on membranes in an anaerobic environment. Fatty acid profiles of cultures after exposure to Al(2)O(3) or TiO(2) nanoparticles were analyzed and compared with the profiles of non-exposed cultures or cultures exposed to bulk materials. Analysis revealed dose-effect changes in membrane composition exclusively when cells were exposed to Al(2)O(3) nanoparticles in a concentration range of 3-5 g/L, but were not present in cultures exposed to bulk material. On the other hand, the tested concentrations of nano-TiO(2) did not significantly affect the membrane profile of the exposed bacterium. The results suggest the possibility that Al(2)O(3) induces changes in bacterial membranes by direct physical interaction, which was supported by TEM image analysis.

Butyrivibrio hungatei sp. nov. and Pseudobutyrivibrio xylanivorans sp. nov., butyrate-producing bacteria from the rumen.

Two novel Gram-negative, anaerobic, non-spore-forming, butyrate-producing bacterial species, strains Mz 5T and JK 615T, were isolated from the rumen fluid of cow and sheep. Both strains were curved rods that were motile by means of single polar or subpolar flagellum and common in the rumen microbial ecosystem. Strain Mz 5T produced high xylanase, proteinase, pectin hydrolase and DNase activities; 1,4-beta-endoglucanase was also detected in the culture medium. The bacterium utilized a wide range of carbohydrates. Glucose was fermented to formate, butyrate, lactate, succinate and ethanol. The DNA G + C content was 42.1 mol%. The complete 16S rDNA sequence was obtained and phylogenetic relationships were determined. Strain Mz 5T and related isolates were located in clostridial cluster XIVa and were closely related to Pseudobutyrivibrio ruminis, Butyrivibrio crossotus, Roseburia cecicola and Eubacterium rectale. The name proposed for this novel bacterium is Pseudobutyrivibrio xylanivorans; the type strain is Mz 5T (=DSM 14809T =ATCC BAA-455T). Strain JK 615T produced no fibrolytic activity, but utilized a wide range of carbohydrates. Glucose was fermented to formate, acetate, butyrate and ethanol. The DNA G + C content was 44-8 mol%. The complete 16S rDNA sequence was obtained and phylogenetic relationships were determined. Strain JK 615T was located in clostridial cluster XIVa and was closely related to Clostridium proteoclasticum, Butyrivibrio fibrisolvens and Eubacterium halii. The name proposed for this novel bacterium is Butyrivibrio hungatei; the type strain is JK 615T (=DSM 14810T =ATCC BAA-456T).