PERSONAL DE APOYO
RASTELLI Silvia Elena
congresos y reuniones científicas
Título:
PCR-DGGE analisys of arsenic influence on planktonic and sessile bacterial comunities from drinking water
Autor/es:
RASTELLI SILVIA E., VIERA MARISA Y ROSALES BLANCA M.
Lugar:
Mar del Plata
Reunión:
Congreso; VIII Congreso Argentino de Microbiologia General -SAMIGE-; 2012
Institución organizadora:
Asociación de Microbiología Argentina
Resumen:
Several microorganisms growing in
aquatic environments are able to adhere, multiply and develop on solid surfaces
in interacting and organized 3D structures including their extracellular
polymeric substance (EPS), named biofilms.
Many problems in drinking water networks (corrosion, obstruction, increased
resistance to biocides or contaminants, persistence of pathogenic species) are
due to the existence of biofilms. Arsenic in natural waters is a serious global
problem due to its adverse impact on human health. However there are many
microorganisms able to tolerate or metabolize this contaminant. The goals of
this work were to study the effect of arsenic on: 1) the planktonic bacterial
community present in drinking water, 2) the biofilm growing on several
substrates used in drinking water distribution systems and 3) culturable
bacteria in the presence of different arsenic concentrations. With these aims,
two closed drinking water circuits with a 50L tank storage coupled to a
polypropylene pipe (200 cm)
with a removable cell were built. Coupons of 1x1x0.02 cm of four substrata: a
low carbon steel (Fe), zinc (Zn), a copper alloy (Cu) and polypropylene (PP) were
placed in the cell. Water was impelled with a pump at laminar flux. In one of
the circuits, the drinking water was supplemented with 5 mg L-1
As(V). To characterize planktonic communities, 1L water from the tap (at the
beginning of the experiment) and 1L water from both circuit tanks (at the end
of the experiment) were filtered through 0.22 µm sterile membrane. Then, four
coupons of each material were extracted to study the structure of sessile
community. Each coupon was rinsed with sterile physiologic solution, scrapped
with sterile scalpel and poured into 1ml sterile physiologic solution. One of
them was used to analyze culturable sessile bacterial community in nutrient
broth with different As(V) concentrations (50, 200 and 300 mg L-1),
the remaining 3 coupons were combined. Both total and culturable sessile and
total planktonic DNA was extracted using a commercial kit and amplified by PCR
using 341F-GC clamp and 907R primers. The microbial ecological analysis of the
communities was performed by denaturing gradient gel electrophoresis (DGGE).
The results indicate that the presence of 5 mg L-1 As(V) produced a
change in the total planktonic community structure, diminishing their
diversity. The results obtained on biofilms showed a higher diversity in those
biofilms formed on materials susceptible to bacterial colonization (Zn, Fe) in
the presence of As. This could be related to a defense mechanism against the
presence of arsenic. The presence of As did not provoke a significant
difference in the bacterial community developed on those materials less
susceptible to bacterial colonization (Cu, PP). It was possible to obtain
culturable bacteria tolerating up to 300 mg L-1 As from all the
biofilms, however, the diversity of those cultures diminished when the As
concentration increased.