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AbstractAbstract
[en] The study of heterotrophic bacterial activities sensitivity with respect to temperature and resources is fundamental for our understanding of global change impact on the microbial compartment. In this work, in situ and experimental approaches have been carried out in Marseilles' Bay (SOLEMIO station) to address this issue. Simultaneous measurements of bacterial production (BP), bacterial respiration (BR), alkaline phosphatase activity (phos) and ectoaminopeptidase activity (prot) have been performed. Kinetic temperatures (12-32 deg. C) of these activities (BP, BR, phos and prot) have been also conducted. The results demonstrate that i) the optimum temperature and Q10 values vary seasonally, ii) BGE value does not necessarily decrease with increasing temperature and iii) whatever the in situ conditions, the bacterial assemblage has a in situ temperature BGE value close to the optimal temperature of BP activity. Enrichments experiments in PO4 and glucose incubated at in situ temperature and in situ temperature + 3 deg. C allow to observe that the synergistic nature of the interaction between temperature and resources. The assumption of a scenario assuming that BP, prot and phos changes during a temperature change suggests that prot:BP and phos:BP ratios decrease with a temperature increase and increase with a temperature decrease. If we assume phos as an important provider of P and prot for N that might influence ultimately the C:N:P ratio of rates through heterotrophic prokaryotes. Finally, these experiments show that temperature and PO4 availability are the main factors controlling heterotrophic bacteria activities. The study on OM availability and associated timing (pulsed or continuous) conducted during four seasonal minicosm cultures demonstrates that at different seasons and according to the delivery mode of OM, BA, BP and BR are varying significantly. However, the BA, BP and the BR does not show significant differences between the tanks with pulse OM addition (P) and continuous OM addition (C) suggesting that predominant bacterial communities are insensitive to the nature of nutritional disturbance whereas bacterial activity is highly dependent of the OM addition. (author)
[fr]
L'etude de la sensibilite des activites bacteriennes heterotrophes vis-a-vis la temperature et des ressources nutritives est essentielle dans notre comprehension de l'impact du changement global sur le compartiment microbien. Dans le cadre de cette these, une approche in situ et experimentale en baie de Marseille (station SOLEMIO) est utilisee afin de repondre a cette problematique. Des mesures simultanees de la PB, de la RB, de l'activite de la phosphatase alcaline (phos) et de l'activite d'une ectoaminopeptidase (prot) sont realisees. Des cinetiques temperatures (12-32 deg. C) de ces 4 activites sont egalement effectuees. Les resultats montrent que 1) les temperatures optimales et les Q10 varient saisonnierement, 2) le BGE ne diminue pas necessairement lorsque la temperature augmente et 3) quelles que soit les conditions in situ, l'assemblage bacterien possede un BGE a la temperature in situ proche de sa temperature optimale. Des experiences d'enrichissements en PO4 et glucose incubees a temperature in situ et temperature in situ + 3 deg. C permettent de constater que la nature de l'interaction entre la temperature et les ressources est principalement synergetique. L'hypothese d'un scenario supposant des changements relatifs de PB, prot et phos lors d'un changement de temperature suggere que les taux prot/PB et phos/PB diminuent avec une augmentation de la temperature et augmentent avec une diminution de la temperature. Si nous supposons que phos est un important fournisseur de P et prot de N alors cela devrait influencer le rapport C/N/P a travers les procaryotes heterotrophes. Enfin, ces experiences montrent que la temperature et la disponibilite du PO4 sont les principaux facteurs controlant les activites des bacteries heterotrophes. L'etude sur le mode d'apport de la MO (pulse ou en continu) menee a partir de 4 cultures saisonnieres en minicosme montre que selon les conditions saisonnieres et le mode d'apport de la MO, l'AB, la PB et la RB varient significativement. Toutefois, l'AB, la PB, la RB et le BGE ne montrent pas de differences significatives entre les reservoirs d'ajouts pulses de MO (P) et d'ajouts continus de MO (C) suggerant des communautes bacteriennes peu sensibles a la nature de la perturbation nutritionnelle alors que les activites bacteriennes sont fortement dependantes des additions de MO. (auteur)Original Title
Role de la temperature et des ressources nutritives dans le controle des activites des bacteries marines heterotrophes: approches in situ et experimentales
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18 Dec 2014; 244 p; [290 refs.]; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses; These Docteur d'Aix-Marseille Universite, Specialite: Oceanographie
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