Agriculture Reference
In-Depth Information
suspension demonstrated uptake of both the red dye and bacteria (Buchanan and others
1999) with similar results reported for intact oranges and grapefruit (Merker and others
1999). In other work, Solomon and Matthews (2005) used FluoSpheres (fl uorescent
microbeads) as an indicator to study
E. coli
O157:H7 internalization in lettuce. When
mature lettuce plants were surface-irrigated with FluoSpheres, microscopic examina-
tion of the root, stem, and leaf tissue revealed internalized FluoSpheres within these
portions of growing plants. No signifi cant difference was found between the numbers
of beads and
E. coli
O157:H7 cells internalized. Niemira (2007) subsequently con-
fi rmed these microbeads as an appropriate surrogate for uptake of
E. coli
O157:H7 in
lettuce through the plant vascular system (Figs. 3.3 , 3.4 ).
Figure 3.3.
Romaine lettuce leaf pieces following perfusion with
E. coli
O157:H7 in-
oculum, SEM micrographs. In left image, arrows indicate bacterial cells in intercellular
spaces; letter
A
indicates area of magnifi cation in right image.
Figure 3.4.
Romaine lettuce leaf pieces following perfusion with microbeads, SEM mi-
crographs. Letter
A
indicates area of magnifi cation in right image, showing microbeads
in vascular elements.
