Manganese nodules contain, besides manganese, other even more toxic heavy metals,
including cobalt, nickel, and copper (Yang and Ehrlich, 1976). Heavy metal resistance of
the seven manganese-oxidizing strains was determined using a modification of the
method described by Austin et al. (1977), i.e., M-medium was used in place of the medium
employed by Austin et al. (1977) and the following concentration of each heavy metal :
MnS0
4
. H
2
O (150/rg/ml Mn 2+ ) was replaced by NiCl
2
. 6 H
2
O (100 µg/ml Ni2+ ),
C0SO4 . 7H
2
0 (100 µg/ml Co 2+ ) and CuSO
4
. 5H
2
O (100 yug/ml Cu2+). The inoculated test media were incubated for six days at 26°C. The resistance patterns of seven of the
manganese-oxidizing isolates showed that all strains grew well in the presence of 150
µg/ml Mn
+ , i.e., similar growth response on Mn 2+ containing medium as on unamended
medium (Tab. 4). Only strain 57 displayed sensitivity to Mn 2+ . The other heavy metals
inhibited growth of all strains tested, except in the case of strain 57 (pZPl) and its
derivative. However, the cured strain was observed also to be sensitive to 100 µg/ml
copper.
Genus
Strain
Mn (150)
Resistance patterna
Co(100)
Mi(100)
Cu(100)
Pseudomonas sp
7
R
S
S
s
Pseudomonas sp
12
R
S
S
s
Pseudomonas sp
17
R
S
S
s
Pseudomonas sp
18
R
S
S
s
Pseudomonas sp
55
R
S
s
s
Pseudomonas sp
57 (pZPl)
R
R
R
R
Pseudomonas sp
Unidentified
57
(S)
R
R
S
gram-negative rod
4D-I
R
S
s
S
Table 4 : Heavy metal resistance pattern observed for eight manganese-oxidizing bacterial strains.
R = growth ; S = no growth ; (S) very weak growth on heavy metal-containing medium. The numbers in
parenthesis are the final concentrations of metals (µg/ml) after addition of the metal to M-medium.
The resistance pattern observed for Pseudomonas 57 (pZPl) and its cured variant suggest
that the curing of pZPl results in a sensitivity of strain 57 to manganese and copper. The
effect of these metals on viable cell counts is shown in Figure 1.
1 a
1b
1c
TIME Ch)
TIME Ch)
Figure l
modified
TIME Ch)
: Growth measurements (viable cells) of Pseudomonas 57 (pZP l) (0) and Pseudomonas 57 (□) in
K broth (a) unamended, (b) amended with 70 µg/ml Cu 2+ , (c) amended with 170 µg/ml Mn 2+ .
338
including cobalt, nickel, and copper (Yang and Ehrlich, 1976). Heavy metal resistance of
the seven manganese-oxidizing strains was determined using a modification of the
method described by Austin et al. (1977), i.e., M-medium was used in place of the medium
employed by Austin et al. (1977) and the following concentration of each heavy metal :
MnS0
4
. H
2
O (150/rg/ml Mn 2+ ) was replaced by NiCl
2
. 6 H
2
O (100 µg/ml Ni2+ ),
C0SO4 . 7H
2
0 (100 µg/ml Co 2+ ) and CuSO
4
. 5H
2
O (100 yug/ml Cu2+). The inoculated test media were incubated for six days at 26°C. The resistance patterns of seven of the
manganese-oxidizing isolates showed that all strains grew well in the presence of 150
µg/ml Mn
+ , i.e., similar growth response on Mn 2+ containing medium as on unamended
medium (Tab. 4). Only strain 57 displayed sensitivity to Mn 2+ . The other heavy metals
inhibited growth of all strains tested, except in the case of strain 57 (pZPl) and its
derivative. However, the cured strain was observed also to be sensitive to 100 µg/ml
copper.
Genus
Strain
Mn (150)
Resistance patterna
Co(100)
Mi(100)
Cu(100)
Pseudomonas sp
7
R
S
S
s
Pseudomonas sp
12
R
S
S
s
Pseudomonas sp
17
R
S
S
s
Pseudomonas sp
18
R
S
S
s
Pseudomonas sp
55
R
S
s
s
Pseudomonas sp
57 (pZPl)
R
R
R
R
Pseudomonas sp
Unidentified
57
(S)
R
R
S
gram-negative rod
4D-I
R
S
s
S
Table 4 : Heavy metal resistance pattern observed for eight manganese-oxidizing bacterial strains.
R = growth ; S = no growth ; (S) very weak growth on heavy metal-containing medium. The numbers in
parenthesis are the final concentrations of metals (µg/ml) after addition of the metal to M-medium.
The resistance pattern observed for Pseudomonas 57 (pZPl) and its cured variant suggest
that the curing of pZPl results in a sensitivity of strain 57 to manganese and copper. The
effect of these metals on viable cell counts is shown in Figure 1.
1 a
1b
1c
TIME Ch)
TIME Ch)
Figure l
modified
TIME Ch)
: Growth measurements (viable cells) of Pseudomonas 57 (pZP l) (0) and Pseudomonas 57 (□) in
K broth (a) unamended, (b) amended with 70 µg/ml Cu 2+ , (c) amended with 170 µg/ml Mn 2+ .
338