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Utilização da fracção respirada da 14C-leucina como indicador da eficiência de crescimento bacteriano
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Advisor(s)
Abstract(s)
A comunidade bacteriana é, reconhecidamente, o mais importante elemento do
ecossistema global. No entanto, os conhecimentos existentes sobre a sua dinâmica são
ainda relativamente escassos. Isto deve-se, em parte às dificuldades existentes para
efectuar medições rotineiras de respiração bacteriana (RB) e eficiência de crescimento
bacteriana (BGE). Este trabalho teve como objectivo testar a utilização da fracção
respirada de MC-leucina como indicador de RB e, consequentemente, da BGE, em três
ambientes tróficamente muito distintos, e em escalas temporais também distintas. Para
este propósito foram realizados: um mesocosmos no qual se efectuou o
acompanhamento de uma florescência fitoplanctónica; uma série de perfis verticais ao
longo de três transectos perpendiculares à costa da Galiza; e um longo período de
amostragens no estuário do rio Guadiana. Para conseguir os valores de RB, foi
necessário calcular um factor de conversão teórico f (ugC.(mol leucina respirada)`1),
que apresentou uma variação de duas ordens de grandeza entre os ambientes estudados.
Em todos os ambientes os valores de RB e a BGE obtidos se enquadram nos valores
descritos por outros autores para ambientes semelhantes, o que aponta a favor da
validade desta nova metodologia. É no entanto necessário efectuar uma calibração com
outros métodos de medição de RB, seja por consumo de O2 ou libertação de CO2.
The bacterial community is recognized as the global ecosystem”s most important element. However, existent knowledge about its dynamics is still relatively scarce. This is partly due to the existent difficulties to perform routine measurements of both bacterial respiration (RB) and bacterial growth efficiency (BGE). This work had as objective to test the use of the respired fraction of “C-leucine as an indication of RB and, consequently, BGE, in three trophically very different environments, in different time scales. It was carried out for this purpose: a mesocosm in which a phytoplanctonic bloom was followed; a series of vertical profiles along three transects perpendicular to the Galician coast, and a long series of samplings in the river Guadiana estuary. To attain the RB values, it was necessary to calculate a theoretical conversion factor f (ugC.(mol leucina respirada)`1), which showed a variation of two orders of magnitude among the sampled environments. In all the enviromnents, RB and BGE obtained fit the values described for similar environments by other authors, which points in favour of the Validity of this new methodology. It is however necessary to make a calibration with other RB measurement methods, be it by O2 consumption or CO2 release.
The bacterial community is recognized as the global ecosystem”s most important element. However, existent knowledge about its dynamics is still relatively scarce. This is partly due to the existent difficulties to perform routine measurements of both bacterial respiration (RB) and bacterial growth efficiency (BGE). This work had as objective to test the use of the respired fraction of “C-leucine as an indication of RB and, consequently, BGE, in three trophically very different environments, in different time scales. It was carried out for this purpose: a mesocosm in which a phytoplanctonic bloom was followed; a series of vertical profiles along three transects perpendicular to the Galician coast, and a long series of samplings in the river Guadiana estuary. To attain the RB values, it was necessary to calculate a theoretical conversion factor f (ugC.(mol leucina respirada)`1), which showed a variation of two orders of magnitude among the sampled environments. In all the enviromnents, RB and BGE obtained fit the values described for similar environments by other authors, which points in favour of the Validity of this new methodology. It is however necessary to make a calibration with other RB measurement methods, be it by O2 consumption or CO2 release.