Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...

22j 2 Physicochemical Approaches to Studying Plant Growth Promoting Rhizobacteria
Figure 2.1 Infrared spectra of dried biomass of A. brasilense (nonendophytic
strain Sp7) grown (a) in a standard phosphate–
malate medium (control) and in the same medium in the
presence of 0.2 mM Co 2þ (b), Cu 2þ (c) or Zn 2þ (d) [10,24].
under moderate heavy metal stress (Figure 2.1b–d). The most prominent feature of
the metal-stressed cells is the appearance of a relatively strong and well-resolved
band at about 1727 cm 1 (Figure 2.1b–d) featuring polyester n(C¼O) vibrations. On
the contrary, in the control cells where the amide I and amide II bands of cellular
proteins (at about 1650 and 1540 cm 1 , respectively) dominate (Figure 2.1a), there is
only a weak shoulder at about 1730 cm 1 . Together with an increased FTIR absorption
in the regions of methylene ( CH2 ) bending vibrations (at 1460–1440 cm 1 ),