GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 119-128
13
RELATIONS BETWEEN BACTERIAL EXTRACELLULAR ENZYME ACTIVITIES AND HETEROTROPHIC SUBSTRATE UPTAKE IN A BRACKISH
WATER ENVIRONMENT
H.-G. HOPPE
Institut für Meereskunde an der Universität Kiel Düsternbrooker Weg 20, 23 KIEL(FRG)
ABSTRACT - Extracellular enzymes mediate the decomposition of polymeric organic compounds in natural
waters. In many cases these enzymes comprise a component linked to the bacterial fraction of the aquatic
community and react in close association with these cells. An annual survey of microbial activities in a brackish
water fjord exhibited an excellent correlation between V m of proteases (ability to split the substrate analogue
methylumbelliferyl-leucine) and V m as well as TR for leucine uptake by microorganisms. Hydrolysis rates (HR)
for the decomposition of naturally occurring competitive substrate analogues of the model substrates
(methylumbelliferyl-(MUF)-leucine, MUF-α-D-glucose, MUF-N-acetyl-glucosamine, MUF-phosphate) drastically declined after chlorophyll a and bacterial abundance had dropped in autumn. H R for protease and
phosphatase were higher in offshore areas than in polluted inshore waters, whereas the opposite was true for
α-glucosidase and glucosaminidase.
Key words : extracellular enzymes, bacteria, heterotrophic substrate uptake
RÉSUMÉ - Les enzymes extracellulaires permettent la décomposition des composés organiques polymériques
en milieu marin. Très souvent, une partie de ces enzymes est liée à la fraction bactérienne et réagit en association
étroite avec ces cellules. Un suivi annuel de l’activité bactérienne dans l’eau saumâtre d’un fjord a montré une
excellente corrélation entre le V m des protéases (capacité à couper un analogue de substrat, la méthylumbelliferyl-leucine) et le V m ou le T r d'absorption de la leucine par les bactéries. Les taux d’hydrolyse (HR) pour la
décomposition de substrats naturels analogues du substrat testé (méthylumbelliferyl)-(MUF)-leucine, MUF-αD-glucose, M U F-N-acétyl-glucosamine, MUF-phosphate) ont fortement diminué après la chute de la teneur en
chlorophylle a et des numérations bactériennes, qui a lieu en automne. Les H R des protéases et phosphatases
ont été plus élevés dans les eaux du large que dans les eaux côtières polluées, alors que l’inverse s’est produit pour
l’α-glucosidase et la glucosamine.
Mots clés : enzymes extracellulaires, bactéries, absorption hétérotrophe du substrat.
INTRODUCTION
Considerable amounts of dissolved organic compounds in sea water are in the form of
polymeric, oligomeric or dimeric molecular structures often requiring enzymatic breakdown prior to their incorporation into the bacterial cell. The fraction of combined organic
molecules from total DOC has only occasionally been determined and results cover a
wide range. The latter observation is not surprising, because ratios of molecular size
fractions may depend on factors such as organic nutrient supply, aging and chemical
conversion. Through acid hydrolysis of sea water samples it has been shown that the
concentration of dissolved combined amino acids is about 5 times that of dissolved free
amino acids (DFAA) (Degens, 1970). From culture experiments with water of an eutrophic fjord Bauerfeind (1982) found that the ratio between dissolved free monosaccharides
119
IFREMER, Actes de Colloques, 3, 1986, pp. 119-128
13
RELATIONS BETWEEN BACTERIAL EXTRACELLULAR ENZYME ACTIVITIES AND HETEROTROPHIC SUBSTRATE UPTAKE IN A BRACKISH
WATER ENVIRONMENT
H.-G. HOPPE
Institut für Meereskunde an der Universität Kiel Düsternbrooker Weg 20, 23 KIEL(FRG)
ABSTRACT - Extracellular enzymes mediate the decomposition of polymeric organic compounds in natural
waters. In many cases these enzymes comprise a component linked to the bacterial fraction of the aquatic
community and react in close association with these cells. An annual survey of microbial activities in a brackish
water fjord exhibited an excellent correlation between V m of proteases (ability to split the substrate analogue
methylumbelliferyl-leucine) and V m as well as TR for leucine uptake by microorganisms. Hydrolysis rates (HR)
for the decomposition of naturally occurring competitive substrate analogues of the model substrates
(methylumbelliferyl-(MUF)-leucine, MUF-α-D-glucose, MUF-N-acetyl-glucosamine, MUF-phosphate) drastically declined after chlorophyll a and bacterial abundance had dropped in autumn. H R for protease and
phosphatase were higher in offshore areas than in polluted inshore waters, whereas the opposite was true for
α-glucosidase and glucosaminidase.
Key words : extracellular enzymes, bacteria, heterotrophic substrate uptake
RÉSUMÉ - Les enzymes extracellulaires permettent la décomposition des composés organiques polymériques
en milieu marin. Très souvent, une partie de ces enzymes est liée à la fraction bactérienne et réagit en association
étroite avec ces cellules. Un suivi annuel de l’activité bactérienne dans l’eau saumâtre d’un fjord a montré une
excellente corrélation entre le V m des protéases (capacité à couper un analogue de substrat, la méthylumbelliferyl-leucine) et le V m ou le T r d'absorption de la leucine par les bactéries. Les taux d’hydrolyse (HR) pour la
décomposition de substrats naturels analogues du substrat testé (méthylumbelliferyl)-(MUF)-leucine, MUF-αD-glucose, M U F-N-acétyl-glucosamine, MUF-phosphate) ont fortement diminué après la chute de la teneur en
chlorophylle a et des numérations bactériennes, qui a lieu en automne. Les H R des protéases et phosphatases
ont été plus élevés dans les eaux du large que dans les eaux côtières polluées, alors que l’inverse s’est produit pour
l’α-glucosidase et la glucosamine.
Mots clés : enzymes extracellulaires, bactéries, absorption hétérotrophe du substrat.
INTRODUCTION
Considerable amounts of dissolved organic compounds in sea water are in the form of
polymeric, oligomeric or dimeric molecular structures often requiring enzymatic breakdown prior to their incorporation into the bacterial cell. The fraction of combined organic
molecules from total DOC has only occasionally been determined and results cover a
wide range. The latter observation is not surprising, because ratios of molecular size
fractions may depend on factors such as organic nutrient supply, aging and chemical
conversion. Through acid hydrolysis of sea water samples it has been shown that the
concentration of dissolved combined amino acids is about 5 times that of dissolved free
amino acids (DFAA) (Degens, 1970). From culture experiments with water of an eutrophic fjord Bauerfeind (1982) found that the ratio between dissolved free monosaccharides
119