Presence of Functional Genes for Sulfur Metabolism and Proteorhodopsin-driven Energy Conversion in Planktonic Prokaryotes of Concepcion Bay

PÉREZ, B.; AGUAYO, P.; ALDUNATE, M.; BRESCIANO, J.; LEVIPAN, H.; MANDAKOVIC, D.; MARCOS, M,; FONTES, M.L.; ALLEN, E.; DE LA IGLESIA, R.; MOLINA, V.; TREFAULT, N.; UGALDE, J.; ULLOA, O.; VAULOT, D.; HANSELMANN, K.

Foz do Iguazu

Congreso; 26° Congresso Brasileiro de Microbiologia, 2° Encontro Nacional de Professores de Microbiologia, Latin America ISME Symposium y Simpósio Internacional de Bactérias Lácticas; 2011

Concepción Bay is characterized by having a seasonal upwelling pattern, which supplies the water mass with high amounts of nutrients and low oxygen. Furthermore, sulfur compounds of sediments are advected to the water column and oxidized to thiosulfate in the oxycline, so sulphide-oxidizing metabolism may be an important catabolic process present in this area. This area is also characterized by having the maximum level of chlorophyll between the surficial and intermediate depths, and these data can be used as a measurement of light penetration. In this context, we propose that at higher depths, communities with an increased sulphide-oxidizing metabolism will be present. On the other hand, bacteria that carry out light-activated mechanisms to generate energy should be present in the light penetrated layers. Water samples were analyzed by flow cytometry in order to quantify and identify bacterioplankton populations. Additionally, we used two different approaches to study functional genes. General sulphide-oxidizing bacteria were identified by PCR (soxB gene) and by CARD-FISH technique (GSO probe). The presence of protorhodopsin (pr gene) was also identified by PCR. The flow cytometry analyses showed two bacterial populations at 5 m depth. Below this depth, only one bacterioplankton population was found. Regarding the functional approach, a higher relative abundance of GSO to total gammaproteobacteria at 8m depth (oxycline) suggests that these bacteria could be thiosulphate-oxidizers, by using nitrate as an electron acceptor. Also, the presence of pr gene at the upper layers suggests that bacteria are able to use organic carbon for cell synthesis (i.e., photoorganoheterotrophs). Future work will be performed in order to study the expression of these genes in this eutrophic system.