Genetic Diversity and Phylogeny of Antagonistic Bacteria against Phytophthora nicotianae Isolated from Tobacco Rhizosphere

The genetic diversity of antagonistic bacteria from the tobacco rhizosphere was examined by BOXAIR-PCR, 16S-RFLP, 16S rRNA sequence homology and phylogenetic analysis methods. These studies revealed that 4.01% of the 6652 tested had some inhibitory activity against Phytophthora nicotianae. BOXAIR-PCR analysis revealed 35 distinct amplimers aligning at a 91% similarity level, reflecting a high degree of genotypic diversity among the antagonistic bacteria. A total of 25 16S-RFLP patterns were identified representing over 33 species from 17 different genera. Our results also found a significant amount of bacterial diversity among the antagonistic bacteria compared to other published reports. For the first time; Delftia tsuruhatensis, Stenotrophomonas maltophilia, Advenella incenata, Bacillus altitudinis, Kocuria palustris, Bacillus licheniformis, Agrobacterium tumefaciens and Myroides odoratimimus are reported to display antagonistic activity towards Phytophthora nicotianae. Furthermore, the majority (75%) of the isolates assayed for antagonistic activity were Gram-positives compared to only 25% that were Gram-negative bacteria

Cultivation-Independent Methods Reveal Differences among Bacterial Gut Microbiota in Triatomine Vectors of Chagas Disease

Chagas disease is one of the most important endemic diseases of South and Central America. Its causative agent is the protozoan Trypanosoma cruzi, which is transmitted to humans by blood-feeding insects known as triatomine bugs. These vectors mainly belong to Rhodnius, Triatoma and Panstrongylus genera of Reduviidae. The bacterial communities in the guts of these vectors may have important effects on the biology of T. cruzi. For this reason, we analyzed the bacterial diversity hosted in the gut of different species of triatomines using cultivation-independent methods. Among Rhodnius sp., we observed similar bacterial communities from specimens obtained from insectaries or sylvatic conditions. Endosymbionts of the Arsenophonus genus were preferentially associated with insects of the Panstrongylus and Triatoma genera, whereas the bacterial genus Serratia and Candidatus Rohrkolberia were typical of Rhodnius and Dipetalogaster, respectively. The diversity of the microbiota tended to be the largest in the Triatoma genus, with species of both Arsenophonus and Serratia being detected in T. infestans

Transformer la politique forestière à Porto Rico par une approche ascendante

Après un petit rappel sur l\u27historique politique de Porto Rico, l\u27intervention s\u27articule principalement autour d\u27une lutte pour la préservation des forêts. Une lutte qui trouve son origine dans une série de protestations contre l\u27exploitation minière dans le pays

Influence of hydrodynamics and nutrients on biofilm structure

Hydrodynamic conditions control two interlinked parameters; mass transfer and drag, and will, therefore, significantly influence many of the processes involved in biofilm development. The goal of this research was to determine the effect of flow velocity and nutrients on biofilm structure. Biofilms were grown in square glass capillary flow cells under laminar and turbulent flows. Biofilms were observed microscopically under flow conditions using image analysis. Mixed species bacterial biofilms were grown with glucose (40 mg/l) as the limiting nutrient. Biofilms grown under laminar conditions were patchy and consisted of roughly circular cell clusters separated by interstitial voids. Biofilms in the turbulent flow cell were also patchy but these biofilms consisted of patches of ripples and elongated 'streamers' which oscillated in the flow. To assess the influence of changing nutrient conditions on biofilm structure the glucose concentration was increased from 40 to 400 mg/l on an established 21 day old biofilm growing in turbulent flow. The cell clusters grew rapidly and the thickness of the biofilm increased from 30 µm to 130 µm within 17 h. The ripples disappeared after 10 hours. After 5 d the glucose concentration was reduced back to 40 mg/l. There was a loss of biomass and patches of ripples were re-established within a further 2 d

CHEMOTACIC AND GROWTH RESPONSES TO EXPLOSIVES OF DESULFOVIBRIO VULGARIS H. AND SULFATE-REDUCING BACTERIA ISOLATED FROM TROPICAL MARINE SEDIMENTS

Bombing sites used for military training activities can have considerable amounts of contaminants and pose significant risks for people and the environment. Until 2003, the eastern part of Vieques (Puerto Rico) was used by the US Navy as a bombing range. Currently, leaching of explosive compounds from unexploded ordnance represents a serious threat to the marine ecosystem. The contribution of microorganisms in natural attenuation of explosives, including sulfate-reducing bacteria (SRB) has been demonstrated in soils but little is known about their contribution in marine environments. Characterization assays were employed to assess the effects of explosive compounds (TNT, RDX, HMX) on Desulfovibrio vulgaris Hildenborough and five novel SRB isolated from marine sediments in costal waters of Vieques. Pure cultures were combined with media in a covered 96-well micro plate and the opacity was monitored in real time as the bacteria grew in a temperature-controlled plate reader. A dose-response curve was used to estimate minimum inhibitory concentrations (MICs) for TNT, RDX and HMX in 0, 1.5 and 3.0% (w/v) NaCI media. Some of the bacterial isolates grew better in explosive-containing environments than in regular media while at low salt D. vulgaris grew without inhibition at saturated RDX levels. Higher salt concentrations (1.5 and 3.00/0) did not support D. vulgaris growth in the presence of RDX. However, this organism did tolerate high levels of TNT at different NaCI concentrations. Elucidating the diversity and behavior of SRBs to explosive compounds in tropical sediments could help us understand the role of these microbial populations in contaminated marine environments

CHEMOTACIC AND GROWTH RESPONSES TO EXPLOSIVES OF DESULFOVIBRIO VULGARIS H. AND SULFATE-REDUCING BACTERIA ISOLATED FROM TROPICAL MARINE SEDIMENTS

Bombing sites used for military training activities can have considerable amounts of contaminants and pose significant risks for people and the environment. Until 2003, the eastern part of Vieques (Puerto Rico) was used by the US Navy as a bombing range. Currently, leaching of explosive compounds from unexploded ordnance represents a serious threat to the marine ecosystem. The contribution of microorganisms in natural attenuation of explosives, including sulfate-reducing bacteria (SRB) has been demonstrated in soils but little is known about their contribution in marine environments. Characterization assays were employed to assess the effects of explosive compounds (TNT, RDX, HMX) on Desulfovibrio vulgaris Hildenborough and five novel SRB isolated from marine sediments in costal waters of Vieques. Pure cultures were combined with media in a covered 96-well micro plate and the opacity was monitored in real time as the bacteria grew in a temperature-controlled plate reader. A dose-response curve was used to estimate minimum inhibitory concentrations (MICs) for TNT, RDX and HMX in 0, 1.5 and 3.0% (w/v) NaCI media. Some of the bacterial isolates grew better in explosive-containing environments than in regular media while at low salt D. vulgaris grew without inhibition at saturated RDX levels. Higher salt concentrations (1.5 and 3.00/0) did not support D. vulgaris growth in the presence of RDX. However, this organism did tolerate high levels of TNT at different NaCI concentrations. Elucidating the diversity and behavior of SRBs to explosive compounds in tropical sediments could help us understand the role of these microbial populations in contaminated marine environments