AME 83:251-262 (2019)  -  DOI: https://doi.org/10.3354/ame01921

ABSTRACT: In situ dissolved B₁₂ concentration in marine ecosystems is controlled by the balance between rates of release of B₁₂ by prokaryotes, uptake by prokaryotes and eukaryotes, and abiotic degradation. We used chemostats at a range of specific growth rates (μ, d^-1; 0.1 to 1) with natural communities of prokaryotes and monospecific cultures of a B₁₂ producer, Dinoroseobacter shibae. We measured the dissolved B₁₂ concentration produced in the culture (B_12-d), the B₁₂ in the particulate fraction (B_12-p), cell concentration, respiration rate, particulate organic carbon and nitrogen (POC, PON), and the 16S amplicon composition. Total dissolved B₁₂ concentrations (0.92 to 4.90 pmol l^-1) were comparable to those found in the surface ocean. B_12-p concentration was 6 to 35 times higher than B_12-d. B_12-d, B_12-p, and community composition showed no relation to μ for either natural populations or D. shibae. The chemostats allowed calculation of the rates of production: B_12-d (0.34 ± 0.28 pmol l^-1 d^-1) and B_12-p (5.65 ± 2.34 pmol l^-1 d^-1), and the B₁₂ cell quota (900 to 3300 molecules cell^-1). In multispecies and D. shibae cultures, B₁₂ production rates per cell increased with respiration rates (volumetric or per cell), and with rates of cellular organic carbon and nitrogen production. Rates increased with μ, but not the concentrations of B_12-d or of B_12-p. To understand the physiological and ecological dynamics of B₁₂, concentrations alone are insufficient since they do not provide rates, which are important in understanding the dynamics between producers and consumers.

KEY WORDS: Marine bacteria · Intracellular and dissolved B₁₂ · Continuous cultures

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Cite this article as: Villegas-Mendoza J, Cajal-Medrano R, Maske H (2019) B12 production by marine microbial communities and Dinoroseobacter shibae continuous cultures under different growth and respiration rates. Aquat Microb Ecol 83:251-262. https://doi.org/10.3354/ame01921 Export citation Share:    Facebook - - linkedIn