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Aquatic Microbial Ecology

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AME 19:119-128 (1999)  -  doi:10.3354/ame019119

Growth efficiency, growth rate and the remineralization of organic substrate by bacterioplankton--revisiting the Pirt model

Ramón Cajal-Medrano1,2, Helmut Maske1,*

1Ecología, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE), Apdo Postal 2732, Ensenada, CP 22880, Baja California, Mexico
2Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Apdo Postal 453, Ensenada CP 22880, Baja California, Mexico
*Addressee for correspondence. E-mail:

ABSTRACT: The growth yield of aquatic bacteria plays a critical role in the biogeochemical cycle of organic carbon in the sea. The Pirt model (1982) proposes a relationship of specific growth rate (μ, d-1), respiration rate (r, d-1) and growth yield (Y, unitless) of bacteria when the growth rate is limited by the concentration of the organic substrate and carbon stoichiometry is applied. Published data from natural populations of bacterioplankton within a temperature range of 10 to 25°C follow the Pirt model, where the growth yield is approaching asymptotically a maximum value (ε) with increasing growth rate. The specific rate of the maintenance metabolism (a, d-1) is the shape factor defining the curve. From the model a relationship between the specific respiration rate and the growth rate {r = [μ(1/ε - 1) + a/ε]} can be derived. Based on the published data these model parameters were estimated: ε = 0.51 and a = 0.58. Our model results should help explain the wide range of growth efficiencies reported for natural bacterioplankton.

KEY WORDS: Bacterioplankton · Growth efficiency · Respiration rate · Growth rate

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