Bacteria Belonging (bacteria + belonging)

Distribution by Scientific Domains

Selected Abstracts

Volatile organic compounds: a potential direct long-distance mechanism for antagonistic action of Fusarium oxysporum strain MSA 35

Daniela Minerdi
Summary Fusarium oxysporum MSA 35 [wild-type (WT) strain] is an antagonistic Fusarium that lives in association with a consortium of bacteria belonging to the genera Serratia, Achromobacter, Bacillus and Stenotrophomonas in an Italian soil suppressive to Fusarium wilt. Typing experiments and virulence tests provided evidence that the F. oxysporum isolate when cured of the bacterial symbionts [the cured (CU) form], is pathogenic, causing wilt symptoms identical to those caused by F. oxysporum f. sp. lactucae. Here, we demonstrate that small volatile organic compounds (VOCs) emitted from the WT strain negatively influence the mycelial growth of different formae speciales of F. oxysporum. Furthermore, these VOCs repress gene expression of two putative virulence genes in F. oxysporum lactucae strain Fuslat10, a fungus against which the WT strain MSA 35 has antagonistic activity. The VOC profile of the WT and CU fungus shows different compositions. Sesquiterpenes, mainly caryophyllene, were present in the headspace only of WT MSA 35. No sesquiterpenes were found in the volatiles of ectosymbiotic Serratia sp. strain DM1 and Achromobacter sp. strain MM1. Bacterial volatiles had no effects on the growth of the different ff. spp. of F. oxysporum examined. Hyphae grown with VOC from WT F. oxysporum f. sp. lactucae strain MSA 35 were hydrophobic whereas those grown without VOCs were not, suggesting a correlation between the presence of volatiles in the atmosphere and the phenotype of the mycelium. This is the first report of VOC production by antagonistic F. oxysporum MSA 35 and their effects on pathogenic F. oxysporum. The results obtained in this work led us to propose a new potential direct long-distance mechanism for antagonism by F. oxysporum MSA 35 mediated by VOCs. Antagonism could be the consequence of both reduction of pathogen mycelial growth and inhibition of pathogen virulence gene expression. [source]

A pyrene-degrading consortium from deep-sea sediment of the West Pacific and its key member Cycloclasticus sp.


Summary A pyrene-degrading bacterial consortium was obtained from deep-sea sediments of the Pacific Ocean. The consortium degraded many kinds of polycyclic aromatic hydrocarbons (PAHs), including naphthalene, phenanthrene, pyrene, acenaphthene, fluorene, anthracene, fluoranthene, 2-methylnaphthalene and 2,6-dimethylnaphthalene, but it did not grow with chrysene and benzo[,]pyrene. With methods of plate cultivation and polymerase chain reaction,denaturing gradient gel electrophoresis (PCR-DGGE), 72 bacteria belonging to 22 genera were detected from this consortium. Among the detected bacteria, the following genera frequently occurred: Flavobacterium, Cycloclasticus, Novosphingobium, Halomonas, Achromobacter, Roseovarius and Alcanivorax. The first two genera showed the strongest bands in denaturing gradient gel electrophoresis (DGGE) profiles and appeared in all PAH treatments. By now, only one isolate designated P1 was confirmed to be a pyrene degrader. It was identified to be Cycloclasticus spirillensus (100%). Although P1 can degrade pyrene independently, other bacteria, such as Novosphingobium sp. (Band 14), Halomonas sp. (Band 16) and an unidentified bacterium (Band 35), were involved in pyrene degradation in some way; they persist in the consortium in the test of dilution to extinction if only the consortium was motivated with pyrene. However, the secondary most important member Flavobacterium sp. evaded from the community at high dilutions. As a key member of the consortium, P1 distinguished itself by both cell morphology and carbon source range among the isolates of this genus. Based on intermediate analyses of pyrene degradation, P1 was supposed to take an upper pathway different from that previously reported. Together with the results of obtained genes from P1 homology with those responsible for naphthalene degradation, its degradation to pyrene is supposed to adopt another set of genes unique to presently detected. Summarily, an efficient pyrene-degrading consortium was obtained from the Pacific Ocean sediment, in which Cycloclasticus bacterium played a key role. This is the first report to exploit the diversity of pyrene-degrading bacteria in oceanic environments. [source]

PCR DGGE and RT-PCR DGGE show diversity and short-term temporal stability in the Clostridium coccoides,Eubacterium rectale group in the human intestinal microbiota

Johanna Maukonen
Abstract As the Clostridium coccoides,Eubacterium rectale (Erec; clostridial phylogenetic cluster XIVa) group is one of the major groups of the human intestinal microbiota, DNA- and RNA-based population analysis techniques (denaturing gradient gel electrophoresis; DGGE) were developed and applied to assess the diversity and temporal stability (6 months,2 years) of this faecal clostridial microbiota in 12 healthy adults. The stability of the Erec group was compared with the stability of the predominant bacterial microbiota, which was also assessed with PCR-DGGE. In addition, the Erec group was quantified with a hybridization-based method. According to our results, the Erec group was diverse in each subject, but interindividual uniqueness was not as clear as that of the predominant bacteria. The Erec group was found to be temporally as stable as the predominant bacteria. Over 200 clones obtained from two samples proved the developed method to be specific. However, the amount of bacteria belonging to the Erec group was not related to the diversity of that same bacterial group. In conclusion, the newly developed DGGE method proved to be a valuable and specific tool for the direct assessment of the stability of the Erec group, demonstrating diversity in addition to short-term stability in most of the subjects studied. [source]

Genetic diversity and biogeography of haloalkaliphilic sulphur-oxidizing bacteria belonging to the genus Thioalkalivibrio

Mirjam Foti
Abstract A group of 85 isolates of haloalkaliphilic obligately chemolithoautotrophic sulphur-oxidizing bacteria belonging to the genus Thioalkalivibrio were recently obtained from soda lakes in Mongolia, Kenya, California, Egypt and Siberia. They have been analyzed by repetitive extragenic palindromic (rep)-PCR genomic fingerprinting technique with BOX- and (GTG)5-primer set. Cluster analysis was performed using combined fingerprint profiles and a dendrogram similarity value (r) of 0.8 was used to define the same genotype. Fifty-six genotypes were found among the isolates, revealing a high genetic diversity. The strains can be divided into two major clusters, including isolates from the Asiatic (Siberia and Mongolia) and the African (Kenya and Egypt) continents, respectively. The majority (85.9%) of the genotypes were found in only one area, suggesting an endemic character of the Thioalkalivibrio strains. Furthermore, a correlation between fingerprint clustering, geographic origin and the characteristics of the lake of origin was found. [source]

Characterization of exopolysaccharides produced by three moderately halophilic bacteria belonging to the family Alteromonadaceae

J.A. Mata
Abstract Aims:, To study the exopolysaccharides (EPSs) produced by three novel moderately halophilic species belonging to the family Alteromonadaceae to optimize EPS yields, characterize their physical and chemical properties and evaluate possible biotechnological applications for these polymers. Methods and Results:, EPSs synthesized by Idiomarina fontislapidosi F32T, Idiomarina ramblicola R22T and Alteromonas hispanica F23T were collected and analysed under optimum conditions: MY medium supplemented with 7·5% (w/v) salts; 32°C; and 1% (w/v) glucose. Polymers were synthesized mainly during the early stationary growth phase with yields ranging from 1 to 1·5 g l,1. The Idiomarina species each produced an anionic EPS composed mainly of glucose, mannose and galactose. A. hispanica synthesized an anionic EPS composed mainly of glucose, mannose and xylose. Solutions of all the polymers were low in viscosity and pseudoplastic in their behaviour. They showed emulsifying activity and the capacity to bind some metals. Conclusions:, The Alteromonadaceae species studied in this work produced EPSs with physical and chemical properties different from those produced by other halophilic and nonhalophilic bacteria, suggesting that the wide diversity of micro-organisms being encountered nowadays in hypersaline environments offers enormous potential resources for biotechnological applications. Significance and Impact of the Study:, We have optimized the EPS production and analysed new biopolymers produced by some recently described, moderately halophilic bacteria. These biopolymers are chemically and physically different from others already in use in biotechnology and offer hopes for new applications, especially in the case of A. hispanica, which may prove to be a viable source of xylo-oligosaccharides. [source]

The Flavobacterium psychrophilum OmpA, an outer membrane glycoprotein, induces a humoral response in rainbow trout

F. Dumetz
Abstract Aims:, The purpose of this study was to characterize OmpA, a major glycoprotein isolated from the membrane fraction of Flavobacterium psychrophilum, and to evaluate its potential as antigenic unit in a possible vaccine. Methods and Results:, The expression product of ompA is a 465-amino-acid protein precursor that contains a 21-amino acid signal peptide and has overall homology (up to 60% identity) with similarly sized proteins of some bacteria belonging to the Flavobacteriaceae family. The carboxy-terminal region contains the ,OmpA/MotB' domain/signature and five putative ,Thrombospondin type 3 repeats' domains have been identified in the central region. OmpA was clearly detected in the outer membrane fraction and its surface exposure was demonstrated. OmpA is one of the immunodominant antigens and binding of specific anti-OmpA antibodies lead to cell lysis in the presence of complement. Fish immunized with OmpA emulsified with Freund's adjuvant developed a high antibody titter. Conclusions:, Collectively, the data obtained here indicate that OmpA may be involved in Fl. psychrophilum/host cell interactions and appears to be a potential immunogen for a vaccine. Significance and Impact of the Study:, This study is one step in the direction of understanding pathogenesis of Fl. psychrophilum and development of future vaccine. [source]

Microbial degradation of the biocide polyhexamethylene biguanide: isolation and characterization of enrichment consortia and determination of degradation by measurement of stable isotope incorporation into DNA

L.P. O'Malley
Abstract Aims:, To isolate micro-organisms capable of utilizing polyhexamethylene biguanide (PHMB) as a sole source of nitrogen, and to demonstrate biodegradation of the biocide. Methods and Results:, Two consortia of bacteria were successfully enriched at the expense of PHMB, using sand from PHMB-treated swimming pools as inoculum. Both consortia were shown to contain bacteria belonging to the genera Sphingomonas, Azospirillum and Mesorhizobium. It was shown that the presence of both Sphingomonas and Azospirillum spp. was required for extensive growth of the consortia. In addition, the Sphingomonads were the only isolates capable of growth in axenic cultures dosed with PHMB. Using a stable isotope (15N),labelled PHMB, metabolism of the biocide by both consortia was demonstrated. By comparing the level of 15N atom incorporation into bacterial DNA after growth on either 15N-PHMB or 15N-labelled NH4Cl, it was possible to estimate the percentage of PHMB biodegradation. Conclusions:, The microbial metabolism of nitrogen from the biguanide moiety of PHMB has been demonstrated. It was revealed that Sphingomonas and Azospirillum spp. are the principal organisms responsible for growth at the expense of PHMB. Significance and Impact of the Study:, This is the first study to demonstrate the microbial metabolism of PHMB. [source]

Characterization of lactic acid bacteria strains on the basis of neutral volatile compounds produced in whey

G. Mauriello
G. MAURIELLO, L. MOIO, G. MOSCHETTI, P. PIOMBINO, F. ADDEO AND S. COPPOLA. 2001. Aims: Seventy-eight strains of lactic acid bacteria belonging to five genera and showing six different phenotype combinations of Lac (lactose fermentation), Prt (proteolytic activity) and Cit (citrate degradation) characters were investigated for their main flavouring properties with the aim to detect variability among and within the groups. Methods and Results: High resolution gas chromatography,mass spectrometry analysis of neutral volatile compounds produced in whey showed that, considering both neo-formation compounds and substances quantified in the whey cultures at different concentrations in comparison to the extract from sterile whey, the groups of lactococci, enterococci, thermophilic streptococci and mesophilic lactobacilli produced a higher number of volatiles than thermophilic lactobacilli and leuconostocs. Applying principal component analysis (PCA) to the results, enterococci, mesophilic lactobacilli and thermophilic streptococci showed a broad diversity, while lactococci included rather similar strains as well as strains with special flavouring properties. Applying PCA to thermophilic streptococci and enterococci, to lactococci and enterococci, to lactococci and thermophilic streptococci, or to mesophilic and thermophilic lactobacilli, the strains gathered consistently with their systematic position. Conclusions: The study evidenced strains producing some volatile compounds responsible for food flavouring. Flavouring properties were variable among the systematic groups and in some cases different within the same bacterial group. Significance and Impact of the Study: The potential of the findings is discussed with reference to the development of flavouring adjuncts for the dairy industry. [source]

A colony immunoblotting method for quantitative detection of a Bifidobacterium animalis probiotic strain in human faeces

H. Duez
A colony immunoblotting method has been developed to allow detection of the probiotic Bifidobacterium animalis strain DN-173 010 in human faecal samples. Rabbits were immunized with heat-killed DN-173 010 bacteria resulting in the production of an antiserum highly specific for bacteria belonging to Bif. animalis species. Of the 89 strains representative of 29 different bifidobacterial species tested, only the 15 strains of the Bif. animalis species could be detected with the antiserum. In Western immunoblotting the serum reacts with a protein of 45-kDa apparent molecular weight. None of the bacteria classically encountered in human faecal samples and able to grow on non-selective Columbia blood agar (enterobacteria, Bacteroides or Lactobacillus for instance) reacted with the antiserum. Taking advantage of the high specificity of the antiserum and of the absence of Bif. animalis bacteria in faeces samples of five human volunteers, we demonstrated that strain DN-173 010 survives the intestinal transit. Being based on a combination of semiselective cultivation and colony immunoblotting techniques, the method allowed detection of the Bif. animalis strain even when it represented only one thousandth of the total bifidobacterial population. [source]

Detection of Ralstonia solanacearum in Potato Tubers by Polymerase Chain Reaction

K.-H. Pastrik
Abstract A new polymerase chain reaction (PCR) assay was developed for the detection of Ralstonia solanacearum in potato tubers. The designed primers PS-1/PS-2 based on the sequence data of the 16S rRNA gene. Using the optimized PCR protocol, it was possible to detect R. solanacearum cells artificially added to concentrated potato extracts in the range of 1,10 colony-forming units (CFU) per PCR reaction mixture (10,100 CFU/ml potato homogenate). No amplification products were obtained, when bacteria belonging to other species or genera were submitted to PCR under the same conditions. A total of 10 different DNA extraction methods were adapted for the isolation of R. solanacearum DNA from potato homogenates and were compared for their suitability as pre-PCR procedures. Zusammenfassung Es wurde ein neuer PCR-Test entwickelt für die Detektion von Ralstonia solanacearum in Kartoffel-Knollen. Die entwickelten Primer PS-1/PS-2 basierten auf Sequenzdaten des 16S rRNA Gens. Mit dem optimierten PCR Protokoll war es möglich künstlich zugegebene R. solanacearum Zellen in konzentrierten Kartoffel-Homogenaten zu detektieren, bei einer Nachweis-Empfindlichkeit von 1,10 CFU pro PCR-Mix (10,100 CFU pro ml Kartoffel-Homogenat). Mit dem optimierten PCR Protokoll wurden keine Amplifikationsprodukte bei Bakterien anderer Arten oder Gattungen erhalten. Außerdem wurden 10 unterschiedliche DNA-Extraktionsmethoden getestet zur Isolierung von Ralstonia solanacearum DNA aus Kartoffel-Homogenat und ihre Eignung für die PCR verglichen. [source]

Effect of Thymus vulgaris essential oil on intestinal bacterial microbiota of rainbow trout, Oncorhynchus mykiss (Walbaum) and bacterial isolates

Paola Navarrete
Abstract The application of natural and innocuous compounds has potential in aquaculture as an alternative to antibiotics. We evaluated the effect of diet supplementation with Thymus vulgaris essential oil (TVEO) on the allochthonous microbial composition of rainbow trout. DNA was extracted directly from the intestinal contents, and the V3-V4 regions of the 16S rRNA genes were amplified by PCR. The bacterial composition was analysed using temporal temperature gradient electrophoresis (TTGE). No significant changes (P>0.05) were detected in the TTGE profiles of TVEO-treated trout compared with the controls. The Dice similarity index revealed a high stability (Cs >70%) of the intestinal microbiota in both groups during the 5-week period. Sequence analyses of the TTGE bands revealed the same bacterial composition in both groups, with most bacteria belonging to the Proteobacteria and Firmicutes phyla. The in vitro antibacterial activity of TVEO was assessed using a range of normal intestinal isolates and fish pathogens. The inhibitory concentrations for all the tested bacteria were higher than the TVEO levels used in trout, which may explain the in vivo results. [source]

Modified implant surfaces show different biofilm compositions under in vivo conditions

Birte Größner-Schreiber
Abstract Objective: Plaque accumulation on implant surfaces can result in peri-implantitis with potential implant loss. The aim of the present study was to examine the influence of zirconium nitride (ZrN) as a potential implant surface on the biofilm composition and diversity in vivo. Material and methods: ZrN- or titanium (Ti)-coated glass specimens and ZrN or roughened Ti discs were used as substrates. Pure glass and polished titanium served as controls. The specimens were mounted on removable intraoral splints in five adults. After 24 h of intraoral exposure, the biofilms were analyzed applying single-strand conformation polymorphism (SSCP analysis) of 16S rRNA genes. Sequence analysis of the dominant bands excised from the SSCP fingerprints allowed to taxonomically describe bacteria derived from biofilm samples. Results: The highest number of bands was counted on pure glass and Ti 800. ZrN-coated glass and ZrN-coated titanium discs showed the lowest values for species richness. However, no significant differences were observed regarding the diversity of the identified bacterial species among all the surfaces examined. A total of 46 different bacteria were identified. The dominant bands within the fingerprints indicated bacteria belonging to the Streptococcus group as identified by their 16S rDNA sequence. Conclusion: A coating of glass surfaces with ZrN significantly reduced the species richness in early bacterial colonization but the diversity was not significantly changed. In consideration of the results obtained by this and former studies a ZrN coating appears to rather modify the quantity of early bacterial adherence than the quality of the microbial community structure. [source]