Transport of Escherichia coli strains isolated from springs in Kampala, Uganda - Transport of Multiple Escherichia Coli Transport in Saturated Porous Media - page 97

1200

Chloride

Nitrate

800

400

0

0 50 100 150 200

Concentration (mg/L)

Fig. 7.2: Relation between EC and nitrate and chloride concentrations

7.4.2 Bacteria characterization (serotyping and cell characteristics)
The E. coli serotyping showed four different O serogroups (O14, O21, O91, and O108),
while 16 of the strains were O-untypable and six strains were not typed. The results indicated
that 58 % of the serotyped E. coli strains exhibited the same serotype (O21 H7), while the
remaining identified serotypes were O108:H45, O14:H15, O14:H4, and O91:H28. Identified
H types with untypable O-serogroups were H31, H8, and H6. For some of the strains, both
the O serogroup and H type were untypable (O-nt: H?; see Table 7.1 ) .

Cell characteristics (motility, hydrophobicity, cell aggregation, zeta potential and average cell
size) of 40 randomly selected E. coli strains were determined. Cell motility measured as the
growth and diameter of migration on agar plates ranged between 0.2 cm (SL43 and FA01) to
9 cm (SL21 and H31; Table 7.2 ) . The hydrophobicity varied from less than 1% (FR05) to
44.6% (SL20), and auto-aggregation ranged from no auto-aggregation (SL41) to 64% (SL14),
respectively. Average cell surface charge ranged from -12.4 mV for FR04 to -31.2 mV for
IN01, whereas the average size ranged from 1.76 µ m for SL08 to 3.22 µm for FR04. Apart
from the measured average cell size, the standard deviations from the mean values of all
measured cell characteristics were high. From these results, we concluded that the cell
properties varied considerably among the strains.