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

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

Fusobacterium nucleatum supports the growth of Porphyromonas gingivalis in oxygenated and carbon-dioxide-depleted environments

Copyright © 2002 Society for General MicrobiologyThe authors compared the differences in tolerance to oxygen of the anaerobic periodontopathic bacteria Fusobacterium nucleatum and Porphyromonas gingivalis, and explored the possibility that F. nucleatum might be able to support the growth of P. gingivalis in aerated and CO2-depleted environments. Both micro-organisms were grown as monocultures and in co-culture in the presence and absence of CO2 and under different aerated conditions using a continuous culture system. At steady state, viable counts were performed and the activities of the enzymes superoxide dismutase and NADH oxidase/peroxidase were assayed in P. gingivalis. In co-culture, F. nucleatum was able to support the growth of P. gingivalis in aerated and CO2-depleted environments in which P. gingivalis, as a monoculture, was not able to survive. F. nucleatum not only appeared to have a much higher tolerance to oxygen than P. gingivalis, but a significant increase in its numbers occurred under moderately oxygenated conditions. F. nucleatum might have an additional indirect role in dental plaque maturation, contributing to the reducing conditions necessary for the survival of P. gingivalis and possibly other anaerobes less tolerant to oxygen. Additionally, F. nucleatum is able to generate a capnophilic environment essential for the growth of P. gingivalis.P. I. Diaz, P. S. Zilm and A. H. Roger