GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 427-433
49
ADAPTIVE FEATURES OF A BACTERIOLYTIC ENZYME FROM THE STYLE
OF THE MUSSEL CHOROMYTILUS MERIDIONALIS IN RESPONSE TO
ENVIRONMENTAL FLUCTUATIONS
L.J. SEIDERER and F.T. ROBB
Departments of Zoology and Microbiology, University of Cape Town, RONDEBOSCH,
7700 (SOUTH AFRICA)
ABSTRACT - The extracellular digestive apparatus of bivalve molluscs consists of a crystalline style containing
diverse degradative enzymes which are released during rotation and dissolution of the style. Bacteriolytic
substances have been reported previously in crystalline style extracts of bivalves, and have been identified as true
lysozymes or N-acetyl-muramyl- hydrolase. This paper will review the occurrence of a temperature-regulated
bacteriolytic enzyme in the black mussel Choromytilus meridionalis, which is an inhabitant of coastal reefs on
the south and south west coast of South Africa. This agent is unable to lyse Micrococcus luteus or Escherichia
coli, both of which are susceptible to lysis by a true lysozyme. It appears to have a restricted spectrum of activity
which includes both free-living and kelp-associated gram-negative bacteria. In addition, the level of activity
varies dramatically according to the environmental water temperature. When upwelling occurs, the water is cold
(9°C) and is poor in phytoplankton and macrophyte debris. Under these conditions bacteriolytic activity is at its
maximum and bacteria predominate as a nitrogen-rich exploitable food resource with a C:N ratio of approximately 3.5:1. These phases of upwelling are interspersed with an opposite flow of phytoplankton-rich warm
surface water. Under these conditions bacteriolytic activity of the style is at a minimum.
RÉSUMÉ - Le système digestif extracellulaire des mollusques bivalves est constitué d’un stylet cristallin contenant diverses enzymes de dégradation qui sont libérées lors de la rotation et la dissolution du stylet. Des
substances bactériolytiques ont déjà été signalées dans des extraits de stylet cristallin de bivalves et identifiées
comme véritables lysozyme ou N-acetylmuramyl-hydrolase. Le présent travail étudie la présence d une enzyme
bactériolytique régulée par la température chez le bivalve Choromytilus meridionalis qui est présent sur la côte
rocheuse du Sud et du Sud-Ouest de l’Afrique du Sud. Cette enzyme est incapable de lyser Micrococcus luteus ou
Escherichia coli qui sont tous deux susceptibles d’être lysés par un vrai lysozyme. Elle présente un spectre
d’activité limité qui inclut les bactéries gram négative libres ou associées aux algues. En outre, le niveau d’activité
varie considérablement en fonction de la température de l'eau environnante. Lors de «l’upwelling» l'eau a une
température d’environ 9°C et est pauvre en phytoplancton et débris de macrophytes. Dans ces conditions,
l’activité bactériolytique est maximale et les bactéries constituent la principale source d’aliment assimilable riche
en azote, avec un rapport C : N est égal à 3.5 : 1. Ces phases «d’upwelling» sont entrecoupées par un courant
opposé d’eau chaude de surface riche en phytoplancton. Dans ces conditions, l’activité bactériolytique du stylet
est minimale.
INTRODUCTION
Newell et al. (1980) have shown that the protein component of kelp debris amounts to as
much as 23 - 28 % of the dry weight of freshly powdered Laminaria pallida frond. Since
microbial conversion of nitrogen from kelp detritus is achieved with an efficiency of as
much as 83 -94 % (see Stuart et ai, 1981 ; Koop et al, 1982a, 1982b), it seems likely that
much of the protein originally released during fragmentation of kelp will become potentially available to consumers in the form of microbial biomass associated with the
particulate fraction. The following work was therefore undertaken to investigate the
427
IFREMER, Actes de Colloques, 3, 1986, pp. 427-433
49
ADAPTIVE FEATURES OF A BACTERIOLYTIC ENZYME FROM THE STYLE
OF THE MUSSEL CHOROMYTILUS MERIDIONALIS IN RESPONSE TO
ENVIRONMENTAL FLUCTUATIONS
L.J. SEIDERER and F.T. ROBB
Departments of Zoology and Microbiology, University of Cape Town, RONDEBOSCH,
7700 (SOUTH AFRICA)
ABSTRACT - The extracellular digestive apparatus of bivalve molluscs consists of a crystalline style containing
diverse degradative enzymes which are released during rotation and dissolution of the style. Bacteriolytic
substances have been reported previously in crystalline style extracts of bivalves, and have been identified as true
lysozymes or N-acetyl-muramyl- hydrolase. This paper will review the occurrence of a temperature-regulated
bacteriolytic enzyme in the black mussel Choromytilus meridionalis, which is an inhabitant of coastal reefs on
the south and south west coast of South Africa. This agent is unable to lyse Micrococcus luteus or Escherichia
coli, both of which are susceptible to lysis by a true lysozyme. It appears to have a restricted spectrum of activity
which includes both free-living and kelp-associated gram-negative bacteria. In addition, the level of activity
varies dramatically according to the environmental water temperature. When upwelling occurs, the water is cold
(9°C) and is poor in phytoplankton and macrophyte debris. Under these conditions bacteriolytic activity is at its
maximum and bacteria predominate as a nitrogen-rich exploitable food resource with a C:N ratio of approximately 3.5:1. These phases of upwelling are interspersed with an opposite flow of phytoplankton-rich warm
surface water. Under these conditions bacteriolytic activity of the style is at a minimum.
RÉSUMÉ - Le système digestif extracellulaire des mollusques bivalves est constitué d’un stylet cristallin contenant diverses enzymes de dégradation qui sont libérées lors de la rotation et la dissolution du stylet. Des
substances bactériolytiques ont déjà été signalées dans des extraits de stylet cristallin de bivalves et identifiées
comme véritables lysozyme ou N-acetylmuramyl-hydrolase. Le présent travail étudie la présence d une enzyme
bactériolytique régulée par la température chez le bivalve Choromytilus meridionalis qui est présent sur la côte
rocheuse du Sud et du Sud-Ouest de l’Afrique du Sud. Cette enzyme est incapable de lyser Micrococcus luteus ou
Escherichia coli qui sont tous deux susceptibles d’être lysés par un vrai lysozyme. Elle présente un spectre
d’activité limité qui inclut les bactéries gram négative libres ou associées aux algues. En outre, le niveau d’activité
varie considérablement en fonction de la température de l'eau environnante. Lors de «l’upwelling» l'eau a une
température d’environ 9°C et est pauvre en phytoplancton et débris de macrophytes. Dans ces conditions,
l’activité bactériolytique est maximale et les bactéries constituent la principale source d’aliment assimilable riche
en azote, avec un rapport C : N est égal à 3.5 : 1. Ces phases «d’upwelling» sont entrecoupées par un courant
opposé d’eau chaude de surface riche en phytoplancton. Dans ces conditions, l’activité bactériolytique du stylet
est minimale.
INTRODUCTION
Newell et al. (1980) have shown that the protein component of kelp debris amounts to as
much as 23 - 28 % of the dry weight of freshly powdered Laminaria pallida frond. Since
microbial conversion of nitrogen from kelp detritus is achieved with an efficiency of as
much as 83 -94 % (see Stuart et ai, 1981 ; Koop et al, 1982a, 1982b), it seems likely that
much of the protein originally released during fragmentation of kelp will become potentially available to consumers in the form of microbial biomass associated with the
particulate fraction. The following work was therefore undertaken to investigate the
427