GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 19X4
IFREMER, Actes de Colloques, 3, 1986, pp. 185-189
20
MAINTENANCE OF DISCRETE BACTERIAL POPULATIONS IN ADJACENT
MARINE HABITATS
F.T. ROBB. D. MUIR and C. DAVIS
Department of Microbiology, University of Cape Town, RONDEBOSCH,
7700 (SOUTH AFRICA).
ABSTRACT - Some mechanisms of selection which operate on marine Vibrio and Pseudomonas strains during
survival in dilute environments have been examined. Mannitol uptake and utilisation systems are more efficient
in the Vibrio strain compared with the Pseudomonas strain during starvation survival. A Vibrio mutant strain
lacking mannitol uptake showed no greater loss of viability during starvation survival than mannitol positive
strains. The Vibrio strain appears to be constitutive with respect to mannitol uptake systems, whereas the
Pseudomonas strain examined is inducible. Active uptake systems for glucose, glutamate, alanine and aspartic
acid were efficiently maintained during starvation survival in the Vibrio strain. These results suggest that
membrane uptake systems are maintained during starvation survival and that they could provide a basis for the
segregation and maintenance of bacterial populations in the kelp ecosystem which was observed in previous
work by our group.
Key words : starvation survival, mannitol utilization.
RÉSUMÉ - Quelques mécanismes de sélectivité influençant les souches marines de Vibrio et Pseudomonas
pendant leur survie en milieu appauvri ont été étudiés. Le mannitol peut être assimilé et utilisé plus efficacement
en période de jeûne par la souche de Vibrio que par celle de Pseudomonas. Une souche mutante de Vibrio
incapable d’assimiler le mannitol peut aussi bien survivre à un jeûne qu’une souche ayant cette propriété.
L’assimilation du mannitol est constitutive chez le Vibrio alors que ce mécanisme est inductible chez le
Pseudomonas étudié. Pendant la période de jeûne, l’assimilation active du glucose, du glutamate, de l’alanine et
de l’acide aspartique est maintenue chez le Vibrio. Ces résultats suggèrent que les systèmes d’absorption
membranaire sont fonctionnels pendant le jeûne, et pourraient être à l’origine de la sélection et du maintien de
certaines souches en milieu marin, comme ceci a déjà été observé par notre groupe.
Mots clés : survie à jeûn, utilisation de mannitol.
INTRODUCTION
Davis et al. ( 1983) have shown that different nearshore habitats contain bacterial populations with markedly differing component strains. These bacteria most probably originate
in the water column and subsequently develop into various communities as a result of
selection. The water column contains a largely dormant bacterial population with a low
plate count. Several studies have examined the physiological adaptations of marine
bacterial strains to starvation survival, and it is known that dormant bacteria maintain
viability (Amy and Morita, 1983) and active membrane uptake systems (Faquin and
Oliver, 1984) during long periods of dormancy. Our previous work (Davis et al., 1983)
indicated that bacterial communities on beached kelp consisted largely (94 %) of Vibrio
strains which were able to ferment mannitol, the principle soluble carbohydrate in kelp
(Newell et al., 1980). This is in contrast with adjacent populations where a significant
proportion of Pseudomonas strains occurred. The present study was undertaken in order
185
IFREMER, Actes de Colloques, 3, 1986, pp. 185-189
20
MAINTENANCE OF DISCRETE BACTERIAL POPULATIONS IN ADJACENT
MARINE HABITATS
F.T. ROBB. D. MUIR and C. DAVIS
Department of Microbiology, University of Cape Town, RONDEBOSCH,
7700 (SOUTH AFRICA).
ABSTRACT - Some mechanisms of selection which operate on marine Vibrio and Pseudomonas strains during
survival in dilute environments have been examined. Mannitol uptake and utilisation systems are more efficient
in the Vibrio strain compared with the Pseudomonas strain during starvation survival. A Vibrio mutant strain
lacking mannitol uptake showed no greater loss of viability during starvation survival than mannitol positive
strains. The Vibrio strain appears to be constitutive with respect to mannitol uptake systems, whereas the
Pseudomonas strain examined is inducible. Active uptake systems for glucose, glutamate, alanine and aspartic
acid were efficiently maintained during starvation survival in the Vibrio strain. These results suggest that
membrane uptake systems are maintained during starvation survival and that they could provide a basis for the
segregation and maintenance of bacterial populations in the kelp ecosystem which was observed in previous
work by our group.
Key words : starvation survival, mannitol utilization.
RÉSUMÉ - Quelques mécanismes de sélectivité influençant les souches marines de Vibrio et Pseudomonas
pendant leur survie en milieu appauvri ont été étudiés. Le mannitol peut être assimilé et utilisé plus efficacement
en période de jeûne par la souche de Vibrio que par celle de Pseudomonas. Une souche mutante de Vibrio
incapable d’assimiler le mannitol peut aussi bien survivre à un jeûne qu’une souche ayant cette propriété.
L’assimilation du mannitol est constitutive chez le Vibrio alors que ce mécanisme est inductible chez le
Pseudomonas étudié. Pendant la période de jeûne, l’assimilation active du glucose, du glutamate, de l’alanine et
de l’acide aspartique est maintenue chez le Vibrio. Ces résultats suggèrent que les systèmes d’absorption
membranaire sont fonctionnels pendant le jeûne, et pourraient être à l’origine de la sélection et du maintien de
certaines souches en milieu marin, comme ceci a déjà été observé par notre groupe.
Mots clés : survie à jeûn, utilisation de mannitol.
INTRODUCTION
Davis et al. ( 1983) have shown that different nearshore habitats contain bacterial populations with markedly differing component strains. These bacteria most probably originate
in the water column and subsequently develop into various communities as a result of
selection. The water column contains a largely dormant bacterial population with a low
plate count. Several studies have examined the physiological adaptations of marine
bacterial strains to starvation survival, and it is known that dormant bacteria maintain
viability (Amy and Morita, 1983) and active membrane uptake systems (Faquin and
Oliver, 1984) during long periods of dormancy. Our previous work (Davis et al., 1983)
indicated that bacterial communities on beached kelp consisted largely (94 %) of Vibrio
strains which were able to ferment mannitol, the principle soluble carbohydrate in kelp
(Newell et al., 1980). This is in contrast with adjacent populations where a significant
proportion of Pseudomonas strains occurred. The present study was undertaken in order
185