codée par l’ADN plasmidique: Les fonctions attribuées aux plasmides restent énigmatiques, bien qu’il ait été mis
en évidence a partir de l'étude du Pseudomonas souche 57, que le plasmide serait associe a l'oxydation
enzymatique d u manganèse, peut-être par codage d’un mécanisme de détoxification du manganèse et du cuivre.
Il est supposé que les plasmides, transmissibles par eux-mêmes, confèrent aux bactéries marines une efficace
stratégie écologique de survie en milieu naturel, puisqu’ils codent pour des fonctions écologiques avantageuses
telles que la capacité à oxyder le manganèse et à détoxifier les métaux lourds.
The presence of plasmids in bacteria can extend the metabolic capability of the host and
alter phenotypes such as resistance to anti-bacterial agents, toxin production, surface
adhesiveness, and ability to catabolize unusual substrates. The ubiquitous occurrence of
manganese oxidation mediated by a variety of microorganisms in fresh water (Ghiorse
and Hirsch, 1979), on the surfaces of marine manganese nodules, and in seawater and
sediment surrounding manganese nodules (Ehrlich, 1966 ; Nealson, 1978 ; Schuett and
Ottow, 1978) and the observation of spontaneous loss of the ability to oxidize manganese
by fresh water isolates during prolonged storage (Gregory and Staley, 1982) allows the
hypothesis that bacterial manganese oxidation is, in part, plasmid encoded. A study by
Lidstrom et ai, (1983) offered evidence for plasmid encoded manganese oxidation by a
marine Pseudomonas strain 63-B.
The objective of the study reported here was to investigate the association of plasmids
with manganese oxidation in bacterial strains isolated from sediment, manganese nodules
and seawater from the Pacific Ocean and Mediterranean Sea. Thus, an understanding of
the ubiquitous occurrence of manganese-oxidizing bacteria in the marine environment
was sought.
To elucidate the association of plasmids with manganese-oxidizing bacteria, 40 manganeseoxidizing bacterial strains, isolated from manganese nodules and samples of seawater and
sediment collected at the sediment-seawater interface of the Pacific Ocean, and an
additional seven strains from water samples collected from the Mediterranean Sea were
included in this study. The Pacific isolates had been stored for up to 8 years at 4°C,
without spontaneous loss of ability to produce manganese oxide. Of the strains, 26 were
identified as Pseudomonas spp. These had been isolated either from manganese nodules
(25 strains) or the top layer of sediment (1 strain). Ten were Alcaligenes spp., isolated
from manganese nodules and water samples collected at deep ocean sites (4 strains) or
sediment (1 strain), five strains were identified as Vibrio spp., these having been isolated
from the top layer of a sediment sample (Schuett, 1979).
A yeast extract-proteose peptone medium (YP medium), prepared with artificial seawater, was used for growth and storage of the culture. The medium contained (g/l) yeast
extract (Difco Laboratories, Detroit, MI) 2.0 ; and proteose-peptone (Difco) 2.0 ; pH
adjusted to 7.2. A medium containing Mn 2+ and artificial seawater (M-medium) was used
for manganese oxide detection and was composed (in g/l) of yeast extract (Difco) 2.0 ,
tryptone (Difco) 2.0 ; Na-acetate (Difco) 1.0 ; MnSO
4
.H
2
O (Baker Chemical Co.,
Phillipsburg, NJ) 0.2 ; and Bacto-agar (Difco) 15.0 ; pH adjusted to 7.2. Artificial Sea
Water (ASW) was composed of (g/l) NaCl 11.7 ; KCl 0.35 ; and MgS0
4
.7H
2
3.5.
Oxidation of Mn
2+ to Mn 4+ was measured using o-tolidine reagent (Sigma) according to
the methods of Morgan and Stumm (1965) and also employed as a spot test.
Plasmid deoxyribonucleic acid (DNA) was extracted and analyzed using a modification
of the rapid screening method of Kado and Liu (1981). Modifications were as follows : To
obtain complete lysis, cells were incubated before lysis in the presence of 5 mg/ml
lysozyme (Sigma, St. Louis, MO). After lysis with Sodium dodecilsulfate (SDS), plasmid
DNA was prepared by agarose gel (0.7 %, BBL, Cockeysville, MD) electrophoresis for
334
en évidence a partir de l'étude du Pseudomonas souche 57, que le plasmide serait associe a l'oxydation
enzymatique d u manganèse, peut-être par codage d’un mécanisme de détoxification du manganèse et du cuivre.
Il est supposé que les plasmides, transmissibles par eux-mêmes, confèrent aux bactéries marines une efficace
stratégie écologique de survie en milieu naturel, puisqu’ils codent pour des fonctions écologiques avantageuses
telles que la capacité à oxyder le manganèse et à détoxifier les métaux lourds.
The presence of plasmids in bacteria can extend the metabolic capability of the host and
alter phenotypes such as resistance to anti-bacterial agents, toxin production, surface
adhesiveness, and ability to catabolize unusual substrates. The ubiquitous occurrence of
manganese oxidation mediated by a variety of microorganisms in fresh water (Ghiorse
and Hirsch, 1979), on the surfaces of marine manganese nodules, and in seawater and
sediment surrounding manganese nodules (Ehrlich, 1966 ; Nealson, 1978 ; Schuett and
Ottow, 1978) and the observation of spontaneous loss of the ability to oxidize manganese
by fresh water isolates during prolonged storage (Gregory and Staley, 1982) allows the
hypothesis that bacterial manganese oxidation is, in part, plasmid encoded. A study by
Lidstrom et ai, (1983) offered evidence for plasmid encoded manganese oxidation by a
marine Pseudomonas strain 63-B.
The objective of the study reported here was to investigate the association of plasmids
with manganese oxidation in bacterial strains isolated from sediment, manganese nodules
and seawater from the Pacific Ocean and Mediterranean Sea. Thus, an understanding of
the ubiquitous occurrence of manganese-oxidizing bacteria in the marine environment
was sought.
To elucidate the association of plasmids with manganese-oxidizing bacteria, 40 manganeseoxidizing bacterial strains, isolated from manganese nodules and samples of seawater and
sediment collected at the sediment-seawater interface of the Pacific Ocean, and an
additional seven strains from water samples collected from the Mediterranean Sea were
included in this study. The Pacific isolates had been stored for up to 8 years at 4°C,
without spontaneous loss of ability to produce manganese oxide. Of the strains, 26 were
identified as Pseudomonas spp. These had been isolated either from manganese nodules
(25 strains) or the top layer of sediment (1 strain). Ten were Alcaligenes spp., isolated
from manganese nodules and water samples collected at deep ocean sites (4 strains) or
sediment (1 strain), five strains were identified as Vibrio spp., these having been isolated
from the top layer of a sediment sample (Schuett, 1979).
A yeast extract-proteose peptone medium (YP medium), prepared with artificial seawater, was used for growth and storage of the culture. The medium contained (g/l) yeast
extract (Difco Laboratories, Detroit, MI) 2.0 ; and proteose-peptone (Difco) 2.0 ; pH
adjusted to 7.2. A medium containing Mn 2+ and artificial seawater (M-medium) was used
for manganese oxide detection and was composed (in g/l) of yeast extract (Difco) 2.0 ,
tryptone (Difco) 2.0 ; Na-acetate (Difco) 1.0 ; MnSO
4
.H
2
O (Baker Chemical Co.,
Phillipsburg, NJ) 0.2 ; and Bacto-agar (Difco) 15.0 ; pH adjusted to 7.2. Artificial Sea
Water (ASW) was composed of (g/l) NaCl 11.7 ; KCl 0.35 ; and MgS0
4
.7H
2
3.5.
Oxidation of Mn
2+ to Mn 4+ was measured using o-tolidine reagent (Sigma) according to
the methods of Morgan and Stumm (1965) and also employed as a spot test.
Plasmid deoxyribonucleic acid (DNA) was extracted and analyzed using a modification
of the rapid screening method of Kado and Liu (1981). Modifications were as follows : To
obtain complete lysis, cells were incubated before lysis in the presence of 5 mg/ml
lysozyme (Sigma, St. Louis, MO). After lysis with Sodium dodecilsulfate (SDS), plasmid
DNA was prepared by agarose gel (0.7 %, BBL, Cockeysville, MD) electrophoresis for
334