Use of Indigenous Bacteria from Arsenic Contaminated Soil for Arsenic Bioremediation - Management of Natural Resources in a Changing Environment - page 155

Table 2 Minimum inhibitory
concentration (MIC) of the
test metals to KUMAs1 in
two different media

MIC values (mM) in
Nutrient broth Metal tested Minimal broth

As(III) 17 15

As(V) 395 355

Cd(II) 4 2

Zn(II) 2 1

Cr(VI) 15 9

Co(II) 1 0.2

Ni(II) 8 3

Table 3 Sensitivity of
KUMAs1 to different
antibiotics

Diameter of
inhibition zone (cm) Antibiotics discs

Tetracycline (30 ʼ g/disc)

3

Imipenem (10 ʼ g/disc) 3

Tobramycin (10 ʼ g/disc) -

Polymyxin B (300 units) 1

Gentamycin (10 ʼ g/disc) 2.5

Amikacin (30 ʼ g/disc) 2.2

Netillin (30 ʼ g/disc) 2.7

Colistin (10 ʼ g/disc) -

Ciprofl oxacin (5 ʼ g/disc) 3

Kanamycin (50 ʼ g/disc) -

Ampicillin (50 ʼ g/disc) 3.5

Ticarcillin/Clavulanicacid
(75/10

2.9

ʼ g/disc)

presence of 2 mM As(V) than in presence of equimolar As(III), which might be due
to less toxicity of As(V) than As(III) to the strain. However, the requirement of As(V)
for its growth warrants further investigation, as it grew better in presence of As(V) in
comparison to the control set. Earlier it has been advocated that the microorganisms
can use As(V) for their growth as electron acceptor suggesting possible mechanism
of arsenic resistance (Ahmann et al. 1994 ; Anderson and Cook 2004 ). KUMAs1
grew optimally at 37 °C (Fig. 3c, d ) and at pH 7.0 (Fig. 3e, f ) in presence of either
As(V) or As(III). In phase contrast microscopic study, the treated cells showed no
difference in shape and size (Fig. 4 ) when compared with the cells of control set sug-
gesting non-toxic effect of both forms of arsenic at that concentration.

Arsenate Reduction

Study of As(V) reduction was carried out in presence of 0.07 mM, 0.14 mM, and
0.21 mM of As(V) in MB as mentioned earlier. The strain grew well in presence of
As(V) comparably with the control set and reduced As(V) optimally during steady