IQUIBICEN   23947
INSTITUTO DE QUIMICA BIOLOGICA DE LA FACULTAD DE CIENCIAS EXACTAS Y NATURALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
SEASONAL CHANGES IN MICROBIOTA DIVERSITY OF SOILS FROM MORENO DISTRICTBUENOS AIRES EXPOSED TO INTENSIVE PERIURBAN AGRICULTURE.
Autor/es:
LAURA J. RAIGER IUSTMAN; DIANA VULLO
Lugar:
San Miguel de Tucuman
Reunión:
Congreso; XII Congreso Argentino de Microbiologia General SAMIGE 2017; 2017
Institución organizadora:
SAMIGE
Resumen:
Hydrocarbon contamination has become a tough problem worldwide. One of the most widelydistributed of these compounds is diesel, a complex mixture of n-alkanes, branched alkanes, andsmall amounts of aromatic moieties.Pseudomonas species are capable to use n-alkanes as carbon source by activating the hydrocarbonas a key first step using the enzyme 1-alkane monooxygenase encoded by alkB. Diesel degradationhas been studied mostly under aerobic conditions in this genus, however in the environment unevendistribution of water flow, nutrients, and microbial populations creates a dynamic spectrum of aerobic,microaerobic, and anaerobic conditions.Pseudomonas extremaustralis is a bacterium isolated from Antarctica that shows high stressresistance and a wide microaerobic metabolism. P. extremaustralis is also capable to grow usingdiesel as sole carbon source only when cultured in biofilm condition. In this work we analyzedRNA-deep sequence experiments comparing the expression profile in aerobic and microaerobicplanktonic cultures. Surprising, genes involved in n-alkane degradation presented differentialexpression in microaerobic conditions in comparison with aerobic cultures. The alkB gene, encodingthe key enzyme for alkane degradation, alkane 1-monoxygenase, praA and praB encodinghydrocarbon facilitating proteins, and other genes related with this pathway such as those coding analcohol and aldehyde dehydrogenase that were found up-regulated under low oxygen conditions.Additionally, genes encoding for some steps of fatty acid b-oxidation were also up-regulated whilerubredoxin coding genes necessaries for the oxidation reaction of alkanes presented a non-differentialexpression between aerobic and microaerobic conditions. In-silico analysis of the promotor zone ofalkB gene showed a putative Anr-box upstream the ATG, suggesting a regulation driven by oxygenavailability. Cultures in minimal medium showed that P.extremaustralis was able to grow undermicroaerobic condition using diesel as sole carbon source in presence or absence of KNO3 assecondary electron acceptor. Degradation of n-alkanes (C13 to C19 fraction) after 7 days reached20.5 % and 22.87% when KNO3 was present or absent, respectively, indicating that the remnantoxygen present in this culture condition was the responsible of alkane oxidation step. Under aerobicconditions P. extremaustralis was able to grow only in a biofilm structure tightly attached to the bottleglass at the culture-air interface but no alkane degradation was observed, in line with alkB expressionexperiments. This study showed a novel effect of microaerobiosis on alkane degradation pathway in aPseudomonas species.