STUDIA UNIVERSITATIS BABEŞ-BOLYAI, PHYSICA, SPECIAL ISSUE, 2003
METABOLIC ACTIVITY OF BACTERIA IN ZERO MAGNETIC FIELD.
THE INFLUENCE OF GEOMAGNETIC FLUCTUATIONS
Silvia Neamţu1, V.V. Morariu1, E. Boldiszar2,
1
National R&D Institute for Isotopic and Molecular
Technologies, P.O. Box 700, 3400 Cluj-Napoca
2
Microbiology Department, University of Agricultural
Sciences and Veterinary Medicine, Cluj-Napoca
ABSTRACT. The degradation of glucose, lactose and albumin by
Salmonella, E. Coli and nonspecific bacteria activity in zero magnetic
field (ZMF) and geomagnetic field as control was investigated using
spectrophotometric and two electrophoresis methods. The results showed
that ZMF conditions generally favor the bacteria activity and growth.
Significant sensitivity of bacteria to natural variations of magnetic field
was also observed. In the presence of major magnetic storms metabolic
activity of gram(-) germs was inhibited.
INTRODUCTION
Zero magnetic field (ZMF) is an important reference in studies concerning
the effect of geomagnetic field (GMF) on living systems and also is a tool to
investigate the sensitivity of organisms to an extremely change of magnetic
environment (magnetic polarity reversal, spaceflight inframagnetic field,
interplanetary very low magnetic field). There are few but significant evidences
concerning cellular [1,2,3] and whole organism [4] response to the lack of static
component of geomagnetic field. In order to enlarge the picture of the simplest
organisms behavior in ZMF we investigated the metabolic activity of Salmonella,
E. Coli and nonspecific gram(-) bacteria during the lag phase of cells
multiplication. The effect obtained was compared with the results of bacteria
growth tests (data not published) and was analyzed in respect with the variation of
geomagnetic activity during the period of experiments. Our experimental set up
consists of a coil that compensates the static component of geomagnetic field.
However the natural fluctuations remain operative. Such analysis allows us to
perceive or to remove the possible contribution of natural magnetic disturbance
(magnetic storms) to the effect recorded and also to emphasize the sensitivity of
bacteria or of any system investigated to inframagnetic field (nT, Hz).
MATERIALS AND METHOD
Static geomagnetic field ( 0,47 G) has been compensated with a factor of
100 in a pair of Helmholtz coils oriented along geomagnetic field lines. A group of
bacteria cultures was exposed in ZMF in the space delimited by the coils and
another group to natural GMF environment as control, in the same room at a
significant distance from the coil. The temperature was kept at 25 C.
SILVIA NEAMŢU, V.V. MORARIU, E. BOLDISZAR
Metabolic activity of bacteria was measured by the degradation of sugar
and albumin substrate in the presence of specific bacteria (Slamonella sp. and E.
Coli sp.) and gram(-) bacteria. Salmonella and E. Coli activity was investigated in
media with a minimum content of nutritive substance but rich in sugars (glucose,
lactose) in the presence of blue bromthymol. The degree of glucose and lactose
degradation was estimated spectrophotometrically by the decrease of bromthymol
absorption peak. The pH variation of the medium has been determined
simultaneously.
Agarose and SDS polyacrilamide electrophoresis methods were used to
estimate the effect of gram(-) germs on albumin substrate.
Variation of natural fluctuation of GMF represented by Ap index values of
geomagnetic activity (GMA) was downloaded from National Geophysical Data
Center, USA for each period of the experiment.
RESULTS AND DISCUSSION
The decrease of glucose and lactose concentration in Salmonella
respectively E. Coli cultures as a consequence of metabolic activity of bacteria in
GMF and ZMF conditions is illustrated in Fig. 1a and 2a. Concomitant change of
pH in cells suspension is also presented in Fig 1b and 2b.
8.5
100
geomagnetic field
zero magnetic field
geomagnetic field
zero magnetic field
8.0
80
60
7.0
pH
Glucose (%)
7.5
40
6.5
6.0
20
5.5
0
5.0
0
4
7
Incubation time (hours)
10
0
2
4
6
8
10
Incubation time [hours]
Fig. 1a - Glucose degradation (a) and pH variation (b) in the presence of Salmonella sp.
exposed in geomagnetic field and zero magnetic field at 24 0 C
After 4 hours glucose was significantly reduced in Slamonella cells
suspensions exposed in ZMF (49,5% vs. GMF) and is entire metabolized after 7
hour in both magnetic environments. In the same time pH decrease attained 6,8%
METABOLIC ACTIVITY OF BACTERIA IN ZMF. THE INFLUENCE OF GMA FLUCTUATIONS
in ZMF. These results show the positive influence of ZMF on Salmonella germs
activity and support the data obtained in the bacteria growth tests.
The decrease of lactose concentration and pH in E. coli cells suspension
was less pronounced in ZMF conditions in respect with GMF. On the other hand,
E. coli growth tests showed no changes. The sensitivity of bacteria to the changes
of GMF seems to depend on the bacterial type.
8.5
100
8.0
7.5
60
pH
7.0
40
6.5
20
geomagnetic field
zero magnetic field
6.0
geomagnetic field
zero magnetic field
0
5.5
0
4
7
10
Incubation time [hours]
0
2
4
6
8
10
Incubation time [hours]
Fig. 2– a)Lactose degradation and b) pH variation in presence of E. coli exposed in
geomagnetic field and in zero magnetic field at 240C
30
camp geomagnetic
camp magnetic cavsinul
25
20
Fa/A*100
Lactose (%)
80
15
10
5
0
In the prezence
of tiomersal
Fig. 3 – The percentage of new proteic fraction after 5 days of albumin incubation in
geomagnetic field and in zero magnetic field with and without tiomersal
SILVIA NEAMŢU, V.V. MORARIU, E. BOLDISZAR
Bacteriological tests revealed the growth of gram(-) germs on the albumin
as nutritive media. Both agarose gel electrophoresis and SDS poliacrylamide
electrophoresis of albumin revealed significant increase of the degradation process
in ZMF conditions. The increase of integrated aria of albumin band from 15% in
GMF to ~25% in ZMF observed in the 5th incubation day (Fig.3) was explained by
the appearance of new protein fractions due to the bacteria metabolic activity.
Alb Albumin
(0)
GMF
(1)
ZMF
(2)
GMF (3) ZMF (4)
Etalon
+ tiomersal + tiomersal
GM
92,5 KDa
67 KDa
45 KDa
Fig 5. - SDS poliacrylamide gel electrophoresis of albumin exposed 3 days in geomagnetic
field and zero magnetic field with and without tiomersal as bactericide agent
GMA variation [Ap index]
100
80
60
40
20
0
Exp1
Exp2
Exp3 Exp4
Exp5
Experiment [nr]
Exp6
METABOLIC ACTIVITY OF BACTERIA IN ZMF. THE INFLUENCE OF GMA FLUCTUATIONS
Fig. 6. – Variation of geomagnetic field activity during the experiments performed
The same results were obtained after 3 days of incubation using the second
electrophoresis method. In the sample exposed to ZMF (Fig 4- poz 2) it was
detected a protein fraction with molecular weight close to that of albumin, that
emphasize significant degradation of the albumin molecule.The presence of small
proteins showed less pronounced activity of bacteria in GMF (Fig 5-GMF(1)). A
positive effect of ZMF on metabolic activity of gram(-) bacteria was also recorded
in the cells growth experiments (data not shown).
Two series of investigations (albumin electrophoresis, bacteria growth
tests) showed however no significant effects. The relation between biological
effects recorded in ZMF and the variation of geomagnetic field activity (GMA)
during the period of the experiments (Fig 6) revealed the presence of major storm
in these two cases. In this context we may assign the lack of ZMF effect to the
influence of natural magnetic disturbances on the bacteria behavior. Stimulation of
metabolic activity of bacteria in ZMF is emphasized in quiet periods of GMA and
screened in the presence of major storms. This screening of the effect can be
explained by the inhibitory effect of disturbed magnetic field on the bacteria
behavior. The negative response of bacteria activity to magnetic storms is in
agreement with other results reported in the literature [5]
CONCLUSIONS
The results of our investigations prove the favorable influence of ZMF on
metabolic activity and growth of bacteria and are in agreement with the behavior of
simplest organisms in these magnetic field conditions. Some variability related to
species is revealed by the response of E.coli.
The sensitivity of bacteria to natural variations of magnetic filed can
explain the apparent inconstant behavior of these organisms in zero magnetic field
conditions and point out the necessity to take into account the influence of this
environmental factor in the analysis of ZMF experiments.
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