Leptothrix Maged S. Ahmad

Journal of Applied Sciences Research, 4(10): 1230-1241, 2008
© 2008, INSInet Publication
Evaluating the Efficacy of Two Leptothrix Species for Removal of Iron
Maged S. Ahmad
Botany Department, Faculty of Science, Beni Suef University, Beni Suef.
Abstract: T wo strains of Leptothrix sp. were used for leachate iron from Abu Tarture mine. Abu Tarture
deposits composed mainly of hematite, pyrite, ankerite and jarosite. M össbauer spectroscopy results
indicated that Leptothrix AT06 sp. was more efficient in removing different iron phases than Leptothrix
AT22 sp. Treatment of phosphate ore by 10mM EDTA prior bacterial treatment lead to completely
leachate hematite and pyrite, and almost reduced ankerite and jarosite for both organisms. The total iron
reduced from 2.91% before to 1.08% after treatment by Leptothrix AT06 with chelating agent EDTA.
Amino acid analysis of some protein fractions revealed that protein of Leptothrix AT06 sp. characterized
by the presence of proline, cystine, methionine, isoleucine, leucine, tyrosine, arginine and lysine while
protein of Leptothrix AT22 sp. was mainly composed of glutamic acid and glycine in the bacterial cells.
Key words: Leptothrix, Iron phases, Deferration, phosphate ore
INTRODUCTION
Iron is an essential element for all life forms.
Naturally abundant iron (Fe) minerals exert a
s ig n ific an t in flu e nc e o n so il a n d s e d im e n t
geochemistry [8 ]. As a result, much consideration has
been vested in iron redox reactions in aquatic and
sedimentary environments. Reduction of iron in natural
systems mediated by both abiotic and biotic
mechanisms has been well documented [8 ].
This metal is involved in great enzymatic processes
including electron transfer in the respiratory chain,
redox reactions with inorganic substrates (oxygenase,
hydrogenase, ribonucleotide reductase) and DNA
cleavage (endonuclease III) [3 2 ]. Despite the abundant of
this metal in nature, it occurs as an insoluble forms in
ferric hydroxide complexes in the presence of oxygen
and water [3 5 ] except in acid solution [9 ] . Therefore, under
such iron-limiting conditions, microorganisms have
developed different solutions to solve the problem of
assimilation of the ferric form of ion from the
environment. One class of intracellular iron storage
compounds is represented by ferritin in eukaryotes and
bacterioferritin in prokaryotes [1 4 ].
W ard et al. [3 3 ] reported that lactoferrin is a member
of the transferrin family of iron-binding proteins.
Likewise they found that lactoferrin consists of two
repeated iron-binding lobes that bind one iron atom
each. The second class is siderophores, which have
been identified as intracellular iron storage compounds
in various fungal systems [2 2 ].
The siderophores are biosynthesized by the
organisms under negative iron control. They are
released to the environment where the ferrisiderophore
complexes are formed. The complexes are taken up by
microorganisms; siderophore was coined to designate
a family of low molecular mass, ferric specific
ligands elaborated by microorganisms to combate
iron deficiency [1 3 ].
Agarwala et al. [2 ] suggested a possible role for iron
in the synthesis of soluble proteins. They also showed
that iron deficiency caused a marked decrease in
growth, spore formation and soluble protein, coupled
with its increase in supplying iron. Makita et al.[2 1 ]
found that Fe accumulates mainly in electron opaque
granules and in the cell wall, both characterized by the
presence of polysaccharides and cysteine-rich proteins.
The main problem of Abu Tartur phosphate is the
high iron content (4%) which lies above the admissible
limit of commercially used phosphate concentrates.
This high content of iron degrades the ore and limits
it use in industry. So, the idea of the present work is
to use Leptothrix sp as a tool in leachate or even
partially leaching iron from Egyptian phosphate ores as
well as their possibilities for biosynthesis of
metallothioneins.
M ATERIALS AND M ETHODS
Sample Localities: Phosphate sample collected from
154 m depth of mine Abu Tartur phosphate deposit,
Egypt.
Organism Used: Two strains of Leptothrix sp. were
sheathed bacteria isolated from enriched soil with iron
from Aswan Governorate, Egypt. The medium used
Corresponding Author: Maged S. Ahmad, Botany Department, Faculty of Science, Beni Suef University, Beni Suef.
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J. Appl. Sci. Res., 4(10): 1230-1241, 2008
for isolation process was ferric ammonium citrate
(W ino g ra d sk y's m e d ium ).T h e o rg a n ism s were
tentatively identified according to Krieg [1 8 ] and
Holt et al. [1 5 ]. Both strains- Leptothrix AT06 and
Leptothrix AT22- oxidized iron and manganese ions.
Starvation: A heavy inoculum of the bacteria was
inoculated at 50 ml mineral broth in flask 250 ml
capacity. The mineral broth was free from ferrous ions.
The culture was incubated at 30 o C in a shaker (New
Bruinsweek, N.J.,) at 180 rpm for 2 weeks.
phosphate buffer of pH 7.1 was used for the
fractionation of the bacterial protein. The void volume
and the uniformity of packing were determined using
blue Dextran 2000 and the bromophenol blue. The
concentrate of bacterial protein was applied to the
column and allowed to pass into the gel by running the
column. Phosphate buffer was then added without
disturbing the gel surface, 14 fractions, each of 2 ml
was collected from the effluent of Sephadex G 50
column.
RESULTS AND DISCUSSION
Preparation of the Sample: The phosphate ore are
prepared for different treatments by successive stages
of crushing to obtain size fractions of the range 50100µm.
Treatment of the Sample by Sheathed Bacteria: The
bacterial strains inoculated at concentration 10 8 cell/ml
in 5% (w/v) crushed phosphate ore. The phosphate ore
was suspended in 50 ml mineral broth. T he culture was
incubated in incubator shaker at 180 rpm and 30 o C for
2 weeks. After a proper incubation period the culture
was filtered through W hatman N o . 1 filter paper to get
rid of water for about 3 hours and then centrifuged at
3000 g for 5 minutes. The supernatant was drained off
and residue of phosphate ore was subjected for
Mössbauer spectroscopy (Type MR-260/MR= 360) for
detection of iron fraction. Total iron content was
determined by atomic absorption spectroscopy.
Treatment of the Sample by Chelating Agent Prior
Sheathed Bacterial Treatment: EDTA was used as
chelating agent of phosphate. 5 g of phosphate ore
was suspended in 10mM EDTA solution (100 ml).
The solution was shaked over night at 200 rpm. The
ore was sieved (60 mesh) to get rid of EDTA residues,
then phosphate ore was added to mineral broth at
concentration 5% (w/v), and flasks inoculated with
sheathed bacteria. The rest of experiment was preceded
as mentioned above.
Amino Acid Determination: Amino acid composition
was determined using an automatic amino acid analyzer
model LC 3000 eppendorf Biotronik, Germany in the
Regional Center for Mycology and Biotechnology, AlAzhar University, Cairo.
Protein Determination: Total cellular protein of the
bacterial strain was determined using Folin-phenol
reagent according to Lowery et al. [2 0 ]; bovine serum
albumin was used as a standard protein.
Gel Filtration: A Pharmacia column (1.5x30cm)
packed with Sephadex G 50 equilibrated with
Results:
Identification of Leptothrix sp.: Both isolates
formed smooth colonies. Microscopically, they were
rod shaped, single or in pairs with sheath formation
(Fig. 1)-assignment as Leptothrix AT06- or very long
sheath (Fig. 2)-assignment as Leptothrix AT22. Sheath
formation asserted via a dilute crystal staining
solution [2 9 ]. Gram-negative and chemoorganotroph.
Glucose and peptone were the optimum carbon and
energy sources respectively. The only difference
between the two iron bacteria that Leptothrix AT06
was tolerated incubation temperature up to 40 o C and
utilized glycerol while Leptothrix AT22 not recorded
growth at 37 o C or utilized glycerol.
Poly-âhydroxybutyrate granules were detected inside the
cells. Both isolates have the ability to oxidize and
deposit Mn 2 + [2 6 ].
Two properties distinguish genus Leptothrix from
genus Sphaerotilus [1 ]. Leptothrix species oxidize Mn 2 +
and are usually found in oligotrophic, iron -and
manganese- rich sediments, while Sphaerotilus species
did not oxidize Mn 2 + and typically thrives in rich
organic nutrients. However, these organisms according
to Boone and Castenholz [6 ], are a member of the
B e ta p rote ob a c te ria c la s s I I o f th e p h ylum
Proteobacteria.
Deferration of Iron by Leptothrix sp.: The iron ore
structure mainly composed of magnite, pyrite and
hematite. The ability of sheathed bacteria to deferrate
phosphate ore from Abu Tartur was confirmed by
Mössbauer spectroscopic analysis. Typical absorption
peaks of pyrite (FeS 2 ), hematite (Fe 2 O 3 ), ankerite
Ca(Fe)CO 3 ) 2 , jarosite KFe 3 (SO 4 ) 2 (OH) 6 and total Fe by
Mössbauer are presented in Fig. (3). Mössbauer
spectroscopic analysis of phosphate ore after sheathed
bacteria treatment (Figs. 4 and 5) showed that area of
hematite (a, b, c and d) were completely disappeared,
that might due to the ability of bacteria to deferrate
iron phase of hematite. Also total area of ankerite
peaks (e and f) was smaller than control one, that
indicated ankerite partially reduced. Alternatively,
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J. Appl. Sci. Res., 4(10): 1230-1241, 2008
Table 1:
Sam ple
M ossbauer param eters of treated sam ples
Com ponent
M ossbauer param eter
assignm ent
--------------------------------------------------Ä
ä
H
A(rel.)
O re without any treatm ent
a
2.28
1.28
0.08
Fe 2 + in trans position in m otm orillonite
---------------------------------------------------------------------------------------------------------------------------b
1.48
1.22
0.03
ankerite
---------------------------------------------------------------------------------------------------------------------------c
1.02
0.35
0.17
Fe 3 + in cis position in m otm orillonite
---------------------------------------------------------------------------------------------------------------------------d
0.61
0.32
0.65
pyrite
---------------------------------------------------------------------------------------------------------------------------e
-0.19
0.34
511
0.06
hem atite
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------O re+Leptothrix AT06
a
2.79
1.11
0.44
Fe 2 + in trans position in m otm orillonite
---------------------------------------------------------------------------------------------------------------------------b
2.07
1.01
0.35
ankerite
---------------------------------------------------------------------------------------------------------------------------d
0.61
0.25
0.21
pyrite
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------O re+Leptothrix AT22
a
2.32
1.28
0.05
Fe 2 + in trans position in m otm orillonite
---------------------------------------------------------------------------------------------------------------------------b
1.5
1.24
0.03
ankerite
---------------------------------------------------------------------------------------------------------------------------c
1.02
0.35
0.46
Fe 3 + in cis position in m otm orillonite
---------------------------------------------------------------------------------------------------------------------------d
0.59
0.31
0.46
pyrite
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------O re+Leptothrix AT06+10m M ED TA
b
0.6
0.31
1
ankerite
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------O re+Leptothrix AT22+10m M ED TA
a
2.3
1.28
0.07
Fe 2 + in trans position in m otm orillonite
---------------------------------------------------------------------------------------------------------------------------b
0.6
0.31
0.93
ankerite
Fig. 1: A photograph of Leptothrix AT06 sp. (x=1000).
jarosite (g and h) and pyrite (i and j) peaks not showed
change in their transmission (%) or area, whereas the
bacteria not utilized these two types of ferrous
compounds. Data from atomic absorption of total Fe
was not reduced markedly.
Upon deferration of ore after treatment of bacterial
culture with chelating agent EDTA at concentration
10mM, bacterial strains showed high efficiency of
deferration (Figs. 6 and 7). Peaks of hematite and
pyrite completely disappeared whilst peak spectra of
ankerite diminished greatly. A jarosite spectrum was
still after treatment with 10mM EDTA but in a
small range; specifically for Leptothrix AT06 (Fig.
6). Mossbauer parameters and assignments of the
spectral components are shown in table (1). Atomic
absorption spectroscopy shows that all the used
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Fig. 2: A photograph of Leptothrix AT22 sp. (x=1000).
Fig. 3: Mössbauer spectroscopic analysis of phosphate ore from Abu T artur mine: a, b, c, d= Hematite peaks;
e, f= Ankerite peaks; g, h= Jarosite peaks; i, j= Pyrite peaks, k, l= Total Fe peaks.
Fig. 4: Mössbauer spectroscopic analysis of phosphate ore after treatment with Leptothrix AT06 sp.
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J. Appl. Sci. Res., 4(10): 1230-1241, 2008
Fig. 5: Mössbauer spectroscopic analysis of phosphate ore after treatment with Leptothrix AT22 sp.
Fig. 6: M össbauer spectroscopic analysis of phosphate ore after chelation with10mM EDTA and treatment with
Leptothrix AT06 sp.
Table 2: Total cellular protein of two Leptothrix sp before and after
treatm ent phosphate ore with 10m M EDTA.
Treatm ent
Protein content (µg/m l)
Leptothrix AT06
230
10m M ED TA and Leptothrix AT06
764
Leptothrix AT22
271
10m M ED TA and Leptothrix AT22
890
bacteria decreased the iron content with different
percentages. A reasonable leaching was obtained by
Leptothrix AT06 with chelating agent EDTA in which
the total iron decreased from 2.91% (before) to 1.82%
(after). Meanwhile, the cellular protein of Leptothrix
AT06 and Leptothrix AT22 were about 2.5- and threefolds than that before treatment with ED TA
respectively (Table 2).
Fractionation of Leptothrix AT06 sp. protein on Sephadex
G50 using a pharm acia colum n (1.5 x 30 cm ) cultivated
on phosphate ore at 30 o C for two weeks.
No
Iron Conc.
Protein Conc.
Fe/Protein
m l)
(µg/m l)
(µg/m l)
Ratio
1
0.435
17
25.5 -3
2
1.957
501
3.91 -3
3
0.802
115
7.0 -3
4
0.164
15
10.9 -3
5
0.00
0.00
0.00
6
0.00
0.00
0.00
7
0.106
0.00
0.00
8
0.393
88
4.5 -3
9
0.384
338
1.1 -3
10
0.338
143
2.4 -3
11
0.206
313
0.6 -3
12
0.177
119
1.5 -3
13
0.00
30
0.00
14
0.00
0.0
0.00
Table 3:
Fraction
Each (5
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
Fraction
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J. Appl. Sci. Res., 4(10): 1230-1241, 2008
Fig. 7: Mössbauer spectroscopic analysis of phosphate ore after chelation with 10 mM EDTA and treatment with
Leptothrix AT22 sp.
Fig. 8: Amino acid analysis of fraction N o 2 for Leptothrix AT06 sp.
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Fig. 9: Amino acid analysis of fraction N o 6 for Leptothrix AT06 sp. after treatment of phosphate ore with10mM
EDTA.
Protein Fractionation of Two Leptothrix Species
Cultivated on Phosphate Ore: Data presented in
Tables (3 and 4) showed that the protein content of the
Leptothrix AT06 and Leptothrix AT06 with chelating
agent EDTA is scattered over a wide range of
fractions. Leptothrix AT06 shows cellular protein in 10
fractions only while Leptothrix AT06 with EDTA
exhibited protein in all fractions. The highest protein
content of Leptothrix AT06 was detected in fraction
number 2 followed by fractions number 9, 11 and 10
while fractions number 5, 6, 7 and 14 had no
detectable amounts of proteins. Iron was found to be
associated with ten fractions only. On the other hand,
Leptothrix AT06 after treatment of phosphate ore with
10mM EDTA exhibited protein content and iron in all
fractions. The highest protein fraction recorded in
numbers 7 and 8, while the highest iron content was
recorded in fraction number 6.
Fraction number 2 for Leptothrix AT06 sp contains
high concentration of protein that chelated a high level
of iron ions. Its hydrolyzate revealed the presence of 8
amino acids; (Fig. 8) shows their concentrations, µg/ml.
The most characteristic one was lysine. Morelikely,
fraction number 6 for Leptothrix AT06 with EDTA
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Table 4: Fractionation of Leptothrix A T06 sp. protein after
treatm ent of phosphate ore with 10m M ED TA on colum n
of Sephadex G50.
Fraction N o
Iron Conc.
Protein Conc.
Fe/Protein
Each (5 m l)
(µg/m l)
(µg/m l)
Ratio
Fraction 1
0.85
83
10.2 -3
Fraction 2
3.33
36
92.5 -3
Fraction 3
0.78
11
70.9 -3
Fraction 4
1.44
22
65.4 -3
Fraction 5
0.5
13
38.5 -3
Fraction 6
11.46
44
260.5 -3
Fraction 7
0.92
130
7.1 -3
Fraction 8
0.56
121
4.6 -3
Fraction 9
1.28
58
22.1 -3
Fraction 10
0.57
50
11.4 -3
Fraction 11
0.2
19
10.5 -3
Fraction 12
2.16
19
113.7 -3
Fraction 13
1.79
20
89.5 -3
Fraction 14
1.43
16
89.4 -3
only. The highest protein content was detected in
fraction number 10 and followed by fraction number9.
Leptothrix AT22 with chelating agent EDTA exhibited
cellular protein and iron in 12 fractions, each. The
highest protein content and iron concentration were
detected in fraction 9.
Fraction 10 for Leptothrix AT22 showed least
number of amino acid between all tested fractions.
It recorded 4 types of amino acids with nearly
equivalent percentage of serine and glutamic acids, and
in other side glycine and valine,(Fig. 10). Similarly,
fraction number 9 for Leptothrix AT22 with chelating
agent EDTA showed 5 amino acids in its structure
with the presence of citrulline as characteristic amino
acid, (Fig. 11).
Table 5: Fractionation of Leptothrix A T22 sp. protein on Sephadex
G50 using a pharm acia colum n (1.5 x 30 cm ) cultivated
on phosphate ore at 30 o C for two weeks.
Fraction N o
Iron Conc.
Protein Conc.
Fe/Protein
Each (5 m l)
(µg/m l)
(µg/m l)
Ratio
Fraction 1
0.119
26
4.57 -3
Fraction 2
0.2
19
10.5 -3
Fraction 3
0.000
44
0.00
Fraction 4
0.000
0.00
0
Fraction 5
1.25
34
36.8
Fraction 6
0.000
0.00
0.00
Fraction 7
0.000
18
0.00
Fraction 8
0.26
137
1.89 -3
Fraction 9
0.204
390
0.52 -3
Fraction 10
0.667
506
1.3 -3
Fraction 11
0.000
106
0.00
Fraction 12
0.000
0.00
0.00
Fraction 13
0.000
0.00
0.00
Fraction 14
0.000
0.00
0.00
Discussion: Iron is the most abundant transition
element in the Earth's crust. Approximately one-third of
the Earth's mass is estimated to be iron. Its
concentration is relatively high in most crustily rocks
(lowest in limestone, which is more or less pure
calcium carbonate) [1 2 ].
The idea of the present work depends mainly on
the fact that some aerobic microorganisms are capable
of oxidizing the iron from ferrous to ferric:
Table 6: Fractionation of Leptothrix AT 22 sp. protein after
treatm ent of phosphate ore with 10m M ED TA on colum n
of Sephadex G50.
Fraction N o
Iron Conc.
Protein Conc.
Fe/Protein
Each (5 m l)
(µg/m l)
(µg/m l)
Ratio
Fraction 1
0.96
42
22.8-3
Fraction 2
3.62
99
36.5-3
Fraction 3
1.55
29
53.4-3
Fraction 4
0.00
00
0.00
Fraction 5
1.25
34
36.8-3
Fraction 6
1.23
35
35.1-3
Fraction 7
0.89
76
11.7-3
Fraction 8
0.38
132
2.9-3
Fraction 9
7.08
154
46.0-3
Fraction 10
0.58
105
5.5-3
Fraction 11
0.75
57
13.2-3
Fraction 12
0.44
31
14.2-3
Fraction 13
0.25
29
8.6-3
Fraction 14
0.00
00
0.00
revealed 13 amino acids in its structure. There were
proline, cystine, isoleucine, leucine and arginine as
characteristic amino acids, (Fig. 9).
Results of protein fractionation of Leptothrix AT22
and Leptothrix AT22 with chelating agent EDTA are
presented in Tables (5 and 6). Leptothrix AT22 shows
cellular protein in 9 fractions and iron in 6 fractions
4Fe 2 + + 4H + + O 2 6 4Fe 3 + + 2H 2 O
The oxidation of the iron takes place rapidly
inside the cell. Two species of Leptothrix were isolated
from
niche enriched with magnate, pyrite and
hematite; consequently reflect a specific environmental
condition. Regulation of uptake of Fe metal would
seem reasonable in order correctly to fulfill this
need. Temperatures inside Abu Tartur mine between 30
and 35 o C that it suitable for growth of Leptothrix
species, particularly Leptothrix AT22. On the other
hand, these bacteria and other various bacteria are able
to acidify the medium, which ensures a better solubility
of ferric ions and enables iron uptake [2 5 ].
Chemical analysis of phosphate ore show that
about 50% of the total iron in the form of pyrite,
the rather high relative area of the component of pyrite
(~ 70% on the average). However, the amount of
dissolved iron in the form of free ferric or its
hydrolysis product is extremely low. The actual uptake
of iron in the form of pyrite by Leptothrix AT06 and
Leptothrix AT22 is confirmed by the measurements of
M össbauer spectroscopy and atomic absorption
spectroscopy in which the percentages of total iron
before and after each treatment are determined.
Accordingly, Theil and Raymond [3 0 ] stated that
occurrence of iron-bearing minerals in phosphate ore
makes the M össbauer spectroscopy a powerful
technique for their investigation.
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J. Appl. Sci. Res., 4(10): 1230-1241, 2008
Fig. 10: Amino acid analysis of fraction N o 10 for Leptothrix AT22 sp.
The results indicated that Leptothrix AT06 and
Leptothrix AT22 utilized hematite (Fe 2 O 3 ) completely
and partially utilized ankerite Ca(Fe)CO 3 ) 2 . In Fig. (3)
the relative area indicates that hematite exists in small
relative amounts (4-7%). The uptake of these iron
phases was p ro b ab ly thro ugho ut sidero phore.
Siderophores are defined by their ferric specific
chelating property. The formation of siderophores is
induced only under iron stress [2 4 ]. The growth of two
species of Leptothrix in minimal broth free from
ferrous ions was satisfied to produce siderophore prior
any treatment with phosphate ore.
Pyrite uptake is achieved firstly by chelation of
phosphorus through 10µM EDTA because average
phosphorus content (P 2 O 5 ) 25.5% that inhibit growth of
majority of bacteria. Uptake hematite, ankerite, pyrite
and to great extent jarosite appeared as iron-rich
protein which called siderophore or even other biogenic
minerals such as ferric oxyhydroxide [1 9 ] or goethite [3 4 ]
or iron hydrogen carbonate [7 ]. Protein content ascertain
hematite and pyrite uptake which increased 2.5-folds
for Leptothrix AT06 and three-folds for Leptothrix
AT22 than previous treatment. Meanwhile, reduction of
total iron content from 2.91 (before) to 1.08% (after)
treatment, i.e. about 62.9% reduction, indicated high
efficiency of last treatment. Previously, investigations
recorded about 20 and 35% reduction of pyrite by
Acidithiobacillus ferrooxidans [1 7 ,1 0 ]. However, similar
results were obtained by Tugel et al. [3 1 ] when added
acid to samples and produced Fe 2 + recoveries which
were four times greater than those without acid.
Iron was found to be associated with different
fractions of low and high molecular weight proteins.
Induction
of
high quantities of low and high
molecular weight protein to chelate metal ions
and reduce its harmful effect on the cell could be
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J. Appl. Sci. Res., 4(10): 1230-1241, 2008
Fig. 11: Amino acid analysis of fraction N o 9 for Leptothrix AT 22 sp. after treatment of phosphate ore
with10mM EDTA.
suggested. These results indicated that phytochelation
or metallothionein (M T) - like protein formation as a
mechanism of iron tolerance has not been synthesized.
Detoxification of excess amounts of this metal can be
achieved by siderophores or transferritins. They have
the capacity to bind 60µM iron [1 1 ]. These results are in
harmony with those obtained by Moller et al. [2 3 ] and
Alavandi and Ananthan [3 ] who reported that the
presence of iron-binding protein/peptide is one of the
mechanisms of metal tolerance.
A high amount of aspartic acid is usually related
to the presence of iron in growth media. Certain amino
acids especially aspartic acid are conjugated to nonpeptide molecules. Sometimes this route is a mean of
detoxification [5 ]. Also, presence of glycine, cystine and
methionine (two latter found in Leptothrix AT06) is
remarkable. Glycine is one of the amino acids which
act as intermediates in incorporating or disposing small
molecules and producing the most unexpected
biomolecules. It's well known that a variety of
biopolymers have potential applications as metalbinding agents, e.g. thiol groups in sulfur-containing
amino acids [1 6 ,4 ].
Ferritins, iron-containing proteins, are also known
to bind a variety of divalent metal ions in vitro and in
vivo [2 7 ]. The previous authors suggested that ferritin
serves as the initial chelator of metal ions, and the
synthesis of MT is initiated as a second line of
d e fe n s e . A s d e m o n s tr a te d b y S c h u ltz a n d
Hutchinson [2 8 ], the MT-like proteins are not the sole
representatives for metal tolerance. The results
presented in this investigation are in accordance
with the previous results and ensured that two
species of Leptothrix have developed several protective
mechanisms to help their survival under the presence
of high concentration of iron. Hence, the isolated
Leptothrix AT06 and Leptothrix AT22 can be used in
iron deferration from phosphate ore of Abu Tartur
mine. This leachate should pretreatment with chelating
agent such as 10µM EDTA.
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J. Appl. Sci. Res., 4(10): 1230-1241, 2008
ACKNOW LEDGM ENT
I would like to thank Dr. M. A. Ahmad, Physics
Dept., Faculty of Science, Al-Azhar University for
providing Abu Tartur samples and undertaking the
spectroscopic measurements.
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