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Exoproteolytic activity determined by flow injection analysis: its potential importance for bacterial growth in coastal marine ponds

Published online by Cambridge University Press:  15 January 1994

Daniel Delmas
Affiliation:
CREMA - L'Houmeau, CNRS-IFREMER, case 5, 17137 L'Houmeau, France
Catherine Legrand
Affiliation:
CREMA - L'Houmeau, CNRS-IFREMER, case 5, 17137 L'Houmeau, France
Christian Bechemin
Affiliation:
CREMA - L'Houmeau, CNRS-IFREMER, case 5, 17137 L'Houmeau, France
Cécile Collinot
Affiliation:
CREMA - L'Houmeau, CNRS-IFREMER, case 5, 17137 L'Houmeau, France
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Abstract

The measurement of the fluorescent 4-methyl-7-coumarinylamine released from the hydrolysis of a non-fluorescent peptide model substrate by exoproteolytic enzymes has been adapted to flow injection analysis (FIA). FIA allows samples to be processed very quickly (less than 2 min for triplicate determinations) with good sensitivity (< 0.1 μM) and reproducibility (relative standard deviation < 3% at the 0.2 μM level). In a coastal marine pond, exoproteolytic activity was closely related to bacterioplankton biomass. The high activity measured in pond water (maximum velocity: VM = 1.46 to 2.54 μM.h−1) emphasizes the importance of dissolved protein hydrolysis for bacterial growth and for dissolved organic nitrogen cycling. The mean turnover time of dissolved peptides was 7.6 days, and amino acids liberated by exoproteolytic activity could potentially support, on average, 40% of the bacterial nitrogen demand.

Type
Research Article
Copyright
© IFREMER-Gauthier-Villars, 1994

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