31
Tecnología y Ciencias del Agua
, vol. VIII, núm. 3, mayo-junio de 2017, pp. 27-37
Aburto-Medina
et al
.
, Prevalence of
Enterobacteriaceae
and contaminants survey in sediments of the Atoyac River
ISSN 2007-2422
•
agar plates containing ampicillin (50
m
g ml
-1
).
The screening of inserts from transformants was
performed by direct PCR amplification from
white colonies using the 16S primers 63F (CAG
GCC TAA CAC ATG CAA GTC) and 1389R
(ACG GGC GGT GTG TAC AAG). Heating
at 94°C for 10 min preceded standard cycling
conditions (as above). Amplified inserts were
grouped on the basis of restriction fragment
length polymorphism (RFLP) patterns using a
combination of the two restriction endonucle-
ases
Cfo
I and
Alu
I (Sigma) at 37°C for 3 hrs.
Representative clones of each RFLP group were
sequenced. The sequencing analysis was per-
formed at the UNAM biotechnology institute
(Mexico). The sequences length was 600 to 700
nucleotides in average.
Phylogenetic analyses
The sequences obtained were compared with
the European Bioinformatics Institute and
Genebank databases by online FastA searches
(Pearson & Lipman, 1988) and to the Check
Chimera program (Cole
et al
., 2003). The profile
alignment technique of ClustalW (Thompson,
Higgins, & Gibson, 1994) was used to obtain
preliminary alignments that were manually
refined in GeneDoc Multiple Sequence Align-
ment Editor ver. 2.6.002 (Nicholas & Nicholas,
1997) taking into account of secondary struc-
ture. Phylogenetic analyses were performed
with the Phylip software package (Felsenstein,
2001), using the Jukes-Cantor distance and the
neighbour-joining methods. The significance of
the branching order was determined by boot-
strap analysis with 1000 re-sampled data sets.
Results and discussion
Water quality
Total coliforms, fecal coliforms, and biochemi-
cal oxygen demand (BOD) values are shown in
table 3. These values indicate that the waters are
heavily contaminated according to the Mexican
maximum limits (NOM-003-Semarnat-1997).
Metals, semimetals and other elements in
sediments
Element concentrations for As, Ba, Ca, Cu,
Fe, K, Mn, Mo, Pb, Rb, Sr, Ti, Zn, and Zr were
obtained for sampling point A1 (table 4). The
concentrations of As, Mo and Pb were below the
detection level. The mean of values for Fe, Mn,
Pb, and Zn detected in this study are below the
permissible limits of the USEPA (1977) and the
Ontario Ministry of the Environment and Ener-
gy (OME, 1976) except for Cu, which is slightly
above the USEPA limit. They are also below
the values determined for lead and arsenic in
river sediments collected near the river origin
in the state of Tlaxcala (García-Nieto
et al
., 2011)
but above for Fe and Mn in agricultural soils
located further south Puebla city that have been
irrigated with the river waters for more than 30
years (Méndez-García, Rodríguez-Domínguez,
& Palacios-Mayorga, 2000). This suggests that
heavy metal concentrations in sediments vary
Table 3. MPN of total and fecal coliforms and BOD for sampling points A1-A3. A: Atoyac River.
Code
Fecal coliforms (thermal
tolerance)
(MPN/100 ml)
Total coliforms
(MPN/100 ml)
BOD
(mg/l)
A1
9
240
123
A2
14
210
125
A3
15
240
120
MON
240
___
20
MON: Maximum limits of Mexican Official Norm (NOM-003-Semarnat-1997).
