GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 81-87
8
A LABORATORY MODEL SYSTEM FOR ANALYSING MICROBIAL INTERACTIONS OCCURRING IN ANOXIC ESTUARINE SEDIMENTS
R.A. HERBERT and S.M. KEITH
Department of Biological Sciences, University of Dundee, DUNDEE (UK)
ABSTRACT - Defined mixed populations of Clostridium butyricum, Desulfovibrio desulfuricans and Chromatium vinosum co-existed for long periods when grown in a single stage chemostat with glucose as sole carbon
source.The nature and availability of the inorganic nitrogen source exerted a major effect on carbon flow in the
experimental system. The data show that both the Clostridium butyricum and Desulfovibrio desulfuricans
isolates can utilise NO
3
as an e - acceptor with an increase in cell yield. Under these growth conditions the free S 2levels were lower resulting in more stable mixed populations. In addition the data show that the Clostridium
butyricum produces more oxidised fermentation end-products (acetate) when NO3 was available and more
reduced products (butyrate) when grown on NH 4
+ .
Key words : carbon flow, Chromatium vinosum , strain PT121, Clostridium butyricum , strain SS6, Desulfovibrio desulfuricans , strain DT101, microbial interactions.
RÉSUMÉ - Des populations mixtes de Clostridium butyricum, Desulfovibrio desulfuricans, et Chromatium
vinosum co-existent pendant de longues périodes, lorsqu’elles se développent dans un chemostat à une seule
étape avec du glucose pour seule source de carbone. La nature et la disponibilité de la source d’azote inorganique
exercent un effet important sur le flux de carbone du système expérimental. Les données montrent que les isolats
de Clostridium butyricum, ceux de Desulfovibrio desulfuricans et ceux de Chromatium vinosum peuvent
utiliser NO3 comme accepteur d’électrons, avec une augmentation de la production des cellules. Sous ces
conditions de croissance les niveaux des ions S
2 " libres sont plus faibles et il en résulte des populations mixtes
plus stables. Les expériences montrent également que Clostridium butyricum fabrique plus de produits finaux
de fermentation oxydés (acetate) lorsque NO3' est disponible, et plus de produits réduits (butyrate) lorsqu’elle
se développe sur NH 4
+ .
Mots clés: flux de carbone, Chromatium vinosum, souche PT121, Clostridium butyricum, souche SS6,
Desulfovibrio desulfuricans, souche DT101, interactions microbiennes.
INTRODUCTION
Minéralisation of organic detritus in anoxic sediments is a highly complex process. This is
primarily due to the restricted metabolic potential of the individual anaerobic microorganisms present in such habitats. Complete mineralisation does not take place within
one species of micro-organism but within associations of physiologically different types
of micro-organisms. Each physiological group exploits only a small fraction of the
detrital energy available and supplies the remainder in the form of excreted metabolic
end-products to the next member of the detrital food chain. The microbial processes
which take place in anoxic sediments are related to the quantity and quality of available
organic carbon and the concentration of available electron acceptors such as NO3",
SO4 2 ', Mn 4+ and CO2.
Strict anaerobes are commonly isolated from sediments in the Tay estuary (Keith,
Macfarlane and Herbert, 1982, Keith, Herbert and Harfoot,1982) and for the purposes of
81
IFREMER, Actes de Colloques, 3, 1986, pp. 81-87
8
A LABORATORY MODEL SYSTEM FOR ANALYSING MICROBIAL INTERACTIONS OCCURRING IN ANOXIC ESTUARINE SEDIMENTS
R.A. HERBERT and S.M. KEITH
Department of Biological Sciences, University of Dundee, DUNDEE (UK)
ABSTRACT - Defined mixed populations of Clostridium butyricum, Desulfovibrio desulfuricans and Chromatium vinosum co-existed for long periods when grown in a single stage chemostat with glucose as sole carbon
source.The nature and availability of the inorganic nitrogen source exerted a major effect on carbon flow in the
experimental system. The data show that both the Clostridium butyricum and Desulfovibrio desulfuricans
isolates can utilise NO
3
as an e - acceptor with an increase in cell yield. Under these growth conditions the free S 2levels were lower resulting in more stable mixed populations. In addition the data show that the Clostridium
butyricum produces more oxidised fermentation end-products (acetate) when NO3 was available and more
reduced products (butyrate) when grown on NH 4
+ .
Key words : carbon flow, Chromatium vinosum , strain PT121, Clostridium butyricum , strain SS6, Desulfovibrio desulfuricans , strain DT101, microbial interactions.
RÉSUMÉ - Des populations mixtes de Clostridium butyricum, Desulfovibrio desulfuricans, et Chromatium
vinosum co-existent pendant de longues périodes, lorsqu’elles se développent dans un chemostat à une seule
étape avec du glucose pour seule source de carbone. La nature et la disponibilité de la source d’azote inorganique
exercent un effet important sur le flux de carbone du système expérimental. Les données montrent que les isolats
de Clostridium butyricum, ceux de Desulfovibrio desulfuricans et ceux de Chromatium vinosum peuvent
utiliser NO3 comme accepteur d’électrons, avec une augmentation de la production des cellules. Sous ces
conditions de croissance les niveaux des ions S
2 " libres sont plus faibles et il en résulte des populations mixtes
plus stables. Les expériences montrent également que Clostridium butyricum fabrique plus de produits finaux
de fermentation oxydés (acetate) lorsque NO3' est disponible, et plus de produits réduits (butyrate) lorsqu’elle
se développe sur NH 4
+ .
Mots clés: flux de carbone, Chromatium vinosum, souche PT121, Clostridium butyricum, souche SS6,
Desulfovibrio desulfuricans, souche DT101, interactions microbiennes.
INTRODUCTION
Minéralisation of organic detritus in anoxic sediments is a highly complex process. This is
primarily due to the restricted metabolic potential of the individual anaerobic microorganisms present in such habitats. Complete mineralisation does not take place within
one species of micro-organism but within associations of physiologically different types
of micro-organisms. Each physiological group exploits only a small fraction of the
detrital energy available and supplies the remainder in the form of excreted metabolic
end-products to the next member of the detrital food chain. The microbial processes
which take place in anoxic sediments are related to the quantity and quality of available
organic carbon and the concentration of available electron acceptors such as NO3",
SO4 2 ', Mn 4+ and CO2.
Strict anaerobes are commonly isolated from sediments in the Tay estuary (Keith,
Macfarlane and Herbert, 1982, Keith, Herbert and Harfoot,1982) and for the purposes of
81