Biology Reference
In-Depth Information
have undergone transport in an aquifer. These strains may start transport among a wide
variety of microorganisms that have infiltrated from the surface into the groundwater system,
and, after considerable transport has taken place, they may end up as one of the few
microorganisms remaining in the system.
In this study, we hypothesized that if the segment sticking efficiency reduces with transport
distance, as we have seen in many laboratory studies in literature, , then the minimum
sticking efficiency of a number of E. coli strains harvested from natural springs (or:
termination points of flow lines, when the transport distance is likely to be extended) is also
expected to be low.
6.2 Materials and methods
6.2.1 The study area
Kampala is underlain by a variety of meta-sedimentary rocks and weathering has produced a
pronounced topography. The town has a shallow aquifer in the weathered regolith and site
investigations showed the presence of preferential flow paths, although it is not known how
far these extend (Howard et al., 2003). Previous studies in Uganda indicated that the top of
the regolith is composed of fine material, with increasingly coarser (sandy clay) material
found at depth with productive aquifers commonly associated with these layers (Howard et
al., 2003; Kulabako et al., 2007). Recharge tends to occur during two distinct wet seasons,
although Kampala experiences rainfall throughout the year due to its proximity to Lake
Victoria (Nyenje et al., 2010). Kampala has many springs, and usually these springs are
protected with a concrete slab and a small protected area upstream of the spring ( Fig. 6.1 ) . In
Kampala, six E. coli strains were isolated from springs similar to that indicated in Fig. 6. 1 .
They were located in Formal Residential areas ( E. coli strains named FR02, FR05, and
FR08), an urban FArm (FA03) and informal residential areas or SLums (SL03, SL20).
Sampling was undertaken in July 2010. Thereto, 250 ml spring water was collected in sterile
polypropylene bottles, by means of a syringe 100 ml of each sample was passed through 0.45
µ m cellulose acetate filter, the filter is then placed on chromucult agar (DifcoTM LB Broth,
Miller) plate and transported to the microbiological laboratory of Makerere University and
incubated at 37 o C for 24 hours. The purple color of E. coli cells on chromucult agar plates
allowed us to detect the E. coli among different bacteria species in growing on the agar
plates. A sterile toothpick was used to pick a single colony of E. coli from agar plates and
inoculated into 5 ml of Nutrient broth followed by incubation at 37 o C for 24 hours. 1-2 ml of
freshly grown E. coli cells were then inoculated into sterile vials (Microbank™-Dry, PRO-
LAB DIAGNOSTICS, Toronto, Canada) containing porous beads saturated with
cryopreservative (cryovials), which serve as carriers to support microorganisms. The vials are
then stored at -70 o C and then transported to the UNESCO-IHE laboratory, Delft, the
Netherlands.
Search WWH ::




Custom Search