Formação de clamidósporos pela fase micelial do Paracoccidioides brasiliensis

To investigate the role of some adverse environmental conditions in chlamy-dospore formation by the mycelial form of P. brasiliensis, we cultured four P. brasiliensis isolates (18, Bt4, 1183, Pb9) at 25°C within solid agar medium either rich or poor in nutrients. Isolates 18 and 1183 were also cultured under anaerobiosis in a nitrogen atmosphere. Isolate 18 produced great number of terminal and intercalary chlamydospore after 7-10 days of culture in a medium poor in nutrients (2% agar with 0.1% dextrose and polypepton). The three other isolates also produced chlamydospores under the same conditions, but in lower numbers. Chlamydospore production by isolate 18 was abolished when the fungus was cultured in two agar media rich in nutrients (brain heart infusion and potato dextrose agar). Anaerobic incubation of isolate 18 under an atmosphere of N2 showed small mycelial outgrowth with numerous chlamydospores. At the electron microscopical level, the chlamydospores showed one or various nuclei and numerous mitochondria, indicating great potential for further development. Accordingly, chlamydospores produced multiple budding after only 24 h incubation at 35°C. The results demonstrate that under adverse environmental conditions P. brasiliensis mycelial form produces chlamydospores within a short period of time.O papel do conteúdo nutritivo do meio de cultura e de oxigênio na produção de clamidósporos pela fase micelial do Paracoccidioides brasiliensis foi investigado. Quatro cepas do fungo (18, Bt4, 1183, Pb9) foram cultivadas, a 25°C, em meio sólido rico e pobre em nutrientes. As cepas 18 e 1183 foram também cultivadas em anerobiose em atmosfera de nitrogênio. A cepa 18 produziu grande número de clamidósporos terminais e intercalares após 7-10 dias de cultura em meio sólido pobre em nutrientes (agar 2%, com dextrose e polipeptona 0,1%). As outras três cepas produziram número significativamente menor de esporos. A cepa 18 não produziu clamidósporos quando cultivada em dois meios ricos em nutrientes (infusão de cérebro e coração, e agar dextrose de batata). A incubação anaeróbica da cepa 18 em atmosfera de nitrogênio apresentou pequeno crescimento micelial com a presença de numerosos clamidósporos. À nivel ultraestrutural, os clamidósporos apresentaram um ou mais núcleos e numerosas mitocôndrias, indicativos de potencial para posterior desenvolvimento. Assim, os esporos produziram gemulação múltipla 1 dia após incubação a 35°C. Os resultados demonstraram que, sob condições ambientais adversas, a fase micelial do P. brasiliensis produz clamidósporos em curto período de tempo. É possível que o fungo encontre condições semelhantes no solo, produzindo os esporos, que poderiam desempenhar papel na propagação da paracoccidioidomicose

Chlamydospore formation by Paracoccidioides brasiliensis mycelial form

To investigate the role of some adverse environmental conditions in chlamy-dospore formation by the mycelial form of P. brasiliensis, we cultured four P. brasiliensis isolates (18, Bt4, 1183, Pb9) at 25°C within solid agar medium either rich or poor in nutrients. Isolates 18 and 1183 were also cultured under anaerobiosis in a nitrogen atmosphere. Isolate 18 produced great number of terminal and intercalary chlamydospore after 7-10 days of culture in a medium poor in nutrients (2% agar with 0.1% dextrose and polypepton). The three other isolates also produced chlamydospores under the same conditions, but in lower numbers. Chlamydospore production by isolate 18 was abolished when the fungus was cultured in two agar media rich in nutrients (brain heart infusion and potato dextrose agar). Anaerobic incubation of isolate 18 under an atmosphere of N2 showed small mycelial outgrowth with numerous chlamydospores. At the electron microscopical level, the chlamydospores showed one or various nuclei and numerous mitochondria, indicating great potential for further development. Accordingly, chlamydospores produced multiple budding after only 24 h incubation at 35°C. The results demonstrate that under adverse environmental conditions P. brasiliensis mycelial form produces chlamydospores within a short period of time

Photocatalytic Reduction of Nitrobenzene to Aniline in an Aqueous Suspension of Titanium(IV) Oxide Particles in the Presence of Oxalic Acid as a Hole Scavenger and Promotive Effect of Dioxygen in the System

Nitrobenzene was effectively and selectively reduced to aniline in an acidic aqueous suspension of titanium(IV) oxide photocatalyst in the presence of oxalic acid as a hole scavenger and the aniline yield was improved in the presence of a small amount of dioxygen