High Contribution of SAR11 to Microbial Activity in the North West Mediterranean Sea
- 382 Downloads
We investigated the abundance and activity of SAR11 on a monthly time scale between January 2008 and October 2008 in the oligotrophic NW Mediterranean Sea. Applying MICRO-CARD-FISH, we observed that SAR11 had a large contribution to bulk abundance (37 ± 6% of DAPI-stained cells) and to bulk bacterial heterotrophic production (BHP), as estimated from leucine incorporation (55 ± 15% of DAPI-cells assimilating leucine) in surface waters (5 m) throughout the study period. SAR11 contributed also substantially to the assimilation of glucose, ATP, and a combination of amino acids (44 ± 17%, 37 ± 14%, and 43 ± 12% of DAPI cells assimilating these compounds, respectively), organic compounds that provide either single or combined sources of C, P, and N. Temporal changes in the abundance of SAR11 cells that assimilated leucine, glucose, amino acids, and ATP revealed a pattern consistent with that of substrate-active DAPI cells, suggesting that the activity of SAR11 can explain to a large extent the variability in total cells contributing to the utilization of these compounds. Short-term nutrient enrichment experiments performed on each sampling date revealed a strong co-limitation of at least two of the three elements analyzed (C, N, P), in particular, during summer and early autumn. The in situ abundance of SAR11 cells assimilating leucine appeared to increase with P limitation as determined in the nutrient enrichment experiments (r = 0.81, p = 0.015). Our results demonstrate that SAR11 is an important component of the active bacterial community in the NW Mediterranean Sea. Our observations further indicate that the activity of the bulk bacterial community is linked to the activity of SAR11, possibly due to its adaptation to nutrient limitation.
KeywordsParticulate Organic Carbon Dissolve Organic Nitrogen Dissolve Organic Matter Delaware Estuary Bacterial Heterotrophic Production
We thank the captain and the crew of the R/V Nereis for their enthusiasm and support aboard. We also thank the members of the Service d'Observation of the Observatoire Océanologique in Banyuls for their help in sample collection. L. Zudaire provided the CTD profiles for all cruises. We also thank four reviewers for their critical comments on a previous version of this manuscript. This work was conducted as part of the national project MEDEA (INSU-LEFE-CYBER).
- 1.Carlson C (2002) Production and removal processes. In: Hansell DA, Carlson CA (eds) Biogeochemistry of marine dissolved organic matter. Academic, San DiegoGoogle Scholar
- 19.Longnecker K, Lomas M, Van Mooy B (2010) Abundance and diversity of heterotrophic bacterial cells assimilating phosphate in the subtropical North Atlantic Ocean. Environ Microbiol 2:2773–2782Google Scholar
- 30.Tréguer P, Le Corre P (1975) Manuel d'analyse des sels nutritifs dans l'eau de mer. Laboratoire d’Océanographie Chimique, Université de Bretagne Occidentale, Brest, p 110Google Scholar
- 40.Fukuda R, Ogawa H, Nagata T, Koike I (1998) Direct determination of carbon and nitrogen contents of natural bacterial assemblages in marine environments. Appl Environ Microb 64:3352–3358Google Scholar
- 41.Smith DC, Azam F (1992) A simple, economical method for measuring bacterial protein synthesis rates in seawater using 3H-leucine. Mar Microb Food Webs 6:107–114Google Scholar
- 42.Kirchman D (1993) Leucine incorporation as a measure of biomass production by heterotrophic bacteria. In: Kemp PF, Sherr BF, Sherr EB, Cole JJ (eds) Handbook of methods in aquatic microbial ecology. Lewis, Boca Raton, pp 509–512Google Scholar
- 45.Tanaka T, Rassoulzadegan F, Thingstad T (2004) Orthophosphate uptake by heterotrophic bacteria, cyanobacteria, and autotrophic nanoflagellates in Villefranche Bay, northwestern Mediterranean: vertical, seasonal, and short-term variations of the competitive relationship for phosphorus. Limnol Oceanogr 49:1063–1072CrossRefGoogle Scholar
- 47.Dolan J, Thingstad T, Rassoulzadegan F (1995) Phosphate transfer between microbial size-fractions in Villefranche Bay (NW Mediterranean Sea), France in autumn 1992. Ophelia 41:71–85Google Scholar
- 50.Alonso-Sáez L, Balagué V, Sa EL, Sanchez O, Gonzalez JM, Pinhassi J, Massana R, Pernthaler J, Pedrós-Alió C, Gasol JM (2007) Seasonality in bacterial diversity in north-west Mediterranean coastal waters: assessment through clone libraries, fingerprinting and FISH. FEMS Microbiol Ecol 60:98–112PubMedCrossRefGoogle Scholar
- 62.Lauro FM, McDougald D, Thomas T, Williams TJ, Egan S, Rice S, DeMaere MZ, Ting L, Ertan H, Johnson J, Ferriera S, Lapidus A, Anderson I, Kyrpides N, Munk AC, Detter C, Han CS, Brown MV, Robb FT, Kjelleberg S, Cavicchioli R (2009) The genomic basis of trophic strategy in marine bacteria. PNAS 106:15527–15533PubMedCrossRefGoogle Scholar