Lead uptake by Purple phototrophic Bacteria (Bioremediation)

1. PROMPT LEAD EXPOSURE OF AQUEOUS
ENVIRONMENT BIOMONITORED BY
PHOTOSYNTHETIC BACTERIA
Saed AL-Atawneh
Department of Medical Physics and Informatics
University of Szeged
October
2018

2. - Toxic heavy metals: mercury, lead, chrome
Introduction
Heavy metal contamination in Drinking Water
Source:http://www.epa.gov/sites/production/files/styles/large/publi
c/2017-08/pbinfographic_thumbnail_0.png
-The permissible level of lead
contamination in drinking water
(World Health Organization limit) is
as low as 10 µg/l ≈ 50 nM.
Source:http://www.epa.gov/sites/production/files/styles/larg
e/public/2017-08/pbinfographic_thumbnail_0.png

3. Why photosynthetic purple bacteria?
Photosynthetic apparatus
Kis M.,et al. , Photobiology. B. Biology, 2015.
LH2
(peripheral antenna)
LH1
(core antenna)
Reaction
center
TEM picture of Rhodobacter sphaeroides
Advantages:
1. Varied habitat and metabolisms
2. Relatively short generation time
3. Excellent model system
4. Easily adapts
5. Monitoring environmental pollution
6. Bioremediation
500 fs
5 ps
100 fs

4. Bacterial Biosorption
Prasad et al. 2006
Main types of Bacterial Biosorption
Ions adsorb to the cell
surface groups and
they diffuse through
the cell membrane
Ions can use other non
toxic metal channels
Ions bind to the negatively charged
phosphate, sulfate and carboxylic
acid groups.

5. Experiment
Fluorescence
Flash Induction
of Absorption
Change
OpticalChemicals
Bacterial Strain
& Growth
Cell culture
“Rubrivivax (Rvx.)
gelatinosus “
Pb(II)-Acetate
Pb(CH3COO)2*3H2O
Sample (cells) + Pb(II)-Acetatebound
Steady-State
Absorption

6. Results and Discussion
Steady-state absorption spectrum.
-The absorption spectra of intact cells were
measured by dual beam spectrophotometer
-Both red absorption bands characteristic of
the peripheral (808 nm) and core (870 nm)
antenna complexes demonstrate prompt
decomposition after treatment with lead
acetate in the few mM concentration range
Fig. 1. Steady state red absorption spectra of
intact cells of photosynthetic bacteria
Rubrivivax gelatinosus after prompt addition
of Pb(II) acetate to the culture.
LH2
LH1
LH2
LH2
LH1

7. Results and Discussion
Fig. 2. Kinetics (inset) and lead(II)-dependent
amplitude of flash-induced electrochromic
response of the carotenoids.
Flash-induced absorption change kinetics.
- The flash-induced absorption change indicating
that the magnitude of the membrane potential was
changed
- whole cells of Rubrivivax gelatinosus upon
treatment with 0-4 mM Pb(II) measured by
absorption change at 530 nm (vs. 510 nm).
https://www.promegaconnections.com

8. Fig. 3. BChl fluorescence (F) induction kinetics
(inset) and lead-dependent changes of the
maximum fluorescence (Fmax).
Results and Discussion
Induction and relaxation of bacteriochlorophyll (BChl)
fluorescence.
-The induction and decay were measured by a home built
fluorometer .
-The light source was a laser diode (808-nm wavelength
and 2W light power).

9. Results and Discussion
Fig. 4. Relaxation of the BChl
fluorescence after flash excitation
- BChl fluorescence gives information about the
pathways of re-opening of the closed reaction
centers in the dark.
- The prompt effect of lead(II) ions is expressed as
significant decrease of the maximum fluorescence
.
Closed R.C
Open R.C
Reaction
center

10. Conclusion
- Photosynthetic Purple bacteria are sensitive bioindicators of lead(II) contamination of
aqueous cultures.
- The absorption spectrum was decreased by 62.5% with 3mM of lead-acetate
contamination.
- The absorption Amplitude (A530-510) of carotenoid was decreased by 50.0% with 4mM of
lead- acetate.
- The Fluorescence–Induction was decreased by 27% with 6mM of Lead–acetate and also
the Relaxation Fluorescence was decreased by 48.7% with 4mM of lead-acetate.
- The Pb(II) ions cause prompt and detectable physiological changes by disconnection and
damage of the antenna pigments, LHCs.

11. Thanks for your attention